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authorPetr Vandrovec <petr@vandrovec.name>2007-08-12 10:12:52 +0200
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-08-12 01:42:37 -0700
commitb8d3f2448b8f4ba24f301e23585547ba1acc1f04 (patch)
parent3864e8ccbba1dcdea87398ab80fdc8ae0fab7c45 (diff)
Do not replace whole memcpy in apply alternatives
apply_alternatives uses memcpy() to apply alternatives. Which has the unfortunate effect that while applying memcpy alternative to memcpy itself it tries to overwrite itself with nops - which causes #UD fault as it overwrites half of an 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 the main memcpy loop is not in first two bytes it will work fine. Signed-off-by: Petr Vandrovec <petr@vandrovec.name> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 files changed, 3 insertions, 1 deletions
diff --git a/arch/x86_64/lib/memcpy.S b/arch/x86_64/lib/memcpy.S
index 0ea0ddc875a7..c22981fa2f3a 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 .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