X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=lttng-context-callstack.c;h=0876b12269ecc26a90c73b948d8c0dc9bb954f6e;hb=c08fa736f5e9d57bf93d217fa69745cb7e98a2d5;hp=d95cbc2eef3f7117f0fcb38508ff173106f9fadf;hpb=3c1a57e8ce82366ce96774e4ac1d7481c561cc4c;p=lttng-modules.git diff --git a/lttng-context-callstack.c b/lttng-context-callstack.c index d95cbc2e..0876b122 100644 --- a/lttng-context-callstack.c +++ b/lttng-context-callstack.c @@ -1,4 +1,5 @@ -/* +/* SPDX-License-Identifier: (GPL-2.0 or LGPL-2.1) + * * lttng-context-callstack.c * * LTTng callstack event context. @@ -6,45 +7,32 @@ * Copyright (C) 2014 Mathieu Desnoyers * Copyright (C) 2014 Francis Giraldeau * - * This library is free software; you can redistribute it and/or - * modify it under the terms of the GNU Lesser General Public - * License as published by the Free Software Foundation; only - * version 2.1 of the License. - * - * This library is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU - * Lesser General Public License for more details. + * The callstack context can be added to any kernel event. It records + * either the kernel or the userspace callstack, up to a max depth. The + * context is a CTF sequence, such that it uses only the space required + * for the number of callstack entries. * - * You should have received a copy of the GNU Lesser General Public - * License along with this library; if not, write to the Free Software - * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA - * - * The callstack context can be added to any kernel - * event. It records either the kernel or the userspace callstack, up to a - * max depth. The context is a CTF sequence, such that it uses only the space - * required for the number of callstack entries. - * - * It allocates callstack buffers per-CPU up to 4 interrupt nesting. This - * nesting limit is the same as defined in the ring buffer. It therefore uses a - * fixed amount of memory, proportional to the number of CPUs: + * It allocates callstack buffers per-CPU up to 4 interrupt nesting. + * This nesting limit is the same as defined in the ring buffer. It + * therefore uses a fixed amount of memory, proportional to the number + * of CPUs: * * size = cpus * nest * depth * sizeof(unsigned long) * - * Which is about 800 bytes per-CPUs on 64-bit host and a depth of 25. The - * allocation is done at the initialization to avoid memory allocation - * overhead while tracing, using a shallow stack. + * Which is 4096 bytes per CPU on 64-bit host and a depth of 128. + * The allocation is done at the initialization to avoid memory + * allocation overhead while tracing, using a shallow stack. * * The kernel callstack is recovered using save_stack_trace(), and the * userspace callstack uses save_stack_trace_user(). They rely on frame - * pointers. These are usually available for the kernel, but the compiler - * option -fomit-frame-pointer frequently used in popular Linux distributions - * may cause the userspace callstack to be unreliable, and is a known - * limitation of this approach. If frame pointers are not available, it - * produces no error, but the callstack will be empty. We still provide the - * feature, because it works well for runtime environments having frame - * pointers. In the future, unwind support and/or last branch record may - * provide a solution to this problem. + * pointers. These are usually available for the kernel, but the + * compiler option -fomit-frame-pointer frequently used in popular Linux + * distributions may cause the userspace callstack to be unreliable, and + * is a known limitation of this approach. If frame pointers are not + * available, it produces no error, but the callstack will be empty. We + * still provide the feature, because it works well for runtime + * environments having frame pointers. In the future, unwind support + * and/or last branch record may provide a solution to this problem. * * The symbol name resolution is left to the trace reader. */ @@ -61,15 +49,26 @@ #include "wrapper/vmalloc.h" #include "lttng-tracer.h" -#define MAX_ENTRIES 25 /* BUG: saving more than 30 entries causes trace corruption */ +#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 stack_trace items[RING_BUFFER_MAX_NESTING]; + struct lttng_cs_dispatch dispatch[RING_BUFFER_MAX_NESTING]; }; struct field_data { - int mode; struct lttng_cs __percpu *cs_percpu; + enum lttng_cs_ctx_modes mode; }; struct lttng_cs_type { @@ -78,26 +77,21 @@ struct lttng_cs_type { void (*save_func)(struct stack_trace *trace); }; -enum lttng_cs_ctx_modes { - CALLSTACK_KERNEL = 0, - CALLSTACK_USER = 1, -}; - static struct lttng_cs_type cs_types[] = { { - .name = "callstack_kernel", - .save_func_name = "save_stack_trace", - .save_func = NULL, + .