[PATCH v2 0/4] Unload linux/kernel.h

[PATCH v2 0/4] Unload linux/kernel.h

[Yury Norov (NVIDIA)]

kernel.h hosts declarations that can be placed better.

Testing (0-Day):
alpha                               defconfig    gcc-15.1.0
arc                                 defconfig    gcc-15.1.0
arc                   randconfig-001-20251202    gcc-8.5.0
arc                   randconfig-002-20251202    gcc-12.5.0
arm                                 defconfig    clang-22
arm                   randconfig-001-20251202    clang-17
arm                   randconfig-002-20251202    clang-22
arm                   randconfig-003-20251202    clang-22
arm                   randconfig-004-20251202    gcc-14.3.0
arm                       spear13xx_defconfig    gcc-15.1.0
arm64                               defconfig    gcc-15.1.0
arm64                 randconfig-001-20251202    clang-22
arm64                 randconfig-002-20251202    clang-22
arm64                 randconfig-003-20251202    clang-16
arm64                 randconfig-004-20251202    clang-22
csky                                defconfig    gcc-15.1.0
csky                  randconfig-001-20251202    gcc-13.4.0
csky                  randconfig-002-20251202    gcc-15.1.0
hexagon                             defconfig    clang-22
hexagon               randconfig-001-20251202    clang-22
hexagon               randconfig-002-20251202    clang-22
i386                             allmodconfig    gcc-14
i386                             allyesconfig    gcc-14
i386        buildonly-randconfig-001-20251202    clang-20
i386        buildonly-randconfig-002-20251202    gcc-14
i386        buildonly-randconfig-003-20251202    clang-20
i386        buildonly-randconfig-004-20251202    clang-20
i386        buildonly-randconfig-005-20251202    clang-20
i386        buildonly-randconfig-006-20251202    gcc-14
i386                                defconfig    clang-20
i386                  randconfig-001-20251202    clang-20
i386                  randconfig-002-20251202    gcc-14
i386                  randconfig-003-20251202    gcc-14
i386                  randconfig-004-20251202    clang-20
i386                  randconfig-005-20251202    gcc-14
i386                  randconfig-006-20251202    clang-20
i386                  randconfig-007-20251202    clang-20
i386                  randconfig-011-20251202    clang-20
i386                  randconfig-012-20251202    clang-20
i386                  randconfig-013-20251202    gcc-14
i386                  randconfig-014-20251202    gcc-14
i386                  randconfig-015-20251202    gcc-14
i386                  randconfig-016-20251202    clang-20
i386                  randconfig-017-20251202    clang-20
loongarch                           defconfig    clang-19
loongarch             randconfig-001-20251202    gcc-15.1.0
loongarch             randconfig-002-20251202    clang-22
m68k                                defconfig    gcc-15.1.0
microblaze                       allyesconfig    gcc-15.1.0
microblaze                          defconfig    gcc-15.1.0
nios2                         10m50_defconfig    gcc-11.5.0
nios2                            allmodconfig    gcc-11.5.0
nios2                             allnoconfig    gcc-11.5.0
nios2                               defconfig    gcc-11.5.0
nios2                 randconfig-001-20251202    gcc-8.5.0
nios2                 randconfig-002-20251202    gcc-8.5.0
openrisc                         allmodconfig    gcc-15.1.0
openrisc                          allnoconfig    gcc-15.1.0
openrisc                            defconfig    gcc-15.1.0
parisc                            allnoconfig    gcc-15.1.0
parisc                           allyesconfig    gcc-15.1.0
parisc                              defconfig    gcc-15.1.0
parisc                generic-32bit_defconfig    gcc-15.1.0
parisc                randconfig-001-20251202    gcc-9.5.0
parisc                randconfig-002-20251202    gcc-15.1.0
parisc64                            defconfig    gcc-15.1.0
powerpc                          allmodconfig    gcc-15.1.0
powerpc                           allnoconfig    gcc-15.1.0
powerpc               randconfig-001-20251202    clang-22
powerpc               randconfig-002-20251202    gcc-10.5.0
powerpc64             randconfig-001-20251202    clang-22
powerpc64             randconfig-002-20251202    clang-22
riscv                             allnoconfig    gcc-15.1.0
riscv                               defconfig    clang-22
riscv                    nommu_k210_defconfig    clang-22
riscv                 randconfig-001-20251202    gcc-9.5.0
riscv                 randconfig-002-20251202    clang-22
s390                              allnoconfig    clang-22
s390                                defconfig    clang-22
s390                  randconfig-001-20251202    clang-17
s390                  randconfig-002-20251202    gcc-13.4.0
sh                                allnoconfig    gcc-15.1.0
sh                                  defconfig    gcc-15.1.0
sh                    randconfig-001-20251202    gcc-15.1.0
sh                    randconfig-002-20251202    gcc-12.5.0
sh                          rsk7269_defconfig    gcc-15.1.0
sh                     sh7710voipgw_defconfig    gcc-15.1.0
sparc                             allnoconfig    gcc-15.1.0
sparc                               defconfig    gcc-15.1.0
sparc                 randconfig-001-20251202    gcc-8.5.0
sparc                 randconfig-002-20251202    gcc-8.5.0
sparc64                          allmodconfig    clang-22
sparc64                             defconfig    clang-20
sparc64               randconfig-001-20251202    gcc-8.5.0
sparc64               randconfig-002-20251202    gcc-10.5.0
um                                allnoconfig    clang-22
um                                  defconfig    clang-22
um                             i386_defconfig    gcc-14
um                    randconfig-001-20251202    clang-17
um                    randconfig-002-20251202    gcc-14
um                           x86_64_defconfig    clang-22
x86_64                           allmodconfig    clang-20
x86_64                            allnoconfig    clang-20
x86_64                           allyesconfig    clang-20
x86_64      buildonly-randconfig-001-20251202    gcc-14
x86_64      buildonly-randconfig-002-20251202    gcc-14
x86_64      buildonly-randconfig-003-20251202    clang-20
x86_64      buildonly-randconfig-004-20251202    gcc-13
x86_64      buildonly-randconfig-005-20251202    gcc-14
x86_64      buildonly-randconfig-006-20251202    gcc-13
x86_64                              defconfig    gcc-14
x86_64                randconfig-011-20251202    clang-20
x86_64                randconfig-012-20251202    gcc-13
x86_64                randconfig-013-20251202    gcc-14
x86_64                randconfig-014-20251202    clang-20
x86_64                randconfig-015-20251202    clang-20
x86_64                randconfig-016-20251202    clang-20
x86_64                          rhel-9.4-rust    clang-20
xtensa                            allnoconfig    gcc-15.1.0
xtensa                randconfig-001-20251202    gcc-11.5.0
xtensa                randconfig-002-20251202    gcc-11.5.0

