[PATCH v8 07/43] vmlinux.lds.h: Fix ALIGN(8) omission causing NULL ptr on i386

From: Jim Cromie via B4 Relay <devnull+jim.cromie.gmail.com@kernel.org>
Date: 2026-09-05 18:13:58
Also in: b4-sent, dri-devel, linux-arch, linux-doc, linux-kbuild, linux-kselftest, lkml
Reply to: Jim Cromie via B4 Relay, 2026-09-05

From: Jim Cromie <jim.cromie@gmail.com>

Almost all uses of the BOUNDED_SECTION macros are ALIGN(8), either
explicitly, or by being below an aligned section containing x*8 byte
objects.  The noteworthy exception is BOUNDED_SECTION(__dyndbg), which
immediately follows BOUNDED_SECTION(__dyndbg_classes).

On i386, struct _ddebug_classmap is 28 bytes, so without an explicit
ALIGN(8) in the macro, the following __dyndbg section gets misaligned,
causing a NULL ptr deref in dynamic_debug_init().

So fix this with an explicit ALIGN(8) in the existing BOUNDED_SECTION
macros, and introduce _ALIGNED variants to handle the cases with an
explicit . = ALIGN(x)

Also add explicit alignments for: EXCEPTION_TABLE, ORC_UNWIND_TABLE,
TRACEDATA, INIT_SETUP, and NOTES.

update BOUNDED_SECTION uses inside . = ALIGN(x) stanzas to use
_ALIGNED variants, but keep the outer ALIGNs so the symbols between
them are not "re-aligned".

In particular, scripts/sorttable.c does not tolerate sloppy padding.

At the top of ORC_UNWIND_TABLE, add . = ALIGN(4) to match the struct
orc_header __align() call in the code:

commit b9f174c811e3 ("x86/unwind/orc: Add ELF section with ORC version identifier")

Suggested-by: Louis Chauvet <louis.chauvet@bootlin.com>  # _ALIGNED variants.
Link: https://lore.kernel.org/lkml/177402491426.6181.12855763650074831089.b4-review@b4/ (local)
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
v3:

sashiko complained about NOTES and .BTF_ids.
gemini asserts that NOTES are natively 4-byte aligned, add comment repeating it.
.BTF_ids doesnt use BOUNDED_BY, since start/end isnt needed;
sashiko evidently got confused by immediately preceding usage.

v2:

sashiko picked up 2 cases, added to the explicit list above
https://sashiko.dev/#/patchset/20260515-asm-generic-1-v3-0-680b273666d4%40gmail.com
---
 include/asm-generic/bounded_sections.lds.h | 17 ++++++++++++++---
 include/asm-generic/vmlinux.lds.h          | 18 ++++++++++--------
 2 files changed, 24 insertions(+), 11 deletions(-)

diff --git a/include/asm-generic/bounded_sections.lds.h b/include/asm-generic/bounded_sections.lds.h
index 268cdc34389b..8ff3e3420f60 100644
--- a/include/asm-generic/bounded_sections.lds.h
+++ b/include/asm-generic/bounded_sections.lds.h

@@ -3,19 +3,30 @@
 #ifndef _ASM_GENERIC_BOUNDED_SECTIONS_H
 #define _ASM_GENERIC_BOUNDED_SECTIONS_H
 
-#define BOUNDED_SECTION_PRE_LABEL(_sec_, _label_, _BEGIN_, _END_)	\
+#define BOUNDED_SECTION_PRE_LABEL_ALIGNED(_sec_, _label_, _BEGIN_, _END_, _ALIGNED_) \
+	. = ALIGN(_ALIGNED_);						\
 	_BEGIN_##_label_ = .;						\
 	KEEP(*(_sec_))							\
 	_END_##_label_ = .;
 
-#define BOUNDED_SECTION_POST_LABEL(_sec_, _label_, _BEGIN_, _END_)	\
+#define BOUNDED_SECTION_PRE_LABEL(_sec_, _label_, _BEGIN_, _END_)	\
+	BOUNDED_SECTION_PRE_LABEL_ALIGNED(_sec_, _label_, _BEGIN_, _END_, 8)
+
+#define BOUNDED_SECTION_POST_LABEL_ALIGNED(_sec_, _label_, _BEGIN_, _END_, _ALIGNED_) \
+	. = ALIGN(_ALIGNED_);						\
 	_label_##_BEGIN_ = .;						\
 	KEEP(*(_sec_))							\
 	_label_##_END_ = .;
 
