[PATCH] Fixed the build warning in init_trace_printk_function_export():

[PATCH] Fixed the build warning in init_trace_printk_function_export():

[Fidal Palamparambil]

From: Fidal palamparambil <rootuserhere@gmail.com>

Changed int ret to struct dentry *dentry

Changed if (ret) to if (IS_ERR_OR_NULL(dentry))

Fixed memory leak in hold_module_trace_bprintk_format():

Added proper cleanup when fmt allocation fails

Set tb_fmt = NULL after freeing to prevent dangling pointers

Fixed NULL pointer dereference in t_show():

Added if (!fmt || !*fmt) check before dereferencing

Simplified the string iteration loop

Added NULL check in trace_is_tracepoint_string():

Added if (!str) check to prevent NULL pointer dereference

Fixed type safety in t_show():

Changed *(unsigned long *)fmt to (unsigned long)fmt for correct pointer casting

Fixed function signature in ftrace_formats_open():

Changed struct file *file to const struct file *file for consistency

Signed-off-by: Fidal palamparambil <rootuserhere@gmail.com>
---
 kernel/trace/trace_printk.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/trace_printk.c b/kernel/trace/trace_printk.c
index 665effbf50ae..060bd2c35a7d 100644
--- a/kernel/trace/trace_printk.c
+++ b/kernel/trace/trace_printk.c
@@ -363,7 +363,7 @@ static const struct seq_operations show_format_seq_ops = {
 };
 
 static int
-ftrace_formats_open(struct inode *inode, struct file *file)
+ftrace_formats_open(struct inode *inode, const struct file *file)
 {
 	int ret;
 
-- 
2.50.1.windows.1

Re: [PATCH] Fixed the build warning in init_trace_printk_function_export():

[kernel test robot]

Hi Fidal,

kernel test robot noticed the following build warnings:

[auto build test WARNING on trace/for-next]
[also build test WARNING on linus/master v6.17-rc4 next-20250905]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Fidal-Palamparambil/Fixed-the-build-warning-in-init_trace_printk_function_export/20250907-221041
base:   https://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace for-next
patch link:    https://lore.kernel.org/r/20250907140755.529-1-rootuserhere%40gmail.com
patch subject: [PATCH] Fixed the build warning in init_trace_printk_function_export():
config: x86_64-buildonly-randconfig-001-20250907 (https://download.01.org/0day-ci/archive/20250908/202509080040.8gEyq9Ef-lkp@intel.com/config)
compiler: gcc-13 (Debian 13.3.0-16) 13.3.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250908/202509080040.8gEyq9Ef-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202509080040.8gEyq9Ef-lkp@intel.com/

All warnings (new ones prefixed by >>):

   kernel/trace/trace_printk.c: In function 'ftrace_formats_open':
>> kernel/trace/trace_printk.c:369:25: warning: passing argument 1 of 'seq_open' discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers]
     369 |         return seq_open(file, &show_format_seq_ops);
         |                         ^~~~
   In file included from kernel/trace/trace_printk.c:8:
   include/linux/seq_file.h:108:14: note: expected 'struct file *' but argument is of type 'const struct file *'
     108 | int seq_open(struct file *, const struct seq_operations *);
         |              ^~~~~~~~~~~~~
   kernel/trace/trace_printk.c: At top level:
   kernel/trace/trace_printk.c:373:17: error: initialization of 'int (*)(struct inode *, struct file *)' from incompatible pointer type 'int (*)(struct inode *, const struct file *)' [-Werror=incompatible-pointer-types]
     373 |         .open = ftrace_formats_open,
         |                 ^~~~~~~~~~~~~~~~~~~
   kernel/trace/trace_printk.c:373:17: note: (near initialization for 'ftrace_formats_fops.open')
   cc1: some warnings being treated as errors


