linux-kernel - [PATCH v4 5/7] x86/kernel: Move ENTRY

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Message-ID: <20241205112804.3416920-14-ardb+git@google.com>
Date: Thu,  5 Dec 2024 12:28:10 +0100
From: Ard Biesheuvel <ardb+git@...gle.com>
To: linux-kernel@...r.kernel.org
Cc: x86@...nel.org, Ard Biesheuvel <ardb@...nel.org>, Tom Lendacky <thomas.lendacky@....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>, Kees Cook <keescook@...omium.org>, Brian Gerst <brgerst@...il.com>, 
	Kevin Loughlin <kevinloughlin@...gle.com>
Subject: [PATCH v4 5/7] x86/kernel: Move ENTRY_TEXT to the start of the image

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

Since commit

  7734a0f31e99 ("x86/boot: Robustify calling startup_{32,64}() from the decompressor code")

it is no longer necessary for .head.text to appear at the start of the
image. Since ENTRY_TEXT needs to appear PMD-aligned, it is easier to
just place it at the start of the image, rather than line it up with the
end of the .text section. The amount of padding required should be the
same, but this arrangement also permits .head.text to be split off and
emitted separately, which is needed by a subsequent change.

Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 arch/x86/kernel/vmlinux.lds.S | 26 ++++++++++----------
 1 file changed, 13 insertions(+), 13 deletions(-)

diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index fab3ac9a4574..1ce7889cd12b 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -121,19 +121,6 @@ SECTIONS
 	.text :  AT(ADDR(.text) - LOAD_OFFSET) {
 		_text = .;
 		_stext = .;
-		/* bootstrapping code */
-		HEAD_TEXT
-		TEXT_TEXT
-		SCHED_TEXT
-		LOCK_TEXT
-		KPROBES_TEXT
-		SOFTIRQENTRY_TEXT
-#ifdef CONFIG_MITIGATION_RETPOLINE
-		*(.text..__x86.indirect_thunk)
-		*(.text..__x86.return_thunk)
-#endif
-		STATIC_CALL_TEXT
-
 		ALIGN_ENTRY_TEXT_BEGIN
 		*(.text..__x86.rethunk_untrain)
 		ENTRY_TEXT
@@ -147,6 +134,19 @@ SECTIONS
 		*(.text..__x86.rethunk_safe)
 #endif
 		ALIGN_ENTRY_TEXT_END
+
+		/* bootstrapping code */
+		HEAD_TEXT
+		TEXT_TEXT
+		SCHED_TEXT
+		LOCK_TEXT
+		KPROBES_TEXT
+		SOFTIRQENTRY_TEXT
+#ifdef CONFIG_MITIGATION_RETPOLINE
+		*(.text..__x86.indirect_thunk)
+		*(.text..__x86.return_thunk)
+#endif
+		STATIC_CALL_TEXT
 		*(.gnu.warning)
 
 	} :text = 0xcccccccc
-- 
2.47.0.338.g60cca15819-goog