Nie mam pod ręką ~ = RHEL5, więc pokazane dane wyjściowe pochodzą z Fedory 20, chociaż proces powinien być w większości taki sam ( nazwa funkcji uległa zmianie ).
Musisz zainstalować odpowiedni kernel-debug-debuginfopakiet dla swojego jądra (przy założeniu dystrybucji RHEL lub pochodnej). Ten pakiet zawiera vmlinuxobraz (nieskompresowana, nie pozbawiona wersji wersja jądra):
# rpm -ql kernel-debug-debuginfo | grep vmlinux
/usr/lib/debug/lib/modules/3.14.7-200.fc20.x86_64+debug/vmlinux
tego obrazu można użyć bezpośrednio z gdb
# gdb /usr/lib/debug/lib/modules/3.14.7-200.fc20.x86_64+debug/vmlinux
GNU gdb (GDB) Fedora 7.7.1-13.fc20
Copyright (C) 2014 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
...
Reading symbols from /usr/lib/debug/lib/modules/3.14.7-200.fc20.x86_64+debug/vmlinux...done.
(gdb) disassemble link_path_walk
Dump of assembler code for function link_path_walk:
0xffffffff81243d50 <+0>: callq 0xffffffff817ea840 <__fentry__>
0xffffffff81243d55 <+5>: push %rbp
0xffffffff81243d56 <+6>: mov %rsp,%rbp
0xffffffff81243d59 <+9>: push %r15
0xffffffff81243d5b <+11>: mov %rsi,%r15
0xffffffff81243d5e <+14>: push %r14
0xffffffff81243d60 <+16>: push %r13
0xffffffff81243d62 <+18>: push %r12
0xffffffff81243d64 <+20>: push %rbx
0xffffffff81243d65 <+21>: mov %rdi,%rbx
0xffffffff81243d68 <+24>: sub $0x78,%rsp
0xffffffff81243d6c <+28>: mov %gs:0x28,%rax
0xffffffff81243d75 <+37>: mov %rax,0x70(%rsp)
0xffffffff81243d7a <+42>: xor %eax,%eax
0xffffffff81243d7c <+44>: movzbl (%rdi),%eax
0xffffffff81243d7f <+47>: cmp $0x2f,%al
....
Możesz również użyć objdump(1)na vmlinuxobrazie:
# objdump -rDlS /usr/lib/debug/lib/modules/3.14.7-200.fc20.x86_64+debug/vmlinux > vmlinux.out
Flagi to:
-D
--disassemble-all
Like -d, but disassemble the contents of all sections, not just those expected to contain instructions.
-r
--reloc
Print the relocation entries of the file. If used with -d or -D, the relocations are printed interspersed with the
disassembly.
-S
--source
Display source code intermixed with disassembly, if possible. Implies -d.
-l
--line-numbers
Label the display (using debugging information) with the filename and source line numbers corresponding to the object
code or relocs shown. Only useful with -d, -D, or -r.
Możesz tam wyszukać funkcję:
ffffffff81243d50 <link_path_walk>:
link_path_walk():
/usr/src/debug/kernel-3.14.fc20/linux-3.14.7-200.fc20.x86_64/fs/namei.c:1729
*
* Returns 0 and nd will have valid dentry and mnt on success.
* Returns error and drops reference to input namei data on failure.
*/
static int link_path_walk(const char *name, struct nameidata *nd)
{
ffffffff81243d50: e8 eb 6a 5a 00 callq ffffffff817ea840 <__entry_text_start>
ffffffff81243d55: 55 push %rbp
ffffffff81243d56: 48 89 e5 mov %rsp,%rbp
ffffffff81243d59: 41 57 push %r15
ffffffff81243d5b: 49 89 f7 mov %rsi,%r15
ffffffff81243d5e: 41 56 push %r14
ffffffff81243d60: 41 55 push %r13
ffffffff81243d62: 41 54 push %r12
ffffffff81243d64: 53 push %rbx
ffffffff81243d65: 48 89 fb mov %rdi,%rbx
ffffffff81243d68: 48 83 ec 78 sub $0x78,%rsp
ffffffff81243d6c: 65 48 8b 04 25 28 00 mov %gs:0x28,%rax
ffffffff81243d73: 00 00
ffffffff81243d75: 48 89 44 24 70 mov %rax,0x70(%rsp)
ffffffff81243d7a: 31 c0 xor %eax,%eax
/usr/src/debug/kernel-3.14.fc20/linux-3.14.7-200.fc20.x86_64/fs/namei.c:1733
struct path next;
int err;
while (*name=='/')
ffffffff81243d7c: 0f b6 07 movzbl (%rdi),%eax
ffffffff81243d7f: 3c 2f cmp $0x2f,%al
ffffffff81243d81: 75 10 jne ffffffff81243d93 <link_path_walk+0x43>
ffffffff81243d83: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1)
/usr/src/debug/kernel-3.14.fc20/linux-3.14.7-200.fc20.x86_64/fs/namei.c:1734
name++;
ffffffff81243d88: 48 83 c3 01 add $0x1,%rbx
/usr/src/debug/kernel-3.14.fc20/linux-3.14.7-200.fc20.x86_64/fs/namei.c:1733
static int link_path_walk(const char *name, struct nameidata *nd)
{
struct path next;
int err;
while (*name=='/')
....
i dopasuj przesunięcie do rzeczywistej linii kodu.