linux-kernel - [RFC PATCH 5/5] x86/boot: Use '.data.relocs' section for performing relocations during decompression

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Message-Id: <f312df8f38602b536cd2c5c960cae1f127da6ed7.1769434279.git.houwenlong.hwl@antgroup.com>
Date: Mon, 26 Jan 2026 21:33:55 +0800
From: Hou Wenlong <houwenlong.hwl@...group.com>
To: linux-kernel@...r.kernel.org
Cc: Lai Jiangshan <jiangshan.ljs@...group.com>,
	Hou Wenlong <houwenlong.hwl@...group.com>,
	Thomas Gleixner <tglx@...nel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Ard Biesheuvel <ardb@...nel.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Masahiro Yamada <masahiroy@...nel.org>,
	Vitaly Kuznetsov <vkuznets@...hat.com>,
	Thomas Weißschuh <linux@...ssschuh.net>,
	Brian Gerst <brgerst@...il.com>
Subject: [RFC PATCH 5/5] x86/boot: Use '.data.relocs' section for performing relocations during decompression

When CONFIG_RELOCATABLE_UNCOMPRESSED_KERNEL is enabled, all the
relocations are already in the '.data.relocs' section of the kernel
binary, so there is no need to generate 'vmlinux.relocs' again. Use it
directly for performing relocations during decompression.

Signed-off-by: Hou Wenlong <houwenlong.hwl@...group.com>
---
 arch/x86/boot/compressed/Makefile | 6 ++++--
 arch/x86/boot/compressed/misc.c   | 8 ++++++++
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 68f9d7a1683b..ca629a9b9bce 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -12,7 +12,7 @@
 # vmlinux.bin is:
 #	vmlinux stripped of debugging and comments
 # vmlinux.bin.all is:
-#	vmlinux.bin + vmlinux.relocs
+#	vmlinux.bin + vmlinux.relocs (CONFIG_RELOCATABLE_UNCOMPRESSED_KERNEL=n)
 # vmlinux.bin.(gz|bz2|lzma|...) is:
 #	(see scripts/Makefile.lib size_append)
 #	compressed vmlinux.bin.all + u32 size of vmlinux.bin.all
@@ -76,7 +76,7 @@ LDFLAGS_vmlinux += -T
 hostprogs	:= mkpiggy
 HOST_EXTRACFLAGS += -I$(srctree)/tools/include
 
-sed-voffset := -e 's/^\([0-9a-fA-F]*\) [ABbCDGRSTtVW] \(_text\|__start_rodata\|_sinittext\|__inittext_end\|__bss_start\|_end\)$$/\#define VO_\2 _AC(0x\1,UL)/p'
+sed-voffset := -e 's/^\([0-9a-fA-F]*\) [ABbCDGRSTtVW] \(_text\|__start_rodata\|_sinittext\|__inittext_end\|__bss_start\|_end\|__relocation_end\)$$/\#define VO_\2 _AC(0x\1,UL)/p'
 
 quiet_cmd_voffset = VOFFSET $@
       cmd_voffset = $(NM) $< | sed -n $(sed-voffset) > $@
@@ -132,7 +132,9 @@ $(obj)/vmlinux.relocs: vmlinux.unstripped FORCE
 	$(call if_changed,relocs)
 
 vmlinux.bin.all-y := $(obj)/vmlinux.bin
+ifndef CONFIG_RELOCATABLE_UNCOMPRESSED_KERNEL
 vmlinux.bin.all-$(CONFIG_X86_NEED_RELOCS) += $(obj)/vmlinux.relocs
+endif
 
 $(obj)/vmlinux.bin.gz: $(vmlinux.bin.all-y) FORCE
 	$(call if_changed,gzip)
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index 0f41ca0e52c0..d0f4e8302276 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -232,6 +232,14 @@ static void handle_relocations(void *output, unsigned long output_len,
 	}
 	debug_putstr("Performing relocations... ");
 
+#ifdef CONFIG_RELOCATABLE_UNCOMPRESSED_KERNEL
+	/*
+	 * If CONFIG_RELOCATABLE_UNCOMPRESSED_KERNEL is enabled, the relocations is in
+	 * '.data.reloc' section of kernel binary.
+	 */
+	output_len = VO___relocation_end - VO__text;
+#endif
+
 	/*
 	 * Process relocations: 32 bit relocations first then 64 bit after.
 	 * Two sets of binary relocations are added to the end of the kernel
-- 
2.31.1