Messages in this thread | | | Date | Thu, 8 Feb 2018 21:31:46 +0100 | From | Borislav Petkov <> | Subject | Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f |
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On Thu, Feb 08, 2018 at 08:44:06PM +0100, Peter Zijlstra wrote: > /* > - * Since some emulators terminate on UD2, we cannot use it for WARN. > - * Since various instruction decoders disagree on the length of UD1, > - * we cannot use it either. So use UD0 for WARN. > + * Despite that some emulators terminate on UD2, we use it for WARN. > * > - * (binutils knows about "ud1" but {en,de}codes it as 2 bytes, whereas > - * our kernel decoder thinks it takes a ModRM byte, which seems consistent > - * with various things like the Intel SDM instruction encoding rules) > + * Since various instruction decoders/specs disagree on the encoding of > + * UD0/UD1, ^
Does that comma mean the sentence continues somewhere?
> */ > > -#define ASM_UD0 ".byte 0x0f, 0xff" > +#define ASM_UD0 ".byte 0x0f, 0xff" /* + ModRM (for Intel) */
> #define ASM_UD1 ".byte 0x0f, 0xb9" /* + ModRM */ > #define ASM_UD2 ".byte 0x0f, 0x0b" > > #define INSN_UD0 0xff0f > #define INSN_UD2 0x0b0f > > -#define LEN_UD0 2 > +#define LEN_UD2 2 > > #ifdef CONFIG_GENERIC_BUG > > @@ -77,7 +74,7 @@ do { \ > unreachable(); \ > } while (0) > > -#define __WARN_FLAGS(flags) _BUG_FLAGS(ASM_UD0, BUGFLAG_WARNING|(flags)) > +#define __WARN_FLAGS(flags) _BUG_FLAGS(ASM_UD2, BUGFLAG_WARNING|(flags)) > > #include <asm-generic/bug.h> > > diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c > index 446c9ef8cfc3..3d9b2308e7fa 100644 > --- a/arch/x86/kernel/traps.c > +++ b/arch/x86/kernel/traps.c > @@ -181,7 +181,7 @@ int fixup_bug(struct pt_regs *regs, int trapnr) > break; > > case BUG_TRAP_TYPE_WARN: > - regs->ip += LEN_UD0; > + regs->ip += LEN_UD2; > return 1;
So patch looks ok but it broke objtool:
init/main.o: warning: objtool: do_one_initcall()+0x13b: unreachable instruction /bin/sh: line 1: 25800 Segmentation fault ./tools/objtool/objtool orc generate --no-fp "arch/x86/kernel/process_64.o" make[2]: *** [arch/x86/kernel/process_64.o] Error 139 make[1]: *** [arch/x86/kernel] Error 2 make[1]: *** Waiting for unfinished jobs.... arch/x86/entry/common.o: warning: objtool: prepare_exit_to_usermode()+0x7b: unreachable instruction arch/x86/events/core.o: warning: objtool: perf_assign_events()+0x24e: unreachable instruction kernel/fork.o: warning: objtool: free_task()+0x4b: unreachable instruction arch/x86/events/amd/core.o: warning: objtool: amd_pmu_cpu_starting()+0xcc: unreachable instruction arch/x86/events/amd/ibs.o: warning: objtool: perf_ibs_start()+0x10e: unreachable instruction arch/x86/events/amd/iommu.o: warning: objtool: perf_iommu_start()+0x1c0: unreachable instruction arch/x86/events/amd/power.o: warning: objtool: __pmu_event_start()+0x8e: unreachable instruction ...
-- Regards/Gruss, Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
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