Introduce lazy system call event creation
[lttng-modules.git] / src / lttng-syscalls.c
index 3139a556822e543fcca852a40d96c968c34062d8..c5be18051191bbb6dd0ac335389e27c469662bba 100644 (file)
@@ -29,6 +29,7 @@
 #include <wrapper/rcu.h>
 #include <wrapper/syscall.h>
 #include <lttng/events.h>
+#include <lttng/utils.h>
 
 #ifndef CONFIG_COMPAT
 # ifndef is_compat_task
@@ -63,6 +64,13 @@ void syscall_entry_event_probe(void *__data, struct pt_regs *regs, long id);
 static
 void syscall_exit_event_probe(void *__data, struct pt_regs *regs, long ret);
 
+static
+void syscall_entry_event_notifier_probe(void *__data, struct pt_regs *regs,
+               long id);
+static
+void syscall_exit_event_notifier_probe(void *__data, struct pt_regs *regs,
+               long ret);
+
 /*
  * Forward declarations for old kernels.
  */
@@ -285,6 +293,7 @@ typedef __kernel_old_time_t time_t;
 
 struct trace_syscall_entry {
        void *event_func;
+       void *event_notifier_func;
        const struct lttng_event_desc *desc;
        const struct lttng_event_field *fields;
        unsigned int nrargs;
@@ -301,6 +310,7 @@ struct trace_syscall_entry {
 #define TRACE_SYSCALL_TABLE(_template, _name, _nr, _nrargs)    \
        [ _nr ] = {                                             \
                .event_func = __event_probe__syscall_entry_##_template, \
+               .event_notifier_func = __event_notifier_probe__syscall_entry_##_template, \
                .nrargs = (_nrargs),                            \
                .fields = __event_fields___syscall_entry_##_template, \
                .desc = &__event_desc___syscall_entry_##_name,  \
@@ -316,6 +326,7 @@ static const struct trace_syscall_entry sc_table[] = {
 #define TRACE_SYSCALL_TABLE(_template, _name, _nr, _nrargs)    \
        [ _nr ] = {                                             \
                .event_func = __event_probe__compat_syscall_entry_##_template, \
+               .event_notifier_func = __event_notifier_probe__compat_syscall_entry_##_template, \
                .nrargs = (_nrargs),                            \
                .fields = __event_fields___compat_syscall_entry_##_template, \
                .desc = &__event_desc___compat_syscall_entry_##_name, \
@@ -338,6 +349,7 @@ const struct trace_syscall_entry compat_sc_table[] = {
 #define TRACE_SYSCALL_TABLE(_template, _name, _nr, _nrargs)    \
        [ _nr ] = {                                             \
                .event_func = __event_probe__syscall_exit_##_template, \
+               .event_notifier_func = __event_notifier_probe__syscall_exit_##_template, \
                .nrargs = (_nrargs),                            \
                .fields = __event_fields___syscall_exit_##_template, \
                .desc = &__event_desc___syscall_exit_##_name, \
@@ -353,6 +365,7 @@ static const struct trace_syscall_entry sc_exit_table[] = {
 #define TRACE_SYSCALL_TABLE(_template, _name, _nr, _nrargs)    \
        [ _nr ] = {                                             \
                .event_func = __event_probe__compat_syscall_exit_##_template, \
+               .event_notifier_func = __event_notifier_probe__compat_syscall_exit_##_template, \
                .nrargs = (_nrargs),                            \
                .fields = __event_fields___compat_syscall_exit_##_template, \
                .desc = &__event_desc___compat_syscall_exit_##_name, \
@@ -375,28 +388,168 @@ struct lttng_syscall_filter {
        DECLARE_BITMAP(sc_compat_exit, NR_compat_syscalls);
 };
 
-static void syscall_entry_event_unknown(struct lttng_event *event,
-       struct pt_regs *regs, unsigned int id)
+static void syscall_entry_event_unknown(struct hlist_head *unknown_action_list_head,
+       struct pt_regs *regs, long id)
+{
+       unsigned long args[LTTNG_SYSCALL_NR_ARGS];
+       struct lttng_event *event;
+
+       lttng_syscall_get_arguments(current, regs, args);
+       hlist_for_each_entry_rcu(event, unknown_action_list_head, u.syscall.node) {
+               if (unlikely(in_compat_syscall()))
+                       __event_probe__compat_syscall_entry_unknown(event, id, args);
+               else
+                       __event_probe__syscall_entry_unknown(event, id, args);
+       }
+}
+
+static void syscall_entry_event_notifier_unknown(
+               struct hlist_head *unknown_dispatch_list_head,
+               struct pt_regs *regs, long id)
 {
        unsigned long args[LTTNG_SYSCALL_NR_ARGS];
+       struct lttng_event_notifier *notifier;
 
        lttng_syscall_get_arguments(current, regs, args);
-       if (unlikely(in_compat_syscall()))
-               __event_probe__compat_syscall_entry_unknown(event, id, args);
-       else
-               __event_probe__syscall_entry_unknown(event, id, args);
+       lttng_hlist_for_each_entry_rcu(notifier, unknown_dispatch_list_head, u.syscall.node) {
+               if (unlikely(in_compat_syscall()))
+                       __event_notifier_probe__compat_syscall_entry_unknown(notifier, id, args);
+               else
+                       __event_notifier_probe__syscall_entry_unknown(notifier, id, args);
+       }
+}
+
+static void syscall_exit_event_notifier_unknown(
+               struct hlist_head *unknown_dispatch_list_head,
+               struct pt_regs *regs, long id, long ret)
+{
+       unsigned long args[LTTNG_SYSCALL_NR_ARGS];
+       struct lttng_event_notifier *notifier;
+
+       lttng_syscall_get_arguments(current, regs, args);
+       lttng_hlist_for_each_entry_rcu(notifier, unknown_dispatch_list_head, u.syscall.node) {
+               if (unlikely(in_compat_syscall()))
+                       __event_notifier_probe__compat_syscall_exit_unknown(notifier, id, ret, args);
+               else
+                       __event_notifier_probe__syscall_exit_unknown(notifier, id, ret, args);
+       }
 }
 
 static __always_inline
-void syscall_entry_call_func(void *func, unsigned int nrargs, void *data,
+void syscall_entry_call_func(struct hlist_head *action_list,
+               void *func, unsigned int nrargs,
                struct pt_regs *regs)
 {
+       struct lttng_event *event;
+
+       switch (nrargs) {
+       case 0:
+       {
+               void (*fptr)(void *__data) = func;
+
+               hlist_for_each_entry_rcu(event, action_list, u.syscall.node)
+                       fptr(event);
+               break;
+       }
+       case 1:
+       {
+               void (*fptr)(void *__data, unsigned long arg0) = func;
+               unsigned long args[LTTNG_SYSCALL_NR_ARGS];
+
+               lttng_syscall_get_arguments(current, regs, args);
+               hlist_for_each_entry_rcu(event, action_list, u.syscall.node)
+                       fptr(event, args[0]);
+               break;
+       }
+       case 2:
+       {
+               void (*fptr)(void *__data,
+                       unsigned long arg0,
+                       unsigned long arg1) = func;
+               unsigned long args[LTTNG_SYSCALL_NR_ARGS];
+
+               lttng_syscall_get_arguments(current, regs, args);
+               hlist_for_each_entry_rcu(event, action_list, u.syscall.node)
+                       fptr(event, args[0], args[1]);
+               break;
+       }
+       case 3:
+       {
+               void (*fptr)(void *__data,
+                       unsigned long arg0,
+                       unsigned long arg1,
+                       unsigned long arg2) = func;
+               unsigned long args[LTTNG_SYSCALL_NR_ARGS];
+
+               lttng_syscall_get_arguments(current, regs, args);
+               hlist_for_each_entry_rcu(event, action_list, u.syscall.node)
+                       fptr(event, args[0], args[1], args[2]);
+               break;
+       }
+       case 4:
+       {
+               void (*fptr)(void *__data,
+                       unsigned long arg0,
+                       unsigned long arg1,
+                       unsigned long arg2,
+                       unsigned long arg3) = func;
+               unsigned long args[LTTNG_SYSCALL_NR_ARGS];
+
+               lttng_syscall_get_arguments(current, regs, args);
+               hlist_for_each_entry_rcu(event, action_list, u.syscall.node)
+                       fptr(event, args[0], args[1], args[2], args[3]);
+               break;
+       }
+       case 5:
+       {
+               void (*fptr)(void *__data,
+                       unsigned long arg0,
+                       unsigned long arg1,
+                       unsigned long arg2,
+                       unsigned long arg3,
+                       unsigned long arg4) = func;
+               unsigned long args[LTTNG_SYSCALL_NR_ARGS];
+
+               lttng_syscall_get_arguments(current, regs, args);
+               hlist_for_each_entry_rcu(event, action_list, u.syscall.node)
+                       fptr(event, args[0], args[1], args[2], args[3], args[4]);
+               break;
+       }
+       case 6:
+       {
+               void (*fptr)(void *__data,
+                       unsigned long arg0,
+                       unsigned long arg1,
+                       unsigned long arg2,
+                       unsigned long arg3,
+                       unsigned long arg4,
+                       unsigned long arg5) = func;
+               unsigned long args[LTTNG_SYSCALL_NR_ARGS];
+
+               lttng_syscall_get_arguments(current, regs, args);
+               hlist_for_each_entry_rcu(event, action_list, u.syscall.node)
+                       fptr(event, args[0], args[1], args[2],
+                            args[3], args[4], args[5]);
+               break;
+       }
+       default:
+               break;
+       }
+}
+
+static __always_inline
+void syscall_entry_event_notifier_call_func(struct hlist_head *dispatch_list,
+               void *func, unsigned int nrargs, struct pt_regs *regs)
+{
+       struct lttng_event_notifier *notifier;
+
        switch (nrargs) {
        case 0:
        {
                void (*fptr)(void *__data) = func;
 
