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SubjectRe: [PATCH][v2] uprobes/x86: emulate push insns for uprobe on x86
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?

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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