From cbe8ded48b939b9d55d2c5589ab56caa7b530709 Mon Sep 17 00:00:00 2001 From: Nick Desaulniers Date: Wed, 9 Aug 2023 09:40:26 -0700 Subject: x86/srso: Fix build breakage with the LLVM linker 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@mail.gmail.com/ Reported-by: Nathan Chancellor Reported-by: Daniel Kolesa Reported-by: Naresh Kamboju Suggested-by: Sven Volkinsfeld Signed-off-by: Nick Desaulniers Signed-off-by: Borislav Petkov (AMD) Link: https://github.com/ClangBuiltLinux/linux/issues/1907 Link: https://lore.kernel.org/r/20230809-gds-v1-1-eaac90b0cbcc@google.com --- arch/x86/kernel/vmlinux.lds.S | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) (limited to 'arch/x86') diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index e76813230192..ef06211bae4c 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -529,11 +529,17 @@ 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 -- cgit v1.2.3 From eb3515dc99c7c85f4170b50838136b2a193f8012 Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Wed, 9 Aug 2023 15:05:00 +0200 Subject: x86: Move gds_ucode_mitigated() declaration to header The declaration got placed in the .c file of the caller, but that causes a warning for the definition: arch/x86/kernel/cpu/bugs.c:682:6: error: no previous prototype for 'gds_ucode_mitigated' [-Werror=missing-prototypes] Move it to a header where both sides can observe it instead. Fixes: 81ac7e5d74174 ("KVM: Add GDS_NO support to KVM") Signed-off-by: Arnd Bergmann Signed-off-by: Dave Hansen Tested-by: Daniel Sneddon Cc: stable@kernel.org Link: https://lore.kernel.org/all/20230809130530.1913368-2-arnd%40kernel.org --- arch/x86/include/asm/processor.h | 2 ++ arch/x86/kvm/x86.c | 2 -- 2 files changed, 2 insertions(+), 2 deletions(-) (limited to 'arch/x86') diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 973db0406528..4ae2773b873d 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -731,4 +731,6 @@ bool arch_is_platform_page(u64 paddr); #define arch_is_platform_page arch_is_platform_page #endif +extern bool gds_ucode_mitigated(void); + #endif /* _ASM_X86_PROCESSOR_H */ diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 19d9ff92d699..c381770bcbf1 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -314,8 +314,6 @@ u64 __read_mostly host_xcr0; static struct kmem_cache *x86_emulator_cache; -extern bool gds_ucode_mitigated(void); - /* * When called, it means the previous get/set msr reached an invalid msr. * Return true if we want to ignore/silent this failed msr access. -- cgit v1.2.3