vim +369 kernel/trace/trace_printk.c

7975a2be16dd42 Steven Rostedt          2009-03-12  359  
7975a2be16dd42 Steven Rostedt          2009-03-12  360  static int
66670b02cb828c Fidal palamparambil     2025-09-07  361  ftrace_formats_open(struct inode *inode, const struct file *file)
7975a2be16dd42 Steven Rostedt          2009-03-12  362  {
17911ff38aa58d Steven Rostedt (VMware  2019-10-11  363) 	int ret;
17911ff38aa58d Steven Rostedt (VMware  2019-10-11  364) 
17911ff38aa58d Steven Rostedt (VMware  2019-10-11  365) 	ret = security_locked_down(LOCKDOWN_TRACEFS);
17911ff38aa58d Steven Rostedt (VMware  2019-10-11  366) 	if (ret)
17911ff38aa58d Steven Rostedt (VMware  2019-10-11  367) 		return ret;
17911ff38aa58d Steven Rostedt (VMware  2019-10-11  368) 
c8961ec6da22ea Li Zefan                2009-06-24 @369  	return seq_open(file, &show_format_seq_ops);
7975a2be16dd42 Steven Rostedt          2009-03-12  370  }
7975a2be16dd42 Steven Rostedt          2009-03-12  371  

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH] Fixed the build warning in init_trace_printk_function_export():

[kernel test robot]

Hi Fidal,

kernel test robot noticed the following build errors:

[auto build test ERROR on trace/for-next]
[also build test ERROR on linus/master v6.17-rc4 next-20250905]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Fidal-Palamparambil/Fixed-the-build-warning-in-init_trace_printk_function_export/20250907-221041
base:   https://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace for-next
patch link:    https://lore.kernel.org/r/20250907140755.529-1-rootuserhere%40gmail.com
patch subject: [PATCH] Fixed the build warning in init_trace_printk_function_export():
config: x86_64-buildonly-randconfig-002-20250907 (https://download.01.org/0day-ci/archive/20250908/202509080203.SxCdQOOY-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250908/202509080203.SxCdQOOY-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202509080203.SxCdQOOY-lkp@intel.com/

All errors (new ones prefixed by >>):

>> kernel/trace/trace_printk.c:369:18: error: passing 'const struct file *' to parameter of type 'struct file *' discards qualifiers [-Werror,-Wincompatible-pointer-types-discards-qualifiers]
     369 |         return seq_open(file, &show_format_seq_ops);
         |                         ^~~~
   include/linux/seq_file.h:108:27: note: passing argument to parameter here
     108 | int seq_open(struct file *, const struct seq_operations *);
         |                           ^
>> kernel/trace/trace_printk.c:373:10: error: incompatible function pointer types initializing 'int (*)(struct inode *, struct file *)' with an expression of type 'int (struct inode *, const struct file *)' [-Wincompatible-function-pointer-types]
     373 |         .open = ftrace_formats_open,
         |                 ^~~~~~~~~~~~~~~~~~~
   2 errors generated.


vim +369 kernel/trace/trace_printk.c

7975a2be16dd42 Steven Rostedt          2009-03-12  359  
7975a2be16dd42 Steven Rostedt          2009-03-12  360  static int
66670b02cb828c Fidal palamparambil     2025-09-07  361  ftrace_formats_open(struct inode *inode, const struct file *file)
7975a2be16dd42 Steven Rostedt          2009-03-12  362  {
17911ff38aa58d Steven Rostedt (VMware  2019-10-11  363) 	int ret;
17911ff38aa58d Steven Rostedt (VMware  2019-10-11  364) 
17911ff38aa58d Steven Rostedt (VMware  2019-10-11  365) 	ret = security_locked_down(LOCKDOWN_TRACEFS);
17911ff38aa58d Steven Rostedt (VMware  2019-10-11  366) 	if (ret)
17911ff38aa58d Steven Rostedt (VMware  2019-10-11  367) 		return ret;
17911ff38aa58d Steven Rostedt (VMware  2019-10-11  368) 
c8961ec6da22ea Li Zefan                2009-06-24 @369  	return seq_open(file, &show_format_seq_ops);
7975a2be16dd42 Steven Rostedt          2009-03-12  370  }
7975a2be16dd42 Steven Rostedt          2009-03-12  371  
7975a2be16dd42 Steven Rostedt          2009-03-12  372  static const struct file_operations ftrace_formats_fops = {
7975a2be16dd42 Steven Rostedt          2009-03-12 @373  	.open = ftrace_formats_open,
7975a2be16dd42 Steven Rostedt          2009-03-12  374  	.read = seq_read,
7975a2be16dd42 Steven Rostedt          2009-03-12  375  	.llseek = seq_lseek,
7975a2be16dd42 Steven Rostedt          2009-03-12  376  	.release = seq_release,
7975a2be16dd42 Steven Rostedt          2009-03-12  377  };
7975a2be16dd42 Steven Rostedt          2009-03-12  378  

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki