a1ab12856f
A statically linked executable can have a .plt due to IFUNCs, in which
case .symtab is used not .dynsym. Check the section header link to see
if that is the case, and then use symtab instead.
Example:
Before:
$ cat tstifunc.c
#include <stdio.h>
void thing1(void)
{
printf("thing1\n");
}
void thing2(void)
{
printf("thing2\n");
}
typedef void (*thing_fn_t)(void);
thing_fn_t thing_ifunc(void)
{
int x;
if (x & 1)
return thing2;
return thing1;
}
void thing(void) __attribute__ ((ifunc ("thing_ifunc")));
int main()
{
thing();
return 0;
}
$ gcc --version
gcc (Ubuntu 11.3.0-1ubuntu1~22.04) 11.3.0
Copyright (C) 2021 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ gcc -static -Wall -Wextra -Wno-uninitialized -o tstifuncstatic tstifunc.c
$ readelf -SW tstifuncstatic | grep 'Name\|plt\|dyn'
[Nr] Name Type Address Off Size ES Flg Lk Inf Al
[ 4] .rela.plt RELA 00000000004002e8 0002e8 000258 18 AI 29 20 8
[ 6] .plt PROGBITS 0000000000401020 001020 000190 00 AX 0 0 16
[20] .got.plt PROGBITS 00000000004c5000 0c4000 0000e0 08 WA 0 0 8
$ perf record -e intel_pt//u --filter 'filter main @ ./tstifuncstatic' ./tstifuncstatic
thing1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.008 MB perf.data ]
$ perf script --itrace=be --ns -F+flags,-event,+addr,-period,-comm,-tid,-cpu,-dso
15786.690189535: tr strt 0 [unknown] => 4017cd main+0x0
15786.690189535: tr end call 4017d5 main+0x8 => 401170 [unknown]
15786.690197660: tr strt 0 [unknown] => 4017da main+0xd
15786.690197660: tr end return 4017e0 main+0x13 => 401c1a __libc_start_call_main+0x6a
After:
$ perf script --itrace=be --ns -F+flags,-event,+addr,-period,-comm,-tid,-cpu,-dso
15786.690189535: tr strt 0 [unknown] => 4017cd main+0x0
15786.690189535: tr end call 4017d5 main+0x8 => 401170 thing_ifunc@plt+0x0
15786.690197660: tr strt 0 [unknown] => 4017da main+0xd
15786.690197660: tr end return 4017e0 main+0x13 => 401c1a __libc_start_call_main+0x6a
Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20230131131625.6964-8-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.