[PATCH v6 03/24] vmlinux.lds.h: Fix ALIGN(8) omission causing NULL ptr on i386
From: Jim Cromie <jim.cromie@gmail.com>
Date: 2026-07-08 02:18:33
Also in:
dri-devel, linux-arch, linux-doc, lkml
Subsystem:
generic include/asm header files, the rest · Maintainers:
Arnd Bergmann, Linus Torvalds
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 f5ddf31b7f26..f29fc079e37e 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) { \
@@ -832,16 +832,17 @@ #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); \
@@ -869,7 +870,7 @@ #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
@@ -898,13 +899,14 @@ *(.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