The following commit has been merged into the x86/boot branch of tip: Commit-ID: 6aac80a8da46d70f2ae7ff97c9f45a15c7c9b3ef Gitweb: https://git.kernel.org/tip/6aac80a8da46d70f2ae7ff97c9f45a15c7c9b3ef Author: Ard Biesheuvel <ardb@xxxxxxxxxx> AuthorDate: Tue, 22 Nov 2022 17:10:09 +01:00 Committer: Borislav Petkov <bp@xxxxxxx> CommitterDate: Thu, 24 Nov 2022 08:57:41 +01:00 x86/boot/compressed: Avoid touching ECX in startup32_set_idt_entry() Avoid touching register %ecx in startup32_set_idt_entry(), by folding the MOV, SHL and ORL instructions into a single ORL which no longer requires a temp register. This permits ECX to be used as a function argument in a subsequent patch. Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Link: https://lore.kernel.org/r/20221122161017.2426828-10-ardb@xxxxxxxxxx --- arch/x86/boot/compressed/head_64.S | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index 34d0395..a2d1c03 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -733,7 +733,6 @@ SYM_DATA_END_LABEL(boot32_idt, SYM_L_GLOBAL, boot32_idt_end) */ SYM_FUNC_START(startup32_set_idt_entry) push %ebx - push %ecx /* IDT entry address to %ebx */ leal rva(boot32_idt)(%ebp), %ebx @@ -742,10 +741,8 @@ SYM_FUNC_START(startup32_set_idt_entry) /* Build IDT entry, lower 4 bytes */ movl %eax, %edx - andl $0x0000ffff, %edx # Target code segment offset [15:0] - movl $__KERNEL32_CS, %ecx # Target code segment selector - shl $16, %ecx - orl %ecx, %edx + andl $0x0000ffff, %edx # Target code segment offset [15:0] + orl $(__KERNEL32_CS << 16), %edx # Target code segment selector /* Store lower 4 bytes to IDT */ movl %edx, (%ebx) @@ -758,7 +755,6 @@ SYM_FUNC_START(startup32_set_idt_entry) /* Store upper 4 bytes to IDT */ movl %edx, 4(%ebx) - pop %ecx pop %ebx RET SYM_FUNC_END(startup32_set_idt_entry)
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