* [PATCH v2 1/5] vmlinux.lds.h: refactor BOUNDED_SECTION_* macros into bounded_sections.lds.h
2026-05-07 20:40 [PATCH v2 0/5] dyndbg: fix i386 alignment and KEEP module sections Jim Cromie
@ 2026-05-07 20:40 ` Jim Cromie
2026-05-07 20:40 ` [PATCH v2 2/5] vmlinux.lds.h: drop unused HEADERED_SECTION* macros Jim Cromie
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: Jim Cromie @ 2026-05-07 20:40 UTC (permalink / raw)
To: Arnd Bergmann, Jason Baron, Luis Chamberlain, Petr Pavlu,
Daniel Gomez, Sami Tolvanen, Aaron Tomlin
Cc: linux-arch, linux-kernel, linux-modules, Jim Cromie
Move BOUNDED_SECTION_* macros to a new helper file:
include/asm-generic/bounded_sections.lds.h and include it back into
vmlinux.lds.h. This allows its reuse later to fix a failure to keep
dyndbg sections in some circumstances.
NOTES:
These macros are only for use in vmlinux.lds.h, where the _start &
_end symbols are needed. Modules keep sections separate in ELF
sections, with their boundaries known, so the _start and _end are not
useful, and may confuse tools not expecting them.
This patch ignores a checkpatch warning, because new file is covered
by "GENERIC INCLUDE/ASM HEADER FILES" in MAINTAINERS
CC: Arnd Bergmann <arnd@arndb.de>
CC: linux-arch@vger.kernel.org
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
include/asm-generic/bounded_sections.lds.h | 36 ++++++++++++++++++++++++++++++
include/asm-generic/vmlinux.lds.h | 30 +------------------------
2 files changed, 37 insertions(+), 29 deletions(-)
diff --git a/include/asm-generic/bounded_sections.lds.h b/include/asm-generic/bounded_sections.lds.h
new file mode 100644
index 000000000000..8c29293ca7fb
--- /dev/null
+++ b/include/asm-generic/bounded_sections.lds.h
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#ifndef _ASM_GENERIC_BOUNDED_SECTIONS_H
+#define _ASM_GENERIC_BOUNDED_SECTIONS_H
+
+#define BOUNDED_SECTION_PRE_LABEL(_sec_, _label_, _BEGIN_, _END_) \
+ _BEGIN_##_label_ = .; \
+ KEEP(*(_sec_)) \
+ _END_##_label_ = .;
+
+#define BOUNDED_SECTION_POST_LABEL(_sec_, _label_, _BEGIN_, _END_) \
+ _label_##_BEGIN_ = .; \
+ KEEP(*(_sec_)) \
+ _label_##_END_ = .;
+
+#define BOUNDED_SECTION_BY(_sec_, _label_) \
+ BOUNDED_SECTION_PRE_LABEL(_sec_, _label_, __start, __stop)
+
+#define BOUNDED_SECTION(_sec) BOUNDED_SECTION_BY(_sec, _sec)
+
+#define HEADERED_SECTION_PRE_LABEL(_sec_, _label_, _BEGIN_, _END_, _HDR_) \
+ _HDR_##_label_ = .; \
+ KEEP(*(.gnu.linkonce.##_sec_)) \
+ BOUNDED_SECTION_PRE_LABEL(_sec_, _label_, _BEGIN_, _END_)
+
+#define HEADERED_SECTION_POST_LABEL(_sec_, _label_, _BEGIN_, _END_, _HDR_) \
+ _label_##_HDR_ = .; \
+ KEEP(*(.gnu.linkonce.##_sec_)) \
+ BOUNDED_SECTION_POST_LABEL(_sec_, _label_, _BEGIN_, _END_)
+
+#define HEADERED_SECTION_BY(_sec_, _label_) \
+ HEADERED_SECTION_PRE_LABEL(_sec_, _label_, __start, __stop)
+
+#define HEADERED_SECTION(_sec) HEADERED_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 60c8c22fd3e4..f78300aea8f6 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -211,35 +211,7 @@
# endif
#endif
-#define BOUNDED_SECTION_PRE_LABEL(_sec_, _label_, _BEGIN_, _END_) \
- _BEGIN_##_label_ = .; \
- KEEP(*(_sec_)) \
- _END_##_label_ = .;
-
-#define BOUNDED_SECTION_POST_LABEL(_sec_, _label_, _BEGIN_, _END_) \
- _label_##_BEGIN_ = .; \
- KEEP(*(_sec_)) \
- _label_##_END_ = .;
-
-#define BOUNDED_SECTION_BY(_sec_, _label_) \
