Commit-ID: 36d3793c947f1ef7ba3d24eeeddc1be41adc5ab4 Gitweb: http://git.kernel.org/tip/36d3793c947f1ef7ba3d24eeeddc1be41adc5ab4 Author: H. Peter Anvin <hpa@xxxxxxxxx> AuthorDate: Fri, 8 May 2009 16:45:15 -0700 Committer: H. Peter Anvin <hpa@xxxxxxxxx> CommitDate: Fri, 8 May 2009 17:34:52 -0700 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 <hpa@xxxxxxxxx> --- arch/x86/boot/compressed/head_32.S | 11 ++++++----- arch/x86/boot/compressed/head_64.S | 26 +++++++++++++------------- 2 files changed, 19 insertions(+), 18 deletions(-) diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S index d02a4f0..6710dc7 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.. diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index a0b1842..723c72d 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -260,15 +260,15 @@ ENTRY(startup_64) * Copy the compressed kernel to the end of our buffer * where decompression in place becomes safe. */ - leaq _bss(%rip), %r8 - leaq _bss(%rbx), %r9 + pushq %rsi + leaq (_bss-8)(%rip), %rsi + leaq (_bss-8)(%rbx), %rdi movq $_bss /* - $startup_32 */, %rcx -1: subq $8, %r8 - subq $8, %r9 - movq 0(%r8), %rax - movq %rax, 0(%r9) - subq $8, %rcx - jnz 1b + shrq $3, %rcx + std + rep movsq + cld + popq %rsi /* * Jump to the relocated address. @@ -282,12 +282,12 @@ relocated: /* * Clear BSS (stack is currently empty) */ - xorq %rax, %rax - leaq _bss(%rbx), %rdi - leaq _ebss(%rbx), %rcx + xorl %eax, %eax + leaq _bss(%rip), %rdi + leaq _ebss(%rip), %rcx subq %rdi, %rcx - cld - rep stosb + shrq $3, %rcx + rep stosq /* * Do the decompression, and jump to the new kernel.. -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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