+++ /dev/null
-/*
- * lttng-context-callstack.c
- *
- * LTTng callstack event context.
- *
- * Copyright (C) 2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- * Copyright (C) 2014 Francis Giraldeau <francis.giraldeau@gmail.com>
- *
- * 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 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.
- *
- * The symbol name resolution is left to the trace reader.
- */
-
-#include <linux/module.h>
-#include <linux/slab.h>
-#include <linux/sched.h>
-#include <linux/utsname.h>
-#include <linux/stacktrace.h>
-#include <linux/spinlock.h>
-#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 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;
-}
-
-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->dispatch[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;
-
- /* 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--;
- }
- 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));
- }
-}
-
-static
-void field_data_free(struct field_data *fdata)
-{
- if (!fdata)
- return;
- free_percpu(fdata->cs_percpu);
- kfree(fdata);
-}
-
-static
-struct field_data __percpu *field_data_create(enum lttng_cs_ctx_modes mode)
-{
- int cpu, i;
- struct lttng_cs __percpu *cs_set;
- struct field_data *fdata;
-
- fdata = kzalloc(sizeof(*fdata), 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) {
- 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;
- }
- }
- fdata->mode = mode;
- 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,
- enum lttng_cs_ctx_modes 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(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");
projects / lttng-modules.git / blobdiff