It doesn't do anything useful anymore (it never really did), remove it
and while at it, put all the untrain and return thunk mess under
CPU_UNRET_ENTRY.
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
---
arch/x86/Kconfig | 7 -------
arch/x86/include/asm/nospec-branch.h | 9 ++++-----
arch/x86/kernel/vmlinux.lds.S | 9 +++------
arch/x86/lib/retpoline.S | 23 +++++++++++++++++------
4 files changed, 24 insertions(+), 24 deletions(-)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2593,13 +2593,6 @@ config CPU_IBRS_ENTRY
This mitigates both spectre_v2 and retbleed at great cost to
performance.
-config CPU_SRSO
- bool "Mitigate speculative RAS overflow on AMD"
- depends on CPU_SUP_AMD && X86_64 && RETHUNK
- default y
- help
- Enable the SRSO mitigation needed on AMD Zen1-4 machines.
-
config SLS
bool "Mitigate Straight-Line-Speculation"
depends on CC_HAS_SLS && X86_64
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -211,8 +211,7 @@
* eventually turn into it's own annotation.
*/
.macro VALIDATE_UNRET_END
-#if defined(CONFIG_NOINSTR_VALIDATION) && \
- (defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_SRSO))
+#if defined(CONFIG_NOINSTR_VALIDATION) && defined(CONFIG_CPU_UNRET_ENTRY)
ANNOTATE_RETPOLINE_SAFE
nop
#endif
@@ -290,7 +289,7 @@
*/
.macro UNTRAIN_RET
#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
- defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO)
+ defined(CONFIG_CALL_DEPTH_TRACKING)
VALIDATE_UNRET_END
ALTERNATIVE_3 "", \
CALL_UNTRAIN_RET, X86_FEATURE_UNRET, \
@@ -301,7 +300,7 @@
.macro UNTRAIN_RET_VM
#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
- defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO)
+ defined(CONFIG_CALL_DEPTH_TRACKING)
VALIDATE_UNRET_END
ALTERNATIVE_3 "", \
CALL_UNTRAIN_RET, X86_FEATURE_UNRET, \
@@ -312,7 +311,7 @@
.macro UNTRAIN_RET_FROM_CALL
#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
- defined(CONFIG_CALL_DEPTH_TRACKING)
+ defined(CONFIG_CALL_DEPTH_TRACKING)
VALIDATE_UNRET_END
ALTERNATIVE_3 "", \
CALL_UNTRAIN_RET, X86_FEATURE_UNRET, \
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -141,13 +141,13 @@ SECTIONS
STATIC_CALL_TEXT
ALIGN_ENTRY_TEXT_BEGIN
-#ifdef CONFIG_CPU_SRSO
+#ifdef CONFIG_CPU_UNRET_ENTRY
*(.text.__x86.rethunk_untrain)
#endif
ENTRY_TEXT
-#ifdef CONFIG_CPU_SRSO
+#ifdef CONFIG_CPU_UNRET_ENTRY
/*
* See the comment above srso_untrain_ret_alias()'s
* definition.
@@ -522,12 +522,9 @@ INIT_PER_CPU(irq_stack_backing_store);
"fixed_percpu_data is not at start of per-cpu area");
#endif
-#ifdef CONFIG_RETHUNK
+#ifdef CONFIG_CPU_UNRET_ENTRY
. = ASSERT((__x86_return_thunk & 0x3f) == 0, "__x86_return_thunk not cacheline-aligned");
. = ASSERT((srso_safe_ret & 0x3f) == 0, "srso_safe_ret not cacheline-aligned");
-#endif
-
-#ifdef CONFIG_CPU_SRSO
/*
* GNU ld cannot do XOR so do: (A | B) - (A & B) in order to compute the XOR
* of the two function addresses:
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -132,6 +132,7 @@ SYM_CODE_END(__x86_indirect_jump_thunk_a
*/
#ifdef CONFIG_RETHUNK
+#ifdef CONFIG_CPU_UNRET_ENTRY
/*
* srso_untrain_ret_alias() and srso_safe_ret_alias() are placed at
* special addresses:
@@ -147,7 +148,6 @@ SYM_CODE_END(__x86_indirect_jump_thunk_a
*
* As a result, srso_safe_ret_alias() becomes a safe return.
*/
-#ifdef CONFIG_CPU_SRSO
.section .text.__x86.rethunk_untrain
SYM_START(srso_untrain_ret_alias, SYM_L_GLOBAL, SYM_A_NONE)
@@ -160,14 +160,11 @@ SYM_FUNC_END(srso_untrain_ret_alias)
__EXPORT_THUNK(srso_untrain_ret_alias)
.section .text.__x86.rethunk_safe
-#endif
/* Needs a definition for the __x86_return_thunk alternative below. */
SYM_START(srso_safe_ret_alias, SYM_L_GLOBAL, SYM_A_NONE)
-#ifdef CONFIG_CPU_SRSO
add $8, %_ASM_SP
UNWIND_HINT_FUNC
-#endif
ANNOTATE_UNRET_SAFE
ret
int3
@@ -236,8 +233,6 @@ SYM_CODE_END(__x86_return_thunk)
SYM_FUNC_END(zen_untrain_ret)
__EXPORT_THUNK(zen_untrain_ret)
-EXPORT_SYMBOL(__x86_return_thunk)
-
/*
* SRSO untraining sequence for Zen1/2, similar to zen_untrain_ret()
* above. On kernel entry, srso_untrain_ret() is executed which is a
@@ -293,6 +288,22 @@ SYM_CODE_START(srso_alias_return_thunk)
ud2
SYM_CODE_END(srso_alias_return_thunk)
+#else /* CONFIG_CPU_UNRET_ENTRY */
+
+ .section .text.__x86.return_thunk
+
+SYM_CODE_START(__x86_return_thunk)
+ UNWIND_HINT_FUNC
+ ANNOTATE_NOENDBR
+ ANNOTATE_UNRET_SAFE
+ ret
+ int3
+SYM_CODE_END(__x86_return_thunk)
+
+#endif /* CONFIG_CPU_UNRET_ENTRY */
+
+__EXPORT_THUNK(__x86_return_thunk)
+
#endif /* CONFIG_RETHUNK */
#ifdef CONFIG_CALL_DEPTH_TRACKING
On Wed, Aug 09, 2023 at 09:12:27AM +0200, Peter Zijlstra wrote:
> -#endif
>
> /* Needs a definition for the __x86_return_thunk alternative below. */
> SYM_START(srso_safe_ret_alias, SYM_L_GLOBAL, SYM_A_NONE)
> -#ifdef CONFIG_CPU_SRSO
The comment is no longer needed.
--
Josh