-               fptr(data);
+               lttng_hlist_for_each_entry_rcu(notifier, dispatch_list, u.syscall.node)
+                       fptr(notifier);
                break;
        }
        case 1:
@@ -405,7 +558,8 @@ void syscall_entry_call_func(void *func, unsigned int nrargs, void *data,
                unsigned long args[LTTNG_SYSCALL_NR_ARGS];
 
                lttng_syscall_get_arguments(current, regs, args);
-               fptr(data, args[0]);
+               lttng_hlist_for_each_entry_rcu(notifier, dispatch_list, u.syscall.node)
+                       fptr(notifier, args[0]);
                break;
        }
        case 2:
@@ -416,7 +570,8 @@ void syscall_entry_call_func(void *func, unsigned int nrargs, void *data,
                unsigned long args[LTTNG_SYSCALL_NR_ARGS];
 
                lttng_syscall_get_arguments(current, regs, args);
-               fptr(data, args[0], args[1]);
+               lttng_hlist_for_each_entry_rcu(notifier, dispatch_list, u.syscall.node)
+                       fptr(notifier, args[0], args[1]);
                break;
        }
        case 3:
@@ -428,7 +583,8 @@ void syscall_entry_call_func(void *func, unsigned int nrargs, void *data,
                unsigned long args[LTTNG_SYSCALL_NR_ARGS];
 
                lttng_syscall_get_arguments(current, regs, args);
-               fptr(data, args[0], args[1], args[2]);
+               lttng_hlist_for_each_entry_rcu(notifier, dispatch_list, u.syscall.node)
+                       fptr(notifier, args[0], args[1], args[2]);
                break;
        }
        case 4:
@@ -441,7 +597,8 @@ void syscall_entry_call_func(void *func, unsigned int nrargs, void *data,
                unsigned long args[LTTNG_SYSCALL_NR_ARGS];
 
                lttng_syscall_get_arguments(current, regs, args);
-               fptr(data, args[0], args[1], args[2], args[3]);
+               lttng_hlist_for_each_entry_rcu(notifier, dispatch_list, u.syscall.node)
+                       fptr(notifier, args[0], args[1], args[2], args[3]);
                break;
        }
        case 5:
@@ -455,7 +612,8 @@ void syscall_entry_call_func(void *func, unsigned int nrargs, void *data,
                unsigned long args[LTTNG_SYSCALL_NR_ARGS];
 
                lttng_syscall_get_arguments(current, regs, args);
-               fptr(data, args[0], args[1], args[2], args[3], args[4]);
+               lttng_hlist_for_each_entry_rcu(notifier, dispatch_list, u.syscall.node)
+                       fptr(notifier, args[0], args[1], args[2], args[3], args[4]);
                break;
        }
        case 6:
@@ -470,8 +628,8 @@ void syscall_entry_call_func(void *func, unsigned int nrargs, void *data,
                unsigned long args[LTTNG_SYSCALL_NR_ARGS];
 
                lttng_syscall_get_arguments(current, regs, args);
-               fptr(data, args[0], args[1], args[2],
-                       args[3], args[4], args[5]);
+               lttng_hlist_for_each_entry_rcu(notifier, dispatch_list, u.syscall.node)
+                       fptr(notifier, args[0], args[1], args[2], args[3], args[4], args[5]);
                break;
        }
        default:
@@ -482,7 +640,7 @@ void syscall_entry_call_func(void *func, unsigned int nrargs, void *data,
 void syscall_entry_event_probe(void *__data, struct pt_regs *regs, long id)
 {
        struct lttng_channel *chan = __data;
-       struct lttng_event *event, *unknown_event;
+       struct hlist_head *action_list, *unknown_action_list;
        const struct trace_syscall_entry *table, *entry;
        size_t table_len;
 
@@ -490,119 +648,310 @@ void syscall_entry_event_probe(void *__data, struct pt_regs *regs, long id)
                struct lttng_syscall_filter *filter = chan->sc_filter;
 
                if (id < 0 || id >= NR_compat_syscalls
-                       || (!READ_ONCE(chan->syscall_all) && !test_bit(id, filter->sc_compat_entry))) {
+                       || (!READ_ONCE(chan->syscall_all_entry) && !test_bit(id, filter->sc_compat_entry))) {
                        /* System call filtered out. */
                        return;
                }
                table = compat_sc_table;
                table_len = ARRAY_SIZE(compat_sc_table);
-               unknown_event = chan->sc_compat_unknown;
+               unknown_action_list = &chan->sc_compat_unknown;
        } else {
                struct lttng_syscall_filter *filter = chan->sc_filter;
 
                if (id < 0 || id >= NR_syscalls
-                       || (!READ_ONCE(chan->syscall_all) && !test_bit(id, filter->sc_entry))) {
+                       || (!READ_ONCE(chan->syscall_all_entry) && !test_bit(id, filter->sc_entry))) {
                        /* System call filtered out. */
                        return;
                }
                table = sc_table;
                table_len = ARRAY_SIZE(sc_table);
-               unknown_event = chan->sc_unknown;
+               unknown_action_list = &chan->sc_unknown;
        }
        if (unlikely(id < 0 || id >= table_len)) {
-               syscall_entry_event_unknown(unknown_event, regs, id);
+               syscall_entry_event_unknown(unknown_action_list, regs, id);
                return;
        }
-       if (unlikely(in_compat_syscall()))
-               event = chan->compat_sc_table[id];
-       else
-               event = chan->sc_table[id];
-       if (unlikely(!event)) {
-               syscall_entry_event_unknown(unknown_event, regs, id);
+
+       entry = &table[id];
+       if (!entry->event_func) {
+               syscall_entry_event_unknown(unknown_action_list, regs, id);
                return;
        }
+
+       if (unlikely(in_compat_syscall())) {
+               action_list = &chan->compat_sc_table[id];
+       } else {
+               action_list = &chan->sc_table[id];
+       }
+       if (unlikely(hlist_empty(action_list)))
+               return;
+
+       syscall_entry_call_func(action_list, entry->event_func, entry->nrargs, regs);
+}
+
+void syscall_entry_event_notifier_probe(void *__data, struct pt_regs *regs,
+               long id)
+{
+       struct lttng_event_notifier_group *group = __data;
+       const struct trace_syscall_entry *table, *entry;
+       struct hlist_head *dispatch_list, *unknown_dispatch_list;
+       size_t table_len;
+
+       if (unlikely(in_compat_syscall())) {
+               struct lttng_syscall_filter *filter = group->sc_filter;
+
+               if (id < 0 || id >= NR_compat_syscalls
+                       || (!READ_ONCE(group->syscall_all_entry) &&
+                               !test_bit(id, filter->sc_compat_entry))) {
+                       /* System call filtered out. */
+                       return;
+               }
+               table = compat_sc_table;
+               table_len = ARRAY_SIZE(compat_sc_table);
+               unknown_dispatch_list = &group->event_notifier_compat_unknown_syscall_dispatch;
+       } else {
+               struct lttng_syscall_filter *filter = group->sc_filter;
+
+               if (id < 0 || id >= NR_syscalls
+                       || (!READ_ONCE(group->syscall_all_entry) &&
+                               !test_bit(id, filter->sc_entry))) {
+                       /* System call filtered out. */
+                       return;
+               }
+               table = sc_table;
+               table_len = ARRAY_SIZE(sc_table);
+               unknown_dispatch_list = &group->event_notifier_unknown_syscall_dispatch;
+       }
+       /* Check if the syscall id is out of bound. */
+       if (unlikely(id < 0 || id >= table_len)) {
+               syscall_entry_event_notifier_unknown(unknown_dispatch_list,
+                               regs, id);
+               return;
+       }
+
        entry = &table[id];
-       WARN_ON_ONCE(!entry);
-       syscall_entry_call_func(entry->event_func, entry->nrargs, event, regs);
+       if (!entry->event_notifier_func) {
+               syscall_entry_event_notifier_unknown(unknown_dispatch_list,
+                               regs, id);
+               return;
+       }
+
+       if (unlikely(in_compat_syscall())) {
+               dispatch_list = &group->event_notifier_compat_syscall_dispatch[id];
+       } else {
+               dispatch_list = &group->event_notifier_syscall_dispatch[id];
+       }
+       if (unlikely(hlist_empty(dispatch_list)))
+               return;
+
+       syscall_entry_event_notifier_call_func(dispatch_list,
+                       entry->event_notifier_func, entry->nrargs, regs);
 }
 
