linux-kernel - [RFC/RFT PATCH 12/19] x86/sync_core: Use RIP-relative addressing

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Message-ID: <20260108092526.28586-33-ardb@kernel.org>
Date: Thu,  8 Jan 2026 09:25:39 +0000
From: Ard Biesheuvel <ardb@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: x86@...nel.org,
	Ard Biesheuvel <ardb@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Kees Cook <kees@...nel.org>,
	Uros Bizjak <ubizjak@...il.com>,
	Brian Gerst <brgerst@...il.com>,
	linux-hardening@...r.kernel.org
Subject: [RFC/RFT PATCH 12/19] x86/sync_core: Use RIP-relative addressing

Use RIP-relative accesses for sync_core(). This removes a 32-bit
absolute reference that requires fixing up at runtime when KASLR is
enabled. This is a prerequisite for PIE linking, which only permits
64-bit wide loader-visible absolute references.

Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 arch/x86/include/asm/sync_core.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/sync_core.h b/arch/x86/include/asm/sync_core.h
index 96bda43538ee..547fdc690ecc 100644
--- a/arch/x86/include/asm/sync_core.h
+++ b/arch/x86/include/asm/sync_core.h
@@ -31,7 +31,8 @@ static __always_inline void iret_to_self(void)
 		"pushfq\n\t"
 		"mov %%cs, %0\n\t"
 		"pushq %q0\n\t"
-		"pushq $1f\n\t"
+		"leaq 1f(%%rip), %q0\n\t"
+		"pushq %q0\n\t"
 		"iretq\n\t"
 		"1:"
 		: "=&r" (tmp), ASM_CALL_CONSTRAINT : : "cc", "memory");
-- 
2.47.3