v1: https://lore.kernel.org/all/20251129195304.204082-1-yury.norov@gmail.com/
v2: 
 - more historical context for STACK_MAGIC removal (Christophe);
 - place STACK_MAGIC in i915_selftest.h (Jan);
 - new patch #2: moduleparam: include required headers explicitly (Petr);
 - align Documentation/filesystems/sysfs.rst (Andy);
 - more motivation for linux/tracing.h (Andy, Steven);

Yury Norov (NVIDIA) (4):
  kernel.h: drop STACK_MAGIC macro
  moduleparam: include required headers explicitly
  kernel.h: move VERIFY_OCTAL_PERMISSIONS() to sysfs.h
  tracing: move tracing declarations from kernel.h to a dedicated header

 Documentation/filesystems/sysfs.rst           |   2 +-
 MAINTAINERS                                   |   1 +
 .../drm/i915/gt/selftest_ring_submission.c    |   1 +
 drivers/gpu/drm/i915/i915_selftest.h          |   2 +
 include/linux/kernel.h                        | 209 +-----------------
 include/linux/moduleparam.h                   |   7 +-
 include/linux/sysfs.h                         |  13 ++
 include/linux/tracing.h                       | 203 +++++++++++++++++
 8 files changed, 228 insertions(+), 210 deletions(-)
 create mode 100644 include/linux/tracing.h

-- 
2.43.0

[PATCH v2 1/4] kernel.h: drop STACK_MAGIC macro

[Yury Norov (NVIDIA)]

The macro was introduced in 1994, v1.0.4, for stacks protection. Since
that, people found better ways to protect stacks, and now the macro is
only used by i915 selftests. Move it to a local header and drop from
the kernel.h.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
---
 drivers/gpu/drm/i915/gt/selftest_ring_submission.c | 1 +
 drivers/gpu/drm/i915/i915_selftest.h               | 2 ++
 include/linux/kernel.h                             | 2 --
 3 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/selftest_ring_submission.c b/drivers/gpu/drm/i915/gt/selftest_ring_submission.c
index 87ceb0f374b6..600333ae6c8c 100644
--- a/drivers/gpu/drm/i915/gt/selftest_ring_submission.c
+++ b/drivers/gpu/drm/i915/gt/selftest_ring_submission.c
@@ -3,6 +3,7 @@
  * Copyright © 2020 Intel Corporation
  */
 
+#include "i915_selftest.h"
 #include "intel_engine_pm.h"
 #include "selftests/igt_flush_test.h"
 
diff --git a/drivers/gpu/drm/i915/i915_selftest.h b/drivers/gpu/drm/i915/i915_selftest.h
index bdf3e22c0a34..72922028f4ba 100644
--- a/drivers/gpu/drm/i915/i915_selftest.h
+++ b/drivers/gpu/drm/i915/i915_selftest.h
@@ -26,6 +26,8 @@
 
 #include <linux/types.h>
 
+#define STACK_MAGIC	0xdeadbeef
+
 struct pci_dev;
 struct drm_i915_private;
 
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 5b46924fdff5..61d63c57bc2d 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -40,8 +40,6 @@
 
 #include <uapi/linux/kernel.h>
 
-#define STACK_MAGIC	0xdeadbeef
-
 struct completion;
 struct user;
 
-- 
2.43.0

[PATCH v2 2/4] moduleparam: include required headers explicitly

[Yury Norov (NVIDIA)]

The following patch drops moduleparam.h dependency on kernel.h. In
preparation to it, list all the required headers explicitly.

