linux-kernel - [PATCH v3 11/19] x86: Move return_thunk to _

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Date: Mon, 29 Jan 2024 19:05:14 +0100
From: Ard Biesheuvel <ardb+git@...gle.com>
To: linux-kernel@...r.kernel.org
Cc: Ard Biesheuvel <ardb@...nel.org>, Kevin Loughlin <kevinloughlin@...gle.com>, 
	Tom Lendacky <thomas.lendacky@....com>, Dionna Glaze <dionnaglaze@...gle.com>, 
	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, Andy Lutomirski <luto@...nel.org>, 
	Arnd Bergmann <arnd@...db.de>, Nathan Chancellor <nathan@...nel.org>, 
	Nick Desaulniers <ndesaulniers@...gle.com>, Justin Stitt <justinstitt@...gle.com>, 
	Kees Cook <keescook@...omium.org>, Brian Gerst <brgerst@...il.com>, linux-arch@...r.kernel.org, 
	llvm@...ts.linux.dev
Subject: [PATCH v3 11/19] x86: Move return_thunk to __pitext section

From: Ard Biesheuvel <ardb@...nel.org>

The x86 return thunk will function correctly even when it is called via
a different virtual mapping than the one it was linked at, so it can
safely be moved to .pi.text. This allows other code in that section to
call it.

Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 arch/x86/kernel/vmlinux.lds.S | 2 +-
 arch/x86/lib/retpoline.S      | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index a349dbfc6d5a..77262e804250 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -134,7 +134,7 @@ SECTIONS
 		SOFTIRQENTRY_TEXT
 #ifdef CONFIG_RETPOLINE
 		*(.text..__x86.indirect_thunk)
-		*(.text..__x86.return_thunk)
+		*(.pi.text..__x86.return_thunk)
 #endif
 		STATIC_CALL_TEXT
 
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index 7b2589877d06..003b35445bbb 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -136,7 +136,7 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array)
  * relocations for same-section JMPs and that breaks the returns
  * detection logic in apply_returns() and in objtool.
  */
-	.section .text..__x86.return_thunk
+	.section .pi.text..__x86.return_thunk, "ax"
 
 #ifdef CONFIG_CPU_SRSO
 
-- 
2.43.0.429.g432eaa2c6b-goog