-static void syscall_exit_event_unknown(struct lttng_event *event,
-       struct pt_regs *regs, int id, long ret)
+static void syscall_exit_event_unknown(struct hlist_head *unknown_action_list_head,
+       struct pt_regs *regs, long id, long ret)
 {
        unsigned long args[LTTNG_SYSCALL_NR_ARGS];
+       struct lttng_event *event;
 
        lttng_syscall_get_arguments(current, regs, args);
-       if (unlikely(in_compat_syscall()))
-               __event_probe__compat_syscall_exit_unknown(event, id, ret,
-                       args);
-       else
-               __event_probe__syscall_exit_unknown(event, id, ret, args);
+       hlist_for_each_entry_rcu(event, unknown_action_list_head, u.syscall.node) {
+               if (unlikely(in_compat_syscall()))
+                       __event_probe__compat_syscall_exit_unknown(event, id, ret,
+                               args);
+               else
+                       __event_probe__syscall_exit_unknown(event, id, ret, args);
+       }
+}
+
+static __always_inline
+void syscall_exit_call_func(struct hlist_head *action_list,
+               void *func, unsigned int nrargs,
+               struct pt_regs *regs, long ret)
+{
+       struct lttng_event *event;
+
+       switch (nrargs) {
+       case 0:
+       {
+               void (*fptr)(void *__data, long ret) = func;
+
+               hlist_for_each_entry_rcu(event, action_list, u.syscall.node)
+                       fptr(event, ret);
+               break;
+       }
+       case 1:
+       {
+               void (*fptr)(void *__data,
+                       long ret,
+                       unsigned long arg0) = func;
+               unsigned long args[LTTNG_SYSCALL_NR_ARGS];
+
+               lttng_syscall_get_arguments(current, regs, args);
+               hlist_for_each_entry_rcu(event, action_list, u.syscall.node)
+                       fptr(event, ret, args[0]);
+               break;
+       }
+       case 2:
+       {
+               void (*fptr)(void *__data,
+                       long ret,
+                       unsigned long arg0,
+                       unsigned long arg1) = func;
+               unsigned long args[LTTNG_SYSCALL_NR_ARGS];
+
+               lttng_syscall_get_arguments(current, regs, args);
+               hlist_for_each_entry_rcu(event, action_list, u.syscall.node)
+                       fptr(event, ret, args[0], args[1]);
+               break;
+       }
+       case 3:
+       {
+               void (*fptr)(void *__data,
+                       long ret,
+                       unsigned long arg0,
+                       unsigned long arg1,
+                       unsigned long arg2) = func;
+               unsigned long args[LTTNG_SYSCALL_NR_ARGS];
+
+               lttng_syscall_get_arguments(current, regs, args);
+               hlist_for_each_entry_rcu(event, action_list, u.syscall.node)
+                       fptr(event, ret, args[0], args[1], args[2]);
+               break;
+       }
+       case 4:
+       {
+               void (*fptr)(void *__data,
+                       long ret,
+                       unsigned long arg0,
+                       unsigned long arg1,
+                       unsigned long arg2,
+                       unsigned long arg3) = func;
+               unsigned long args[LTTNG_SYSCALL_NR_ARGS];
+
+               lttng_syscall_get_arguments(current, regs, args);
+               hlist_for_each_entry_rcu(event, action_list, u.syscall.node)
+                       fptr(event, ret, args[0], args[1], args[2], args[3]);
+               break;
+       }
+       case 5:
+       {
+               void (*fptr)(void *__data,
+                       long ret,
+                       unsigned long arg0,
+                       unsigned long arg1,
+                       unsigned long arg2,
+                       unsigned long arg3,
+                       unsigned long arg4) = func;
+               unsigned long args[LTTNG_SYSCALL_NR_ARGS];
+
+               lttng_syscall_get_arguments(current, regs, args);
+               hlist_for_each_entry_rcu(event, action_list, u.syscall.node)
+                       fptr(event, ret, args[0], args[1], args[2], args[3], args[4]);
+               break;
+       }
+       case 6:
+       {
+               void (*fptr)(void *__data,
+                       long ret,
+                       unsigned long arg0,
+                       unsigned long arg1,
+                       unsigned long arg2,
+                       unsigned long arg3,
+                       unsigned long arg4,
+                       unsigned long arg5) = func;
+               unsigned long args[LTTNG_SYSCALL_NR_ARGS];
+
+               lttng_syscall_get_arguments(current, regs, args);
+               hlist_for_each_entry_rcu(event, action_list, u.syscall.node)
+                       fptr(event, ret, args[0], args[1], args[2],
+                            args[3], args[4], args[5]);
+               break;
+       }
+       default:
+               break;
+       }
 }
 
 void syscall_exit_event_probe(void *__data, struct pt_regs *regs, long ret)
 {
        struct lttng_channel *chan = __data;
-       struct lttng_event *event, *unknown_event;
+       struct hlist_head *action_list, *unknown_action_list;
        const struct trace_syscall_entry *table, *entry;
        size_t table_len;
        long id;
 
        id = syscall_get_nr(current, regs);
+
        if (unlikely(in_compat_syscall())) {
                struct lttng_syscall_filter *filter = chan->sc_filter;
 
                if (id < 0 || id >= NR_compat_syscalls
-                       || (!READ_ONCE(chan->syscall_all) && !test_bit(id, filter->sc_compat_exit))) {
+                       || (!READ_ONCE(chan->syscall_all_exit) && !test_bit(id, filter->sc_compat_exit))) {
                        /* System call filtered out. */
                        return;
                }
                table = compat_sc_exit_table;
                table_len = ARRAY_SIZE(compat_sc_exit_table);
-               unknown_event = chan->compat_sc_exit_unknown;
+               unknown_action_list = &chan->compat_sc_exit_unknown;
        } else {
                struct lttng_syscall_filter *filter = chan->sc_filter;
 
                if (id < 0 || id >= NR_syscalls
-                       || (!READ_ONCE(chan->syscall_all) && !test_bit(id, filter->sc_exit))) {
+                       || (!READ_ONCE(chan->syscall_all_exit) && !test_bit(id, filter->sc_exit))) {
                        /* System call filtered out. */
                        return;
                }
                table = sc_exit_table;
                table_len = ARRAY_SIZE(sc_exit_table);
-               unknown_event = chan->sc_exit_unknown;
+               unknown_action_list = &chan->sc_exit_unknown;
        }
        if (unlikely(id < 0 || id >= table_len)) {
-               syscall_exit_event_unknown(unknown_event, regs, id, ret);
+               syscall_exit_event_unknown(unknown_action_list, regs, id, ret);
                return;
        }
-       if (unlikely(in_compat_syscall()))
-               event = chan->compat_sc_exit_table[id];
-       else
-               event = chan->sc_exit_table[id];
-       if (unlikely(!event)) {
-               syscall_exit_event_unknown(unknown_event, regs, id, ret);
+
+       entry = &table[id];
+       if (!entry->event_func) {
+               syscall_exit_event_unknown(unknown_action_list, regs, id, ret);
                return;
        }
-       entry = &table[id];
-       WARN_ON_ONCE(!entry);
 
-       switch (entry->nrargs) {
+       if (unlikely(in_compat_syscall())) {
+               action_list = &chan->compat_sc_exit_table[id];
+       } else {
+               action_list = &chan->sc_exit_table[id];
+       }
+       if (unlikely(hlist_empty(action_list)))
+               return;
+
+       syscall_exit_call_func(action_list, entry->event_func, entry->nrargs,
+                              regs, ret);
+}
+
+static __always_inline
+void syscall_exit_event_notifier_call_func(struct hlist_head *dispatch_list,
+               void *func, unsigned int nrargs, struct pt_regs *regs, long ret)
+{
+       struct lttng_event_notifier *notifier;
+
+       switch (nrargs) {
        case 0:
        {
-               void (*fptr)(void *__data, long ret) = entry->event_func;
+               void (*fptr)(void *__data, long ret) = func;
 
