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f08046cb30
The compiler might optimize a call/ret combination by making it a jmp.
However the thread-stack does not presently cater for that, so that such
control flow is not visible in the call graph. Make it visible by
recording on the stack a branch to the start of a different symbol.
Note, that means when a ret pops the stack, all jmps must be popped off
first.
Example:
$ cat jmp-to-fn.c
__attribute__((noinline)) int bar(void)
{
return -1;
}
__attribute__((noinline)) int foo(void)
{
return bar() + 1;
}
int main()
{
return foo();
}
$ gcc -ggdb3 -Wall -Wextra -O2 -o jmp-to-fn jmp-to-fn.c
$ objdump -d jmp-to-fn
<SNIP>
0000000000001040 <main>:
1040: 31 c0 xor %eax,%eax
1042: e9 09 01 00 00 jmpq 1150 <foo>
<SNIP>
0000000000001140 <bar>:
1140: b8 ff ff ff ff mov $0xffffffff,%eax
1145: c3 retq
<SNIP>
0000000000001150 <foo>:
1150: 31 c0 xor %eax,%eax
1152: e8 e9 ff ff ff callq 1140 <bar>
1157: 83 c0 01 add $0x1,%eax
115a: c3 retq
<SNIP>
$ perf record -o jmp-to-fn.perf.data -e intel_pt/cyc/u ./jmp-to-fn
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0,017 MB jmp-to-fn.perf.data ]
$ perf script -i jmp-to-fn.perf.data --itrace=be -s ~/libexec/perf-core/scripts/python/export-to-sqlite.py jmp-to-fn.db branches calls
2019-01-08 13:24:58.783069 Creating database...
2019-01-08 13:24:58.794650 Writing records...
2019-01-08 13:24:59.008050 Adding indexes
2019-01-08 13:24:59.015802 Done
$ ~/libexec/perf-core/scripts/python/exported-sql-viewer.py jmp-to-fn.db
Before:
main
-> bar
After:
main
-> foo
-> bar
Committer testing:
Install the python2-pyside package, then select these menu options
on the GUI:
"Reports"
"Context sensitive callgraphs"
Then go on expanding the symbols, to get, full picture when doing this
on a fedora:29 with gcc version 8.2.1 20181215 (Red Hat 8.2.1-6) (GCC):
jmp-to-fn
PID:TID
_start (ld-2.28.so)
__libc_start_main
main
foo
bar
To verify that indeed, this fixes the problem.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: http://lkml.kernel.org/r/20190109091835.5570-5-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
105 lines
3.2 KiB
C
105 lines
3.2 KiB
C
/*
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* thread-stack.h: Synthesize a thread's stack using call / return events
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* Copyright (c) 2014, Intel Corporation.
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms and conditions of the GNU General Public License,
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* version 2, as published by the Free Software Foundation.
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*
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* This program is distributed in the hope it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*
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*/
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#ifndef __PERF_THREAD_STACK_H
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#define __PERF_THREAD_STACK_H
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#include <sys/types.h>
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#include <linux/types.h>
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struct thread;
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struct comm;
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struct ip_callchain;
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struct symbol;
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struct dso;
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struct comm;
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struct perf_sample;
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struct addr_location;
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struct call_path;
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/*
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* Call/Return flags.
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*
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* CALL_RETURN_NO_CALL: 'return' but no matching 'call'
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* CALL_RETURN_NO_RETURN: 'call' but no matching 'return'
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* CALL_RETURN_NON_CALL: a branch but not a 'call' to the start of a different
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* symbol
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*/
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enum {
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CALL_RETURN_NO_CALL = 1 << 0,
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CALL_RETURN_NO_RETURN = 1 << 1,
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CALL_RETURN_NON_CALL = 1 << 2,
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};
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/**
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* struct call_return - paired call/return information.
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* @thread: thread in which call/return occurred
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* @comm: comm in which call/return occurred
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* @cp: call path
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* @call_time: timestamp of call (if known)
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* @return_time: timestamp of return (if known)
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* @branch_count: number of branches seen between call and return
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* @call_ref: external reference to 'call' sample (e.g. db_id)
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* @return_ref: external reference to 'return' sample (e.g. db_id)
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* @db_id: id used for db-export
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* @flags: Call/Return flags
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*/
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struct call_return {
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struct thread *thread;
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struct comm *comm;
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struct call_path *cp;
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u64 call_time;
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u64 return_time;
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u64 branch_count;
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u64 call_ref;
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u64 return_ref;
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u64 db_id;
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u32 flags;
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};
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/**
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* struct call_return_processor - provides a call-back to consume call-return
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* information.
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* @cpr: call path root
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* @process: call-back that accepts call/return information
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* @data: anonymous data for call-back
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*/
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struct call_return_processor {
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struct call_path_root *cpr;
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int (*process)(struct call_return *cr, void *data);
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void *data;
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};
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int thread_stack__event(struct thread *thread, int cpu, u32 flags, u64 from_ip,
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u64 to_ip, u16 insn_len, u64 trace_nr);
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void thread_stack__set_trace_nr(struct thread *thread, int cpu, u64 trace_nr);
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void thread_stack__sample(struct thread *thread, int cpu, struct ip_callchain *chain,
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size_t sz, u64 ip, u64 kernel_start);
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int thread_stack__flush(struct thread *thread);
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void thread_stack__free(struct thread *thread);
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size_t thread_stack__depth(struct thread *thread, int cpu);
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struct call_return_processor *
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call_return_processor__new(int (*process)(struct call_return *cr, void *data),
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void *data);
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void call_return_processor__free(struct call_return_processor *crp);
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int thread_stack__process(struct thread *thread, struct comm *comm,
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struct perf_sample *sample,
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struct addr_location *from_al,
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struct addr_location *to_al, u64 ref,
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struct call_return_processor *crp);
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#endif
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