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SubjectRe: [PATCH][v2] uprobes/x86: emulate push insns for uprobe on x86
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On 11/14/17 7:34 AM, Oleg Nesterov wrote:
> On 11/13, Yonghong Song wrote:
>>
>> On 11/13/17 4:59 AM, Oleg Nesterov wrote:
>>>> + switch (opc1) {
>>>> + case 0x50:
>>>> + reg_offset = offsetof(struct pt_regs, r8);
>>>> + break;
>>>> + case 0x51:
>>>> + reg_offset = offsetof(struct pt_regs, r9);
>>>> + break;
>>>> + case 0x52:
>>>> + reg_offset = offsetof(struct pt_regs, r10);
>>>> + break;
>>>> + case 0x53:
>>>> + reg_offset = offsetof(struct pt_regs, r11);
>>>> + break;
>>>> + case 0x54:
>>>> + reg_offset = offsetof(struct pt_regs, r12);
>>>> + break;
>>>> + case 0x55:
>>>> + reg_offset = offsetof(struct pt_regs, r13);
>>>> + break;
>>>> + case 0x56:
>>>> + reg_offset = offsetof(struct pt_regs, r14);
>>>> + break;
>>>> + case 0x57:
>>>> + reg_offset = offsetof(struct pt_regs, r15);
>>>> + break;
>>>> + }
>>>> +#else
>>>> + return -ENOSYS;
>>>> +#endif
>>>
>>> OK, but shouldn't we also return ENOSYS if CONFIG_X86_64=y but the probed task is 32bit?
>>
>> Just tested with a 32bit app on x86 box and segfaults.
>
> Hmm. How did you verify this?

On a x86_32 box, I compiled the test case with static libraries
(including static libc). And I then run this binary on x86_64 with
uprobe enabled. You will need to install glibc-static package to make it
work.

>
> Your v3 doesn't look right and it seems you misunderstood me...
>
>> Yes, we would need to
>> return ENOSYS if the app is 32bit on 64bit system.
>
> Only if insn->length == 2. "push bp" and other valid 32bit push'es should be
> emulated correctly or your patch is wrong. Confused... >
>>> Or in this case uprobe_init_insn(x86_64 => false) should fail and push_setup_xol_ops()
>>> won't be called?
>
> So it doesn't fail?
>
> Oleg.
>

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