-               fptr(event, ret);
+               lttng_hlist_for_each_entry_rcu(notifier, dispatch_list, u.syscall.node)
+                       fptr(notifier, ret);
                break;
        }
        case 1:
        {
-               void (*fptr)(void *__data,
-                       long ret,
-                       unsigned long arg0) = entry->event_func;
+               void (*fptr)(void *__data, long ret, unsigned long arg0) = func;
                unsigned long args[LTTNG_SYSCALL_NR_ARGS];
 
                lttng_syscall_get_arguments(current, regs, args);
-               fptr(event, ret, args[0]);
+               lttng_hlist_for_each_entry_rcu(notifier, dispatch_list, u.syscall.node)
+                       fptr(notifier, ret, args[0]);
                break;
        }
        case 2:
@@ -610,11 +959,12 @@ void syscall_exit_event_probe(void *__data, struct pt_regs *regs, long ret)
                void (*fptr)(void *__data,
                        long ret,
                        unsigned long arg0,
-                       unsigned long arg1) = entry->event_func;
+                       unsigned long arg1) = func;
                unsigned long args[LTTNG_SYSCALL_NR_ARGS];
 
                lttng_syscall_get_arguments(current, regs, args);
-               fptr(event, ret, args[0], args[1]);
+               lttng_hlist_for_each_entry_rcu(notifier, dispatch_list, u.syscall.node)
+                       fptr(notifier, ret, args[0], args[1]);
                break;
        }
        case 3:
@@ -623,11 +973,12 @@ void syscall_exit_event_probe(void *__data, struct pt_regs *regs, long ret)
                        long ret,
                        unsigned long arg0,
                        unsigned long arg1,
-                       unsigned long arg2) = entry->event_func;
+                       unsigned long arg2) = func;
                unsigned long args[LTTNG_SYSCALL_NR_ARGS];
 
                lttng_syscall_get_arguments(current, regs, args);
-               fptr(event, ret, args[0], args[1], args[2]);
+               lttng_hlist_for_each_entry_rcu(notifier, dispatch_list, u.syscall.node)
+                       fptr(notifier, ret, args[0], args[1], args[2]);
                break;
        }
        case 4:
@@ -637,11 +988,12 @@ void syscall_exit_event_probe(void *__data, struct pt_regs *regs, long ret)
                        unsigned long arg0,
                        unsigned long arg1,
                        unsigned long arg2,
-                       unsigned long arg3) = entry->event_func;
+                       unsigned long arg3) = func;
                unsigned long args[LTTNG_SYSCALL_NR_ARGS];
 
                lttng_syscall_get_arguments(current, regs, args);
-               fptr(event, ret, args[0], args[1], args[2], args[3]);
+               lttng_hlist_for_each_entry_rcu(notifier, dispatch_list, u.syscall.node)
+                       fptr(notifier, ret, args[0], args[1], args[2], args[3]);
                break;
        }
        case 5:
@@ -652,11 +1004,12 @@ void syscall_exit_event_probe(void *__data, struct pt_regs *regs, long ret)
                        unsigned long arg1,
                        unsigned long arg2,
                        unsigned long arg3,
-                       unsigned long arg4) = entry->event_func;
+                       unsigned long arg4) = func;
                unsigned long args[LTTNG_SYSCALL_NR_ARGS];
 
                lttng_syscall_get_arguments(current, regs, args);
-               fptr(event, ret, args[0], args[1], args[2], args[3], args[4]);
+               lttng_hlist_for_each_entry_rcu(notifier, dispatch_list, u.syscall.node)
+                       fptr(notifier, ret, args[0], args[1], args[2], args[3], args[4]);
                break;
        }
        case 6:
@@ -668,12 +1021,12 @@ void syscall_exit_event_probe(void *__data, struct pt_regs *regs, long ret)
                        unsigned long arg2,
                        unsigned long arg3,
                        unsigned long arg4,
-                       unsigned long arg5) = entry->event_func;
+                       unsigned long arg5) = func;
                unsigned long args[LTTNG_SYSCALL_NR_ARGS];
 
                lttng_syscall_get_arguments(current, regs, args);
-               fptr(event, ret, args[0], args[1], args[2],
-                       args[3], args[4], args[5]);
+               lttng_hlist_for_each_entry_rcu(notifier, dispatch_list, u.syscall.node)
+                       fptr(notifier, ret, args[0], args[1], args[2], args[3], args[4], args[5]);
                break;
        }
        default:
@@ -681,33 +1034,111 @@ void syscall_exit_event_probe(void *__data, struct pt_regs *regs, long ret)
        }
 }
 
+static
+void syscall_exit_event_notifier_probe(void *__data, struct pt_regs *regs,
+               long ret)
+{
+       struct lttng_event_notifier_group *group = __data;
+       const struct trace_syscall_entry *table, *entry;
+       struct hlist_head *dispatch_list, *unknown_dispatch_list;
+       size_t table_len;
+       long id;
+
+       id = syscall_get_nr(current, regs);
+
+       if (unlikely(in_compat_syscall())) {
+               struct lttng_syscall_filter *filter = group->sc_filter;
+
+               if (id < 0 || id >= NR_compat_syscalls
+                       || (!READ_ONCE(group->syscall_all_exit) &&
+                               !test_bit(id, filter->sc_compat_exit))) {
+                       /* System call filtered out. */
+                       return;
+               }
+               table = compat_sc_exit_table;
+               table_len = ARRAY_SIZE(compat_sc_exit_table);
+               unknown_dispatch_list = &group->event_notifier_exit_compat_unknown_syscall_dispatch;
+       } else {
+               struct lttng_syscall_filter *filter = group->sc_filter;
+
+               if (id < 0 || id >= NR_syscalls
+                       || (!READ_ONCE(group->syscall_all_exit) &&
+                                       !test_bit(id, filter->sc_exit))) {
+                       /* System call filtered out. */
+                       return;
+               }
+               table = sc_exit_table;
+               table_len = ARRAY_SIZE(sc_exit_table);
+               unknown_dispatch_list = &group->event_notifier_exit_unknown_syscall_dispatch;
+       }
+       /* Check if the syscall id is out of bound. */
+       if (unlikely(id < 0 || id >= table_len)) {
+               syscall_exit_event_notifier_unknown(unknown_dispatch_list,
+                               regs, id, ret);
+               return;
+       }
+
+       entry = &table[id];
+       if (!entry->event_notifier_func) {
+               syscall_entry_event_notifier_unknown(unknown_dispatch_list,
+                               regs, id);
+               return;
+       }
+
+       if (unlikely(in_compat_syscall())) {
+               dispatch_list = &group->event_notifier_exit_compat_syscall_dispatch[id];
+       } else {
+               dispatch_list = &group->event_notifier_exit_syscall_dispatch[id];
+       }
+       if (unlikely(hlist_empty(dispatch_list)))
+               return;
+
+       syscall_exit_event_notifier_call_func(dispatch_list,
+                       entry->event_notifier_func, entry->nrargs, regs, ret);
+}
 /*
  * noinline to diminish caller stack size.
  * Should be called with sessions lock held.
  */
 static
-int fill_event_table(const struct trace_syscall_entry *table, size_t table_len,
-       struct lttng_event **chan_table, struct lttng_channel *chan,
+int lttng_create_syscall_event_if_missing(const struct trace_syscall_entry *table, size_t table_len,
+       struct hlist_head *chan_table, struct lttng_event_enabler *event_enabler,
        void *filter, enum sc_type type)
 {
-       const struct lttng_event_desc *desc;
+       struct lttng_channel *chan = event_enabler->chan;
+       struct lttng_session *session = chan->session;
        unsigned int i;
 
-       /* Allocate events for each syscall, insert into table */
+       /* Allocate events for each syscall matching enabler, insert into table */
        for (i = 0; i < table_len; i++) {
+               const struct lttng_event_desc *desc = table[i].desc;
                struct lttng_kernel_event ev;
-               desc = table[i].desc;
+               struct lttng_event *event;
+               struct hlist_head *head;
+               bool found = false;
 
                if (!desc) {
                        /* Unknown syscall */
                        continue;
                }
+               if (lttng_desc_match_enabler(desc,
+                               lttng_event_enabler_as_enabler(event_enabler)) <= 0)
+                       continue;
                /*
-                * Skip those already populated by previous failed
-                * register for this channel.
+                * Check if already created.
                 */
-               if (chan_table[i])
+               head = utils_borrow_hash_table_bucket(
+                       session->events_ht.table, LTTNG_EVENT_HT_SIZE,
+                       desc->name);
+               lttng_hlist_for_each_entry(event, head, hlist) {
+                       if (event->desc == desc
+                               && event->chan == event_enabler->chan)
+                               found = true;
+               }
+               if (found)
                        continue;
+
+               /* We need to create an event for this syscall/enabler. */
                memset(&ev, 0, sizeof(ev));
                switch (type) {
                case SC_TYPE_ENTRY:
@@ -730,18 +1161,19 @@ int fill_event_table(const struct trace_syscall_entry *table, size_t table_len,
                strncpy(ev.name, desc->name, LTTNG_KERNEL_SYM_NAME_LEN - 1);
                ev.name[LTTNG_KERNEL_SYM_NAME_LEN - 1] = '\0';
                ev.instrumentation = LTTNG_KERNEL_SYSCALL;
-               chan_table[i] = _lttng_event_create(chan, &ev, filter,
-                                               desc, ev.instrumentation);
-               WARN_ON_ONCE(!chan_table[i]);
-               if (IS_ERR(chan_table[i])) {
+               event = _lttng_event_create(chan, &ev, filter,
+                                           desc, ev.instrumentation);
+               WARN_ON_ONCE(!event);
+               if (IS_ERR(event)) {
                        /*
                         * If something goes wrong in event registration
                         * after the first one, we have no choice but to
                         * leave the previous events in there, until
                         * deleted by session teardown.
                         */
-                       return PTR_ERR(chan_table[i]);
+                       return PTR_ERR(event);
                }
+               hlist_add_head(&event->u.syscall.node, &chan_table[i]);
        }
        return 0;
 }
@@ -749,8 +1181,9 @@ int fill_event_table(const struct trace_syscall_entry *table, size_t table_len,
 /*
  * Should be called with sessions lock held.
  */
-int lttng_syscalls_register_event(struct lttng_channel *chan, void *filter)
+int lttng_syscalls_register_event(struct lttng_event_enabler *event_enabler, void *filter)
 {
+       struct lttng_channel *chan = event_enabler->chan;
        struct lttng_kernel_event ev;
        int ret;
 
