From: Jeremy Fitzhardinge Date: Tue, 26 Sep 2006 08:52:34 +0000 (+0200) Subject: [PATCH] i386: fix dubious segment register clear in cpu_init() X-Git-Tag: v2.6.19-rc1~1077^2~107 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5758d5dfef1c514200bda3f29ba700f1c3e3bc99;p=linux-2.6 [PATCH] i386: fix dubious segment register clear in cpu_init() Fix a very dubious piece of code in arch/i386/kernel/cpu/common.c:cpu_init(). This clears out %fs and %gs, but clobbers %eax in the process without telling gcc. It turns out that gcc happens to be not using %eax at that point anyway so it doesn't matter much, but it looks like a bomb waiting to go off. This does end up saving an instruction, because gcc wants %eax==0 for the set_debugreg()s below. Signed-off-by: Jeremy Fitzhardinge Signed-off-by: Andi Kleen --- diff --git a/arch/i386/kernel/cpu/common.c b/arch/i386/kernel/cpu/common.c index 70c87de582..730a7ab750 100644 --- a/arch/i386/kernel/cpu/common.c +++ b/arch/i386/kernel/cpu/common.c @@ -675,7 +675,7 @@ old_gdt: #endif /* Clear %fs and %gs. */ - asm volatile ("xorl %eax, %eax; movl %eax, %fs; movl %eax, %gs"); + asm volatile ("movl %0, %%fs; movl %0, %%gs" : : "r" (0)); /* Clear all 6 debug registers: */ set_debugreg(0, 0);