--- /dev/null
+/* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
+ *
+ * lttng-context-callstack-legacy-impl.h
+ *
+ * LTTng callstack event context, legacy implementation. Targets
+ * kernels and architectures not yet using the stacktrace common
+ * infrastructure introduced in the upstream Linux kernel by commit
+ * 214d8ca6ee "stacktrace: Provide common infrastructure" (merged in
+ * Linux 5.2, then gradually introduced within architectures).
+ *
+ * Copyright (C) 2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ * Copyright (C) 2014 Francis Giraldeau <francis.giraldeau@gmail.com>
+ */
+
+#define MAX_ENTRIES 128
+
+enum lttng_cs_ctx_modes {
+ CALLSTACK_KERNEL = 0,
+ CALLSTACK_USER = 1,
+ NR_CALLSTACK_MODES,
+};
+
+struct lttng_cs_dispatch {
+ struct stack_trace stack_trace;
+ unsigned long entries[MAX_ENTRIES];
+};
+
+struct lttng_cs {
+ struct lttng_cs_dispatch dispatch[RING_BUFFER_MAX_NESTING];
+};
+
+struct field_data {
+ struct lttng_cs __percpu *cs_percpu;
+ enum lttng_cs_ctx_modes mode;
+};
+
+struct lttng_cs_type {
+ const char *name;
+ const char *length_name;
+ const char *save_func_name;
+ void (*save_func)(struct stack_trace *trace);
+};
+
+static struct lttng_cs_type cs_types[] = {
+ {
+ .name = "callstack_kernel",
+ .length_name = "_callstack_kernel_length",
+ .save_func_name = "save_stack_trace",
+ .save_func = NULL,
+ },
+ {
+ .name = "callstack_user",
+ .length_name = "_callstack_user_length",
+ .save_func_name = "save_stack_trace_user",
+ .save_func = NULL,
+ },
+};
+
+static
+const char *lttng_cs_ctx_mode_name(enum lttng_cs_ctx_modes mode)
+{
+ return cs_types[mode].name;
+}
+
+static
+const char *lttng_cs_ctx_mode_length_name(enum lttng_cs_ctx_modes mode)
+{
+ return cs_types[mode].length_name;
+}
+
+static
+int init_type(enum lttng_cs_ctx_modes mode)
+{
+ unsigned long func;
+
+ if (cs_types[mode].save_func)
+ return 0;
+ func = kallsyms_lookup_funcptr(cs_types[mode].save_func_name);
+ if (!func) {
+ printk(KERN_WARNING "LTTng: symbol lookup failed: %s\n",
+ cs_types[mode].save_func_name);
+ return -EINVAL;
+ }
+ cs_types[mode].save_func = (void *) func;
+ return 0;
+}
+
+static
+void lttng_cs_set_init(struct lttng_cs __percpu *cs_set)
+{
+ int cpu, i;
+
+ for_each_possible_cpu(cpu) {
+ struct lttng_cs *cs;
+
+ cs = per_cpu_ptr(cs_set, cpu);
+ for (i = 0; i < RING_BUFFER_MAX_NESTING; i++) {
+ struct lttng_cs_dispatch *dispatch;
+
+ dispatch = &cs->dispatch[i];
+ dispatch->stack_trace.entries = dispatch->entries;
+ dispatch->stack_trace.max_entries = MAX_ENTRIES;
+ }
+ }
+}
+
+/* Keep track of nesting inside userspace callstack context code */
+DEFINE_PER_CPU(int, callstack_user_nesting);
+
+static
+struct stack_trace *stack_trace_context(struct lttng_ctx_field *field,
+ struct lib_ring_buffer_ctx *ctx)
+{
+ int buffer_nesting, cs_user_nesting;
+ struct lttng_cs *cs;
+ struct field_data *fdata = field->priv;
+
+ /*
+ * Do not gather the userspace callstack context when the event was
+ * triggered by the userspace callstack context saving mechanism.
+ */
+ cs_user_nesting = per_cpu(callstack_user_nesting, ctx->cpu);
+
+ if (fdata->mode == CALLSTACK_USER && cs_user_nesting >= 1)
+ return NULL;
+
+ /*
+ * get_cpu() is not required, preemption is already
+ * disabled while event is written.
+ *
+ * max nesting is checked in lib_ring_buffer_get_cpu().
+ * Check it again as a safety net.
