Messages in this thread Patch in this message | | | Date | Mon, 14 Aug 2023 13:44:37 +0200 | From | Peter Zijlstra <> | Subject | [PATCH v2 11/11] x86/cpu: Use fancy alternatives to get rid of entry_untrain_ret() |
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Use the new nested alternatives to create what is effectively ALTERNATIVE_5 and merge the dummy entry_untrain_ret stub into UNTRAIN_RET properly.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- arch/x86/include/asm/nospec-branch.h | 33 ++++++++++++++++++--------------- arch/x86/kernel/cpu/bugs.c | 1 - arch/x86/lib/retpoline.S | 7 ------- 3 files changed, 18 insertions(+), 23 deletions(-)
--- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -272,11 +272,15 @@ .endm #ifdef CONFIG_CPU_UNRET_ENTRY -#define CALL_UNTRAIN_RET "call entry_untrain_ret" +#define ALT_UNRET(old) \ + __ALTERNATIVE(__ALTERNATIVE(__ALTERNATIVE(old, call retbleed_untrain_ret, X86_FEATURE_UNRET), \ + call srso_untrain_ret, X86_FEATURE_SRSO), \ + call srso_alias_untrain_ret, X86_FEATURE_SRSO_ALIAS) #else -#define CALL_UNTRAIN_RET "" +#define ALT_UNRET(old) old #endif + /* * Mitigate RETBleed for AMD/Hygon Zen uarch. Requires KERNEL CR3 because the * return thunk isn't mapped into the userspace tables (then again, AMD @@ -292,10 +296,10 @@ #if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \ defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO) VALIDATE_UNRET_END - ALTERNATIVE_3 "", \ - CALL_UNTRAIN_RET, X86_FEATURE_UNRET, \ - "call entry_ibpb", X86_FEATURE_ENTRY_IBPB, \ - __stringify(RESET_CALL_DEPTH), X86_FEATURE_CALL_DEPTH + + __ALTERNATIVE(__ALTERNATIVE(ALT_UNRET(;), + call entry_ibpb, X86_FEATURE_ENTRY_IBPB), + RESET_CALL_DEPTH, X86_FEATURE_CALL_DEPTH) #endif .endm @@ -303,10 +307,10 @@ #if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \ defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO) VALIDATE_UNRET_END - ALTERNATIVE_3 "", \ - CALL_UNTRAIN_RET, X86_FEATURE_UNRET, \ - "call entry_ibpb", X86_FEATURE_IBPB_ON_VMEXIT, \ - __stringify(RESET_CALL_DEPTH), X86_FEATURE_CALL_DEPTH + + __ALTERNATIVE(__ALTERNATIVE(ALT_UNRET(;), + call entry_ibpb, X86_FEATURE_IBPB_ON_VMEXIT), + RESET_CALL_DEPTH, X86_FEATURE_CALL_DEPTH) #endif .endm @@ -314,10 +318,10 @@ #if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \ defined(CONFIG_CALL_DEPTH_TRACKING) VALIDATE_UNRET_END - ALTERNATIVE_3 "", \ - CALL_UNTRAIN_RET, X86_FEATURE_UNRET, \ - "call entry_ibpb", X86_FEATURE_ENTRY_IBPB, \ - __stringify(RESET_CALL_DEPTH_FROM_CALL), X86_FEATURE_CALL_DEPTH + + __ALTERNATIVE(__ALTERNATIVE(ALT_UNRET(;), + call entry_ibpb, X86_FEATURE_ENTRY_IBPB), + RESET_CALL_DEPTH_FROM_CALL, X86_FEATURE_CALL_DEPTH) #endif .endm @@ -352,7 +356,6 @@ 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 @@ -2450,7 +2450,6 @@ 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 @@ -277,13 +277,6 @@ 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
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