From fac60fefe876655d09e5a93ad4c638ebc330c86f Mon Sep 17 00:00:00 2001 From: Nathan Chancellor Date: Wed, 22 Jul 2026 17:09:43 -0700 Subject: [PATCH] x86/boot/compressed: Disable jump tables commit 4a9ec5ec9555ad62dc5b81a37ac946025c2ea002 upstream. After a recent upstream LLVM change to start generating jump and lookup tables in switch statements in more instances [1], linking the compressed x86 boot image when CONFIG_KERNEL_ZSTD is enabled fails with: ld.lld: error: Unexpected run-time relocations (.rela) detected! Dumping the relocations in misc.o, which is the only file influenced by CONFIG_KERNEL_ZSTD in the decompressor, shows dynamic relocations to some string constants, which correspond to the string literals in the switch statement in handle_zstd_error(): Relocation section '.rela.data.rel.ro' at offset 0x277b0 contains 31 entries: Offset Info Type Symbol's Value Symbol's Name + Addend 0000000000000000 0000006600000001 R_X86_64_64 0000000000000000 .rodata.str1.1 + 73a 0000000000000008 0000006600000001 R_X86_64_64 0000000000000000 .rodata.str1.1 + 78e 0000000000000010 0000006600000001 R_X86_64_64 0000000000000000 .rodata.str1.1 + 78e 0000000000000018 0000006600000001 R_X86_64_64 0000000000000000 .rodata.str1.1 + 78e ... This optimization is problematic for the decompressor environment, as it is built as -fPIE without any explicit absolute references (as described at the top of misc.c) while not applying any dynamic relocations, hence the linker assertion. To opt out of this optimization, which is of little value in this special early boot code, and to mirror the other x86 startup code in arch/x86/boot/startup, disable jump tables in the decompressor. Signed-off-by: Nathan Chancellor Signed-off-by: Ingo Molnar Acked-by: Ard Biesheuvel Cc: Bill Wendling Cc: Justin Stitt Cc: Nick Desaulniers Cc: "H. Peter Anvin" Cc: Peter Zijlstra Cc: stable@vger.kernel.org Link: https://github.com/llvm/llvm-project/commit/fa02a6ed66b1700c996b49c96c6bc0eb014c9518 [1] Link: https://patch.msgid.link/20260722-x86-boot-compressed-disable-jt-clang-v2-1-7373d38482fb@kernel.org Closes: https://github.com/ClangBuiltLinux/linux/issues/2165 Signed-off-by: Greg Kroah-Hartman --- arch/x86/boot/compressed/Makefile | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile index ba17496fad1b..bee3c0151a34 100644 --- a/arch/x86/boot/compressed/Makefile +++ b/arch/x86/boot/compressed/Makefile @@ -36,6 +36,7 @@ targets := vmlinux vmlinux.bin vmlinux.bin.gz vmlinux.bin.bz2 vmlinux.bin.lzma \ KBUILD_CFLAGS := -m$(BITS) -O2 $(CLANG_FLAGS) KBUILD_CFLAGS += -std=gnu11 KBUILD_CFLAGS += -fno-strict-aliasing -fPIE +KBUILD_CFLAGS += -fno-jump-tables KBUILD_CFLAGS += -Wundef KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING cflags-$(CONFIG_X86_32) := -march=i386