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, + .name = "callstack_user", + .save_func_name = "save_stack_trace_user", + .save_func = NULL, }, }; static -int init_type(int mode) +int init_type(enum lttng_cs_ctx_modes mode) { unsigned long func; @@ -113,14 +107,26 @@ int init_type(int mode) 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 nesting; + 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. @@ -129,11 +135,11 @@ struct stack_trace *stack_trace_context(struct lttng_ctx_field *field, * Check it again as a safety net. */ cs = per_cpu_ptr(fdata->cs_percpu, ctx->cpu); - nesting = per_cpu(lib_ring_buffer_nesting, ctx->cpu) - 1; - if (nesting >= RING_BUFFER_MAX_NESTING) { + buffer_nesting = per_cpu(lib_ring_buffer_nesting, ctx->cpu) - 1; + if (buffer_nesting >= RING_BUFFER_MAX_NESTING) return NULL; - } - return &cs->items[nesting]; + + return &cs->dispatch[buffer_nesting].stack_trace; } /* @@ -145,71 +151,98 @@ size_t lttng_callstack_get_size(size_t offset, struct lttng_ctx_field *field, struct lib_ring_buffer_ctx *ctx, struct lttng_channel *chan) { - size_t size = 0; 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 (!trace) - return 0; + 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); - size += lib_ring_buffer_align(offset, lttng_alignof(unsigned int)); - size += sizeof(unsigned int); - size += lib_ring_buffer_align(offset, lttng_alignof(unsigned long)); - size += sizeof(unsigned long) * trace->nr_entries; - return size; + + 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 lib_ring_buffer_ctx *ctx, + struct lttng_channel *chan) { struct stack_trace *trace = stack_trace_context(field, ctx); + unsigned int nr_seq_entries; - if (!trace) + 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)); - chan->ops->event_write(ctx, &trace->nr_entries, sizeof(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)); + } } static void field_data_free(struct field_data *fdata) { - int cpu, i; - struct lttng_cs *cs; - if (!fdata) return; - for_each_possible_cpu(cpu) { - cs = per_cpu_ptr(fdata->cs_percpu, cpu); - for (i = 0; i < RING_BUFFER_MAX_NESTING; i++) { - kfree(cs->items[i].entries); - } - } free_percpu(fdata->cs_percpu); kfree(fdata); } static -struct field_data __percpu *field_data_create(unsigned int entries, int type) +struct field_data __percpu *field_data_create(enum lttng_cs_ctx_modes mode) { int cpu, i; - struct stack_trace *item; - struct lttng_cs *cs; struct lttng_cs __percpu *cs_set; - struct field_data* fdata; + struct field_data *fdata; - fdata = kzalloc(sizeof(unsigned long) * entries, GFP_KERNEL); + fdata = kzalloc(sizeof(*fdata), GFP_KERNEL); if (!fdata) return NULL; cs_set = alloc_percpu(struct lttng_cs); @@ -218,17 +251,18 @@ struct field_data __percpu *field_data_create(unsigned int entries, int type) fdata->cs_percpu = cs_set; 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++) { - item = &cs->items[i]; - item->entries = kzalloc(sizeof(unsigned long) * entries, GFP_KERNEL); - if (!item->entries) { - goto error_alloc; - } - item->max_entries = entries; + struct lttng_cs_dispatch *dispatch; + + dispatch = &cs->dispatch[i]; + dispatch->stack_trace.entries = dispatch->entries; + dispatch->stack_trace.max_entries = MAX_ENTRIES; } } - fdata->mode = type; + fdata->mode = mode; return fdata; error_alloc: @@ -245,7 +279,8 @@ void lttng_callstack_destroy(struct lttng_ctx_field *field) } static -int __lttng_add_callstack_generic(struct lttng_ctx **ctx, int mode) +int __lttng_add_callstack_generic(struct lttng_ctx **ctx, + enum lttng_cs_ctx_modes mode) { const char *ctx_name = cs_types[mode].name; struct lttng_ctx_field *field; @@ -262,7 +297,7 @@ int __lttng_add_callstack_generic(struct lttng_ctx **ctx, int mode) ret = -EEXIST; goto error_find; } - fdata = field_data_create(MAX_ENTRIES, mode); + fdata = field_data_create(mode); if (!fdata) { ret = -ENOMEM; goto error_create; @@ -319,14 +354,12 @@ int lttng_add_callstack_to_ctx(struct lttng_ctx **ctx, int type) switch (type) { case LTTNG_KERNEL_CONTEXT_CALLSTACK_KERNEL: return __lttng_add_callstack_generic(ctx, CALLSTACK_KERNEL); +#ifdef CONFIG_X86 case LTTNG_KERNEL_CONTEXT_CALLSTACK_USER: return __lttng_add_callstack_generic(ctx, CALLSTACK_USER); +#endif default: return -EINVAL; } } EXPORT_SYMBOL_GPL(lttng_add_callstack_to_ctx); - -MODULE_LICENSE("GPL and additional rights"); -MODULE_AUTHOR("Francis Giraldeau"); -MODULE_DESCRIPTION("Linux Trace Toolkit Callstack Support");