+#define BOUNDED_SECTION_POST_LABEL(_sec_, _label_, _BEGIN_, _END_)	\
+	BOUNDED_SECTION_POST_LABEL_ALIGNED(_sec_, _label_, _BEGIN_, _END_, 8)
+
 #define BOUNDED_SECTION_BY(_sec_, _label_)				\
 	BOUNDED_SECTION_PRE_LABEL(_sec_, _label_, __start, __stop)
 
-#define BOUNDED_SECTION(_sec)	 BOUNDED_SECTION_BY(_sec, _sec)
+#define BOUNDED_SECTION_BY_ALIGNED(_sec_, _label_, _ALIGNED_)		\
+	BOUNDED_SECTION_PRE_LABEL_ALIGNED(_sec_, _label_, __start, __stop, _ALIGNED_)
+
+#define BOUNDED_SECTION(_sec)   BOUNDED_SECTION_BY(_sec, _sec)
 
 #endif /* _ASM_GENERIC_BOUNDED_SECTIONS_H */

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index b4ece391f7b1..b1a69f8af6d2 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h

@@ -640,7 +640,7 @@
 #define EXCEPTION_TABLE(align)						\
 	. = ALIGN(align);						\
 	__ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) {		\
-		BOUNDED_SECTION_BY(__ex_table, ___ex_table)		\
+		BOUNDED_SECTION_BY_ALIGNED(__ex_table, ___ex_table, align) \
 	}
 
 /*

@@ -650,7 +650,7 @@
 #define BTF								\
 	. = ALIGN(PAGE_SIZE);						\
 	.BTF : AT(ADDR(.BTF) - LOAD_OFFSET) {				\
-		BOUNDED_SECTION_BY(.BTF, _BTF)				\
+		BOUNDED_SECTION_BY_ALIGNED(.BTF, _BTF, PAGE_SIZE)	\
 	}								\
 	. = ALIGN(PAGE_SIZE);						\
 	.BTF_ids : AT(ADDR(.BTF_ids) - LOAD_OFFSET) {			\

@@ -840,16 +840,17 @@
 
 #ifdef CONFIG_UNWINDER_ORC
 #define ORC_UNWIND_TABLE						\
+	. = ALIGN(4);							\
 	.orc_header : AT(ADDR(.orc_header) - LOAD_OFFSET) {		\
-		BOUNDED_SECTION_BY(.orc_header, _orc_header)		\
+		BOUNDED_SECTION_BY_ALIGNED(.orc_header, _orc_header, 4)	\
 	}								\
 	. = ALIGN(4);							\
 	.orc_unwind_ip : AT(ADDR(.orc_unwind_ip) - LOAD_OFFSET) {	\
-		BOUNDED_SECTION_BY(.orc_unwind_ip, _orc_unwind_ip)	\
+		BOUNDED_SECTION_BY_ALIGNED(.orc_unwind_ip, _orc_unwind_ip, 4)\
 	}								\
 	. = ALIGN(2);							\
 	.orc_unwind : AT(ADDR(.orc_unwind) - LOAD_OFFSET) {		\
-		BOUNDED_SECTION_BY(.orc_unwind, _orc_unwind)		\
+		BOUNDED_SECTION_BY_ALIGNED(.orc_unwind, _orc_unwind, 2)	\
 	}								\
 	text_size = _etext - _stext;					\
 	. = ALIGN(4);							\

@@ -877,7 +878,7 @@
 #define TRACEDATA							\
 	. = ALIGN(4);							\
 	.tracedata : AT(ADDR(.tracedata) - LOAD_OFFSET) {		\
-		BOUNDED_SECTION_POST_LABEL(.tracedata, __tracedata, _start, _end) \
+		BOUNDED_SECTION_POST_LABEL_ALIGNED(.tracedata, __tracedata, _start, _end, 4) \
 	}
 #else
 #define TRACEDATA

@@ -906,13 +907,14 @@
 		*(.note.gnu.property)					\
 	}								\
 	.notes : AT(ADDR(.notes) - LOAD_OFFSET) {			\
-		BOUNDED_SECTION_BY(.note.*, _notes)			\
+		/* *(.note.*) are natively 4-byte aligned */		\
+		BOUNDED_SECTION_BY_ALIGNED(.note.*, _notes, 4)		\
 	} NOTES_HEADERS							\
 	NOTES_HEADERS_RESTORE
 
 #define INIT_SETUP(initsetup_align)					\
 		. = ALIGN(initsetup_align);				\
-		BOUNDED_SECTION_POST_LABEL(.init.setup, __setup, _start, _end)
+		BOUNDED_SECTION_POST_LABEL_ALIGNED(.init.setup, __setup, _start, _end, initsetup_align)
 
 #define INIT_CALLS_LEVEL(level)						\
 		__initcall##level##_start = .;				\

-- 
2.55.0

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