Messages in this thread | | | Date | Wed, 22 Apr 2020 18:53:39 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH v2] x86: fix early boot crash on gcc-10 |
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On Wed, Apr 22, 2020 at 04:16:53PM +0200, Martin Liška wrote: > And as I talked to Boris, I would recommend to come up with a "configure" check > that a compiler does not optimize the key code sequence: > > $ cat asm-detect.c > int foo(int a); > int bar(int a) > { > int r = foo(a); > asm (""); > return r; > } > > $ gcc -O2 -c asm-detect.c -S -o/dev/stdout | grep jmp > [no output]
That is a good test to run at the beginning of the compilation I guess.
Without the asm("") it produces:
bar: .LFB0: .cfi_startproc jmp foo@PLT .cfi_endproc
I'd like for LLVM folks to confirm that this is a good test for LLVM too Trying that here with clang gives:
bar: # @bar .cfi_startproc # %bb.0: jmp foo # TAILCALL .Lfunc_end0:
so this *looks* like it would work with LLVM too but I might be missing something...
Thx.
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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