@@ -789,9 +1222,10 @@ int lttng_syscalls_register_event(struct lttng_channel *chan, void *filter)
                        return -ENOMEM;
        }
 #endif
-       if (!chan->sc_unknown) {
+       if (hlist_empty(&chan->sc_unknown)) {
                const struct lttng_event_desc *desc =
                        &__event_desc___syscall_entry_unknown;
+               struct lttng_event *event;
 
                memset(&ev, 0, sizeof(ev));
                strncpy(ev.name, desc->name, LTTNG_KERNEL_SYM_NAME_LEN);
@@ -799,18 +1233,19 @@ int lttng_syscalls_register_event(struct lttng_channel *chan, void *filter)
                ev.instrumentation = LTTNG_KERNEL_SYSCALL;
                ev.u.syscall.entryexit = LTTNG_KERNEL_SYSCALL_ENTRY;
                ev.u.syscall.abi = LTTNG_KERNEL_SYSCALL_ABI_NATIVE;
-               chan->sc_unknown = _lttng_event_create(chan, &ev, filter,
-                                               desc,
-                                               ev.instrumentation);
-               WARN_ON_ONCE(!chan->sc_unknown);
-               if (IS_ERR(chan->sc_unknown)) {
-                       return PTR_ERR(chan->sc_unknown);
+               event = _lttng_event_create(chan, &ev, filter, desc,
+                                           ev.instrumentation);
+               WARN_ON_ONCE(!event);
+               if (IS_ERR(event)) {
+                       return PTR_ERR(event);
                }
+               hlist_add_head(&event->u.syscall.node, &chan->sc_unknown);
        }
 
-       if (!chan->sc_compat_unknown) {
+       if (hlist_empty(&chan->sc_compat_unknown)) {
                const struct lttng_event_desc *desc =
                        &__event_desc___compat_syscall_entry_unknown;
+               struct lttng_event *event;
 
                memset(&ev, 0, sizeof(ev));
                strncpy(ev.name, desc->name, LTTNG_KERNEL_SYM_NAME_LEN);
@@ -818,18 +1253,19 @@ int lttng_syscalls_register_event(struct lttng_channel *chan, void *filter)
                ev.instrumentation = LTTNG_KERNEL_SYSCALL;
                ev.u.syscall.entryexit = LTTNG_KERNEL_SYSCALL_ENTRY;
                ev.u.syscall.abi = LTTNG_KERNEL_SYSCALL_ABI_COMPAT;
-               chan->sc_compat_unknown = _lttng_event_create(chan, &ev, filter,
-                                               desc,
-                                               ev.instrumentation);
-               WARN_ON_ONCE(!chan->sc_unknown);
-               if (IS_ERR(chan->sc_compat_unknown)) {
-                       return PTR_ERR(chan->sc_compat_unknown);
+               event = _lttng_event_create(chan, &ev, filter, desc,
+                                           ev.instrumentation);
+               WARN_ON_ONCE(!event);
+               if (IS_ERR(event)) {
+                       return PTR_ERR(event);
                }
+               hlist_add_head(&event->u.syscall.node, &chan->sc_compat_unknown);
        }
 
-       if (!chan->compat_sc_exit_unknown) {
+       if (hlist_empty(&chan->compat_sc_exit_unknown)) {
                const struct lttng_event_desc *desc =
                        &__event_desc___compat_syscall_exit_unknown;
+               struct lttng_event *event;
 
                memset(&ev, 0, sizeof(ev));
                strncpy(ev.name, desc->name, LTTNG_KERNEL_SYM_NAME_LEN);
@@ -837,18 +1273,19 @@ int lttng_syscalls_register_event(struct lttng_channel *chan, void *filter)
                ev.instrumentation = LTTNG_KERNEL_SYSCALL;
                ev.u.syscall.entryexit = LTTNG_KERNEL_SYSCALL_EXIT;
                ev.u.syscall.abi = LTTNG_KERNEL_SYSCALL_ABI_COMPAT;
-               chan->compat_sc_exit_unknown = _lttng_event_create(chan, &ev,
-                                               filter, desc,
-                                               ev.instrumentation);
-               WARN_ON_ONCE(!chan->compat_sc_exit_unknown);
-               if (IS_ERR(chan->compat_sc_exit_unknown)) {
-                       return PTR_ERR(chan->compat_sc_exit_unknown);
+               event = _lttng_event_create(chan, &ev, filter, desc,
+                                           ev.instrumentation);
+               WARN_ON_ONCE(!event);
+               if (IS_ERR(event)) {
+                       return PTR_ERR(event);
                }
+               hlist_add_head(&event->u.syscall.node, &chan->compat_sc_exit_unknown);
        }
 
-       if (!chan->sc_exit_unknown) {
+       if (hlist_empty(&chan->sc_exit_unknown)) {
                const struct lttng_event_desc *desc =
                        &__event_desc___syscall_exit_unknown;
+               struct lttng_event *event;
 
                memset(&ev, 0, sizeof(ev));
                strncpy(ev.name, desc->name, LTTNG_KERNEL_SYM_NAME_LEN);
@@ -856,31 +1293,32 @@ int lttng_syscalls_register_event(struct lttng_channel *chan, void *filter)
                ev.instrumentation = LTTNG_KERNEL_SYSCALL;
                ev.u.syscall.entryexit = LTTNG_KERNEL_SYSCALL_EXIT;
                ev.u.syscall.abi = LTTNG_KERNEL_SYSCALL_ABI_NATIVE;
-               chan->sc_exit_unknown = _lttng_event_create(chan, &ev, filter,
-                                               desc, ev.instrumentation);
-               WARN_ON_ONCE(!chan->sc_exit_unknown);
-               if (IS_ERR(chan->sc_exit_unknown)) {
-                       return PTR_ERR(chan->sc_exit_unknown);
+               event = _lttng_event_create(chan, &ev, filter, desc,
+                                           ev.instrumentation);
+               WARN_ON_ONCE(!event);
+               if (IS_ERR(event)) {
+                       return PTR_ERR(event);
                }
+               hlist_add_head(&event->u.syscall.node, &chan->sc_exit_unknown);
        }
 
-       ret = fill_event_table(sc_table, ARRAY_SIZE(sc_table),
-                       chan->sc_table, chan, filter, SC_TYPE_ENTRY);
+       ret = lttng_create_syscall_event_if_missing(sc_table, ARRAY_SIZE(sc_table),
+                       chan->sc_table, event_enabler, filter, SC_TYPE_ENTRY);
        if (ret)
                return ret;
-       ret = fill_event_table(sc_exit_table, ARRAY_SIZE(sc_exit_table),
-                       chan->sc_exit_table, chan, filter, SC_TYPE_EXIT);
+       ret = lttng_create_syscall_event_if_missing(sc_exit_table, ARRAY_SIZE(sc_exit_table),
+                       chan->sc_exit_table, event_enabler, filter, SC_TYPE_EXIT);
        if (ret)
                return ret;
 
 #ifdef CONFIG_COMPAT
-       ret = fill_event_table(compat_sc_table, ARRAY_SIZE(compat_sc_table),
-                       chan->compat_sc_table, chan, filter,
+       ret = lttng_create_syscall_event_if_missing(compat_sc_table, ARRAY_SIZE(compat_sc_table),
+                       chan->compat_sc_table, event_enabler, filter,
                        SC_TYPE_COMPAT_ENTRY);
        if (ret)
                return ret;
-       ret = fill_event_table(compat_sc_exit_table, ARRAY_SIZE(compat_sc_exit_table),
-                       chan->compat_sc_exit_table, chan, filter,
+       ret = lttng_create_syscall_event_if_missing(compat_sc_exit_table, ARRAY_SIZE(compat_sc_exit_table),
+                       chan->compat_sc_exit_table, event_enabler, filter,
                        SC_TYPE_COMPAT_EXIT);
        if (ret)
                return ret;
@@ -918,9 +1356,380 @@ int lttng_syscalls_register_event(struct lttng_channel *chan, void *filter)
 }
 
