On Wed, Apr 03, 2024 at 07:10:17PM +0200, Klara Modin wrote:
> With this patch/commit, one of my machines (older P4 Xeon, 32-bit only)
> hangs on boot with CONFIG_RETHUNK=y / CONFIG_MITIGATION_RETHUNK=y.
Ok, this should fix it:
---
From: "Borislav Petkov (AMD)" <bp@xxxxxxxxx>
Date: Mon, 15 Apr 2024 18:15:43 +0200
Subject: [PATCH] x86/retpolines: Enable the default thunk warning only on relevant configs
The using-default-thunk warning check makes sense only with
configurations which actually enable the special return thunks.
Otherwise, it fires on unrelated 32-bit configs on which the special
return thunks won't even work (they're 64-bit only) and, what is more,
those configs even go off into the weeds when booting in the
alternatives patching code, leading to a dead machine.
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Link: https://lore.kernel.org/r/78e0d19c-b77a-4169-a80f-2eef91f4a1d6@xxxxxxxxx
Link: https://lore.kernel.org/r/20240413024956.488d474e@yea
---
arch/x86/lib/retpoline.S | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index e674ccf720b9..391059b2c6fb 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -382,8 +382,15 @@ SYM_FUNC_END(call_depth_return_thunk)
SYM_CODE_START(__x86_return_thunk)
UNWIND_HINT_FUNC
ANNOTATE_NOENDBR
+#if defined(CONFIG_MITIGATION_UNRET_ENTRY) || \
+ defined(CONFIG_MITIGATION_SRSO) || \
+ defined(CONFIG_MITIGATION_CALL_DEPTH_TRACKING)
ALTERNATIVE __stringify(ANNOTATE_UNRET_SAFE; ret), \
"jmp warn_thunk_thunk", X86_FEATURE_ALWAYS
+#else
+ ANNOTATE_UNRET_SAFE
+ ret
+#endif
int3
SYM_CODE_END(__x86_return_thunk)
EXPORT_SYMBOL(__x86_return_thunk)
--
2.43.0
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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