Suggested-by: Petr Pavlu <petr.pavlu@suse.com>
CC: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
---
 include/linux/moduleparam.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h
index 6907aedc4f74..ca7c8107c7c8 100644
--- a/include/linux/moduleparam.h
+++ b/include/linux/moduleparam.h
@@ -2,9 +2,14 @@
 #ifndef _LINUX_MODULE_PARAMS_H
 #define _LINUX_MODULE_PARAMS_H
 /* (C) Copyright 2001, 2002 Rusty Russell IBM Corporation */
+
+#include <linux/array_size.h>
+#include <linux/build_bug.h>
+#include <linux/compiler.h>
 #include <linux/init.h>
 #include <linux/stringify.h>
 #include <linux/kernel.h>
+#include <linux/types.h>
 
 /*
  * The maximum module name length, including the NUL byte.
-- 
2.43.0

[PATCH v2 3/4] kernel.h: move VERIFY_OCTAL_PERMISSIONS() to sysfs.h

[Yury Norov (NVIDIA)]

The macro is related to sysfs, but is defined in kernel.h. Move it to
the proper header, and unload the generic kernel.h.

Now that the macro is removed from kernel.h, linux/moduleparam.h is
decoupled, and kernel.h inclusion can be removed.

Acked-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
---
 Documentation/filesystems/sysfs.rst |  2 +-
 include/linux/kernel.h              | 12 ------------
 include/linux/moduleparam.h         |  2 +-
 include/linux/sysfs.h               | 13 +++++++++++++
 4 files changed, 15 insertions(+), 14 deletions(-)

diff --git a/Documentation/filesystems/sysfs.rst b/Documentation/filesystems/sysfs.rst
index 2703c04af7d0..ffcef4d6bc8d 100644
--- a/Documentation/filesystems/sysfs.rst
+++ b/Documentation/filesystems/sysfs.rst
@@ -120,7 +120,7 @@ is equivalent to doing::
 	    .store = store_foo,
     };
 
-Note as stated in include/linux/kernel.h "OTHER_WRITABLE?  Generally
+Note as stated in include/linux/sysfs.h "OTHER_WRITABLE?  Generally
 considered a bad idea." so trying to set a sysfs file writable for
 everyone will fail reverting to RO mode for "Others".
 
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 61d63c57bc2d..5b879bfea948 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -389,16 +389,4 @@ static inline void ftrace_dump(enum ftrace_dump_mode oops_dump_mode) { }
 # define REBUILD_DUE_TO_DYNAMIC_FTRACE
 #endif
 
-/* Permissions on a sysfs file: you didn't miss the 0 prefix did you? */
-#define VERIFY_OCTAL_PERMISSIONS(perms)						\
-	(BUILD_BUG_ON_ZERO((perms) < 0) +					\
-	 BUILD_BUG_ON_ZERO((perms) > 0777) +					\
-	 /* USER_READABLE >= GROUP_READABLE >= OTHER_READABLE */		\
-	 BUILD_BUG_ON_ZERO((((perms) >> 6) & 4) < (((perms) >> 3) & 4)) +	\
-	 BUILD_BUG_ON_ZERO((((perms) >> 3) & 4) < ((perms) & 4)) +		\
-	 /* USER_WRITABLE >= GROUP_WRITABLE */					\
-	 BUILD_BUG_ON_ZERO((((perms) >> 6) & 2) < (((perms) >> 3) & 2)) +	\
-	 /* OTHER_WRITABLE?  Generally considered a bad idea. */		\
-	 BUILD_BUG_ON_ZERO((perms) & 2) +					\
-	 (perms))
 #endif
diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h
index ca7c8107c7c8..dd2d990b2611 100644
--- a/include/linux/moduleparam.h
+++ b/include/linux/moduleparam.h
@@ -8,7 +8,7 @@
 #include <linux/compiler.h>
 #include <linux/init.h>
 #include <linux/stringify.h>
-#include <linux/kernel.h>
+#include <linux/sysfs.h>
 #include <linux/types.h>
 
 /*
diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
index 9a25a2911652..15ee3ef33991 100644
--- a/include/linux/sysfs.h
+++ b/include/linux/sysfs.h
@@ -798,4 +798,17 @@ static inline void sysfs_put(struct kernfs_node *kn)
 	kernfs_put(kn);
 }
 
+/* Permissions on a sysfs file: you didn't miss the 0 prefix did you? */
+#define VERIFY_OCTAL_PERMISSIONS(perms)						\
+	(BUILD_BUG_ON_ZERO((perms) < 0) +					\
+	 BUILD_BUG_ON_ZERO((perms) > 0777) +					\
+	 /* USER_READABLE >= GROUP_READABLE >= OTHER_READABLE */		\
+	 BUILD_BUG_ON_ZERO((((perms) >> 6) & 4) < (((perms) >> 3) & 4)) +	\
+	 BUILD_BUG_ON_ZERO((((perms) >> 3) & 4) < ((perms) & 4)) +		\
+	 /* USER_WRITABLE >= GROUP_WRITABLE */					\
+	 BUILD_BUG_ON_ZERO((((perms) >> 6) & 2) < (((perms) >> 3) & 2)) +	\
+	 /* OTHER_WRITABLE?  Generally considered a bad idea. */		\
+	 BUILD_BUG_ON_ZERO((perms) & 2) +					\
+	 (perms))
+
 #endif /* _SYSFS_H_ */
-- 
2.43.0

[PATCH v2 4/4] tracing: move tracing declarations from kernel.h to a dedicated header

[Yury Norov (NVIDIA)]

Tracing is a half of the kernel.h in terms of LOCs, although it's
a self-consistent part. It is intended for quick debugging purposes
and isn't used by the normal tracing utilities.

