[PATCH 0/5] PATCH 0/6] dyndbg: fix i386 alignment and KEEP module sections

[PATCH 0/5] PATCH 0/6] dyndbg: fix i386 alignment and KEEP module sections

[Jim Cromie]

This series starts with a fix to a section misalignement on i386, and
follows with cleanups and refactoring for reuse.

When CONFIG_DRM_USE_DYNAMIC_DEBUG=Y (currently marked BROKEN) and
CONFIG_DRM=y, the __dyndbg_classes section gets a single
struct/record.  On i386 this is 28-bytes, breaking the required
ALIGN(8) on the following __dyndbg section.

This breaks dynamic_debug_init() with a NULL pointer dereference; the
section traversal logic encounters padding bytes instead of a valid
descriptor.

the series:

1. adds ALIGN(8) to the BOUNDED_SECTION_* macros

2. refactors BOUNDED_SECTION_* macros for later reuse

3. adds dyndbg.lds.S to KEEP sections in modules
   follows codetag.lds.h model

4. drops unused HEADERED_SECTION_* macros

5. removes redundant (after patch 1) ALIGN(8)s in vmlinux.lds.h

6. adds BOUNDED_SECTION_* _ALIGN variants,
   usea them in ORC_UNWIND_TABLE

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
Jim Cromie (5):
      vmlinux.lds.h: refactor BOUNDED_SECTION_* macros into bounded_sections.lds.h
      vmlinux.lds.h: drop unused HEADERED_SECTION* macros
      vmlinux.lds.h: Fix ALIGN(8) omission causing NULL ptr on i386
      vmlinux.lds.h: remove redundant ALIGN(8) directives
      dyndbg.lds.S: fix lost dyndbg sections in modules

 MAINTAINERS                                |  1 +
 include/asm-generic/bounded_sections.lds.h | 32 +++++++++++++++++
 include/asm-generic/dyndbg.lds.h           | 19 ++++++++++
 include/asm-generic/vmlinux.lds.h          | 58 +++++-------------------------
 scripts/module.lds.S                       |  2 ++
 5 files changed, 62 insertions(+), 50 deletions(-)
---
base-commit: 254f49634ee16a731174d2ae34bc50bd5f45e731
change-id: 20260502-asm-generic-1-32c842a35dd0

Best regards,
-- 
Jim Cromie <jim.cromie@gmail.com>

[PATCH 1/5] vmlinux.lds.h: refactor BOUNDED_SECTION_* macros into bounded_sections.lds.h

[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.

NB: this ignores a checkpatch warning, because new file is covered by
GENERIC INCLUDE/ASM HEADER FILES

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

[PATCH 2/5] vmlinux.lds.h: drop unused HEADERED_SECTION* macros

[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

[PATCH 3/5] vmlinux.lds.h: Fix ALIGN(8) omission causing NULL ptr on i386

[Jim Cromie]

Almost all uses of the BOUNDED_SECTION macros are ALIGN(8), either
explicitly, or by being below an aligned section.  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 macros, and
introduce _ALIGNED variants to handle the rare exceptions.

NOTES:

ORC_UNWIND_TABLE now uses _ALIGNED macros to match the explicit
. = ALIGN(x) instructions, but keeps the instructions so the symbols
between them are not "re-aligned"; scripts/sorttable.c does not
tolerate sloppy padding.

Also add . = ALIGN(4) and change BOUNDED_SECTION to _ALIGNED, to agree
with .orc_header, added here:

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

[PATCH 4/5] vmlinux.lds.h: remove redundant ALIGN(8) directives

[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

[PATCH 5/5] dyndbg.lds.S: fix lost dyndbg sections in modules

[Jim Cromie]

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>
---
 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 2fb1c75afd16..182e50b0fad9 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..f95683aa16b6
--- /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 : {							\
+		BOUNDED_SECTION_BY(__dyndbg, ___dyndbg)			\
+	}								\
+	__dyndbg_classes : {						\
+		BOUNDED_SECTION_BY(__dyndbg_classes, ___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

Re: [PATCH 5/5] dyndbg.lds.S: fix lost dyndbg sections in modules

[Petr Pavlu]

On 5/3/26 2:05 AM, Jim Cromie wrote:
> 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>
> ---
[...]
> diff --git a/include/asm-generic/dyndbg.lds.h b/include/asm-generic/dyndbg.lds.h
> new file mode 100644
> index 000000000000..f95683aa16b6
> --- /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 : {							\
> +		BOUNDED_SECTION_BY(__dyndbg, ___dyndbg)			\
> +	}								\
> +	__dyndbg_classes : {						\
> +		BOUNDED_SECTION_BY(__dyndbg_classes, ___dyndbg_classes)	\
> +	}

The BOUNDED_SECTION_BY() macro always defines the __start and __end
symbols for the section. This is not ideal for modules because these
symbols are created even when no __dyndbg or __dyndbg_classes input
sections are present. Additionally, they cause MOD_DYNDBG_SECTIONS() to
produce dummy output sections with the same names in all modules, even
when dynamic debug is disabled in the config. This unnecessarily
pollutes the modules. Since modules are relocatable files, the usual
method for locating consolidated data in a module is to read its section
table.

The second problem is that MOD_DYNDBG_SECTIONS() should force the
address of all its output sections to 0. Otherwise, when linking modules
with 'ld.bfd -r', sections defined without an address inherit the
location counter, resulting in non-zero sh_addr values in the resulting
.ko files. Non-zero addresses are confusing in this context, typically
worse compressible, and may cause external tools to misbehave.

-- 
Thanks,
Petr