- BOUNDED_SECTION_PRE_LABEL(_sec_, _label_, __start, __stop)
-
-#define BOUNDED_SECTION(_sec) BOUNDED_SECTION_BY(_sec, _sec)
-
-#define HEADERED_SECTION_PRE_LABEL(_sec_, _label_, _BEGIN_, _END_, _HDR_) \
- _HDR_##_label_ = .; \
- KEEP(*(.gnu.linkonce.##_sec_)) \
- BOUNDED_SECTION_PRE_LABEL(_sec_, _label_, _BEGIN_, _END_)
-
-#define HEADERED_SECTION_POST_LABEL(_sec_, _label_, _BEGIN_, _END_, _HDR_) \
- _label_##_HDR_ = .; \
- KEEP(*(.gnu.linkonce.##_sec_)) \
- BOUNDED_SECTION_POST_LABEL(_sec_, _label_, _BEGIN_, _END_)
-
-#define HEADERED_SECTION_BY(_sec_, _label_) \
- HEADERED_SECTION_PRE_LABEL(_sec_, _label_, __start, __stop)
-
-#define HEADERED_SECTION(_sec) HEADERED_SECTION_BY(_sec, _sec)
+#include <asm-generic/bounded_sections.lds.h>
#ifdef CONFIG_TRACE_BRANCH_PROFILING
#define LIKELY_PROFILE() \
--
2.54.0
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH v2 2/5] vmlinux.lds.h: drop unused HEADERED_SECTION* macros
2026-05-07 20:40 [PATCH v2 0/5] dyndbg: fix i386 alignment and KEEP module sections Jim Cromie
2026-05-07 20:40 ` [PATCH v2 1/5] vmlinux.lds.h: refactor BOUNDED_SECTION_* macros into bounded_sections.lds.h Jim Cromie
@ 2026-05-07 20:40 ` Jim Cromie
2026-05-07 20:40 ` [PATCH v2 3/5] vmlinux.lds.h: Fix ALIGN(8) omission causing NULL ptr on i386 Jim Cromie
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: Jim Cromie @ 2026-05-07 20:40 UTC (permalink / raw)
To: Arnd Bergmann, Jason Baron, Luis Chamberlain, Petr Pavlu,
Daniel Gomez, Sami Tolvanen, Aaron Tomlin
Cc: linux-arch, linux-kernel, linux-modules, Jim Cromie
These macros are unused, no point in carrying them any more.
NB: these macros were just moved to bounded_sections.lds.h, from
vmlinux.lds.h, which is the known entity, and therefore more
meaningful in the 1-line summary, so thats what I used as the topic.
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
include/asm-generic/bounded_sections.lds.h | 15 ---------------
1 file changed, 15 deletions(-)
diff --git a/include/asm-generic/bounded_sections.lds.h b/include/asm-generic/bounded_sections.lds.h
index 8c29293ca7fb..268cdc34389b 100644
--- a/include/asm-generic/bounded_sections.lds.h
+++ b/include/asm-generic/bounded_sections.lds.h
@@ -18,19 +18,4 @@
#define BOUNDED_SECTION(_sec) BOUNDED_SECTION_BY(_sec, _sec)
-#define HEADERED_SECTION_PRE_LABEL(_sec_, _label_, _BEGIN_, _END_, _HDR_) \
- _HDR_##_label_ = .; \
- KEEP(*(.gnu.linkonce.##_sec_)) \
- BOUNDED_SECTION_PRE_LABEL(_sec_, _label_, _BEGIN_, _END_)
-
-#define HEADERED_SECTION_POST_LABEL(_sec_, _label_, _BEGIN_, _END_, _HDR_) \
- _label_##_HDR_ = .; \
- KEEP(*(.gnu.linkonce.##_sec_)) \
- BOUNDED_SECTION_POST_LABEL(_sec_, _label_, _BEGIN_, _END_)
-
-#define HEADERED_SECTION_BY(_sec_, _label_) \
- HEADERED_SECTION_PRE_LABEL(_sec_, _label_, __start, __stop)
-
-#define HEADERED_SECTION(_sec) HEADERED_SECTION_BY(_sec, _sec)
-
#endif /* _ASM_GENERIC_BOUNDED_SECTIONS_H */
--
2.54.0
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH v2 3/5] vmlinux.lds.h: Fix ALIGN(8) omission causing NULL ptr on i386
2026-05-07 20:40 [PATCH v2 0/5] dyndbg: fix i386 alignment and KEEP module sections Jim Cromie
2026-05-07 20:40 ` [PATCH v2 1/5] vmlinux.lds.h: refactor BOUNDED_SECTION_* macros into bounded_sections.lds.h Jim Cromie
2026-05-07 20:40 ` [PATCH v2 2/5] vmlinux.lds.h: drop unused HEADERED_SECTION* macros Jim Cromie
@ 2026-05-07 20:40 ` Jim Cromie
2026-05-07 20:40 ` [PATCH v2 4/5] vmlinux.lds.h: remove redundant ALIGN(8) directives Jim Cromie
2026-05-07 20:40 ` [PATCH v2 5/5] dyndbg.lds.S: fix lost dyndbg sections in modules Jim Cromie
4 siblings, 0 replies; 6+ messages in thread
From: Jim Cromie @ 2026-05-07 20:40 UTC (permalink / raw)
To: Arnd Bergmann, Jason Baron, Luis Chamberlain, Petr Pavlu,
Daniel Gomez, Sami Tolvanen, Aaron Tomlin
Cc: linux-arch, linux-kernel, linux-modules, Jim Cromie,
Louis Chauvet
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)
Explicit alignments: EXCEPTION_TABLE, ORC_UNWIND_TABLE
update BOUNDED_SECTION uses inside . = ALIGN(x) 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/
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
include/asm-generic/bounded_sections.lds.h | 17 ++++++++++++++---
include/asm-generic/vmlinux.lds.h | 9 +++++----
2 files changed, 19 insertions(+), 7 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 f78300aea8f6..d3f20b411e16 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -641,7 +641,7 @@
#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) \
}
/*
@@ -833,16 +833,17 @@
#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); \
--
2.54.0
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH v2 4/5] vmlinux.lds.h: remove redundant ALIGN(8) directives
2026-05-07 20:40 [PATCH v2 0/5] dyndbg: fix i386 alignment and KEEP module sections Jim Cromie
` (2 preceding siblings ...)
2026-05-07 20:40 ` [PATCH v2 3/5] vmlinux.lds.h: Fix ALIGN(8) omission causing NULL ptr on i386 Jim Cromie
@ 2026-05-07 20:40 ` Jim Cromie
2026-05-07 20:40 ` [PATCH v2 5/5] dyndbg.lds.S: fix lost dyndbg sections in modules Jim Cromie
4 siblings, 0 replies; 6+ messages in thread
From: Jim Cromie @ 2026-05-07 20:40 UTC (permalink / raw)
To: Arnd Bergmann, Jason Baron, Luis Chamberlain, Petr Pavlu,
Daniel Gomez, Sami Tolvanen, Aaron Tomlin
Cc: linux-arch, linux-kernel, linux-modules, Jim Cromie
The BOUNDED_SECTION_PRE_LABEL and BOUNDED_SECTION_POST_LABEL macros
were recently updated to inherently enforce an 8-byte alignment. This
makes the explicit '. = ALIGN(8);' statements preceding 'naked' macro
calls in vmlinux.lds.h redundant.
Remove these redundant alignment directives to clean up the file and
clarify that the macros handle their own alignment padding.
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
include/asm-generic/vmlinux.lds.h | 13 -------------
1 file changed, 13 deletions(-)
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index d3f20b411e16..d9d2eb708355 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -229,7 +229,6 @@
#ifdef CONFIG_KPROBES
#define KPROBE_BLACKLIST() \
- . = ALIGN(8); \
BOUNDED_SECTION(_kprobe_blacklist)
#else
#define KPROBE_BLACKLIST()
@@ -245,7 +244,6 @@
#ifdef CONFIG_EVENT_TRACING
#define FTRACE_EVENTS() \
- . = ALIGN(8); \
BOUNDED_SECTION(_ftrace_events) \
BOUNDED_SECTION_BY(_ftrace_eval_map, _ftrace_eval_maps)
#else
@@ -262,7 +260,6 @@
#ifdef CONFIG_FTRACE_SYSCALLS
#define TRACE_SYSCALLS() \
- . = ALIGN(8); \
BOUNDED_SECTION_BY(__syscalls_metadata, _syscalls_metadata)
#else
#define TRACE_SYSCALLS()
@@ -277,7 +274,6 @@
#ifdef CONFIG_SERIAL_EARLYCON
#define EARLYCON_TABLE() \
- . = ALIGN(8); \
BOUNDED_SECTION_POST_LABEL(__earlycon_table, __earlycon_table, , _end)
#else
#define EARLYCON_TABLE()
