linux-kernel - [PATCH 3/3] x86/unwind_user: Guard unwind_user_word_size() by UNWIND

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Message-ID: <20251125164349.2592874-4-jremus@linux.ibm.com>
Date: Tue, 25 Nov 2025 17:43:49 +0100
From: Jens Remus <jremus@...ux.ibm.com>
To: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
        x86@...nel.org, Steven Rostedt <rostedt@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Cc: Jens Remus <jremus@...ux.ibm.com>, Josh Poimboeuf <jpoimboe@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Indu Bhagat <indu.bhagat@...cle.com>,
        "Jose E. Marchesi" <jemarch@....org>,
        Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
        Ilya Leoshkevich <iii@...ux.ibm.com>
Subject: [PATCH 3/3] x86/unwind_user: Guard unwind_user_word_size() by UNWIND_USER

The unwind user framework in general requires an architecture-specific
implementation of unwind_user_word_size() to be present for any unwind
method, whether that is fp or a future other method, such as potentially
sframe.

Guard unwind_user_word_size() by the availability of the UNWIND_USER
framework instead of the specific HAVE_UNWIND_USER_FP method.

This facilitates to selectively disable HAVE_UNWIND_USER_FP on x86
(e.g. for test purposes) once a new unwind method is added to unwind
user.

Signed-off-by: Jens Remus <jremus@...ux.ibm.com>
---
 arch/x86/include/asm/unwind_user.h | 28 ++++++++++++++++------------
 1 file changed, 16 insertions(+), 12 deletions(-)

diff --git a/arch/x86/include/asm/unwind_user.h b/arch/x86/include/asm/unwind_user.h
index 12064284bc4e..77d776c7fca9 100644
--- a/arch/x86/include/asm/unwind_user.h
+++ b/arch/x86/include/asm/unwind_user.h
@@ -2,6 +2,22 @@
 #ifndef _ASM_X86_UNWIND_USER_H
 #define _ASM_X86_UNWIND_USER_H
 
+#ifdef CONFIG_UNWIND_USER
+
+static inline int unwind_user_word_size(struct pt_regs *regs)
+{
+	/* We can't unwind VM86 stacks */
+	if (regs->flags & X86_VM_MASK)
+		return 0;
+#ifdef CONFIG_X86_64
+	if (!user_64bit_mode(regs))
+		return sizeof(int);
+#endif
+	return sizeof(long);
+}
+
+#endif /* CONFIG_UNWIND_USER */
+
 #ifdef CONFIG_HAVE_UNWIND_USER_FP
 
 #include <asm/ptrace.h>
@@ -19,18 +35,6 @@
 	.fp_off		= 0,				\
 	.use_fp		= false,
 
-static inline int unwind_user_word_size(struct pt_regs *regs)
-{
-	/* We can't unwind VM86 stacks */
-	if (regs->flags & X86_VM_MASK)
-		return 0;
-#ifdef CONFIG_X86_64
-	if (!user_64bit_mode(regs))
-		return sizeof(int);
-#endif
-	return sizeof(long);
-}
-
 static inline bool unwind_user_at_function_start(struct pt_regs *regs)
 {
 	return is_uprobe_at_func_entry(regs);
-- 
2.51.0