Move it to a separate header. If someone needs to just throw a
trace_printk() in their driver, they will not have to pull all
the heavy tracing machinery.

This is a pure move, except for removing a few 'extern's.

Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
---
 MAINTAINERS             |   1 +
 include/linux/kernel.h  | 195 +-------------------------------------
 include/linux/tracing.h | 203 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 205 insertions(+), 194 deletions(-)
 create mode 100644 include/linux/tracing.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 3468f6827b13..107cadb613da 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -26080,6 +26080,7 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace.git
 F:	Documentation/trace/*
 F:	fs/tracefs/
 F:	include/linux/trace*.h
+F:	include/linux/tracing.h
 F:	include/trace/
 F:	kernel/trace/
 F:	kernel/tracepoint.c
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 5b879bfea948..2e9d65177f45 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -32,6 +32,7 @@
 #include <linux/build_bug.h>
 #include <linux/sprintf.h>
 #include <linux/static_call_types.h>
+#include <linux/tracing.h>
 #include <linux/instruction_pointer.h>
 #include <linux/util_macros.h>
 #include <linux/wordpart.h>
@@ -190,200 +191,6 @@ enum system_states {
 };
 extern enum system_states system_state;
 
-/*
- * General tracing related utility functions - trace_printk(),
- * tracing_on/tracing_off and tracing_start()/tracing_stop
- *
- * Use tracing_on/tracing_off when you want to quickly turn on or off
- * tracing. It simply enables or disables the recording of the trace events.
- * This also corresponds to the user space /sys/kernel/tracing/tracing_on
- * file, which gives a means for the kernel and userspace to interact.
- * Place a tracing_off() in the kernel where you want tracing to end.
- * From user space, examine the trace, and then echo 1 > tracing_on
- * to continue tracing.
- *
- * tracing_stop/tracing_start has slightly more overhead. It is used
- * by things like suspend to ram where disabling the recording of the
- * trace is not enough, but tracing must actually stop because things
- * like calling smp_processor_id() may crash the system.
- *
- * Most likely, you want to use tracing_on/tracing_off.
- */
-
-enum ftrace_dump_mode {
-	DUMP_NONE,
-	DUMP_ALL,
-	DUMP_ORIG,
-	DUMP_PARAM,
-};
-
-#ifdef CONFIG_TRACING
-void tracing_on(void);
-void tracing_off(void);
-int tracing_is_on(void);
-void tracing_snapshot(void);
-void tracing_snapshot_alloc(void);
-
-extern void tracing_start(void);
-extern void tracing_stop(void);
-
-static inline __printf(1, 2)
-void ____trace_printk_check_format(const char *fmt, ...)
-{
-}
-#define __trace_printk_check_format(fmt, args...)			\
-do {									\
-	if (0)								\
-		____trace_printk_check_format(fmt, ##args);		\
-} while (0)
-
-/**
- * trace_printk - printf formatting in the ftrace buffer
- * @fmt: the printf format for printing
- *
- * Note: __trace_printk is an internal function for trace_printk() and
- *       the @ip is passed in via the trace_printk() macro.
- *
- * This function allows a kernel developer to debug fast path sections
- * that printk is not appropriate for. By scattering in various
- * printk like tracing in the code, a developer can quickly see
- * where problems are occurring.
- *
- * This is intended as a debugging tool for the developer only.
- * Please refrain from leaving trace_printks scattered around in
- * your code. (Extra memory is used for special buffers that are
- * allocated when trace_printk() is used.)
- *
- * A little optimization trick is done here. If there's only one
- * argument, there's no need to scan the string for printf formats.
- * The trace_puts() will suffice. But how can we take advantage of
- * using trace_puts() when trace_printk() has only one argument?
- * By stringifying the args and checking the size we can tell
- * whether or not there are args. __stringify((__VA_ARGS__)) will
- * turn into "()\0" with a size of 3 when there are no args, anything
- * else will be bigger. All we need to do is define a string to this,
- * and then take its size and compare to 3. If it's bigger, use
- * do_trace_printk() otherwise, optimize it to trace_puts(). Then just
- * let gcc optimize the rest.
- */
-
-#define trace_printk(fmt, ...)				\
-do {							\
-	char _______STR[] = __stringify((__VA_ARGS__));	\
-	if (sizeof(_______STR) > 3)			\
-		do_trace_printk(fmt, ##__VA_ARGS__);	\
-	else						\
-		trace_puts(fmt);			\
-} while (0)
-
-#define do_trace_printk(fmt, args...)					\
-do {									\
-	static const char *trace_printk_fmt __used			\
-		__section("__trace_printk_fmt") =			\
-		__builtin_constant_p(fmt) ? fmt : NULL;			\
-									\
-	__trace_printk_check_format(fmt, ##args);			\
-									\
-	if (__builtin_constant_p(fmt))					\
-		__trace_bprintk(_THIS_IP_, trace_printk_fmt, ##args);	\
-	else								\
-		__trace_printk(_THIS_IP_, fmt, ##args);			\
-} while (0)
-
-extern __printf(2, 3)
-int __trace_bprintk(unsigned long ip, const char *fmt, ...);
-
-extern __printf(2, 3)
-int __trace_printk(unsigned long ip, const char *fmt, ...);
-
-/**
- * trace_puts - write a string into the ftrace buffer
