[tip: x86/core] x86/alternatives: Clean up preprocessor conditional block comments

[tip-bot2 for Ingo Molnar]

The following commit has been merged into the x86/core branch of tip:

Commit-ID:     5d703825fde301677e8a79b0738927490407f435
Gitweb:        https://git.kernel.org/tip/5d703825fde301677e8a79b0738927490407f435
Author:        Ingo Molnar <mingo@xxxxxxxxxx>
AuthorDate:    Wed, 26 Feb 2025 12:15:15 +01:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Wed, 26 Feb 2025 12:15:15 +01:00

x86/alternatives: Clean up preprocessor conditional block comments

When in the middle of a kernel source code file a kernel developer
sees a lone #else or #endif:

   ...

   #else

   ...

It's not obvious at a glance what those preprocessor blocks are
conditional on, if the starting #ifdef is outside visible range.

So apply the standard pattern we use in such cases elsewhere in
the kernel for large preprocessor blocks:

  #ifdef CONFIG_XXX
  ...
  ...
  ...
  #endif /* CONFIG_XXX */

  ...

  #ifdef CONFIG_XXX
  ...
  ...
  ...
  #else /* !CONFIG_XXX: */
  ...
  ...
  ...
  #endif /* !CONFIG_XXX */

( Note that in the  #else case we use the /* !CONFIG_XXX */ marker
  in the final #endif, not /* CONFIG_XXX */, which serves as an easy
  visual marker to differentiate #else or #elif related #endif closures
  from singular #ifdef/#endif blocks. )

Also clean up __CFI_DEFAULT definition with a bit more vertical alignment
applied, and a pointless tab converted to the standard space we use in
such definitions.

Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
 arch/x86/kernel/alternative.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 83316ea..ea68f0e 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -839,16 +839,16 @@ void __init_or_module noinline apply_returns(s32 *start, s32 *end)
 		}
 	}
 }
-#else
+#else /* !CONFIG_MITIGATION_RETHUNK: */
 void __init_or_module noinline apply_returns(s32 *start, s32 *end) { }
-#endif /* CONFIG_MITIGATION_RETHUNK */
+#endif /* !CONFIG_MITIGATION_RETHUNK */
 
 #else /* !CONFIG_MITIGATION_RETPOLINE || !CONFIG_OBJTOOL */
 
 void __init_or_module noinline apply_retpolines(s32 *start, s32 *end) { }
 void __init_or_module noinline apply_returns(s32 *start, s32 *end) { }
 
-#endif /* CONFIG_MITIGATION_RETPOLINE && CONFIG_OBJTOOL */
+#endif /* !CONFIG_MITIGATION_RETPOLINE || !CONFIG_OBJTOOL */
 
 #ifdef CONFIG_X86_KERNEL_IBT
 
@@ -916,18 +916,18 @@ void __init_or_module noinline apply_seal_endbr(s32 *start, s32 *end)
 	}
 }
 
-#else
+#else /* !CONFIG_X86_KERNEL_IBT: */
 
 void __init_or_module apply_seal_endbr(s32 *start, s32 *end) { }
 
-#endif /* CONFIG_X86_KERNEL_IBT */
+#endif /* !CONFIG_X86_KERNEL_IBT */
 
 #ifdef CONFIG_CFI_AUTO_DEFAULT
-#define __CFI_DEFAULT	CFI_AUTO
+# define __CFI_DEFAULT CFI_AUTO
 #elif defined(CONFIG_CFI_CLANG)
-#define __CFI_DEFAULT	CFI_KCFI
+# define __CFI_DEFAULT CFI_KCFI
 #else
-#define __CFI_DEFAULT	CFI_OFF
+# define __CFI_DEFAULT CFI_OFF
 #endif
 
 enum cfi_mode cfi_mode __ro_after_init = __CFI_DEFAULT;
@@ -1457,7 +1457,7 @@ Efault:
 	return false;
 }
 
-#else
+#else /* !CONFIG_FINEIBT: */
 
 static void __apply_fineibt(s32 *start_retpoline, s32 *end_retpoline,
 			    s32 *start_cfi, s32 *end_cfi, bool builtin)
@@ -1468,7 +1468,7 @@ static void __apply_fineibt(s32 *start_retpoline, s32 *end_retpoline,
 static void poison_cfi(void *addr) { }
 #endif
 
-#endif
+#endif /* !CONFIG_FINEIBT */
 
 void apply_fineibt(s32 *start_retpoline, s32 *end_retpoline,
 		   s32 *start_cfi, s32 *end_cfi)