linux-kernel - [PATCH 1/2] x86/vdso: Fix output operand size of RDPID insn

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Message-ID: <20250616095315.230620-1-ubizjak@gmail.com>
Date: Mon, 16 Jun 2025 11:52:57 +0200
From: Uros Bizjak <ubizjak@...il.com>
To: x86@...nel.org,
	linux-kernel@...r.kernel.org
Cc: Uros Bizjak <ubizjak@...il.com>,
	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>
Subject: [PATCH 1/2] x86/vdso: Fix output operand size of RDPID insn

RDPID instruction outputs to a word-sized register (64-bit on
x86_64 and 32-bit on x86_32). Use unsigned long variable to use
the correct size.

LSL outputs to 32-bit register, use %k operand prefix
to always print 32-bit name of the register.

Fixes: ffebbaedc861 ("x86/vdso: Introduce helper functions for CPU and node number")
Signed-off-by: Uros Bizjak <ubizjak@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
---
 arch/x86/include/asm/segment.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/segment.h b/arch/x86/include/asm/segment.h
index 77d8f49b92bd..93fcf0daba01 100644
--- a/arch/x86/include/asm/segment.h
+++ b/arch/x86/include/asm/segment.h
@@ -244,7 +244,7 @@ static inline unsigned long vdso_encode_cpunode(int cpu, unsigned long node)
 
 static inline void vdso_read_cpunode(unsigned *cpu, unsigned *node)
 {
-	unsigned int p;
+	unsigned long p;
 
 	/*
 	 * Load CPU and node number from the GDT.  LSL is faster than RDTSCP
@@ -254,7 +254,7 @@ static inline void vdso_read_cpunode(unsigned *cpu, unsigned *node)
 	 *
 	 * If RDPID is available, use it.
 	 */
-	alternative_io ("lsl %[seg],%[p]",
+	alternative_io ("lsl %[seg],%k[p]",
 			".byte 0xf3,0x0f,0xc7,0xf8", /* RDPID %eax/rax */
 			X86_FEATURE_RDPID,
 			[p] "=a" (p), [seg] "r" (__CPUNODE_SEG));
-- 
2.49.0