On Thu, Oct 12, 2023 at 05:50:35PM -0000, tip-bot2 for David Kaplan wrote:
> SYM_CODE_START(__x86_return_thunk)
> UNWIND_HINT_FUNC
> ANNOTATE_NOENDBR
> - ANNOTATE_UNRET_SAFE
> - ret
> + ALTERNATIVE __stringify(ANNOTATE_UNRET_SAFE;ret),"ud2", X86_FEATURE_ALWAYS
I'm wondering if panicking people's boxes isn't too harsh.
Also, we don't BUG() if we can continue so perhaps this should be
a really loud warn instead:
---
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index f93e9b96927a..f230f396c9c1 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -357,6 +357,8 @@ extern void entry_ibpb(void);
extern void (*x86_return_thunk)(void);
+extern void check_thunks(void);
+
#ifdef CONFIG_CALL_DEPTH_TRACKING
extern void call_depth_return_thunk(void);
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index bb0ab8466b91..e4b2dfbf3de5 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2849,3 +2849,8 @@ ssize_t cpu_show_gds(struct device *dev, struct device_attribute *attr, char *bu
return cpu_show_common(dev, attr, buf, X86_BUG_GDS);
}
#endif
+
+void check_thunks(void)
+{
+ WARN(1, "Unconverted return thunk\n");
+}
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index 3f3a478b74dd..ca9024ef0a7c 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -366,8 +366,7 @@ SYM_FUNC_END(call_depth_return_thunk)
SYM_CODE_START(__x86_return_thunk)
UNWIND_HINT_FUNC
ANNOTATE_NOENDBR
- ALTERNATIVE __stringify(ANNOTATE_UNRET_SAFE;ret),"ud2", X86_FEATURE_ALWAYS
- int3
+ ALTERNATIVE __stringify(ANNOTATE_UNRET_SAFE;ret;int3),"call check_thunks; ret", X86_FEATURE_ALWAYS
SYM_CODE_END(__x86_return_thunk)
EXPORT_SYMBOL(__x86_return_thunk)
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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