Can I give objdump an address and have it disassemble the containing function?

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I'm finding it really annoying to have to disassemble large swathes of library code just to get enough context to see what is causing a crash. Is there any way that I can just hand objdump an address, and have it find the boundaries of the containing function for me?

EDIT: Better yet, can I have it disassemble an entire stack trace for me?

objdump disassembly c debugging
3 Answers

GDB disassemble

gdb -batch -ex "file $EXECUTABLE" -ex "disassemble/rs $ADDRESS"

For example:

a.c

#include <assert.h>

int myfunc(int i) {
    i = i + 2;
    i = i * 2;
    return i;
}

int main(void) {
    assert(myfunc(1) == 6);
    assert(myfunc(2) == 8);
    return 0;
}

Compile and disassemble myfunc to find an address:

gcc -std=c99 -O0 -g a.c
gdb -batch -ex 'file a.out' -ex "disassemble/rs myfunc"

Output:

Dump of assembler code for function myfunc:
a.c:
3   int myfunc(int i) {
   0x000000000000064a <+0>: 55  push   %rbp
   0x000000000000064b <+1>: 48 89 e5    mov    %rsp,%rbp
   0x000000000000064e <+4>: 89 7d fc    mov    %edi,-0x4(%rbp)

4       i = i + 2;
   0x0000000000000651 <+7>: 83 45 fc 02 addl   $0x2,-0x4(%rbp)

5       i = i * 2;
   0x0000000000000655 <+11>:    d1 65 fc    shll   -0x4(%rbp)

6       return i;
   0x0000000000000658 <+14>:    8b 45 fc    mov    -0x4(%rbp),%eax

7   }
   0x000000000000065b <+17>:    5d  pop    %rbp
   0x000000000000065c <+18>:    c3  retq   
End of assembler dump.

OK, so 0x0000000000000655 is in myfunc, let's confirm it works:

gdb -batch -ex 'file a.out' -ex 'disassemble/rs 0x0000000000000655'

Output: same as previous disassembly.

See also: How to disassemble one single function using objdump?

Tested on Ubuntu 18.04, GDB 8.1.

user_8952450
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