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Message-ID: <20230809072200.450404700@infradead.org>
User-Agent: quilt/0.66
Date:   Wed, 09 Aug 2023 09:12:19 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     x86@kernel.org
Cc:     linux-kernel@vger.kernel.org, peterz@infradead.org,
        David.Kaplan@amd.com, Andrew.Cooper3@citrix.com,
        jpoimboe@kernel.org, gregkh@linuxfoundation.org
Subject: [RFC][PATCH 01/17] x86/alternative: Unconditional custom return thunk
References: <20230809071218.000335006@infradead.org>
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There is infrastructure to rewrite return thunks to point to any
random thunk one desires, unwrap that from CALL_THUNKS, which up to
now was the sole user of that.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 arch/x86/include/asm/nospec-branch.h |    4 ----
 arch/x86/kernel/alternative.c        |    2 --
 2 files changed, 6 deletions(-)

--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -347,11 +347,7 @@ extern void srso_untrain_ret(void);
 extern void srso_untrain_ret_alias(void);
 extern void entry_ibpb(void);
 
-#ifdef CONFIG_CALL_THUNKS
 extern void (*x86_return_thunk)(void);
-#else
-#define x86_return_thunk	(&__x86_return_thunk)
-#endif
 
 #ifdef CONFIG_CALL_DEPTH_TRACKING
 extern void __x86_return_skl(void);
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -698,9 +698,7 @@ void __init_or_module noinline apply_ret
 
 #ifdef CONFIG_RETHUNK
 
-#ifdef CONFIG_CALL_THUNKS
 void (*x86_return_thunk)(void) __ro_after_init = &__x86_return_thunk;
-#endif
 
 /*
  * Rewrite the compiler generated return thunk tail-calls.