From 36d3793c947f1ef7ba3d24eeeddc1be41adc5ab4 Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Fri, 8 May 2009 16:45:15 -0700 Subject: x86, boot: use appropriate rep string for move and clear In the pre-decompression code, use the appropriate largest possible rep movs and rep stos to move code and clear bss, respectively. For reverse copy, do note that the initial values are supposed to be the address of the first (highest) copy datum, not one byte beyond the end of the buffer. rep strings are not necessarily the fastest way to perform these operations on all current processors, but are likely to be in the future, and perhaps more importantly, we want to encourage the architecturally right thing to do here. This also fixes a couple of trivial inefficiencies on 64 bits. [ Impact: trivial performance enhancement, increase code similarity ] Signed-off-by: H. Peter Anvin --- arch/x86/boot/compressed/head_32.S | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) (limited to 'arch/x86/boot/compressed/head_32.S') diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S index d02a4f02be13..6710dc78ac59 100644 --- a/arch/x86/boot/compressed/head_32.S +++ b/arch/x86/boot/compressed/head_32.S @@ -100,11 +100,12 @@ ENTRY(startup_32) * where decompression in place becomes safe. */ pushl %esi - leal _bss(%ebp), %esi - leal _bss(%ebx), %edi + leal (_bss-4)(%ebp), %esi + leal (_bss-4)(%ebx), %edi movl $(_bss - startup_32), %ecx + shrl $2, %ecx std - rep movsb + rep movsl cld popl %esi @@ -135,8 +136,8 @@ relocated: leal _bss(%ebx), %edi leal _ebss(%ebx), %ecx subl %edi, %ecx - cld - rep stosb + shrl $2, %ecx + rep stosl /* * Do the decompression, and jump to the new kernel.. -- cgit v1.2.3