linux-kernel - [PATCH v2 07/15] x86/boot: Grab kernel_info offset from zoffset header directly

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Message-ID: <20230912090051.4014114-24-ardb@google.com>
Date:   Tue, 12 Sep 2023 09:00:58 +0000
From:   Ard Biesheuvel <ardb@...gle.com>
To:     linux-efi@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Ard Biesheuvel <ardb@...nel.org>,
        Evgeniy Baskov <baskov@...ras.ru>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Jones <pjones@...hat.com>,
        Matthew Garrett <mjg59@...f.ucam.org>,
        Gerd Hoffmann <kraxel@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH v2 07/15] x86/boot: Grab kernel_info offset from zoffset
 header directly

From: Ard Biesheuvel <ardb@...nel.org>

Instead of parsing zoffset.h and poking the kernel_info offset value
into the header from the build tool, just grab the value directly in the
asm file that describes this header.

This change has no impact on the resulting bzImage binary.

Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 arch/x86/boot/header.S      | 2 +-
 arch/x86/boot/tools/build.c | 4 ----
 2 files changed, 1 insertion(+), 5 deletions(-)

diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S
index 6059f87b159d..5575d0f06bab 100644
--- a/arch/x86/boot/header.S
+++ b/arch/x86/boot/header.S
@@ -526,7 +526,7 @@ pref_address:		.quad LOAD_PHYSICAL_ADDR	# preferred load addr
 
 init_size:		.long INIT_SIZE		# kernel initialization size
 handover_offset:	.long 0			# Filled in by build.c
-kernel_info_offset:	.long 0			# Filled in by build.c
+kernel_info_offset:	.long ZO_kernel_info
 
 # End of setup header #####################################################
 
diff --git a/arch/x86/boot/tools/build.c b/arch/x86/boot/tools/build.c
index efa4e9c7d713..660627ea6cbb 100644
--- a/arch/x86/boot/tools/build.c
+++ b/arch/x86/boot/tools/build.c
@@ -59,7 +59,6 @@ static unsigned long efi32_stub_entry;
 static unsigned long efi64_stub_entry;
 static unsigned long efi_pe_entry;
 static unsigned long efi32_pe_entry;
-static unsigned long kernel_info;
 static unsigned long startup_64;
 static unsigned long _end;
 
@@ -339,7 +338,6 @@ static void parse_zoffset(char *fname)
 		PARSE_ZOFS(p, efi64_stub_entry);
 		PARSE_ZOFS(p, efi_pe_entry);
 		PARSE_ZOFS(p, efi32_pe_entry);
-		PARSE_ZOFS(p, kernel_info);
 		PARSE_ZOFS(p, startup_64);
 		PARSE_ZOFS(p, _end);
 
@@ -422,8 +420,6 @@ int main(int argc, char ** argv)
 	update_pecoff_text(setup_sectors * 512, i + (sys_size * 16));
 
 	efi_stub_entry_update();
-	/* Update kernel_info offset. */
-	put_unaligned_le32(kernel_info, &buf[0x268]);
 
 	crc = partial_crc32(buf, i, crc);
 	if (fwrite(buf, 1, i, dest) != i)
-- 
2.42.0.283.g2d96d420d3-goog