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

From: Ard Biesheuvel
Date: Mon Nov 25 2024 - 12:05:18 EST


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