+ */
+ cs = per_cpu_ptr(fdata->cs_percpu, ctx->cpu);
+ buffer_nesting = per_cpu(lib_ring_buffer_nesting, ctx->cpu) - 1;
+ if (buffer_nesting >= RING_BUFFER_MAX_NESTING)
+ return NULL;
+
+ return &cs->dispatch[buffer_nesting].stack_trace;
+}
+
+static
+size_t lttng_callstack_length_get_size(size_t offset, struct lttng_ctx_field *field,
+ struct lib_ring_buffer_ctx *ctx,
+ struct lttng_channel *chan)
+{
+ size_t orig_offset = offset;
+
+ offset += lib_ring_buffer_align(offset, lttng_alignof(unsigned int));
+ offset += sizeof(unsigned int);
+ return offset - orig_offset;
+}
+
+/*
+ * In order to reserve the correct size, the callstack is computed. The
+ * resulting callstack is saved to be accessed in the record step.
+ */
+static
+size_t lttng_callstack_sequence_get_size(size_t offset, struct lttng_ctx_field *field,
+ struct lib_ring_buffer_ctx *ctx,
+ struct lttng_channel *chan)
+{
+ struct stack_trace *trace;
+ struct field_data *fdata = field->priv;
+ size_t orig_offset = offset;
+
+ /* do not write data if no space is available */
+ trace = stack_trace_context(field, ctx);
+ if (unlikely(!trace)) {
+ offset += lib_ring_buffer_align(offset, lttng_alignof(unsigned long));
+ return offset - orig_offset;
+ }
+
+ /* reset stack trace, no need to clear memory */
+ trace->nr_entries = 0;
+
+ if (fdata->mode == CALLSTACK_USER)
+ ++per_cpu(callstack_user_nesting, ctx->cpu);
+
+ /* do the real work and reserve space */
+ cs_types[fdata->mode].save_func(trace);
+
+ if (fdata->mode == CALLSTACK_USER)
+ per_cpu(callstack_user_nesting, ctx->cpu)--;
+
+ /*
+ * Remove final ULONG_MAX delimiter. If we cannot find it, add
+ * our own marker to show that the stack is incomplete. This is
+ * more compact for a trace.
+ */
+ if (trace->nr_entries > 0
+ && trace->entries[trace->nr_entries - 1] == ULONG_MAX) {
+ trace->nr_entries--;
+ }
+ offset += lib_ring_buffer_align(offset, lttng_alignof(unsigned long));
+ offset += sizeof(unsigned long) * trace->nr_entries;
+ /* Add our own ULONG_MAX delimiter to show incomplete stack. */
+ if (trace->nr_entries == trace->max_entries)
+ offset += sizeof(unsigned long);
+ return offset - orig_offset;
+}
+
+static
+void lttng_callstack_length_record(struct lttng_ctx_field *field,
+ struct lib_ring_buffer_ctx *ctx,
+ struct lttng_channel *chan)
+{
+ struct stack_trace *trace = stack_trace_context(field, ctx);
+ unsigned int nr_seq_entries;
+
+ lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned int));
+ if (unlikely(!trace)) {
+ nr_seq_entries = 0;
+ } else {
+ nr_seq_entries = trace->nr_entries;
+ if (trace->nr_entries == trace->max_entries)
+ nr_seq_entries++;
+ }
+ chan->ops->event_write(ctx, &nr_seq_entries, sizeof(unsigned int));
+}
+static
+void lttng_callstack_sequence_record(struct lttng_ctx_field *field,
+ struct lib_ring_buffer_ctx *ctx,
+ struct lttng_channel *chan)
+{
+ struct stack_trace *trace = stack_trace_context(field, ctx);
+ unsigned int nr_seq_entries;
+
+ lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned long));
+ if (unlikely(!trace)) {
+ return;
+ }
+ nr_seq_entries = trace->nr_entries;
+ if (trace->nr_entries == trace->max_entries)
+ nr_seq_entries++;
+ chan->ops->event_write(ctx, trace->entries,
+ sizeof(unsigned long) * trace->nr_entries);
+ /* Add our own ULONG_MAX delimiter to show incomplete stack. */
+ if (trace->nr_entries == trace->max_entries) {
+ unsigned long delim = ULONG_MAX;
+
+ chan->ops->event_write(ctx, &delim, sizeof(unsigned long));
+ }
+}
projects / lttng-modules.git / blobdiff