Messages in this thread | | | Date | Thu, 14 May 2020 15:14:12 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH v5 00/18] Rework READ_ONCE() to improve codegen |
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On Thu, May 14, 2020 at 03:07:08PM +0200, Marco Elver wrote: > On Thu, 14 May 2020 at 14:27, Peter Zijlstra <peterz@infradead.org> wrote: > > > > On Thu, May 14, 2020 at 01:01:04PM +0100, Will Deacon wrote: > > > > > > +#if __has_feature(undefined_sanitizer) > > > > > > Hmm, this might want to be __has_feature(undefined_behavior_sanitizer) > > > (and damn is that hard for a Brit to type out!) > > > > (I know right, it should be behaviour, dammit!) > > > > I tried without the condition, eg.: > > > > +#define __no_sanitize_undefined \ > > + __attribute__((no_sanitize("undefined"))) > > > > and it still generated UBSAN gunk. > > Which ubsan calls are left? I'm trying to reproduce.
To be more precise, the patches were on top of:
git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git entry-v5-the-rest
$ grep ubsan poke_int3_handler-clang10.asm 0074 74: R_X86_64_PLT32 __ubsan_handle_load_invalid_value-0x4 0083 83: R_X86_64_PLT32 __ubsan_handle_load_invalid_value-0x4 01c5 1c5: R_X86_64_PLT32 __ubsan_handle_builtin_unreachable-0x4
I think the config was defconfig_x86-64 inspired with KASAN+UBSAN enabled.
So I build with:
touch arch/x86/kernel/alterantive.c; make CC=clang-10 V=1 O=defconfig-build/ arch/x86/kernel/alterantive.o
And then dump the output with:
./objdump-func.sh defconfig-build/arch/x86/kernel/alterantive.o poke_int3_handler
$ # cat objdump-func.sh #!/bin/bash objdump -dr $1 | awk "/^\$/ { P=0; } /$2[^>]*>:\$/ { P=1; O=strtonum(\"0x\" \$1); } { if (P) { o=strtonum(\"0x\" \$1); printf(\"%04x \", o-O); print \$0; } }"
Hope that is enough to reproduce.
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