Messages in this thread |  | | Date | Sat, 30 Apr 2022 13:44:00 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH] objtool: Fix STACK_FRAME_NON_STANDARD reloc type |
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On Fri, Apr 29, 2022 at 03:56:36PM -0700, Josh Poimboeuf wrote: > On Fri, Apr 29, 2022 at 02:00:44PM +0200, Peter Zijlstra wrote: > > On Fri, Apr 29, 2022 at 11:20:24AM +0200, Peter Zijlstra wrote: > > > > > > STACK_FRAME_NON_STANDARD results in inconsistent relocation types > > > depending on .c or .S usage: > > > > > > Relocation section '.rela.discard.func_stack_frame_non_standard' at offset 0x3c01090 contains 5 entries: > > > Offset Info Type Symbol's Value Symbol's Name + Addend > > > 0000000000000000 00020c2200000002 R_X86_64_PC32 0000000000047b40 do_suspend_lowlevel + 0 > > > 0000000000000008 0002461e00000001 R_X86_64_64 00000000000480a0 machine_real_restart + 0 > > > 0000000000000010 0000001400000001 R_X86_64_64 0000000000000000 .rodata + b3d4 > > > 0000000000000018 0002444600000002 R_X86_64_PC32 00000000000678a0 __efi64_thunk + 0 > > > 0000000000000020 0002659d00000001 R_X86_64_64 0000000000113160 __crash_kexec + 0 > > > > So that weird .rodata entry is optprobe_template_func. > > > > It being in .rodata also means it's not validated and there is no ORC > > data generated, is that all intentional? The changelog for: > > > > 877b145f0f47 ("x86/kprobes: Move trampoline code into RODATA") > > > > doesn't really say anything useful about any of that :/ > > > > I also don't see any kprobe/optprobe hooks in unwind.h, so what happens > > if we hit an optprobe? > > Same as for any other generated code, the unwinder will try to fall back > to frame pointers, and if that doesn't work, the unwind stops. > > That commit didn't change anything since it was already not being > directly executed anyway, but rather used to generate code on the fly. > > And before that commit it was being ignored by ORC anyway, thanks to > STACK_FRAME_NON_STANDARD. Which can now be removed since this code is > now data and objtool will no longer try to understand it.
Right; but I suppose I'm wondering if we should fix this. It seems a rather sub-optimal state of affairs.
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