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Date: Sun, 12 Aug 2007 10:12:52 +0200 From: Petr Vandrovec <petr@...drovec.name> To: ak@...e.de Cc: discuss@...-64.org, linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org Subject: [PATCH] Fix triplefault on x86-64 bootup Hello, after I upgraded kernel on my box to current git, only thing it did was rebooting in a loop. After some digging I found that it is silly to apply alternative to memcpy by using that every same memcpy... Sorry if it is known bug, I do not see it reported in my LKML mailbox... Petr From: Petr Vandrovec <petr@...drovec.name> Do not replace whole memcpy in apply alternatives apply_alternatives uses memcpy() to apply alternatives. Which has unfortunate effect that while applying memcpy alternative memcpy itself it tries to overwrite itself with nops - which causes #UD fault as it overwrites half of instruction in copy loop, and from this point on only possible outcome is triplefault and reboot. So let's overwrite only first two instructions of memcpy - as long as main memcpy loop is not in first two bytes it will work fine. Signed-off-by: Petr Vandrovec <petr@...drovec.name> --- commit 7c6f7d582f301e16899a43fd6c775ed103e8a8d2 tree 112d7320e8a21120e4e43f1ac91918ca0352ff56 parent f81e9b8cc6301f6328eafaa553ef35441874b1a4 author Petr Vandrovec <petr@...drovec.name> Sun, 12 Aug 2007 01:05:11 -0700 committer Petr Vandrovec <petr@...drovec.name> Sun, 12 Aug 2007 01:05:11 -0700 arch/x86_64/lib/memcpy.S | 4 +++- 1 files changed, 3 insertions(+), 1 deletions(-) diff --git a/arch/x86_64/lib/memcpy.S b/arch/x86_64/lib/memcpy.S index 0ea0ddc..c22981f 100644 --- a/arch/x86_64/lib/memcpy.S +++ b/arch/x86_64/lib/memcpy.S @@ -124,6 +124,8 @@ ENDPROC(__memcpy) .quad memcpy .quad 1b .byte X86_FEATURE_REP_GOOD - .byte .Lfinal - memcpy + /* Replace only beginning, memcpy is used to apply alternatives, so it + * is silly to overwrite itself with nops - reboot is only outcome... */ + .byte 2b - 1b .byte 2b - 1b .previous - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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