Re: [x86.git#mm] stack protector fixes, vmsplice exploit

From: pageexec
Date: Thu Feb 14 2008 - 17:45:03 EST


On 14 Feb 2008 at 17:35, Jakub Jelinek wrote:

> Where do you see a mispredicted branch?

try it with -Os (gentoo gcc 4.2.2):

0000000000000000 <foo>:
0: 48 83 ec 58 sub $0x58,%rsp
4: 65 48 8b 04 25 28 00 00 00 mov %gs:0x28,%rax
d: 48 89 44 24 48 mov %rax,0x48(%rsp)
12: 31 c0 xor %eax,%eax
14: 48 89 e7 mov %rsp,%rdi
17: e8 00 00 00 00 callq 1c <foo+0x1c> 18: R_X86_64_PC32
bar+0xfffffffffffffffc
1c: 48 8b 54 24 48 mov 0x48(%rsp),%rdx
21: 65 48 33 14 25 28 00 00 00 xor %gs:0x28,%rdx
2a: b8 06 00 00 00 mov $0x6,%eax
2f: 74 05 je 36 <foo+0x36>
31: e8 00 00 00 00 callq 36 <foo+0x36> 32: R_X86_64_PC32
__stack_chk_fail+0xfffffffffffffffc
36: 48 83 c4 58 add $0x58,%rsp
3a: c3 retq

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