diff options
| author | Arvind Sankar <nivedita@alum.mit.edu> | 2020-02-02 12:13:53 -0500 |
|---|---|---|
| committer | Ard Biesheuvel <ardb@kernel.org> | 2020-02-22 23:37:37 +0100 |
| commit | 8a3abe30de9fffec8b44adeb78f93ecb0f09b0c5 (patch) | |
| tree | da73671e10adac0ad36d768e1a1dd0c58a8daac2 /arch/x86/boot | |
| parent | b75e2b076d00751579c73cfbbc8a7eac7d2a0468 (diff) | |
| download | linux-8a3abe30de9fffec8b44adeb78f93ecb0f09b0c5.tar.bz2 | |
x86/boot: Micro-optimize GDT loading instructions
Rearrange the instructions a bit to use a 32-bit displacement once
instead of 2/3 times. This saves 8 bytes of machine code.
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200202171353.3736319-8-nivedita@alum.mit.edu
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Diffstat (limited to 'arch/x86/boot')
| -rw-r--r-- | arch/x86/boot/compressed/head_64.S | 15 |
1 files changed, 8 insertions, 7 deletions
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index c36e6156b6a3..a4f5561c1c0e 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -69,8 +69,9 @@ SYM_FUNC_START(startup_32) subl $1b, %ebp /* Load new GDT with the 64bit segments using 32bit descriptor */ - addl %ebp, gdt+2(%ebp) - lgdt gdt(%ebp) + leal gdt(%ebp), %eax + movl %eax, 2(%eax) + lgdt (%eax) /* Load segment registers with our descriptors */ movl $__BOOT_DS, %eax @@ -355,9 +356,9 @@ SYM_CODE_START(startup_64) */ /* Make sure we have GDT with 32-bit code segment */ - leaq gdt(%rip), %rax - movq %rax, gdt64+2(%rip) - lgdt gdt64(%rip) + leaq gdt64(%rip), %rax + addq %rax, 2(%rax) + lgdt (%rax) /* * paging_prepare() sets up the trampoline and checks if we need to @@ -625,12 +626,12 @@ SYM_FUNC_END(.Lno_longmode) .data SYM_DATA_START_LOCAL(gdt64) .word gdt_end - gdt - 1 - .quad 0 + .quad gdt - gdt64 SYM_DATA_END(gdt64) .balign 8 SYM_DATA_START_LOCAL(gdt) .word gdt_end - gdt - 1 - .long gdt + .long 0 .word 0 .quad 0x00cf9a000000ffff /* __KERNEL32_CS */ .quad 0x00af9a000000ffff /* __KERNEL_CS */ |