linux-kernel - [PATCH] x86: select ARCH_WANT_FRAME_POINTERS again when UNWINDER_FRAME

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Date: Sun,  4 Feb 2024 21:20:03 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: x86@...nel.org
Cc: Josh Poimboeuf <jpoimboe@...nel.org>,
	Masahiro Yamada <masahiroy@...nel.org>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] x86: select ARCH_WANT_FRAME_POINTERS again when UNWINDER_FRAME_POINTER=y

It took me some time to understand the purpose of the tricky code at
the end of arch/x86/Kconfig.debug.

Without it, the following would be shown:

  WARNING: unmet direct dependencies detected for FRAME_POINTER

because commit 81d387190039 ("x86/kconfig: Consolidate unwinders into
multiple choice selection") removed 'select ARCH_WANT_FRAME_POINTERS'.

The correct and more straightforward approach should have been to move
it where 'select FRAME_POINTER' is located.

Several architectures properly handle the conditional selection of
ARCH_WANT_FRAME_POINTERS. For example, 'config UNWINDER_FRAME_POINTER'
in arch/arm/Kconfig.debug.

Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
---

 arch/x86/Kconfig.debug | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index c5d614d28a75..74777a97e394 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -248,6 +248,7 @@ config UNWINDER_ORC

 config UNWINDER_FRAME_POINTER
 	bool "Frame pointer unwinder"
+	select ARCH_WANT_FRAME_POINTERS
 	select FRAME_POINTER
 	help
 	  This option enables the frame pointer unwinder for unwinding kernel
@@ -271,7 +272,3 @@ config UNWINDER_GUESS
 	  overhead.

 endchoice
-
-config FRAME_POINTER
-	depends on !UNWINDER_ORC && !UNWINDER_GUESS
-	bool
-- 
2.40.1