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/*
* thread-stack.c: Synthesize a thread's stack using call / return events
* Copyright (c) 2014, Intel Corporation.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms and conditions of the GNU General Public License,
* version 2, as published by the Free Software Foundation.
*
* This program is distributed in the hope it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*
*/
#include "thread.h"
#include "event.h"
#include "util.h"
#include "debug.h"
#include "thread-stack.h"
#define STACK_GROWTH 4096
struct thread_stack_entry {
u64 ret_addr;
};
struct thread_stack {
struct thread_stack_entry *stack;
size_t cnt;
size_t sz;
u64 trace_nr;
};
static int thread_stack__grow(struct thread_stack *ts)
{
struct thread_stack_entry *new_stack;
size_t sz, new_sz;
new_sz = ts->sz + STACK_GROWTH;
sz = new_sz * sizeof(struct thread_stack_entry);
new_stack = realloc(ts->stack, sz);
if (!new_stack)
return -ENOMEM;
ts->stack = new_stack;
ts->sz = new_sz;
return 0;
}
static struct thread_stack *thread_stack__new(void)
{
struct thread_stack *ts;
ts = zalloc(sizeof(struct thread_stack));
if (!ts)
return NULL;
if (thread_stack__grow(ts)) {
free(ts);
return NULL;
}
return ts;
}
static int thread_stack__push(struct thread_stack *ts, u64 ret_addr)
{
int err = 0;
if (ts->cnt == ts->sz) {
err = thread_stack__grow(ts);
if (err) {
pr_warning("Out of memory: discarding thread stack\n");
ts->cnt = 0;
}
}
ts->stack[ts->cnt++].ret_addr = ret_addr;
return err;
}
static void thread_stack__pop(struct thread_stack *ts, u64 ret_addr)
{
size_t i;
/*
* In some cases there may be functions which are not seen to return.
* For example when setjmp / longjmp has been used. Or the perf context
* switch in the kernel which doesn't stop and start tracing in exactly
* the same code path. When that happens the return address will be
* further down the stack. If the return address is not found at all,
* we assume the opposite (i.e. this is a return for a call that wasn't
* seen for some reason) and leave the stack alone.
*/
for (i = ts->cnt; i; ) {
if (ts->stack[--i].ret_addr == ret_addr) {
ts->cnt = i;
return;
}
}
}
int thread_stack__event(struct thread *thread, u32 flags, u64 from_ip,
u64 to_ip, u16 insn_len, u64 trace_nr)
{
if (!thread)
return -EINVAL;
if (!thread->ts) {
thread->ts = thread_stack__new();
if (!thread->ts) {
pr_warning("Out of memory: no thread stack\n");
return -ENOMEM;
}
thread->ts->trace_nr = trace_nr;
}
/*
* When the trace is discontinuous, the trace_nr changes. In that case
* the stack might be completely invalid. Better to report nothing than
* to report something misleading, so reset the stack count to zero.
*/
if (trace_nr != thread->ts->trace_nr) {
thread->ts->trace_nr = trace_nr;
thread->ts->cnt = 0;
}
if (flags & PERF_IP_FLAG_CALL) {
u64 ret_addr;
if (!to_ip)
return 0;
ret_addr = from_ip + insn_len;
if (ret_addr == to_ip)
return 0; /* Zero-length calls are excluded */
return thread_stack__push(thread->ts, ret_addr);
} else if (flags & PERF_IP_FLAG_RETURN) {
if (!from_ip)
return 0;
thread_stack__pop(thread->ts, to_ip);
}
return 0;
}
void thread_stack__free(struct thread *thread)
{
if (thread->ts) {
zfree(&thread->ts->stack);
zfree(&thread->ts);
}
}
void thread_stack__sample(struct thread *thread, struct ip_callchain *chain,
size_t sz, u64 ip)
{
size_t i;
if (!thread || !thread->ts)
chain->nr = 1;
else
chain->nr = min(sz, thread->ts->cnt + 1);
chain->ips[0] = ip;
for (i = 1; i < chain->nr; i++)
chain->ips[i] = thread->ts->stack[thread->ts->cnt - i].ret_addr;
}
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