@@ -285,11 +281,9 @@
#ifdef CONFIG_SECURITY
#define LSM_TABLE() \
- . = ALIGN(8); \
BOUNDED_SECTION_PRE_LABEL(.lsm_info.init, _lsm_info, __start, __end)
#define EARLY_LSM_TABLE() \
- . = ALIGN(8); \
BOUNDED_SECTION_PRE_LABEL(.early_lsm_info.init, _early_lsm_info, __start, __end)
#else
#define LSM_TABLE()
@@ -315,7 +309,6 @@
#ifdef CONFIG_ACPI
#define ACPI_PROBE_TABLE(name) \
- . = ALIGN(8); \
BOUNDED_SECTION_POST_LABEL(__##name##_acpi_probe_table, \
__##name##_acpi_probe_table,, _end)
#else
@@ -324,7 +317,6 @@
#ifdef CONFIG_THERMAL
#define THERMAL_TABLE(name) \
- . = ALIGN(8); \
BOUNDED_SECTION_POST_LABEL(__##name##_thermal_table, \
__##name##_thermal_table,, _end)
#else
@@ -404,12 +396,10 @@
__end_init_stack = .;
#define JUMP_TABLE_DATA \
- . = ALIGN(8); \
BOUNDED_SECTION_BY(__jump_table, ___jump_table)
#ifdef CONFIG_HAVE_STATIC_CALL_INLINE
#define STATIC_CALL_DATA \
- . = ALIGN(8); \
BOUNDED_SECTION_BY(.static_call_sites, _static_call_sites) \
BOUNDED_SECTION_BY(.static_call_tramp_key, _static_call_tramp_key)
#else
@@ -454,7 +444,6 @@
*(.rodata) *(.rodata.*) *(.data.rel.ro*) \
SCHED_DATA \
RO_AFTER_INIT_DATA /* Read only after init */ \
- . = ALIGN(8); \
BOUNDED_SECTION_BY(__tracepoints_ptrs, ___tracepoints_ptrs) \
*(__tracepoints_strings)/* Tracepoints: strings */ \
} \
@@ -947,12 +936,10 @@
/* Alignment must be consistent with (kunit_suite *) in include/kunit/test.h */
#define KUNIT_TABLE() \
- . = ALIGN(8); \
BOUNDED_SECTION_POST_LABEL(.kunit_test_suites, __kunit_suites, _start, _end)
/* Alignment must be consistent with (kunit_suite *) in include/kunit/test.h */
#define KUNIT_INIT_TABLE() \
- . = ALIGN(8); \
BOUNDED_SECTION_POST_LABEL(.kunit_init_test_suites, \
__kunit_init_suites, _start, _end)
--
2.54.0
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH v2 5/5] dyndbg.lds.S: fix lost dyndbg sections in modules
2026-05-07 20:40 [PATCH v2 0/5] dyndbg: fix i386 alignment and KEEP module sections Jim Cromie
` (3 preceding siblings ...)
2026-05-07 20:40 ` [PATCH v2 4/5] vmlinux.lds.h: remove redundant ALIGN(8) directives Jim Cromie
@ 2026-05-07 20:40 ` Jim Cromie
4 siblings, 0 replies; 6+ messages in thread
From: Jim Cromie @ 2026-05-07 20:40 UTC (permalink / raw)
To: Arnd Bergmann, Jason Baron, Luis Chamberlain, Petr Pavlu,
Daniel Gomez, Sami Tolvanen, Aaron Tomlin
Cc: linux-arch, linux-kernel, linux-modules, Jim Cromie
With CONFIG_DRM_USE_DYNAMIC_DEBUG=y, several build configs had
problems with __dyndbg* sections getting lost in drm drivers. Fix
this by following the model demonstrated in codetag.lds.h.
Introduce include/asm-generic/dyndbg.lds.h, to bundle dynamic-debug's
multiple sections together, into 2 macros:
vmlinux.lds.h DATA_DATA: move the 2 BOUNDED_SECTION_BY(__dyndbg*)
calls into dyndbg.lds.h DYNDBG_SECTIONS(). vmlinux.lds.h now includes
the new file and calls the new macro.
MOD_DYNDBG_SECTIONS declares the 2 BOUNDED_SECTION_BY calls, but wraps
them with output section syntax to keep them as known and separate ELF
sections in the module.ko. The KEEP fixes the lost section.
dyndbg.lds.h includes (reuses) bounded-section.lds.h
scripts/module.lds.S: now calls MOD_DYNDBG_SECTIONS right before the
CODETAG macro (consistent with their placements in vmlinux.lds.h), and
also includes dyndbg.lds.h
This isolates vmlinux.lds.h from further __dyndbg section additions.
