From: Peter Zijlstra peterz@infradead.org
commit e7c25c441e9e0fa75b4c83e0b26306b702cfe90d upstream.
Since there can only be one active return_thunk, there only needs be one (matching) untrain_ret. It fundamentally doesn't make sense to allow multiple untrain_ret at the same time.
Fold all the 3 different untrain methods into a single (temporary) helper stub.
Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation") Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Signed-off-by: Borislav Petkov (AMD) bp@alien8.de Link: https://lore.kernel.org/r/20230814121149.042774962@infradead.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/include/asm/nospec-branch.h | 19 +++++-------------- arch/x86/kernel/cpu/bugs.c | 1 + arch/x86/lib/retpoline.S | 7 +++++++ 3 files changed, 13 insertions(+), 14 deletions(-)
--- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -268,9 +268,9 @@ .endm
#ifdef CONFIG_CPU_UNRET_ENTRY -#define CALL_ZEN_UNTRAIN_RET "call retbleed_untrain_ret" +#define CALL_UNTRAIN_RET "call entry_untrain_ret" #else -#define CALL_ZEN_UNTRAIN_RET "" +#define CALL_UNTRAIN_RET "" #endif
/* @@ -289,15 +289,10 @@ defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO) VALIDATE_UNRET_END ALTERNATIVE_3 "", \ - CALL_ZEN_UNTRAIN_RET, X86_FEATURE_UNRET, \ + CALL_UNTRAIN_RET, X86_FEATURE_UNRET, \ "call entry_ibpb", X86_FEATURE_ENTRY_IBPB, \ __stringify(RESET_CALL_DEPTH), X86_FEATURE_CALL_DEPTH #endif - -#ifdef CONFIG_CPU_SRSO - ALTERNATIVE_2 "", "call srso_untrain_ret", X86_FEATURE_SRSO, \ - "call srso_alias_untrain_ret", X86_FEATURE_SRSO_ALIAS -#endif .endm
.macro UNTRAIN_RET_FROM_CALL @@ -305,15 +300,10 @@ defined(CONFIG_CALL_DEPTH_TRACKING) VALIDATE_UNRET_END ALTERNATIVE_3 "", \ - CALL_ZEN_UNTRAIN_RET, X86_FEATURE_UNRET, \ + CALL_UNTRAIN_RET, X86_FEATURE_UNRET, \ "call entry_ibpb", X86_FEATURE_ENTRY_IBPB, \ __stringify(RESET_CALL_DEPTH_FROM_CALL), X86_FEATURE_CALL_DEPTH #endif - -#ifdef CONFIG_CPU_SRSO - ALTERNATIVE_2 "", "call srso_untrain_ret", X86_FEATURE_SRSO, \ - "call srso_alias_untrain_ret", X86_FEATURE_SRSO_ALIAS -#endif .endm
@@ -351,6 +341,7 @@ extern void retbleed_untrain_ret(void); extern void srso_untrain_ret(void); extern void srso_alias_untrain_ret(void);
+extern void entry_untrain_ret(void); extern void entry_ibpb(void);
extern void (*x86_return_thunk)(void); --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -2458,6 +2458,7 @@ static void __init srso_select_mitigatio * like ftrace, static_call, etc. */ setup_force_cpu_cap(X86_FEATURE_RETHUNK); + setup_force_cpu_cap(X86_FEATURE_UNRET);
if (boot_cpu_data.x86 == 0x19) { setup_force_cpu_cap(X86_FEATURE_SRSO_ALIAS); --- a/arch/x86/lib/retpoline.S +++ b/arch/x86/lib/retpoline.S @@ -290,6 +290,13 @@ SYM_CODE_START(srso_return_thunk) ud2 SYM_CODE_END(srso_return_thunk)
+SYM_FUNC_START(entry_untrain_ret) + ALTERNATIVE_2 "jmp retbleed_untrain_ret", \ + "jmp srso_untrain_ret", X86_FEATURE_SRSO, \ + "jmp srso_alias_untrain_ret", X86_FEATURE_SRSO_ALIAS +SYM_FUNC_END(entry_untrain_ret) +__EXPORT_THUNK(entry_untrain_ret) + SYM_CODE_START(__x86_return_thunk) UNWIND_HINT_FUNC ANNOTATE_NOENDBR