- * @str: the string to record
- *
- * Note: __trace_bputs is an internal function for trace_puts and
- *       the @ip is passed in via the trace_puts macro.
- *
- * This is similar to trace_printk() but is made for those really fast
- * paths that a developer wants the least amount of "Heisenbug" effects,
- * where the processing of the print format is still too much.
- *
- * This function allows a kernel developer to debug fast path sections
- * that printk is not appropriate for. By scattering in various
- * printk like tracing in the code, a developer can quickly see
- * where problems are occurring.
- *
- * This is intended as a debugging tool for the developer only.
- * Please refrain from leaving trace_puts scattered around in
- * your code. (Extra memory is used for special buffers that are
- * allocated when trace_puts() is used.)
- *
- * Returns: 0 if nothing was written, positive # if string was.
- *  (1 when __trace_bputs is used, strlen(str) when __trace_puts is used)
- */
-
-#define trace_puts(str) ({						\
-	static const char *trace_printk_fmt __used			\
-		__section("__trace_printk_fmt") =			\
-		__builtin_constant_p(str) ? str : NULL;			\
-									\
-	if (__builtin_constant_p(str))					\
-		__trace_bputs(_THIS_IP_, trace_printk_fmt);		\
-	else								\
-		__trace_puts(_THIS_IP_, str, strlen(str));		\
-})
-extern int __trace_bputs(unsigned long ip, const char *str);
-extern int __trace_puts(unsigned long ip, const char *str, int size);
-
-extern void trace_dump_stack(int skip);
-
-/*
- * The double __builtin_constant_p is because gcc will give us an error
- * if we try to allocate the static variable to fmt if it is not a
- * constant. Even with the outer if statement.
- */
-#define ftrace_vprintk(fmt, vargs)					\
-do {									\
-	if (__builtin_constant_p(fmt)) {				\
-		static const char *trace_printk_fmt __used		\
-		  __section("__trace_printk_fmt") =			\
-			__builtin_constant_p(fmt) ? fmt : NULL;		\
-									\
-		__ftrace_vbprintk(_THIS_IP_, trace_printk_fmt, vargs);	\
-	} else								\
-		__ftrace_vprintk(_THIS_IP_, fmt, vargs);		\
-} while (0)
-
-extern __printf(2, 0) int
-__ftrace_vbprintk(unsigned long ip, const char *fmt, va_list ap);
-
-extern __printf(2, 0) int
-__ftrace_vprintk(unsigned long ip, const char *fmt, va_list ap);
-
-extern void ftrace_dump(enum ftrace_dump_mode oops_dump_mode);
-#else
-static inline void tracing_start(void) { }
-static inline void tracing_stop(void) { }
-static inline void trace_dump_stack(int skip) { }
-
-static inline void tracing_on(void) { }
-static inline void tracing_off(void) { }
-static inline int tracing_is_on(void) { return 0; }
-static inline void tracing_snapshot(void) { }
-static inline void tracing_snapshot_alloc(void) { }
-
-static inline __printf(1, 2)
-int trace_printk(const char *fmt, ...)
-{
-	return 0;
-}
-static __printf(1, 0) inline int
-ftrace_vprintk(const char *fmt, va_list ap)
-{
-	return 0;
-}
-static inline void ftrace_dump(enum ftrace_dump_mode oops_dump_mode) { }
-#endif /* CONFIG_TRACING */
-
 /* Rebuild everything on CONFIG_DYNAMIC_FTRACE */
 #ifdef CONFIG_DYNAMIC_FTRACE
 # define REBUILD_DUE_TO_DYNAMIC_FTRACE
diff --git a/include/linux/tracing.h b/include/linux/tracing.h
new file mode 100644
index 000000000000..1989e6328c59
--- /dev/null
+++ b/include/linux/tracing.h
@@ -0,0 +1,203 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_TRACING_H
+#define _LINUX_TRACING_H
+
+#include <linux/compiler_attributes.h>
+#include <linux/instruction_pointer.h>
+#include <linux/stringify.h>
+
+/*
+ * General tracing related utility functions - trace_printk(),
+ * tracing_on/tracing_off and tracing_start()/tracing_stop
+ *
+ * Use tracing_on/tracing_off when you want to quickly turn on or off
+ * tracing. It simply enables or disables the recording of the trace events.
+ * This also corresponds to the user space /sys/kernel/tracing/tracing_on
+ * file, which gives a means for the kernel and userspace to interact.
+ * Place a tracing_off() in the kernel where you want tracing to end.
+ * From user space, examine the trace, and then echo 1 > tracing_on
+ * to continue tracing.
+ *
+ * tracing_stop/tracing_start has slightly more overhead. It is used
+ * by things like suspend to ram where disabling the recording of the
+ * trace is not enough, but tracing must actually stop because things
+ * like calling smp_processor_id() may crash the system.
+ *
+ * Most likely, you want to use tracing_on/tracing_off.
+ */
+
+enum ftrace_dump_mode {
+	DUMP_NONE,
+	DUMP_ALL,
+	DUMP_ORIG,
+	DUMP_PARAM,
+};
+
+#ifdef CONFIG_TRACING
+void tracing_on(void);
+void tracing_off(void);
+int tracing_is_on(void);
+void tracing_snapshot(void);
+void tracing_snapshot_alloc(void);
+
+void tracing_start(void);
+void tracing_stop(void);
+
+static inline __printf(1, 2)
+void ____trace_printk_check_format(const char *fmt, ...)
+{
+}
+#define __trace_printk_check_format(fmt, args...)			\
+do {									\
+	if (0)								\
+		____trace_printk_check_format(fmt, ##args);		\
+} while (0)
+
+/**
+ * trace_printk - printf formatting in the ftrace buffer
+ * @fmt: the printf format for printing
+ *
+ * Note: __trace_printk is an internal function for trace_printk() and
