__cyg_profile_func_enter is not called with correct address ?

[robert song <robertsong dot linux at gmail dot com>]

Hello, everyone. I used -finstrument-functions option to trace some
program, and I found that address past to __cyg_profile_func_{enter,
exit} is not so precise.

The example is as below.

foo.c :
  int foo()
  {
    return 1;
  }
  int bar()
  {
    return 2;
  }

main.c :
  #include <stdio.h>
  extern int foo(), bar();
  void *ptr = foo;

  int main(int argc, char *argv[])
  {
    foo();
    bar();
    return 0 ;
  }

tracer.c :
  #define _GNU_SOURCE
  #include <stdio.h>

  void __cyg_profile_func_enter(void *this_fn, void *call_site)
  __attribute__((no_instrument_function));
  void __cyg_profile_func_exit(void *this_fn, void *call_site)
  __attribute__((no_instrument_function));

  void __cyg_profile_func_enter(void *this_fn, void *call_site)
  {
    printf("addr:%lx\n", this_fn);
  }

  void __cyg_profile_func_exit(void *this_fn, void *call_site)
  {
    printf("addr:%lx\n", this_fn);
  }

$ cc -fPIC -finstrument-functions -g -shared -o foo.so foo.c
$ cc -finstrument-functions -g -o main main.c tracer.c foo.so -Wl,-rpath `pwd`

The addresses past to __cyg_profile_func_{enter,exit} are as below:
addr:8048514 <- main
addr:8048418 <- foo
addr:8048418 <- foo
addr:37b4b7  <- bar
addr:37b4b7  <- bar
addr:8048514 <- main

$ readelf -s main | grep foo
     7: 08048418    75 FUNC    GLOBAL DEFAULT  UND foo
    69: 08048418    75 FUNC    GLOBAL DEFAULT  UND foo

As you can see, foo is undefined symbol but has the value of
0x08048418, and I think the relocated address (0x37b46c) of foo
should be more reasonable, just like bar() function.

Now I don't have a good method to deal with the problem, Can anyone
give me some advise to do the trick in __cyg_profile_func_enter() to
get the correct address ?


Best wishes,
robert