[PATCH v3 4/6] x86/kernel: Move ENTRY_TEXT to the start of the image

[Ard Biesheuvel]

From: Ard Biesheuvel <ardb@xxxxxxxxxx>

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.

Considering that ENTRY_TEXT needs to appear PMD-aligned, move it to the
start of the image, where the alignment requirement is trivially met.
Doing so removes the need to place ENTRY_TEXT at the end of .text and
right before .rodata, which appears PMD aligned as well. This will allow
.head.text to be moved into a separate output section in a subsequent
patch, without incurring more padding overhead.

Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
---
 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 68efd8cd8bf1..c98bc91bafef 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
-- 
2.47.0.371.ga323438b13-goog