+ *       the @ip is passed in via the trace_printk() macro.
+ *
+ * This function allows a kernel developer to debug fast path sections
+ * that printk is not appropriate for. By scattering in various
+ * printk like tracing in the code, a developer can quickly see
+ * where problems are occurring.
+ *
+ * This is intended as a debugging tool for the developer only.
+ * Please refrain from leaving trace_printks scattered around in
+ * your code. (Extra memory is used for special buffers that are
+ * allocated when trace_printk() is used.)
+ *
+ * A little optimization trick is done here. If there's only one
+ * argument, there's no need to scan the string for printf formats.
+ * The trace_puts() will suffice. But how can we take advantage of
+ * using trace_puts() when trace_printk() has only one argument?
+ * By stringifying the args and checking the size we can tell
+ * whether or not there are args. __stringify((__VA_ARGS__)) will
+ * turn into "()\0" with a size of 3 when there are no args, anything
+ * else will be bigger. All we need to do is define a string to this,
+ * and then take its size and compare to 3. If it's bigger, use
+ * do_trace_printk() otherwise, optimize it to trace_puts(). Then just
+ * let gcc optimize the rest.
+ */
+
+#define trace_printk(fmt, ...)				\
+do {							\
+	char _______STR[] = __stringify((__VA_ARGS__));	\
+	if (sizeof(_______STR) > 3)			\
+		do_trace_printk(fmt, ##__VA_ARGS__);	\
+	else						\
+		trace_puts(fmt);			\
+} while (0)
+
+#define do_trace_printk(fmt, args...)					\
+do {									\
+	static const char *trace_printk_fmt __used			\
+		__section("__trace_printk_fmt") =			\
+		__builtin_constant_p(fmt) ? fmt : NULL;			\
+									\
+	__trace_printk_check_format(fmt, ##args);			\
+									\
+	if (__builtin_constant_p(fmt))					\
+		__trace_bprintk(_THIS_IP_, trace_printk_fmt, ##args);	\
+	else								\
+		__trace_printk(_THIS_IP_, fmt, ##args);			\
+} while (0)
+
+__printf(2, 3)
+int __trace_bprintk(unsigned long ip, const char *fmt, ...);
+
+__printf(2, 3)
+int __trace_printk(unsigned long ip, const char *fmt, ...);
+
+/**
+ * trace_puts - write a string into the ftrace buffer
+ * @str: the string to record
+ *
+ * Note: __trace_bputs is an internal function for trace_puts and
+ *       the @ip is passed in via the trace_puts macro.
+ *
+ * This is similar to trace_printk() but is made for those really fast
+ * paths that a developer wants the least amount of "Heisenbug" effects,
+ * where the processing of the print format is still too much.
+ *
+ * This function allows a kernel developer to debug fast path sections
+ * that printk is not appropriate for. By scattering in various
+ * printk like tracing in the code, a developer can quickly see
+ * where problems are occurring.
+ *
+ * This is intended as a debugging tool for the developer only.
+ * Please refrain from leaving trace_puts scattered around in
+ * your code. (Extra memory is used for special buffers that are
+ * allocated when trace_puts() is used.)
+ *
+ * Returns: 0 if nothing was written, positive # if string was.
+ *  (1 when __trace_bputs is used, strlen(str) when __trace_puts is used)
+ */
+
+#define trace_puts(str) ({						\
+	static const char *trace_printk_fmt __used			\
+		__section("__trace_printk_fmt") =			\
+		__builtin_constant_p(str) ? str : NULL;			\
+									\
+	if (__builtin_constant_p(str))					\
+		__trace_bputs(_THIS_IP_, trace_printk_fmt);		\
+	else								\
+		__trace_puts(_THIS_IP_, str, strlen(str));		\
+})
+int __trace_bputs(unsigned long ip, const char *str);
+int __trace_puts(unsigned long ip, const char *str, int size);
+
+void trace_dump_stack(int skip);
+
+/*
+ * The double __builtin_constant_p is because gcc will give us an error
+ * if we try to allocate the static variable to fmt if it is not a
+ * constant. Even with the outer if statement.
+ */
+#define ftrace_vprintk(fmt, vargs)					\
+do {									\
+	if (__builtin_constant_p(fmt)) {				\
+		static const char *trace_printk_fmt __used		\
+		  __section("__trace_printk_fmt") =			\
+			__builtin_constant_p(fmt) ? fmt : NULL;		\
+									\
+		__ftrace_vbprintk(_THIS_IP_, trace_printk_fmt, vargs);	\
+	} else								\
+		__ftrace_vprintk(_THIS_IP_, fmt, vargs);		\
+} while (0)
+
+__printf(2, 0) int
+__ftrace_vbprintk(unsigned long ip, const char *fmt, va_list ap);
+
+__printf(2, 0) int
+__ftrace_vprintk(unsigned long ip, const char *fmt, va_list ap);
+
+void ftrace_dump(enum ftrace_dump_mode oops_dump_mode);
+#else
+static inline void tracing_start(void) { }
+static inline void tracing_stop(void) { }
+static inline void trace_dump_stack(int skip) { }
+
+static inline void tracing_on(void) { }
+static inline void tracing_off(void) { }
+static inline int tracing_is_on(void) { return 0; }
+static inline void tracing_snapshot(void) { }
+static inline void tracing_snapshot_alloc(void) { }
+
+static inline __printf(1, 2)
+int trace_printk(const char *fmt, ...)
+{
+	return 0;
+}
+static __printf(1, 0) inline int
+ftrace_vprintk(const char *fmt, va_list ap)
+{
+	return 0;
+}
+static inline void ftrace_dump(enum ftrace_dump_mode oops_dump_mode) { }
+#endif /* CONFIG_TRACING */
+
+#endif
-- 
2.43.0

