Re: Accessing program counter registers from within C or Aseembler.

[Pawel Sikora]

On Thu, 18 Nov 2004, Jan Engelhardt wrote:

> > > Does anybody know how to access the address of the
> > > current executing instruction in C while the program
> > > is executing?
> >
> > In other words, are you trying to answer "Where in memory am *I*?"
> > or "Where in memory is <that very recent code I want to look at>?"
> >
> > (Hint - for the former, you can probably get very good approximations
> > by just looking at the entry point address for the function:
> >
> > 	(void *) where = &__FUNCTION__;
>
> Well, that's only the function in which you are (i.e. it's an approximation to
> EIP)

Is this good enough ?

(gdb) disassemble __next_eip
0x08048380 <__next_eip+0>:      mov    (%esp),%eax
0x08048383 <__next_eip+3>:      ret

(gdb) disassemble test1
0x08048390 <test1+0>:   call   0x8048380 <__next_eip>
0x08048395 <test1+5>:   mov    %eax,0x80495ec
0x0804839a <test1+10>:  ret

(gdb) c
Continuing.
eip = 0x8048395

*** src ***

void* eip;
register unsigned* __esp asm("esp");
void* __attribute__((noinline)) __next_eip() { return (void *)(*__esp); }
void test1() { eip = __next_eip(); }
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