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authorArvind Sankar2020-06-17 09:19:57 -0400
committerArd Biesheuvel2020-06-17 15:28:58 +0200
commit41d90b0c1108d1e46c48cf79964636c553844f4c (patch)
treeed552688de8cdd89029d691f2d30b41c9338d470 /arch/x86/boot
parent435d1a471598752446a72ad1201b3c980526d869 (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.S11
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)
/*