Re: [PATCH v2 2/4] moduleparam: include required headers explicitly

[Andy Shevchenko]

On Wed, Dec 03, 2025 at 11:23:23AM -0500, Yury Norov (NVIDIA) wrote:
> The following patch drops moduleparam.h dependency on kernel.h. In
> preparation to it, list all the required headers explicitly.

> Suggested-by: Petr Pavlu <petr.pavlu@suse.com>

> CC: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

You can move this line after --- or use --cc when formatting patch,
no need to pollute the commit message with it.

In any case, the change LGTM and you can just replace the above with

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v2 4/4] tracing: move tracing declarations from kernel.h to a dedicated header

[Steven Rostedt]

On Wed,  3 Dec 2025 11:23:25 -0500
"Yury Norov (NVIDIA)" <yury.norov@gmail.com> wrote:

> diff --git a/include/linux/tracing.h b/include/linux/tracing.h
> new file mode 100644
> index 000000000000..1989e6328c59
> --- /dev/null
> +++ b/include/linux/tracing.h

Sorry, and I hope this isn't too much bike shedding, but I'm thinking we
should call it trace_printk.h. It's mostly about using trace_printk() and
other similar debugging aspects. Calling it "tracing.h" makes it sound like
it is part of the generic tracing infrastructure.

Thanks,

-- Steve

Re: [PATCH v2 4/4] tracing: move tracing declarations from kernel.h to a dedicated header

[Andy Shevchenko]

On Wed, Dec 03, 2025 at 11:23:25AM -0500, Yury Norov (NVIDIA) wrote:
> Tracing is a half of the kernel.h in terms of LOCs, although it's
> a self-consistent part. It is intended for quick debugging purposes
> and isn't used by the normal tracing utilities.
> 
> Move it to a separate header. If someone needs to just throw a
> trace_printk() in their driver, they will not have to pull all
> the heavy tracing machinery.
> 
> This is a pure move, except for removing a few 'extern's.

...

>  #include <linux/build_bug.h>
>  #include <linux/sprintf.h>
>  #include <linux/static_call_types.h>
> +#include <linux/tracing.h>

>  #include <linux/instruction_pointer.h>

And kill this one? We really don't care about the mess in the kernel.h right
now, and your header will bring that anyway. Also consider killing other
inclusions that has been moved from kernel.h to tracing.h.

>  #include <linux/util_macros.h>
>  #include <linux/wordpart.h>

...

> +#ifndef _LINUX_TRACING_H
> +#define _LINUX_TRACING_H
> +
> +#include <linux/compiler_attributes.h>
> +#include <linux/instruction_pointer.h>

+ stddef.h // you use NULL

+ string.h // use of strlen()

> +#include <linux/stringify.h>

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v2 4/4] tracing: move tracing declarations from kernel.h to a dedicated header

[Andy Shevchenko]

On Wed, Dec 03, 2025 at 12:10:07PM -0500, Steven Rostedt wrote:
> On Wed,  3 Dec 2025 11:23:25 -0500
> "Yury Norov (NVIDIA)" <yury.norov@gmail.com> wrote:
> 
> > diff --git a/include/linux/tracing.h b/include/linux/tracing.h
> > new file mode 100644
> > index 000000000000..1989e6328c59
> > --- /dev/null
> > +++ b/include/linux/tracing.h
> 
> Sorry, and I hope this isn't too much bike shedding, but I'm thinking we
> should call it trace_printk.h. It's mostly about using trace_printk() and
> other similar debugging aspects. Calling it "tracing.h" makes it sound like
> it is part of the generic tracing infrastructure.