CC: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
v2 - Address linker script review feedback for relocatable modules.
v1 of MOD_DYNDBG_SECTIONS() used the BOUNDED_SECTION_BY() macro, which
proved problematic for kernel modules for two reasons:
1. Unwanted Empty Sections:
BOUNDED_SECTION_BY() automatically generates `__start` and `__stop`
symbols. When applied to `MOD_DYNDBG_SECTIONS()`, the linker assumes
the sections are populated due to the symbol definitions, forcing an
empty `__dyndbg` and `__dyndbg_classes` output section in every
compiled module, even those without dynamic debug configuration.
Since the module loader uses `section_objs()` to locate data via
ELF headers instead of relying on `__start`/`__stop` symbols, these
assignments are completely unnecessary.
2. Non-zero Output Addresses:
During relocatable linking (e.g., `ld.bfd -r`), omitting an explicit
base address causes the section to inherit the current location
counter. This results in non-zero sh_addr values in `.ko` files,
which is confusing, degrades compressibility, and can cause issues
with external tools parsing the ELF.
Fix both issues by dropping `BOUNDED_SECTION_BY()` in favor of a simple
`KEEP(*(...))` constraint and explicitly defining the sections with a `0`
base address: `__dyndbg 0 : ALIGN(8) { ... }`.
---
MAINTAINERS | 1 +
include/asm-generic/dyndbg.lds.h | 19 +++++++++++++++++++
include/asm-generic/vmlinux.lds.h | 6 ++----
scripts/module.lds.S | 2 ++
4 files changed, 24 insertions(+), 4 deletions(-)
diff --git a/MAINTAINERS b/MAINTAINERS
index 882214b0e7db..54bb257b60ee 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -9070,6 +9070,7 @@ DYNAMIC DEBUG
M: Jason Baron <jbaron@akamai.com>
M: Jim Cromie <jim.cromie@gmail.com>
S: Maintained
+F: include/asm-generic/dyndbg.lds.h
F: include/linux/dynamic_debug.h
F: lib/dynamic_debug.c
F: lib/test_dynamic_debug.c
diff --git a/include/asm-generic/dyndbg.lds.h b/include/asm-generic/dyndbg.lds.h
new file mode 100644
index 000000000000..844f1cb82020
--- /dev/null
+++ b/include/asm-generic/dyndbg.lds.h
@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef __ASM_GENERIC_DYNDBG_LDS_H
+#define __ASM_GENERIC_DYNDBG_LDS_H
+
+#include <asm-generic/bounded_sections.lds.h>
+#define DYNDBG_SECTIONS() \
+ . = ALIGN(8); \
+ BOUNDED_SECTION_BY(__dyndbg, ___dyndbg) \
+ BOUNDED_SECTION_BY(__dyndbg_classes, ___dyndbg_classes)
+
+#define MOD_DYNDBG_SECTIONS() \
+ __dyndbg 0 : ALIGN(8) { \
+ KEEP(*(__dyndbg)) \
+ } \
+ __dyndbg_classes 0 : ALIGN(8) { \
+ KEEP(*(__dyndbg_classes)) \
+ }
+
+#endif /* __ASM_GENERIC_DYNDBG_LDS_H */
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index d9d2eb708355..54897d742c6c 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -332,6 +332,7 @@
/*
* .data section
*/
+#include <asm-generic/dyndbg.lds.h>
#define DATA_DATA \
*(.xiptext) \
*(DATA_MAIN) \
@@ -345,10 +346,7 @@
*(.data..do_once) \
STRUCT_ALIGN(); \
*(__tracepoints) \
- /* implement dynamic printk debug */ \
- . = ALIGN(8); \
- BOUNDED_SECTION_BY(__dyndbg_classes, ___dyndbg_classes) \
- BOUNDED_SECTION_BY(__dyndbg, ___dyndbg) \
+ DYNDBG_SECTIONS() \
CODETAG_SECTIONS() \
LIKELY_PROFILE() \
BRANCH_PROFILE() \
diff --git a/scripts/module.lds.S b/scripts/module.lds.S
index b62683061d79..2e62dc5bd5d4 100644
--- a/scripts/module.lds.S
+++ b/scripts/module.lds.S
@@ -10,6 +10,7 @@
#endif
#include <asm-generic/codetag.lds.h>
+#include <asm-generic/dyndbg.lds.h>
SECTIONS {
/DISCARD/ : {
@@ -61,6 +62,7 @@ SECTIONS {
*(.rodata..L*)
}
+ MOD_DYNDBG_SECTIONS()
MOD_SEPARATE_CODETAG_SECTIONS()
}
--
2.54.0
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