linux-hardening - [PATCH v2 1/2] mips: Add support for PC32 relocations in vmlinux

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Message-ID: <20260116093359.2442297-5-ardb+git@google.com>
Date: Fri, 16 Jan 2026 10:34:01 +0100
From: Ard Biesheuvel <ardb+git@...gle.com>
To: linux-kernel@...r.kernel.org
Cc: Ard Biesheuvel <ardb@...nel.org>, Nathan Chancellor <nathan@...nel.org>, Nicolas Schier <nsc@...nel.org>, 
	Kees Cook <kees@...nel.org>, Thomas Bogendoerfer <tsbogend@...ha.franken.de>, 
	linux-kbuild@...r.kernel.org, linux-hardening@...r.kernel.org, 
	linux-mips@...r.kernel.org
Subject: [PATCH v2 1/2] mips: Add support for PC32 relocations in vmlinux

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

MIPS supports PC32 relocations like most other architectures, which will
be used by kallsyms to make its symbol references visible to the linker.

Given that these are place-relative, they can be ignored by the 'relocs'
tool, just like other PC type relocations.

Cc: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 arch/mips/boot/tools/relocs.c | 2 ++
 arch/mips/include/asm/elf.h   | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/arch/mips/boot/tools/relocs.c b/arch/mips/boot/tools/relocs.c
index 9863e1d5c62e..30809f47415a 100644
--- a/arch/mips/boot/tools/relocs.c
+++ b/arch/mips/boot/tools/relocs.c
@@ -79,6 +79,7 @@ static const char *rel_type(unsigned type)
 		REL_TYPE(R_MIPS_HIGHEST),
 		REL_TYPE(R_MIPS_PC21_S2),
 		REL_TYPE(R_MIPS_PC26_S2),
+		REL_TYPE(R_MIPS_PC32),
 #undef REL_TYPE
 	};
 	const char *name = "unknown type rel type name";
@@ -522,6 +523,7 @@ static int do_reloc(struct section *sec, Elf_Rel *rel, Elf_Sym *sym,
 	case R_MIPS_PC16:
 	case R_MIPS_PC21_S2:
 	case R_MIPS_PC26_S2:
+	case R_MIPS_PC32:
 		/*
 		 * NONE can be ignored and PC relative relocations don't
 		 * need to be adjusted.
diff --git a/arch/mips/include/asm/elf.h b/arch/mips/include/asm/elf.h
index dc8d2863752c..aaef0eaa68d5 100644
--- a/arch/mips/include/asm/elf.h
+++ b/arch/mips/include/asm/elf.h
@@ -123,6 +123,8 @@
 #define R_MIPS_LOVENDOR		100
 #define R_MIPS_HIVENDOR		127
 
+#define R_MIPS_PC32		248
+
 #define SHN_MIPS_ACCOMON	0xff00		/* Allocated common symbols */
 #define SHN_MIPS_TEXT		0xff01		/* Allocated test symbols.  */
 #define SHN_MIPS_DATA		0xff02		/* Allocated data symbols.  */
-- 
2.52.0.457.g6b5491de43-goog