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x86/cpu: Cleanup the untrain mess

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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>
This commit is contained in:
Peter Zijlstra 2023-08-14 13:44:34 +02:00 committed by Greg Kroah-Hartman
parent e0f50b0e41
commit 06597b650b
3 changed files with 12 additions and 8 deletions
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12
arch/x86/include/asm/nospec-branch.h
View File

@ -156,9 +156,9 @@
.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
/*
@ -177,14 +177,9 @@
defined(CONFIG_CPU_SRSO)
ANNOTATE_UNRET_END
ALTERNATIVE_2 "", \
CALL_ZEN_UNTRAIN_RET, X86_FEATURE_UNRET, \
CALL_UNTRAIN_RET, X86_FEATURE_UNRET, \
"call entry_ibpb", X86_FEATURE_ENTRY_IBPB
#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
#else /* __ASSEMBLY__ */
@ -209,6 +204,7 @@ 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);
#ifdef CONFIG_RETPOLINE

1
arch/x86/kernel/cpu/bugs.c
View File

@ -2359,6 +2359,7 @@ static void __init srso_select_mitigation(void)
* 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);

7
arch/x86/lib/retpoline.S
View File

@ -230,6 +230,13 @@ 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