From b6ee48d2a69c34bf5dd44319cba19bedbbd35fca Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Tue, 21 May 2019 17:51:23 -0400 Subject: [PATCH] Introduce callstack legacy implementation header Split the callstack code: keep boilerplate code within the C implementation file, and move the parts which depend on the "legacy" (pre-stackwalk) stacktrace kernel API to a separate implementation header. This is a preparation step to introduce a new implementation header for the stackwalk API, added in Linux 5.2 and gradually integrated within each architecture. Signed-off-by: Mathieu Desnoyers --- lttng-context-callstack-legacy-impl.h | 190 ++++++++++++++++++++++++++ lttng-context-callstack.c | 177 +----------------------- 2 files changed, 191 insertions(+), 176 deletions(-) create mode 100644 lttng-context-callstack-legacy-impl.h diff --git a/lttng-context-callstack-legacy-impl.h b/lttng-context-callstack-legacy-impl.h new file mode 100644 index 00000000..a68e8a18 --- /dev/null +++ b/lttng-context-callstack-legacy-impl.h @@ -0,0 +1,190 @@ +/* SPDX-License-Identifier: (GPL-2.0 or LGPL-2.1) + * + * 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 + * Copyright (C) 2014 Francis Giraldeau + */ + +#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 *save_func_name; + void (*save_func)(struct stack_trace *trace); +}; + +static struct lttng_cs_type cs_types[] = { + { + .name = "callstack_kernel", + .save_func_name = "save_stack_trace", + .save_func = NULL, + }, + { + .name = "callstack_user", + .save_func_name = "save_stack_trace_user", + .save_func = NULL, + }, +}; + +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; +} + +/* 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; +} + +/* + * 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_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 int)); + offset += sizeof(unsigned int); + 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 int)); + offset += sizeof(unsigned int); + 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_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; + + if (unlikely(!trace)) { + nr_seq_entries = 0; + lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned int)); + chan->ops->event_write(ctx, &nr_seq_entries, sizeof(unsigned int)); + lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned long)); + return; + } + lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned int)); + 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)); + lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned long)); + 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)); + } +} diff --git a/lttng-context-callstack.c b/lttng-context-callstack.c index 0876b122..3fccfcf2 100644 --- a/lttng-context-callstack.c +++ b/lttng-context-callstack.c @@ -49,182 +49,7 @@ #include "wrapper/vmalloc.h" #include "lttng-tracer.h" -#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 *save_func_name; - void (*save_func)(struct stack_trace *trace); -}; - -static struct lttng_cs_type cs_types[] = { - { - .name = "callstack_kernel", - .save_func_name = "save_stack_trace", - .save_func = NULL, - }, - { - .name = "callstack_user", - .save_func_name = "save_stack_trace_user", - .save_func = NULL, - }, -}; - -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; -} - -/* 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; -} - -/* - * 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_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 int)); - offset += sizeof(unsigned int); - 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 int)); - offset += sizeof(unsigned int); - 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_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; - - if (unlikely(!trace)) { - nr_seq_entries = 0; - lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned int)); - chan->ops->event_write(ctx, &nr_seq_entries, sizeof(unsigned int)); - lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned long)); - return; - } - lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned int)); - 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)); - lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned long)); - 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)); - } -} +#include "lttng-context-callstack-legacy-impl.h" static void field_data_free(struct field_data *fdata) -- 2.34.1