5.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxx>
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Link: https://lore.kernel.org/r/20230814121149.042774962@xxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/include/asm/nospec-branch.h | 12 ++++--------
arch/x86/kernel/cpu/bugs.c | 1 +
arch/x86/lib/retpoline.S | 7 +++++++
3 files changed, 12 insertions(+), 8 deletions(-)
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -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
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2359,6 +2359,7 @@ 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
@@ -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
