diff options
| author | Arvind Sankar <nivedita@alum.mit.edu> | 2020-06-17 09:19:57 -0400 |
|---|---|---|
| committer | Ard Biesheuvel <ardb@kernel.org> | 2020-06-17 15:28:58 +0200 |
| commit | 41d90b0c1108d1e46c48cf79964636c553844f4c (patch) | |
| tree | ed552688de8cdd89029d691f2d30b41c9338d470 /arch/x86/boot | |
| parent | 435d1a471598752446a72ad1201b3c980526d869 (diff) | |
efi/x86: Setup stack correctly for efi_pe_entry
Commit
17054f492dfd ("efi/x86: Implement mixed mode boot without the handover protocol")
introduced a new entry point for the EFI stub to be booted in mixed mode
on 32-bit firmware.
When entered via efi32_pe_entry, control is first transferred to
startup_32 to setup for the switch to long mode, and then the EFI stub
proper is entered via efi_pe_entry. efi_pe_entry is an MS ABI function,
and the ABI requires 32 bytes of shadow stack space to be allocated by
the caller, as well as the stack being aligned to 8 mod 16 on entry.
Allocate 40 bytes on the stack before switching to 64-bit mode when
calling efi_pe_entry to account for this.
For robustness, explicitly align boot_stack_end to 16 bytes. It is
currently implicitly aligned since .bss is cacheline-size aligned,
head_64.o is the first object file with a .bss section, and the heap and
boot sizes are aligned.
Fixes: 17054f492dfd ("efi/x86: Implement mixed mode boot without the handover protocol")
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200617131957.2507632-1-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 | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index e821a7d7d5c4..97d37f0a34f5 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -213,7 +213,6 @@ SYM_FUNC_START(startup_32) * We place all of the values on our mini stack so lret can * used to perform that far jump. */ - pushl $__KERNEL_CS leal startup_64(%ebp), %eax #ifdef CONFIG_EFI_MIXED movl efi32_boot_args(%ebp), %edi @@ -224,11 +223,20 @@ SYM_FUNC_START(startup_32) movl efi32_boot_args+8(%ebp), %edx // saved bootparams pointer cmpl $0, %edx jnz 1f + /* + * efi_pe_entry uses MS calling convention, which requires 32 bytes of + * shadow space on the stack even if all arguments are passed in + * registers. We also need an additional 8 bytes for the space that + * would be occupied by the return address, and this also results in + * the correct stack alignment for entry. + */ + subl $40, %esp leal efi_pe_entry(%ebp), %eax movl %edi, %ecx // MS calling convention movl %esi, %edx 1: #endif + pushl $__KERNEL_CS pushl %eax /* Enter paged protected Mode, activating Long Mode */ @@ -784,6 +792,7 @@ SYM_DATA_LOCAL(boot_heap, .fill BOOT_HEAP_SIZE, 1, 0) SYM_DATA_START_LOCAL(boot_stack) .fill BOOT_STACK_SIZE, 1, 0 + .balign 16 SYM_DATA_END_LABEL(boot_stack, SYM_L_LOCAL, boot_stack_end) /* |