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[2/2] x86/efistub: Don't clear BSS twice in mixed mode

Message ID 20240322161751.3046943-6-ardb+git@google.com
State New
Headers show
Series EFI mixed mode fixes | expand

Commit Message

Ard Biesheuvel March 22, 2024, 4:17 p.m. UTC 
From: Ard Biesheuvel <ardb@kernel.org>

Clearing BSS should only be done once, at the very beginning.
efi_pe_entry() is the entrypoint from the firmware, which may not clear
BSS and so it is done explicitly. However, efi_pe_entry() is also used
as an entrypoint by the mixed mode startup code, in which case BSS will
already have been cleared, and doing it again at this point will corrupt
global variables holding the firmware's GDT/IDT and segment selectors.

So make the memset() conditional on whether the EFI stub is running in
native mode.

Fixes: b3810c5a2cc4a666 ("x86/efistub: Clear decompressor BSS in native EFI entrypoint")
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 drivers/firmware/efi/libstub/x86-stub.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c
index 2096ae09438e..1edf93e63897 100644
--- a/drivers/firmware/efi/libstub/x86-stub.c
+++ b/drivers/firmware/efi/libstub/x86-stub.c
@@ -476,7 +476,8 @@  efi_status_t __efiapi efi_pe_entry(efi_handle_t handle,
 	efi_status_t status;
 	char *cmdline_ptr;
 
-	memset(_bss, 0, _ebss - _bss);
+	if (efi_is_native())
+		memset(_bss, 0, _ebss - _bss);
 
 	efi_system_table = sys_table_arg;