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x86/build: Keep local relocations with ld.lld

PATCH New Kees Cook 2 participants 2 messages Apr 4, 2019 – Apr 5, 2019 x86

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Kees Cook

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PATCH 1/1 x86/build: Keep local relocations with ld.lld

The LLVM linker (ld.lld) defaults to removing local relocations, which causes KASLR boot failures. ld.bfd and ld.gold already handle this correctly. This adds the explicit instruction "--discard-none" during the link phase. There is no change in output for ld.bfd and ld.gold, but ld.lld now produces an image with all the needed relocations.

Link https://github.com/ClangBuiltLinux/linux/issues/404
Signed-off-by Kees Cook <[email protected]>
---
 arch/x86/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
arch/x86/Makefile +1 -1
index a587805c6687..56e748a7679f 100644
@@ -47,7 +47,7 @@ export REALMODE_CFLAGS
 export BITS
 
 ifdef CONFIG_X86_NEED_RELOCS
-        LDFLAGS_vmlinux := --emit-relocs
+        LDFLAGS_vmlinux := --emit-relocs --discard-none
 endif
 
 #
Signature · 5 lines
2.17.1


-- 
Kees Cook
merge bot
#1 lore raw
x86/build: Keep local relocations with ld.lld
Commit-ID:  7c21383f3429dd70da39c0c7f1efa12377a47ab6
Gitweb:     https://git.kernel.org/tip/7c21383f3429dd70da39c0c7f1efa12377a47ab6
Author:     Kees Cook <[email protected]>
AuthorDate: Thu, 4 Apr 2019 14:40:27 -0700
Committer:  Borislav Petkov <[email protected]>
CommitDate: Fri, 5 Apr 2019 12:34:35 +0200

x86/build: Keep local relocations with ld.lld

The LLVM linker (ld.lld) defaults to removing local relocations, which causes KASLR boot failures. ld.bfd and ld.gold already handle this correctly. This adds the explicit instruction "--discard-none" during the link phase. There is no change in output for ld.bfd and ld.gold, but ld.lld now produces an image with all the needed relocations.

Signed-off-by Kees Cook <[email protected]>
Signed-off-by Borislav Petkov <[email protected]>
Cc "H. Peter Anvin" <[email protected]>
Cc Ingo Molnar <[email protected]>
Cc Nick Desaulniers <[email protected]>
Cc Thomas Gleixner <[email protected]>
Cc [email protected]
Cc x86-ml <[email protected]>
Link https://lkml.kernel.org/r/20190404214027.GA7324@beast open here
Link https://github.com/ClangBuiltLinux/linux/issues/404
---
 arch/x86/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
arch/x86/Makefile +1 -1
index a587805c6687..56e748a7679f 100644
@@ -47,7 +47,7 @@ export REALMODE_CFLAGS
 export BITS
 
 ifdef CONFIG_X86_NEED_RELOCS
-        LDFLAGS_vmlinux := --emit-relocs
+        LDFLAGS_vmlinux := --emit-relocs --discard-none
 endif
 
 #