X-Git-Url: http://git.liburcu.org/?p=lttng-modules.git;a=blobdiff_plain;f=lttng-context-callstack.c;h=195990a6e3e1292bebce8277a7b3bdefbd0d5acb;hp=d95cbc2eef3f7117f0fcb38508ff173106f9fadf;hb=HEAD;hpb=3c1a57e8ce82366ce96774e4ac1d7481c561cc4c diff --git a/lttng-context-callstack.c b/lttng-context-callstack.c deleted file mode 100644 index d95cbc2e..00000000 --- a/lttng-context-callstack.c +++ /dev/null @@ -1,332 +0,0 @@ -/* - * lttng-context-callstack.c - * - * LTTng callstack event context. - * - * 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. - * - * 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. - * - * 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. - * - * The symbol name resolution is left to the trace reader. - */ - -#include -#include -#include -#include -#include -#include -#include "lttng-events.h" -#include "wrapper/ringbuffer/backend.h" -#include "wrapper/ringbuffer/frontend.h" -#include "wrapper/vmalloc.h" -#include "lttng-tracer.h" - -#define MAX_ENTRIES 25 /* BUG: saving more than 30 entries causes trace corruption */ - -struct lttng_cs { - struct stack_trace items[RING_BUFFER_MAX_NESTING]; -}; - -struct field_data { - int mode; - struct lttng_cs __percpu *cs_percpu; -}; - -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->items[nesting]; -} - -/* - * 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 (!trace) - return 0; - - /* 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); - 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; -} - -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); - - if (!trace) - return; - lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned int)); - chan->ops->event_write(ctx, &trace->nr_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); -} - -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) -{ - int cpu, i; - struct stack_trace *item; - struct lttng_cs *cs; - struct lttng_cs __percpu *cs_set; - struct field_data* fdata; - - fdata = kzalloc(sizeof(unsigned long) * entries, GFP_KERNEL); - if (!fdata) - return NULL; - cs_set = alloc_percpu(struct lttng_cs); - if (!cs_set) - goto error_alloc; - - fdata->cs_percpu = cs_set; - for_each_possible_cpu(cpu) { - 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; - } - } - fdata->mode = type; - return fdata; - -error_alloc: - field_data_free(fdata); - return NULL; -} - -static -void lttng_callstack_destroy(struct lttng_ctx_field *field) -{ - struct field_data *fdata = field->priv; - - field_data_free(fdata); -} - -static -int __lttng_add_callstack_generic(struct lttng_ctx **ctx, int mode) -{ - const char *ctx_name = cs_types[mode].name; - struct lttng_ctx_field *field; - struct field_data *fdata; - int ret; - - ret = init_type(mode); - if (ret) - return ret; - field = lttng_append_context(ctx); - if (!field) - return -ENOMEM; - if (lttng_find_context(*ctx, ctx_name)) { - ret = -EEXIST; - goto error_find; - } - fdata = field_data_create(MAX_ENTRIES, mode); - if (!fdata) { - ret = -ENOMEM; - goto error_create; - } - - field->event_field.name = ctx_name; - field->event_field.type.atype = atype_sequence; - field->event_field.type.u.sequence.elem_type.atype = atype_integer; - field->event_field.type.u.sequence.elem_type.u.basic.integer.size = sizeof(unsigned long) * CHAR_BIT; - field->event_field.type.u.sequence.elem_type.u.basic.integer.alignment = lttng_alignof(long) * CHAR_BIT; - field->event_field.type.u.sequence.elem_type.u.basic.integer.signedness = lttng_is_signed_type(unsigned long); - field->event_field.type.u.sequence.elem_type.u.basic.integer.reverse_byte_order = 0; - field->event_field.type.u.sequence.elem_type.u.basic.integer.base = 16; - field->event_field.type.u.sequence.elem_type.u.basic.integer.encoding = lttng_encode_none; - - field->event_field.type.u.sequence.length_type.atype = atype_integer; - field->event_field.type.u.sequence.length_type.u.basic.integer.size = sizeof(unsigned int) * CHAR_BIT; - field->event_field.type.u.sequence.length_type.u.basic.integer.alignment = lttng_alignof(unsigned int) * CHAR_BIT; - field->event_field.type.u.sequence.length_type.u.basic.integer.signedness = lttng_is_signed_type(unsigned int); - field->event_field.type.u.sequence.length_type.u.basic.integer.reverse_byte_order = 0; - field->event_field.type.u.sequence.length_type.u.basic.integer.base = 10; - field->event_field.type.u.sequence.length_type.u.basic.integer.encoding = lttng_encode_none; - - field->get_size_arg = lttng_callstack_get_size; - field->record = lttng_callstack_record; - field->priv = fdata; - field->destroy = lttng_callstack_destroy; - wrapper_vmalloc_sync_all(); - return 0; - -error_create: - field_data_free(fdata); -error_find: - lttng_remove_context_field(ctx, field); - return ret; -} - -/** - * lttng_add_callstack_to_ctx - add callstack event context - * - * @ctx: the lttng_ctx pointer to initialize - * @type: the context type - * - * Supported callstack type supported: - * LTTNG_KERNEL_CONTEXT_CALLSTACK_KERNEL - * Records the callstack of the kernel - * LTTNG_KERNEL_CONTEXT_CALLSTACK_USER - * Records the callstack of the userspace program (from the kernel) - * - * Return 0 for success, or error code. - */ -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); - case LTTNG_KERNEL_CONTEXT_CALLSTACK_USER: - return __lttng_add_callstack_generic(ctx, CALLSTACK_USER); - 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");