This is a note to let you know that I've just added the patch titled
x86/srso: Fix build breakage with the LLVM linker
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-srso-fix-build-breakage-with-the-llvm-linker.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From cbe8ded48b939b9d55d2c5589ab56caa7b530709 Mon Sep 17 00:00:00 2001
From: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Date: Wed, 9 Aug 2023 09:40:26 -0700
Subject: x86/srso: Fix build breakage with the LLVM linker
From: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
commit cbe8ded48b939b9d55d2c5589ab56caa7b530709 upstream.
The assertion added to verify the difference in bits set of the
addresses of srso_untrain_ret_alias() and srso_safe_ret_alias() would fail
to link in LLVM's ld.lld linker with the following error:
ld.lld: error: ./arch/x86/kernel/vmlinux.lds:210: at least one side of
the expression must be absolute
ld.lld: error: ./arch/x86/kernel/vmlinux.lds:211: at least one side of
the expression must be absolute
Use ABSOLUTE to evaluate the expression referring to at least one of the
symbols so that LLD can evaluate the linker script.
Also, add linker version info to the comment about XOR being unsupported
in either ld.bfd or ld.lld until somewhat recently.
Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Closes: https://lore.kernel.org/llvm/CA+G9fYsdUeNu-gwbs0+T6XHi4hYYk=Y9725-wFhZ7gJMspLDRA@xxxxxxxxxxxxxx/
Reported-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Reported-by: Daniel Kolesa <daniel@xxxxxxxxxxxxx>
Reported-by: Naresh Kamboju <naresh.kamboju@xxxxxxxxxx>
Suggested-by: Sven Volkinsfeld <thyrc@xxxxxxx>
Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Link: https://github.com/ClangBuiltLinux/linux/issues/1907
Link: https://lore.kernel.org/r/20230809-gds-v1-1-eaac90b0cbcc@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/vmlinux.lds.S | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -518,11 +518,17 @@ INIT_PER_CPU(irq_stack_backing_store);
#ifdef CONFIG_CPU_SRSO
/*
- * GNU ld cannot do XOR so do: (A | B) - (A & B) in order to compute the XOR
+ * GNU ld cannot do XOR until 2.41.
+ * https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=f6f78318fca803c4907fb8d7f6ded8295f1947b1
+ *
+ * LLVM lld cannot do XOR until lld-17.
+ * https://github.com/llvm/llvm-project/commit/fae96104d4378166cbe5c875ef8ed808a356f3fb
+ *
+ * Instead do: (A | B) - (A & B) in order to compute the XOR
* of the two function addresses:
*/
-. = ASSERT(((srso_untrain_ret_alias | srso_safe_ret_alias) -
- (srso_untrain_ret_alias & srso_safe_ret_alias)) == ((1 << 2) | (1 << 8) | (1 << 14) | (1 << 20)),
+. = ASSERT(((ABSOLUTE(srso_untrain_ret_alias) | srso_safe_ret_alias) -
+ (ABSOLUTE(srso_untrain_ret_alias) & srso_safe_ret_alias)) == ((1 << 2) | (1 << 8) | (1 << 14) | (1 << 20)),
"SRSO function pair won't alias");
#endif
Patches currently in stable-queue which might be from ndesaulniers@xxxxxxxxxx are
queue-5.15/x86-srso-fix-build-breakage-with-the-llvm-linker.patch
