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

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[ Upstream commit df7ecce842 ]

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: b3810c5a2c ("x86/efistub: Clear decompressor BSS in native EFI entrypoint")
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Ard Biesheuvel 2024-03-22 17:01:45 +01:00 committed by Sasha Levin
parent f07ffd18d7
commit 4b0c547923
1 changed files with 2 additions and 1 deletions
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3
drivers/firmware/efi/libstub/x86-stub.c
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@ -434,7 +434,8 @@ 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;