1f35cd6538
Improve thread_stack__no_call_return() to better handle 'returns' that
do not match the stack i.e. 'no call'. See code comments for details.
The example below shows how retpolines are affected:
Example:
$ cat simple-retpoline.c
__attribute__((noinline)) int bar(void)
{
return -1;
}
int foo(void)
{
return bar() + 1;
}
__attribute__((indirect_branch("thunk"))) int main()
{
int (*volatile fn)(void) = foo;
fn();
return fn();
}
$ gcc -ggdb3 -Wall -Wextra -O2 -o simple-retpoline simple-retpoline.c
$ objdump -d simple-retpoline
<SNIP>
0000000000001040 <main>:
1040: 48 83 ec 18 sub $0x18,%rsp
1044: 48 8d 05 25 01 00 00 lea 0x125(%rip),%rax # 1170 <foo>
104b: 48 89 44 24 08 mov %rax,0x8(%rsp)
1050: 48 8b 44 24 08 mov 0x8(%rsp),%rax
1055: e8 1f 01 00 00 callq 1179 <__x86_indirect_thunk_rax>
105a: 48 8b 44 24 08 mov 0x8(%rsp),%rax
105f: 48 83 c4 18 add $0x18,%rsp
1063: e9 11 01 00 00 jmpq 1179 <__x86_indirect_thunk_rax>
<SNIP>
0000000000001160 <bar>:
1160: b8 ff ff ff ff mov $0xffffffff,%eax
1165: c3 retq
<SNIP>
0000000000001170 <foo>:
1170: e8 eb ff ff ff callq 1160 <bar>
1175: 83 c0 01 add $0x1,%eax
1178: c3 retq
0000000000001179 <__x86_indirect_thunk_rax>:
1179: e8 07 00 00 00 callq 1185 <__x86_indirect_thunk_rax+0xc>
117e: f3 90 pause
1180: 0f ae e8 lfence
1183: eb f9 jmp 117e <__x86_indirect_thunk_rax+0x5>
1185: 48 89 04 24 mov %rax,(%rsp)
1189: c3 retq
<SNIP>
$ perf record -o simple-retpoline.perf.data -e intel_pt/cyc/u ./simple-retpoline
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0,017 MB simple-retpoline.perf.data ]
$ perf script -i simple-retpoline.perf.data --itrace=be -s ~/libexec/perf-core/scripts/python/export-to-sqlite.py simple-retpoline.db branches calls
2019-01-08 14:03:37.851655 Creating database...
2019-01-08 14:03:37.863256 Writing records...
2019-01-08 14:03:38.069750 Adding indexes
2019-01-08 14:03:38.078799 Done
$ ~/libexec/perf-core/scripts/python/exported-sql-viewer.py simple-retpoline.db
Before:
main
-> __x86_indirect_thunk_rax
-> __x86_indirect_thunk_rax
-> __x86_indirect_thunk_rax
-> bar
After:
main
-> __x86_indirect_thunk_rax
-> __x86_indirect_thunk_rax
-> foo
-> bar
Committer testing:
Chose "Reports", Then "Context-Sensitive Call Graph" and then go on
expanding:
Before:
simple-retpolin
PID:PID
_start
_start
__libc_start_main
main
__x86_indirect_thunk_rax
__x86_indirect_thunk_rax
bar
After:
Remove the "simple.retpoline.db" file, run again the 'perf script' line
to regenerate the .db file and run the exported-sql-viewer.py again to
get the same all the way to 'main', then, from there, including 'main':
main
__x86_indirect_thunk_rax
__x86_indirect_thunk_rax
foo
bar
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/20190109091835.5570-6-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.