diff options
Diffstat (limited to 'tools/perf/util/thread-stack.c')
-rw-r--r-- | tools/perf/util/thread-stack.c | 172 |
1 files changed, 172 insertions, 0 deletions
diff --git a/tools/perf/util/thread-stack.c b/tools/perf/util/thread-stack.c new file mode 100644 index 0000000..85b60d2 --- /dev/null +++ b/tools/perf/util/thread-stack.c @@ -0,0 +1,172 @@ +/* + * 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; +} |