diff options
| author | Arvind Sankar <nivedita@alum.mit.edu> | 2020-02-02 12:13:51 -0500 |
|---|---|---|
| committer | Ard Biesheuvel <ardb@kernel.org> | 2020-02-22 23:37:37 +0100 |
| commit | ef5a7b5eb13ed88ba9690ab27def3a085332cc8c (patch) | |
| tree | 33800f398124e6675d2f2f00a5853f77694c50aa /arch/x86/boot/compressed/head_32.S | |
| parent | cae0e431a02cd63fecaf677ae166f184644125a7 (diff) | |
efi/x86: Remove GDT setup from efi_main
The 64-bit kernel will already load a GDT in startup_64, which is the
next function to execute after return from efi_main.
Add GDT setup code to the 32-bit kernel's startup_32 as well. Doing it
in the head code has the advantage that we can avoid potentially
corrupting the GDT during copy/decompression. This also removes
dependence on having a specific GDT layout setup by the bootloader.
Both startup_32 and startup_64 now clear interrupts on entry, so we can
remove that from efi_main as well.
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200202171353.3736319-6-nivedita@alum.mit.edu
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Diffstat (limited to 'arch/x86/boot/compressed/head_32.S')
| -rw-r--r-- | arch/x86/boot/compressed/head_32.S | 40 |
1 files changed, 34 insertions, 6 deletions
diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S index cb2cb91fce45..356060c5332c 100644 --- a/arch/x86/boot/compressed/head_32.S +++ b/arch/x86/boot/compressed/head_32.S @@ -64,12 +64,6 @@ SYM_FUNC_START(startup_32) cld cli - movl $__BOOT_DS, %eax - movl %eax, %ds - movl %eax, %es - movl %eax, %fs - movl %eax, %gs - movl %eax, %ss /* * Calculate the delta between where we were compiled to run @@ -84,6 +78,19 @@ SYM_FUNC_START(startup_32) 1: popl %ebp subl $1b, %ebp + /* Load new GDT */ + leal gdt(%ebp), %eax + movl %eax, 2(%eax) + lgdt (%eax) + + /* Load segment registers with our descriptors */ + movl $__BOOT_DS, %eax + movl %eax, %ds + movl %eax, %es + movl %eax, %fs + movl %eax, %gs + movl %eax, %ss + /* * %ebp contains the address we are loaded at by the boot loader and %ebx * contains the address where we should move the kernel image temporarily @@ -129,6 +136,16 @@ SYM_FUNC_START(startup_32) cld popl %esi + /* + * The GDT may get overwritten either during the copy we just did or + * during extract_kernel below. To avoid any issues, repoint the GDTR + * to the new copy of the GDT. EAX still contains the previously + * calculated relocation offset of init_size - _end. + */ + leal gdt(%ebx), %edx + addl %eax, 2(%edx) + lgdt (%edx) + /* * Jump to the relocated address. */ @@ -201,6 +218,17 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated) jmp *%eax SYM_FUNC_END(.Lrelocated) + .data + .balign 8 +SYM_DATA_START_LOCAL(gdt) + .word gdt_end - gdt - 1 + .long 0 + .word 0 + .quad 0x0000000000000000 /* Reserved */ + .quad 0x00cf9a000000ffff /* __KERNEL_CS */ + .quad 0x00cf92000000ffff /* __KERNEL_DS */ +SYM_DATA_END_LABEL(gdt, SYM_L_LOCAL, gdt_end) + /* * Stack and heap for uncompression */ |