From: Ard Biesheuvel <ardb+git@google.com>
To: linux-efi@vger.kernel.org
Cc: x86@kernel.org, Ard Biesheuvel <ardb@kernel.org>,
Clayton Craft <clayton@craftyguy.net>
Subject: [PATCH 2/2] x86/efistub: Don't clear BSS twice in mixed mode
Date: Fri, 22 Mar 2024 17:17:54 +0100 [thread overview]
Message-ID: <20240322161751.3046943-6-ardb+git@google.com> (raw)
In-Reply-To: <20240322161751.3046943-4-ardb+git@google.com>
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 --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;
--
2.44.0.396.g6e790dbe36-goog
prev parent reply other threads:[~2024-03-22 16:18 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-22 16:17 [PATCH 0/2] EFI mixed mode fixes Ard Biesheuvel
2024-03-22 16:17 ` [PATCH 1/2] x86/efistub: Call mixed mode boot services on the firmware's stack Ard Biesheuvel
2024-03-22 16:17 ` Ard Biesheuvel [this message]
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