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authorArd Biesheuvel <ardb@kernel.org>2025-05-04 11:52:43 +0200
committerIngo Molnar <mingo@kernel.org>2025-05-04 15:59:43 +0200
commitf932adcc8650eb169efd0fd19f2a450c260d306c (patch)
treec1b5649cc701fa074702dc32b9d3025e0226a9ae
parentae862964cbc562582576da91b0b92742a574c437 (diff)
x86/linkage: Add SYM_PIC_ALIAS() macro helper to emit symbol aliases
Startup code that may execute from the early 1:1 mapping of memory will be confined into its own address space, and only be permitted to access ordinary kernel symbols if this is known to be safe. Introduce a macro helper SYM_PIC_ALIAS() that emits a __pi_ prefixed alias for a symbol, which allows startup code to access it. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: David Woodhouse <dwmw@amazon.co.uk> Cc: Dionna Amalie Glaze <dionnaglaze@google.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Kees Cook <keescook@chromium.org> Cc: Kevin Loughlin <kevinloughlin@google.com> Cc: Len Brown <len.brown@intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Cc: Tom Lendacky <thomas.lendacky@amd.com> Cc: linux-efi@vger.kernel.org Link: https://lore.kernel.org/r/20250504095230.2932860-38-ardb+git@google.com
-rw-r--r--arch/x86/include/asm/linkage.h10
1 files changed, 10 insertions, 0 deletions
diff --git a/arch/x86/include/asm/linkage.h b/arch/x86/include/asm/linkage.h
index b51d8a4673f5..9d38ae744a2e 100644
--- a/arch/x86/include/asm/linkage.h
+++ b/arch/x86/include/asm/linkage.h
@@ -141,5 +141,15 @@
#define SYM_FUNC_START_WEAK_NOALIGN(name) \
SYM_START(name, SYM_L_WEAK, SYM_A_NONE)
+/*
+ * Expose 'sym' to the startup code in arch/x86/boot/startup/, by emitting an
+ * alias prefixed with __pi_
+ */
+#ifdef __ASSEMBLER__
+#define SYM_PIC_ALIAS(sym) SYM_ALIAS(__pi_ ## sym, sym, SYM_L_GLOBAL)
+#else
+#define SYM_PIC_ALIAS(sym) extern typeof(sym) __PASTE(__pi_, sym) __alias(sym)
+#endif
+
#endif /* _ASM_X86_LINKAGE_H */