Messages in this thread | | | Subject | Re: [PATCH][v3] uprobes/x86: emulate push insns for uprobe on x86 | From | Yonghong Song <> | Date | Tue, 14 Nov 2017 14:43:32 -0800 |
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On 11/14/17 8:03 AM, Oleg Nesterov wrote: > On 11/14, Oleg Nesterov wrote: >> >>> +#ifdef CONFIG_X86_64 >>> + if (test_thread_flag(TIF_ADDR32)) >>> + return -ENOSYS; >>> +#endif >> >> No, this doesn't look right, see my previous email. You should do this >> check in the "if (insn->length == 2)" branch below, "push bp" should be >> emulated correctly. >> >> And test_thread_flag(TIF_ADDR32) is not right too. The caller is not >> necessarily the probed task. See is_64bit_mm(mm) in arch_uprobe_analyze_insn(). >> >> And again... please check if uprobe_init_insn() fails or not in this case >> (32bit task does, say, "push r8"). If it fails, your V2 should be fine. >> >> >> To remind, uprobes && 32-bit is broken, let me quote my another email: >> >> The 3rd bug means that you simply can't uprobe a 32bit task on a 64bit >> system, the in_compat_syscall() logic in get_unmapped_area() looks very >> wrong although I need to re-check. > > Yes, > >> I didn't have time for this problem so far. But emulation should work, so >> you can hopefully test your patch. > > Ah, no, sizeof_long() is broken by the same reason, so you can't test it...
Right. I hacked the emulate_push_stack (original name: push_ret_address) with sizeof_long = 4, and 32bit binary uprobe works fine on x86_64 platform then... But that will involve a bigger change to propogate the is_64bit_mm() along the call graph.
> > OK, I'll try to do something tomorrow, then we will see what can we do > with your patch...
Thanks for reviewing! I will wait for your further comments/direction before next step.
> > But it would be nice if you can check what uprobe_init_insn() does in this > case, see above.
As mentioned in my previous email, for 32bit application, compiler won't generate "push %r8" as "%r8" is only available on x86_64 platform. For 32bit app, I see "push %bp" etc which does not have rex_prefix. They cannot be emulated right now due to emulate_push_stack needs change.
> > Oleg. >
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