I am fine with the proposed name, and it makes sense to me.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v2 4/4] tracing: move tracing declarations from kernel.h to a dedicated header

[Yury Norov]

On Wed, Dec 03, 2025 at 12:10:07PM -0500, Steven Rostedt wrote:
> On Wed,  3 Dec 2025 11:23:25 -0500
> "Yury Norov (NVIDIA)" <yury.norov@gmail.com> wrote:
> 
> > diff --git a/include/linux/tracing.h b/include/linux/tracing.h
> > new file mode 100644
> > index 000000000000..1989e6328c59
> > --- /dev/null
> > +++ b/include/linux/tracing.h
> 
> Sorry, and I hope this isn't too much bike shedding, but I'm thinking we
> should call it trace_printk.h. It's mostly about using trace_printk() and
> other similar debugging aspects. Calling it "tracing.h" makes it sound like
> it is part of the generic tracing infrastructure.

I agree. I didn't change the name because it seemingly was a consensus
about it during v1 discussion. Let's wait for more comments. If no
other issues, I can send a quick v3, or you can fix it inplace,
assuming you're moving it yourself.

Thanks,
Yury

Re: [PATCH v2 4/4] tracing: move tracing declarations from kernel.h to a dedicated header

[Andy Shevchenko]

On Wed, Dec 03, 2025 at 07:10:53PM +0200, Andy Shevchenko wrote:
> On Wed, Dec 03, 2025 at 11:23:25AM -0500, Yury Norov (NVIDIA) wrote:

...

> > +#ifndef _LINUX_TRACING_H
> > +#define _LINUX_TRACING_H
> > +
> > +#include <linux/compiler_attributes.h>
> > +#include <linux/instruction_pointer.h>
> 
> + stddef.h // you use NULL
> 
> + string.h // use of strlen()

Why it should not conflict, it might be worth to research more and perhaps even
use intrinsic instead of strlen(). Just a thought spoken loudly.

> > +#include <linux/stringify.h>

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v2 1/4] kernel.h: drop STACK_MAGIC macro

[Christophe Leroy (CS GROUP)]

Le 03/12/2025 à 17:23, Yury Norov (NVIDIA) a écrit :
> The macro was introduced in 1994, v1.0.4, for stacks protection. Since
> that, people found better ways to protect stacks, and now the macro is
> only used by i915 selftests. Move it to a local header and drop from
> the kernel.h.
> 
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Acked-by: Randy Dunlap <rdunlap@infradead.org>
> Acked-by: Jani Nikula <jani.nikula@intel.com>
> Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>

Reviewed-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>

> ---
>   drivers/gpu/drm/i915/gt/selftest_ring_submission.c | 1 +
>   drivers/gpu/drm/i915/i915_selftest.h               | 2 ++
>   include/linux/kernel.h                             | 2 --
>   3 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/selftest_ring_submission.c b/drivers/gpu/drm/i915/gt/selftest_ring_submission.c
> index 87ceb0f374b6..600333ae6c8c 100644
> --- a/drivers/gpu/drm/i915/gt/selftest_ring_submission.c
> +++ b/drivers/gpu/drm/i915/gt/selftest_ring_submission.c
> @@ -3,6 +3,7 @@
>    * Copyright © 2020 Intel Corporation
>    */
>   
> +#include "i915_selftest.h"
>   #include "intel_engine_pm.h"
>   #include "selftests/igt_flush_test.h"
>   
> diff --git a/drivers/gpu/drm/i915/i915_selftest.h b/drivers/gpu/drm/i915/i915_selftest.h
> index bdf3e22c0a34..72922028f4ba 100644
> --- a/drivers/gpu/drm/i915/i915_selftest.h
> +++ b/drivers/gpu/drm/i915/i915_selftest.h
> @@ -26,6 +26,8 @@
>   
>   #include <linux/types.h>
>   
> +#define STACK_MAGIC	0xdeadbeef
> +
>   struct pci_dev;
>   struct drm_i915_private;
>   
> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> index 5b46924fdff5..61d63c57bc2d 100644
> --- a/include/linux/kernel.h
> +++ b/include/linux/kernel.h
> @@ -40,8 +40,6 @@
>   
>   #include <uapi/linux/kernel.h>
>   
> -#define STACK_MAGIC	0xdeadbeef
> -
>   struct completion;
>   struct user;
>   

Re: [PATCH v2 2/4] moduleparam: include required headers explicitly

[Petr Pavlu]

On 12/3/25 5:23 PM, Yury Norov (NVIDIA) wrote:
> The following patch drops moduleparam.h dependency on kernel.h. In
> preparation to it, list all the required headers explicitly.
> 
> Suggested-by: Petr Pavlu <petr.pavlu@suse.com>
> CC: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>

Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>

-- 
Thanks,
Petr

Re: [PATCH v2 3/4] kernel.h: move VERIFY_OCTAL_PERMISSIONS() to sysfs.h

[Petr Pavlu]

On 12/3/25 5:23 PM, Yury Norov (NVIDIA) wrote:
> The macro is related to sysfs, but is defined in kernel.h. Move it to
> the proper header, and unload the generic kernel.h.
> 
> Now that the macro is removed from kernel.h, linux/moduleparam.h is
> decoupled, and kernel.h inclusion can be removed.
> 
> Acked-by: Randy Dunlap <rdunlap@infradead.org>
> Tested-by: Randy Dunlap <rdunlap@infradead.org>
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>

Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>

-- 
Thanks,
Petr