This is a note to let you know that I've just added the patch titled
x86/efistub: Branch straight to kernel entry point from C code
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-efistub-branch-straight-to-kernel-entry-point-from-c-code.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From d2d7a54f69b67cd0a30e0ebb5307cb2de625baac Mon Sep 17 00:00:00 2001
From: Ard Biesheuvel <ardb@xxxxxxxxxx>
Date: Mon, 7 Aug 2023 18:27:00 +0200
Subject: x86/efistub: Branch straight to kernel entry point from C code
From: Ard Biesheuvel <ardb@xxxxxxxxxx>
commit d2d7a54f69b67cd0a30e0ebb5307cb2de625baac upstream.
Instead of returning to the calling code in assembler that does nothing
more than perform an indirect call with the boot_params pointer in
register ESI/RSI, perform the jump directly from the EFI stub C code.
This will allow the asm entrypoint code to be dropped entirely in
subsequent patches.
Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Link: https://lore.kernel.org/r/20230807162720.545787-4-ardb@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/firmware/efi/libstub/x86-stub.c | 22 +++++++++++++++++-----
1 file changed, 17 insertions(+), 5 deletions(-)
--- a/drivers/firmware/efi/libstub/x86-stub.c
+++ b/drivers/firmware/efi/libstub/x86-stub.c
@@ -279,7 +279,7 @@ adjust_memory_range_protection(unsigned
#define TRAMPOLINE_PLACEMENT_BASE ((128 - 8)*1024)
#define TRAMPOLINE_PLACEMENT_SIZE (640*1024 - (128 - 8)*1024)
-void startup_32(struct boot_params *boot_params);
+extern const u8 startup_32[], startup_64[];
static void
setup_memory_protection(unsigned long image_base, unsigned long image_size)
@@ -760,10 +760,19 @@ static efi_status_t exit_boot(struct boo
return EFI_SUCCESS;
}
+static void __noreturn enter_kernel(unsigned long kernel_addr,
+ struct boot_params *boot_params)
+{
+ /* enter decompressed kernel with boot_params pointer in RSI/ESI */
+ asm("jmp *%0"::"r"(kernel_addr), "S"(boot_params));
+
+ unreachable();
+}
+
/*
- * On success, we return the address of startup_32, which has potentially been
- * relocated by efi_relocate_kernel.
- * On failure, we exit to the firmware via efi_exit instead of returning.
+ * On success, this routine will jump to the relocated image directly and never
+ * return. On failure, it will exit to the firmware via efi_exit() instead of
+ * returning.
*/
asmlinkage unsigned long efi_main(efi_handle_t handle,
efi_system_table_t *sys_table_arg,
@@ -905,7 +914,10 @@ asmlinkage unsigned long efi_main(efi_ha
goto fail;
}
- return bzimage_addr;
+ if (IS_ENABLED(CONFIG_X86_64))
+ bzimage_addr += startup_64 - startup_32;
+
+ enter_kernel(bzimage_addr, boot_params);
fail:
efi_err("efi_main() failed!\n");
Patches currently in stable-queue which might be from ardb@xxxxxxxxxx are
queue-6.1/x86-boot-compressed-avoid-touching-ecx-in-startup32_set_idt_entry.patch
queue-6.1/x86-boot-compressed-only-build-mem_encrypt.s-if-amd_mem_encrypt-y.patch
queue-6.1/efi-capsule-loader-fix-incorrect-allocation-size.patch
queue-6.1/x86-decompressor-move-global-symbol-references-to-c-code.patch
queue-6.1/x86-boot-compressed-move-startup32_load_idt-into-.text-section.patch
queue-6.1/x86-decompressor-only-call-the-trampoline-when-changing-paging-levels.patch
queue-6.1/x86-boot-compressed-rename-efi_thunk_64.s-to-efi-mixed.s.patch
queue-6.1/x86-decompressor-merge-trampoline-cleanup-with-switching-code.patch
queue-6.1/x86-boot-compressed-move-efi32_pe_entry-out-of-head_64.s.patch
queue-6.1/efi-verify-that-variable-services-are-supported.patch
queue-6.1/x86-decompressor-call-trampoline-directly-from-c-code.patch
queue-6.1/x86-boot-compressed-pull-global-variable-reference-into-startup32_load_idt.patch
queue-6.1/x86-boot-compressed-simplify-idt-gdt-preserve-restore-in-the-efi-thunk.patch
queue-6.1/x86-decompressor-assign-paging-related-global-variables-earlier.patch
queue-6.1/x86-boot-compressed-move-32-bit-entrypoint-code-into-.text-section.patch
queue-6.1/x86-boot-compressed-move-efi32_pe_entry-into-.text-section.patch
queue-6.1/x86-decompressor-avoid-the-need-for-a-stack-in-the-32-bit-trampoline.patch
queue-6.1/x86-boot-compressed-move-startup32_check_sev_cbit-out-of-head_64.s.patch
queue-6.1/x86-boot-compressed-efi-merge-multiple-definitions-of-image_offset-into-one.patch
queue-6.1/x86-boot-compressed-move-startup32_load_idt-out-of-head_64.s.patch
queue-6.1/decompress-use-8-byte-alignment.patch
queue-6.1/x86-boot-compressed-move-efi32_entry-out-of-head_64.s.patch
queue-6.1/efi-libstub-use-efi_loader_code-region-when-moving-the-kernel-in-memory.patch
queue-6.1/crypto-arm64-neonbs-fix-out-of-bounds-access-on-short-input.patch
queue-6.1/x86-boot-compressed-move-bootargs-parsing-out-of-32-bit-startup-code.patch
queue-6.1/efivarfs-request-at-most-512-bytes-for-variable-names.patch
queue-6.1/x86-boot-compressed-adhere-to-calling-convention-in-get_sev_encryption_bit.patch
queue-6.1/x86-boot-compressed-move-startup32_check_sev_cbit-into-.text.patch
queue-6.1/x86-decompressor-store-boot_params-pointer-in-callee-save-register.patch
queue-6.1/x86-efistub-branch-straight-to-kernel-entry-point-from-c-code.patch
queue-6.1/x86-decompressor-call-trampoline-as-a-normal-function.patch
queue-6.1/x86-decompressor-pass-pgtable-address-to-trampoline-directly.patch
queue-6.1/x86-decompressor-use-standard-calling-convention-for-trampoline.patch
queue-6.1/x86-efi-make-the-deprecated-efi-handover-protocol-optional.patch
