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