 /*
- * Only called at session destruction.
+ * Should be called with sessions lock held.
  */
-int lttng_syscalls_unregister_event(struct lttng_channel *chan)
+int lttng_syscalls_register_event_notifier(
+               struct lttng_event_notifier_enabler *event_notifier_enabler,
+               void *filter)
+{
+       struct lttng_event_notifier_group *group = event_notifier_enabler->group;
+       unsigned int i;
+       int ret = 0;
+
+       wrapper_vmalloc_sync_mappings();
+
+       if (!group->event_notifier_syscall_dispatch) {
+               group->event_notifier_syscall_dispatch =
+                               kzalloc(sizeof(struct hlist_head) * ARRAY_SIZE(sc_table),
+                                       GFP_KERNEL);
+               if (!group->event_notifier_syscall_dispatch)
+                       return -ENOMEM;
+
+               /* Initialize all list_head */
+               for (i = 0; i < ARRAY_SIZE(sc_table); i++)
+                       INIT_HLIST_HEAD(&group->event_notifier_syscall_dispatch[i]);
+
+               /* Init the unknown syscall notifier list. */
+               INIT_HLIST_HEAD(&group->event_notifier_unknown_syscall_dispatch);
+       }
+
+       if (!group->event_notifier_exit_syscall_dispatch) {
+               group->event_notifier_exit_syscall_dispatch =
+                               kzalloc(sizeof(struct hlist_head) * ARRAY_SIZE(sc_table),
+                                       GFP_KERNEL);
+               if (!group->event_notifier_exit_syscall_dispatch)
+                       return -ENOMEM;
+
+               /* Initialize all list_head */
+               for (i = 0; i < ARRAY_SIZE(sc_table); i++)
+                       INIT_HLIST_HEAD(&group->event_notifier_exit_syscall_dispatch[i]);
+
+               /* Init the unknown exit syscall notifier list. */
+               INIT_HLIST_HEAD(&group->event_notifier_exit_unknown_syscall_dispatch);
+       }
+
+#ifdef CONFIG_COMPAT
+       if (!group->event_notifier_compat_syscall_dispatch) {
+               group->event_notifier_compat_syscall_dispatch =
+                               kzalloc(sizeof(struct hlist_head) * ARRAY_SIZE(compat_sc_table),
+                                       GFP_KERNEL);
+               if (!group->event_notifier_syscall_dispatch)
+                       return -ENOMEM;
+
+               /* Initialize all list_head */
+               for (i = 0; i < ARRAY_SIZE(compat_sc_table); i++)
+                       INIT_HLIST_HEAD(&group->event_notifier_compat_syscall_dispatch[i]);
+
+               /* Init the unknown syscall notifier list. */
+               INIT_HLIST_HEAD(&group->event_notifier_compat_unknown_syscall_dispatch);
+       }
+
+       if (!group->event_notifier_exit_compat_syscall_dispatch) {
+               group->event_notifier_exit_compat_syscall_dispatch =
+                               kzalloc(sizeof(struct hlist_head) * ARRAY_SIZE(compat_sc_exit_table),
+                                       GFP_KERNEL);
+               if (!group->event_notifier_exit_syscall_dispatch)
+                       return -ENOMEM;
+
+               /* Initialize all list_head */
+               for (i = 0; i < ARRAY_SIZE(compat_sc_exit_table); i++)
+                       INIT_HLIST_HEAD(&group->event_notifier_exit_compat_syscall_dispatch[i]);
+
+               /* Init the unknown exit syscall notifier list. */
+               INIT_HLIST_HEAD(&group->event_notifier_exit_compat_unknown_syscall_dispatch);
+       }
+#endif
+
+       if (!group->sc_filter) {
+               group->sc_filter = kzalloc(sizeof(struct lttng_syscall_filter),
+                               GFP_KERNEL);
+               if (!group->sc_filter)
+                       return -ENOMEM;
+       }
+
+       if (!group->sys_enter_registered) {
+               ret = lttng_wrapper_tracepoint_probe_register("sys_enter",
+                               (void *) syscall_entry_event_notifier_probe, group);
+               if (ret)
+                       return ret;
+               group->sys_enter_registered = 1;
+       }
+
+       if (!group->sys_exit_registered) {
+               ret = lttng_wrapper_tracepoint_probe_register("sys_exit",
+                               (void *) syscall_exit_event_notifier_probe, group);
+               if (ret) {
+                       WARN_ON_ONCE(lttng_wrapper_tracepoint_probe_unregister("sys_enter",
+                               (void *) syscall_entry_event_notifier_probe, group));
+                       return ret;
+               }
+               group->sys_exit_registered = 1;
+       }
+
+       return ret;
+}
+
+static
+int create_unknown_event_notifier(
+               struct lttng_event_notifier_enabler *event_notifier_enabler,
+               enum sc_type type)
+{
+       struct lttng_event_notifier *notifier;
+       const struct lttng_event_desc *desc;
+       struct lttng_event_notifier_group *group = event_notifier_enabler->group;
+       struct lttng_kernel_event_notifier event_notifier_param;
+       uint64_t user_token = event_notifier_enabler->base.user_token;
+       uint64_t error_counter_index = event_notifier_enabler->error_counter_index;
+       struct lttng_enabler *base_enabler = lttng_event_notifier_enabler_as_enabler(
+               event_notifier_enabler);
+       struct hlist_head *unknown_dispatch_list;
+       int ret = 0;
+       bool found = false;
+       enum lttng_kernel_syscall_abi abi;
+       enum lttng_kernel_syscall_entryexit entryexit;
+       struct hlist_head *head;
+
+       switch (type) {
+       case SC_TYPE_ENTRY:
+               desc = &__event_desc___syscall_entry_unknown;
+               unknown_dispatch_list = &group->event_notifier_unknown_syscall_dispatch;
+               entryexit = LTTNG_KERNEL_SYSCALL_ENTRY;
+               abi = LTTNG_KERNEL_SYSCALL_ABI_NATIVE;
+               break;
+       case SC_TYPE_EXIT:
+               desc = &__event_desc___syscall_exit_unknown;
+               unknown_dispatch_list = &group->event_notifier_exit_unknown_syscall_dispatch;
+               entryexit = LTTNG_KERNEL_SYSCALL_EXIT;
+               abi = LTTNG_KERNEL_SYSCALL_ABI_NATIVE;
+               break;
+       case SC_TYPE_COMPAT_ENTRY:
+               desc = &__event_desc___compat_syscall_entry_unknown;
+               unknown_dispatch_list = &group->event_notifier_compat_unknown_syscall_dispatch;
+               entryexit = LTTNG_KERNEL_SYSCALL_ENTRY;
+               abi = LTTNG_KERNEL_SYSCALL_ABI_COMPAT;
+               break;
+       case SC_TYPE_COMPAT_EXIT:
+               desc = &__event_desc___compat_syscall_exit_unknown;
+               unknown_dispatch_list = &group->event_notifier_exit_compat_unknown_syscall_dispatch;
+               entryexit = LTTNG_KERNEL_SYSCALL_EXIT;
+               abi = LTTNG_KERNEL_SYSCALL_ABI_COMPAT;
+               break;
+       default:
+               BUG_ON(1);
+       }
+
+       /*
+        * Check if already created.
+        */
+       head = utils_borrow_hash_table_bucket(group->event_notifiers_ht.table,
+               LTTNG_EVENT_NOTIFIER_HT_SIZE, desc->name);
+       lttng_hlist_for_each_entry(notifier, head, hlist) {
+               if (notifier->desc == desc &&
+                               notifier->user_token == base_enabler->user_token)
+                       found = true;
+       }
+       if (found)
+               goto end;
+
+       memset(&event_notifier_param, 0, sizeof(event_notifier_param));
+       strncat(event_notifier_param.event.name, desc->name,
+               LTTNG_KERNEL_SYM_NAME_LEN - strlen(event_notifier_param.event.name) - 1);
+
+       event_notifier_param.event.name[LTTNG_KERNEL_SYM_NAME_LEN - 1] = '\0';
+
+       event_notifier_param.event.instrumentation = LTTNG_KERNEL_SYSCALL;
+       event_notifier_param.event.u.syscall.abi = abi;
+       event_notifier_param.event.u.syscall.entryexit = entryexit;
+
+       notifier = _lttng_event_notifier_create(desc, user_token,
+               error_counter_index, group, &event_notifier_param, NULL,
+               event_notifier_param.event.instrumentation);
+       if (IS_ERR(notifier)) {
+               printk(KERN_INFO "Unable to create unknown notifier %s\n",
+                       desc->name);
+               ret = -ENOMEM;
