[PATCH for-stable-6.1 07/23] x86/boot: Drop redundant code setting the root device

[Ard Biesheuvel <ardb+git@google.com>]

From: Ard Biesheuvel <ardb@kernel.org>

[ Commit 7448e8e5d15a3c4df649bf6d6d460f78396f7e1e upstream ]

The root device defaults to 0,0 and is no longer configurable at build
time [0], so there is no need for the build tool to ever write to this
field.

[0] 079f85e624189292 ("x86, build: Do not set the root_dev field in bzImage")

This change has no impact on the resulting bzImage binary.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230912090051.4014114-23-ardb@google.com
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/x86/boot/header.S      | 2 +-
 arch/x86/boot/tools/build.c | 7 -------
 2 files changed, 1 insertion(+), 8 deletions(-)

diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S
index 98dd4c36ccca..f63bf3ec6869 100644
--- a/arch/x86/boot/header.S
+++ b/arch/x86/boot/header.S
@@ -235,7 +235,7 @@ root_flags:	.word ROOT_RDONLY
 syssize:	.long 0			/* Filled in by build.c */
 ram_size:	.word 0			/* Obsolete */
 vid_mode:	.word SVGA_MODE
-root_dev:	.word 0			/* Filled in by build.c */
+root_dev:	.word 0			/* Default to major/minor 0/0 */
 boot_flag:	.word 0xAA55
 
 	# offset 512, entry point
diff --git a/arch/x86/boot/tools/build.c b/arch/x86/boot/tools/build.c
index 0354c223e354..efa4e9c7d713 100644
--- a/arch/x86/boot/tools/build.c
+++ b/arch/x86/boot/tools/build.c
@@ -40,10 +40,6 @@ typedef unsigned char  u8;
 typedef unsigned short u16;
 typedef unsigned int   u32;
 
-#define DEFAULT_MAJOR_ROOT 0
-#define DEFAULT_MINOR_ROOT 0
-#define DEFAULT_ROOT_DEV (DEFAULT_MAJOR_ROOT << 8 | DEFAULT_MINOR_ROOT)
-
 /* Minimal number of setup sectors */
 #define SETUP_SECT_MIN 5
 #define SETUP_SECT_MAX 64
@@ -399,9 +395,6 @@ int main(int argc, char ** argv)
 
 	update_pecoff_setup_and_reloc(i);
 
-	/* Set the default root device */
-	put_unaligned_le16(DEFAULT_ROOT_DEV, &buf[508]);
-
 	/* Open and stat the kernel file */
 	fd = open(argv[2], O_RDONLY);
 	if (fd < 0)
-- 
2.44.0.769.g3c40516874-goog