X-Git-Url: http://git.lttng.org/?a=blobdiff_plain;f=lttng-context-callstack.c;h=3fccfcf270bf34e48053a5ab30b761d1dc5bffd6;hb=b6ee48d2a69c34bf5dd44319cba19bedbbd35fca;hp=57738bed5275bd460f0e7be5bee61540ce1318e2;hpb=60d51de0fde1942b4143bcaf8592fea368952864;p=lttng-modules.git diff --git a/lttng-context-callstack.c b/lttng-context-callstack.c index 57738bed..3fccfcf2 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. - * - * 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. * - * 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. */ @@ -61,162 +49,7 @@ #include "wrapper/vmalloc.h" #include "lttng-tracer.h" -#define MAX_ENTRIES 25 - -struct lttng_cs_nesting { - struct stack_trace stack_trace; - unsigned long entries[MAX_ENTRIES]; -}; - -struct lttng_cs { - struct lttng_cs_nesting level[RING_BUFFER_MAX_NESTING]; -}; - -struct field_data { - struct lttng_cs __percpu *cs_percpu; - int mode; -}; - -struct lttng_cs_type { - const char *name; - const char *save_func_name; - 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_user", - .save_func_name = "save_stack_trace_user", - .save_func = NULL, - }, -}; - -static -int init_type(int 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 -struct stack_trace *stack_trace_context(struct lttng_ctx_field *field, - struct lib_ring_buffer_ctx *ctx) -{ - int nesting; - struct lttng_cs *cs; - struct field_data *fdata = field->priv; - - /* - * 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); - nesting = per_cpu(lib_ring_buffer_nesting, ctx->cpu) - 1; - if (nesting >= RING_BUFFER_MAX_NESTING) { - return NULL; - } - return &cs->level[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) -{ - size_t size = 0; - struct stack_trace *trace; - struct field_data *fdata = field->priv; - - /* do not write data if no space is available */ - trace = stack_trace_context(field, ctx); - if (unlikely(!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)); - return size; - } - - /* reset stack trace, no need to clear memory */ - trace->nr_entries = 0; - - /* do the real work and reserve space */ - cs_types[fdata->mode].save_func(trace); - /* - * 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--; - } - 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; - /* Add our own ULONG_MAX delimiter to show incomplete stack. */ - if (trace->nr_entries == trace->max_entries) - size += sizeof(unsigned long); - return size; -} - -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) @@ -228,7 +61,7 @@ void field_data_free(struct field_data *fdata) } static -struct field_data __percpu *field_data_create(int type) +struct field_data __percpu *field_data_create(enum lttng_cs_ctx_modes mode) { int cpu, i; struct lttng_cs __percpu *cs_set; @@ -247,14 +80,14 @@ struct field_data __percpu *field_data_create(int type) cs = per_cpu_ptr(cs_set, cpu); for (i = 0; i < RING_BUFFER_MAX_NESTING; i++) { - struct lttng_cs_nesting *level; + struct lttng_cs_dispatch *dispatch; - level = &cs->level[i]; - level->stack_trace.entries = level->entries; - level->stack_trace.max_entries = MAX_ENTRIES; + 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: @@ -271,7 +104,8 @@ 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; @@ -345,14 +179,12 @@ 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");