x86/efistub: Don't clear BSS twice in mixed mode
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>
diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c
index 2096ae0..1edf93e6 100644
--- a/drivers/firmware/efi/libstub/x86-stub.c
+++ b/drivers/firmware/efi/libstub/x86-stub.c
@@ -476,7 +476,8 @@
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;