+               goto end;
+       }
+
+       hlist_add_head_rcu(&notifier->u.syscall.node, unknown_dispatch_list);
+
+end:
+       return ret;
+}
+
+static int create_matching_event_notifiers(
+               struct lttng_event_notifier_enabler *event_notifier_enabler,
+               void *filter, const struct trace_syscall_entry *table,
+               size_t table_len, enum sc_type type)
+{
+       struct lttng_event_notifier_group *group = event_notifier_enabler->group;
+       const struct lttng_event_desc *desc;
+       uint64_t user_token = event_notifier_enabler->base.user_token;
+       uint64_t error_counter_index = event_notifier_enabler->error_counter_index;
+       unsigned int i;
+       int ret = 0;
+
+       /* iterate over all syscall and create event_notifier that match */
+       for (i = 0; i < table_len; i++) {
+               struct lttng_event_notifier *event_notifier;
+               struct lttng_kernel_event_notifier event_notifier_param;
+               struct hlist_head *head;
+               int found = 0;
+
+               desc = table[i].desc;
+               if (!desc) {
+                       /* Unknown syscall */
+                       continue;
+               }
+
+               if (!lttng_desc_match_enabler(desc,
+                               lttng_event_notifier_enabler_as_enabler(event_notifier_enabler)))
+                       continue;
+
+               /*
+                * Check if already created.
+                */
+               head = utils_borrow_hash_table_bucket(group->event_notifiers_ht.table,
+                       LTTNG_EVENT_NOTIFIER_HT_SIZE, desc->name);
+               lttng_hlist_for_each_entry(event_notifier, head, hlist) {
+                       if (event_notifier->desc == desc
+                               && event_notifier->user_token == event_notifier_enabler->base.user_token)
+                               found = 1;
+               }
+               if (found)
+                       continue;
+
+               memset(&event_notifier_param, 0, sizeof(event_notifier_param));
+               switch (type) {
+               case SC_TYPE_ENTRY:
+                       event_notifier_param.event.u.syscall.entryexit = LTTNG_KERNEL_SYSCALL_ENTRY;
+                       event_notifier_param.event.u.syscall.abi = LTTNG_KERNEL_SYSCALL_ABI_NATIVE;
+                       break;
+               case SC_TYPE_EXIT:
+                       event_notifier_param.event.u.syscall.entryexit = LTTNG_KERNEL_SYSCALL_EXIT;
+                       event_notifier_param.event.u.syscall.abi = LTTNG_KERNEL_SYSCALL_ABI_NATIVE;
+                       break;
+               case SC_TYPE_COMPAT_ENTRY:
+                       event_notifier_param.event.u.syscall.entryexit = LTTNG_KERNEL_SYSCALL_ENTRY;
+                       event_notifier_param.event.u.syscall.abi = LTTNG_KERNEL_SYSCALL_ABI_COMPAT;
+                       break;
+               case SC_TYPE_COMPAT_EXIT:
+                       event_notifier_param.event.u.syscall.entryexit = LTTNG_KERNEL_SYSCALL_EXIT;
+                       event_notifier_param.event.u.syscall.abi = LTTNG_KERNEL_SYSCALL_ABI_COMPAT;
+                       break;
+               }
+               strncat(event_notifier_param.event.name, desc->name,
+                       LTTNG_KERNEL_SYM_NAME_LEN - strlen(event_notifier_param.event.name) - 1);
+               event_notifier_param.event.name[LTTNG_KERNEL_SYM_NAME_LEN - 1] = '\0';
+               event_notifier_param.event.instrumentation = LTTNG_KERNEL_SYSCALL;
+
+               event_notifier = _lttng_event_notifier_create(desc, user_token,
+                       error_counter_index, group, &event_notifier_param,
+                       filter, event_notifier_param.event.instrumentation);
+               if (IS_ERR(event_notifier)) {
+                       printk(KERN_INFO "Unable to create event_notifier %s\n",
+                               desc->name);
+                       ret = -ENOMEM;
+                       goto end;
+               }
+
+               event_notifier->u.syscall.syscall_id = i;
+       }
+
+end:
+       return ret;
+
+}
+
+int lttng_syscals_create_matching_event_notifiers(
+               struct lttng_event_notifier_enabler *event_notifier_enabler,
+               void *filter)
+{
+       int ret;
+       struct lttng_enabler *base_enabler =
+                       lttng_event_notifier_enabler_as_enabler(event_notifier_enabler);
+       enum lttng_kernel_syscall_entryexit entryexit =
+                       base_enabler->event_param.u.syscall.entryexit;
+
+       if (entryexit == LTTNG_KERNEL_SYSCALL_ENTRY || entryexit == LTTNG_KERNEL_SYSCALL_ENTRYEXIT) {
+               ret = create_matching_event_notifiers(event_notifier_enabler,
+                       filter, sc_table, ARRAY_SIZE(sc_table), SC_TYPE_ENTRY);
+               if (ret)
+                       goto end;
+
+               ret = create_matching_event_notifiers(event_notifier_enabler,
+                       filter, compat_sc_table, ARRAY_SIZE(compat_sc_table),
+                       SC_TYPE_COMPAT_ENTRY);
+               if (ret)
+                       goto end;
+
+               ret = create_unknown_event_notifier(event_notifier_enabler,
+                               SC_TYPE_ENTRY);
+               if (ret)
+                       goto end;
+
+               ret = create_unknown_event_notifier(event_notifier_enabler,
+                               SC_TYPE_COMPAT_ENTRY);
+               if (ret)
+                       goto end;
+       }
+
+       if (entryexit == LTTNG_KERNEL_SYSCALL_EXIT || entryexit == LTTNG_KERNEL_SYSCALL_ENTRYEXIT) {
+               ret = create_matching_event_notifiers(event_notifier_enabler,
+                       filter, sc_exit_table, ARRAY_SIZE(sc_exit_table),
+                       SC_TYPE_EXIT);
+               if (ret)
+                       goto end;
+
+               ret = create_unknown_event_notifier(event_notifier_enabler,
+                               SC_TYPE_EXIT);
+               if (ret)
+                       goto end;
+
+               ret = create_matching_event_notifiers(event_notifier_enabler,
+                       filter, compat_sc_exit_table, ARRAY_SIZE(compat_sc_exit_table),
+                       SC_TYPE_COMPAT_EXIT);
+               if (ret)
+                       goto end;
+
+               ret = create_unknown_event_notifier(event_notifier_enabler,
+                               SC_TYPE_COMPAT_EXIT);
+               if (ret)
+                       goto end;
+       }
+
+end:
+       return ret;
+}
+
+/*
+ * Unregister the syscall event_notifier probes from the callsites.
+ */
+int lttng_syscalls_unregister_event_notifier_group(
+               struct lttng_event_notifier_group *event_notifier_group)
+{
+       int ret;
+
+       /*
+        * Only register the event_notifier probe on the `sys_enter` callsite for now.
+        * At the moment, we don't think it's desirable to have one fired
+        * event_notifier for the entry and one for the exit of a syscall.
+        */
+       if (event_notifier_group->sys_enter_registered) {
+               ret = lttng_wrapper_tracepoint_probe_unregister("sys_enter",
+                               (void *) syscall_entry_event_notifier_probe, event_notifier_group);
+               if (ret)
+                       return ret;
+               event_notifier_group->sys_enter_registered = 0;
+       }
+       if (event_notifier_group->sys_exit_registered) {
+               ret = lttng_wrapper_tracepoint_probe_unregister("sys_exit",
+                               (void *) syscall_exit_event_notifier_probe, event_notifier_group);
+               if (ret)
+                       return ret;
+               event_notifier_group->sys_enter_registered = 0;
+       }
+
+       kfree(event_notifier_group->event_notifier_syscall_dispatch);
+       kfree(event_notifier_group->event_notifier_exit_syscall_dispatch);
+#ifdef CONFIG_COMPAT
+       kfree(event_notifier_group->event_notifier_compat_syscall_dispatch);
+       kfree(event_notifier_group->event_notifier_exit_compat_syscall_dispatch);
+#endif
+       return 0;
+}
+
+int lttng_syscalls_unregister_channel(struct lttng_channel *chan)
 {
        int ret;
 
@@ -1008,15 +1817,16 @@ uint32_t get_sc_tables_len(void)
 }
 
 static
-const char *get_syscall_name(struct lttng_event *event)
+const char *get_syscall_name(const char *desc_name,
+               enum lttng_syscall_abi abi,
+               enum lttng_syscall_entryexit entryexit)
 {
        size_t prefix_len = 0;
 
-       WARN_ON_ONCE(event->instrumentation != LTTNG_KERNEL_SYSCALL);
 
-       switch (event->u.syscall.entryexit) {
+       switch (entryexit) {
        case LTTNG_SYSCALL_ENTRY:
-               switch (event->u.syscall.abi) {
+               switch (abi) {
                case LTTNG_SYSCALL_ABI_NATIVE:
                        prefix_len = strlen(SYSCALL_ENTRY_STR);
                        break;
@@ -1026,7 +1836,7 @@ const char *get_syscall_name(struct lttng_event *event)
                }
                break;
        case LTTNG_SYSCALL_EXIT:
-               switch (event->u.syscall.abi) {
+               switch (abi) {
                case LTTNG_SYSCALL_ABI_NATIVE:
                        prefix_len = strlen(SYSCALL_EXIT_STR);
                        break;
@@ -1037,22 +1847,22 @@ const char *get_syscall_name(struct lttng_event *event)
                break;
        }
        WARN_ON_ONCE(prefix_len == 0);
-       return event->desc->name + prefix_len;
+       return desc_name + prefix_len;
 }
 
-int lttng_syscall_filter_enable_event(struct lttng_channel *chan,
-               struct lttng_event *event)
+static
+int lttng_syscall_filter_enable(
+               struct lttng_syscall_filter *filter,
+               const char *desc_name, enum lttng_syscall_abi abi,
+               enum lttng_syscall_entryexit entryexit)
 {
-       struct lttng_syscall_filter *filter = chan->sc_filter;
        const char *syscall_name;
        unsigned long *bitmap;
        int syscall_nr;
 
-       WARN_ON_ONCE(!chan->sc_table);
-
-       syscall_name = get_syscall_name(event);
+       syscall_name = get_syscall_name(desc_name, abi, entryexit);
 
-       switch (event->u.syscall.abi) {
+       switch (abi) {
        case LTTNG_SYSCALL_ABI_NATIVE:
                syscall_nr = get_syscall_nr(syscall_name);
                break;
@@ -1065,9 +1875,9 @@ int lttng_syscall_filter_enable_event(struct lttng_channel *chan,
        if (syscall_nr < 0)
                return -ENOENT;
 
-       switch (event->u.syscall.entryexit) {
+       switch (entryexit) {
        case LTTNG_SYSCALL_ENTRY:
-               switch (event->u.syscall.abi) {
+               switch (abi) {
                case LTTNG_SYSCALL_ABI_NATIVE:
                        bitmap = filter->sc_entry;
                        break;
@@ -1079,7 +1889,7 @@ int lttng_syscall_filter_enable_event(struct lttng_channel *chan,
                }
                break;
        case LTTNG_SYSCALL_EXIT:
-               switch (event->u.syscall.abi) {
+               switch (abi) {
                case LTTNG_SYSCALL_ABI_NATIVE:
                        bitmap = filter->sc_exit;
                        break;
@@ -1099,19 +1909,76 @@ int lttng_syscall_filter_enable_event(struct lttng_channel *chan,
        return 0;
 }
 
-int lttng_syscall_filter_disable_event(struct lttng_channel *chan,
+int lttng_syscall_filter_enable_event_notifier(
+               struct lttng_event_notifier *notifier)
+{
+       struct lttng_event_notifier_group *group = notifier->group;
+       unsigned int syscall_id = notifier->u.syscall.syscall_id;
+       struct hlist_head *dispatch_list;
+       int ret = 0;
+
+       WARN_ON_ONCE(notifier->instrumentation != LTTNG_KERNEL_SYSCALL);
+
+       ret = lttng_syscall_filter_enable(group->sc_filter,
+               notifier->desc->name, notifier->u.syscall.abi,
+               notifier->u.syscall.entryexit);
+       if (ret) {
+               goto end;
+       }
+
+       switch (notifier->u.syscall.entryexit) {
+       case LTTNG_SYSCALL_ENTRY:
+               switch (notifier->u.syscall.abi) {
+               case LTTNG_SYSCALL_ABI_NATIVE:
+                       dispatch_list = &group->event_notifier_syscall_dispatch[syscall_id];
+                       break;
+               case LTTNG_SYSCALL_ABI_COMPAT:
+                       dispatch_list = &group->event_notifier_compat_syscall_dispatch[syscall_id];
+                       break;
+               }
+               break;
+       case LTTNG_SYSCALL_EXIT:
+               switch (notifier->u.syscall.abi) {
+               case LTTNG_SYSCALL_ABI_NATIVE:
+                       dispatch_list = &group->event_notifier_exit_syscall_dispatch[syscall_id];
+                       break;
+               case LTTNG_SYSCALL_ABI_COMPAT:
+                       dispatch_list = &group->event_notifier_exit_compat_syscall_dispatch[syscall_id];
+                       break;
+               }
+               break;
+       }
+
+       hlist_add_head_rcu(&notifier->u.syscall.node, dispatch_list);
+
+end:
+       return ret ;
+}
+
+int lttng_syscall_filter_enable_event(
+               struct lttng_channel *channel,
                struct lttng_event *event)
 {
-       struct lttng_syscall_filter *filter = chan->sc_filter;
+       WARN_ON_ONCE(event->instrumentation != LTTNG_KERNEL_SYSCALL);
+
+       return lttng_syscall_filter_enable(channel->sc_filter,
+               event->desc->name, event->u.syscall.abi,
+               event->u.syscall.entryexit);
+}
+
+static
+int lttng_syscall_filter_disable(
+               struct lttng_syscall_filter *filter,
+               const char *desc_name, enum lttng_syscall_abi abi,
+               enum lttng_syscall_entryexit entryexit)
+{
        const char *syscall_name;
        unsigned long *bitmap;
        int syscall_nr;
 
-       WARN_ON_ONCE(!chan->sc_table);
+       syscall_name = get_syscall_name(desc_name, abi, entryexit);
 
-       syscall_name = get_syscall_name(event);
-
-       switch (event->u.syscall.abi) {
+       switch (abi) {
        case LTTNG_SYSCALL_ABI_NATIVE:
                syscall_nr = get_syscall_nr(syscall_name);
                break;
@@ -1124,9 +1991,9 @@ int lttng_syscall_filter_disable_event(struct lttng_channel *chan,
        if (syscall_nr < 0)
                return -ENOENT;
 
-       switch (event->u.syscall.entryexit) {
+       switch (entryexit) {
        case LTTNG_SYSCALL_ENTRY:
-               switch (event->u.syscall.abi) {
+               switch (abi) {
                case LTTNG_SYSCALL_ABI_NATIVE:
                        bitmap = filter->sc_entry;
                        break;
@@ -1138,7 +2005,7 @@ int lttng_syscall_filter_disable_event(struct lttng_channel *chan,
                }
                break;
        case LTTNG_SYSCALL_EXIT:
-               switch (event->u.syscall.abi) {
+               switch (abi) {
                case LTTNG_SYSCALL_ABI_NATIVE:
                        bitmap = filter->sc_exit;
                        break;
@@ -1159,6 +2026,32 @@ int lttng_syscall_filter_disable_event(struct lttng_channel *chan,
        return 0;
 }
 
+int lttng_syscall_filter_disable_event_notifier(
+               struct lttng_event_notifier *notifier)
+{
+       struct lttng_event_notifier_group *group = notifier->group;
+       int ret;
+
+       WARN_ON_ONCE(notifier->instrumentation != LTTNG_KERNEL_SYSCALL);
+
+       ret = lttng_syscall_filter_disable(group->sc_filter,
+               notifier->desc->name, notifier->u.syscall.abi,
+               notifier->u.syscall.entryexit);
+       WARN_ON_ONCE(ret != 0);
+
+       hlist_del_rcu(&notifier->u.syscall.node);
+       return 0;
+}
+
+int lttng_syscall_filter_disable_event(
+               struct lttng_channel *channel,
+               struct lttng_event *event)
+{
+       return lttng_syscall_filter_disable(channel->sc_filter,
+               event->desc->name, event->u.syscall.abi,
+               event->u.syscall.entryexit);
+}
+
 static
 const struct trace_syscall_entry *syscall_list_get_entry(loff_t *pos)
 {
@@ -1299,7 +2192,8 @@ long lttng_channel_syscall_mask(struct lttng_channel *channel,
                char state;
 
                if (channel->sc_table) {
-                       if (!READ_ONCE(channel->syscall_all) && filter)
+                       if (!(READ_ONCE(channel->syscall_all_entry)
+                                       || READ_ONCE(channel->syscall_all_exit)) && filter)
                                state = test_bit(bit, filter->sc_entry)
                                        || test_bit(bit, filter->sc_exit);
                        else
@@ -1313,7 +2207,8 @@ long lttng_channel_syscall_mask(struct lttng_channel *channel,
                char state;
 
                if (channel->compat_sc_table) {
-                       if (!READ_ONCE(channel->syscall_all) && filter)
+                       if (!(READ_ONCE(channel->syscall_all_entry)
+                                       || READ_ONCE(channel->syscall_all_exit)) && filter)
                                state = test_bit(bit - ARRAY_SIZE(sc_table),
                                                filter->sc_compat_entry)
                                        || test_bit(bit - ARRAY_SIZE(sc_table),
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