[PATCH] procfs: Fix /proc/self/maps output for 32-bit kernel and compat tasks

[PATCH] procfs: Fix /proc/self/maps output for 32-bit kernel and compat tasks

[Helge Deller]

On a 32-bit kernel addresses should be shown with 8 hex digits, e.g.:

root@debian:~# cat /proc/self/maps
00010000-00019000 r-xp 00000000 08:05 787324     /usr/bin/cat
00019000-0001a000 rwxp 00009000 08:05 787324     /usr/bin/cat
0001a000-0003b000 rwxp 00000000 00:00 0          [heap]
f7551000-f770d000 r-xp 00000000 08:05 794765     /usr/lib/hppa-linux-gnu/libc.so.6
f770d000-f770f000 r--p 001bc000 08:05 794765     /usr/lib/hppa-linux-gnu/libc.so.6
f770f000-f7714000 rwxp 001be000 08:05 794765     /usr/lib/hppa-linux-gnu/libc.so.6
f7d39000-f7d68000 r-xp 00000000 08:05 794759     /usr/lib/hppa-linux-gnu/ld.so.1
f7d68000-f7d69000 r--p 0002f000 08:05 794759     /usr/lib/hppa-linux-gnu/ld.so.1
f7d69000-f7d6d000 rwxp 00030000 08:05 794759     /usr/lib/hppa-linux-gnu/ld.so.1
f7ea9000-f7eaa000 r-xp 00000000 00:00 0          [vdso]
f8565000-f8587000 rwxp 00000000 00:00 0          [stack]

But since commmit 0e3dc0191431 ("procfs: add seq_put_hex_ll to speed up
/proc/pid/maps") even on native 32-bit kernels the output looks like this:

root@debian:~# cat /proc/self/maps
0000000010000-0000000019000 r-xp 00000000 000000008:000000005 787324  /usr/bin/cat
0000000019000-000000001a000 rwxp 000000009000 000000008:000000005 787324  /usr/bin/cat
000000001a000-000000003b000 rwxp 00000000 00:00 0  [heap]
00000000f73d1000-00000000f758d000 r-xp 00000000 000000008:000000005 794765  /usr/lib/hppa-linux-gnu/libc.so.6
00000000f758d000-00000000f758f000 r--p 000000001bc000 000000008:000000005 794765  /usr/lib/hppa-linux-gnu/libc.so.6
00000000f758f000-00000000f7594000 rwxp 000000001be000 000000008:000000005 794765  /usr/lib/hppa-linux-gnu/libc.so.6
00000000f7af9000-00000000f7b28000 r-xp 00000000 000000008:000000005 794759  /usr/lib/hppa-linux-gnu/ld.so.1
00000000f7b28000-00000000f7b29000 r--p 000000002f000 000000008:000000005 794759  /usr/lib/hppa-linux-gnu/ld.so.1
00000000f7b29000-00000000f7b2d000 rwxp 0000000030000 000000008:000000005 794759  /usr/lib/hppa-linux-gnu/ld.so.1
00000000f7e0c000-00000000f7e0d000 r-xp 00000000 00:00 0  [vdso]
00000000f9061000-00000000f9083000 rwxp 00000000 00:00 0  [stack]

This patch brings back the old default 8-hex digit output for
32-bit kernels and compat tasks.

Signed-off-by: Helge Deller <deller@gmx.de>
Fixes: 0e3dc0191431 ("procfs: add seq_put_hex_ll to speed up /proc/pid/maps")
Cc: Andrei Vagin <avagin@openvz.org>

diff --git a/fs/seq_file.c b/fs/seq_file.c
index f5fdaf3b1572..1a15b531aede 100644
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -19,6 +19,7 @@
 #include <linux/printk.h>
 #include <linux/string_helpers.h>
 #include <linux/uio.h>
+#include <linux/compat.h>
 
 #include <linux/uaccess.h>
 #include <asm/page.h>
@@ -759,11 +760,16 @@ void seq_put_hex_ll(struct seq_file *m, const char *delimiter,
 			seq_puts(m, delimiter);
 	}
 
+#ifdef CONFIG_64BIT
 	/* If x is 0, the result of __builtin_clzll is undefined */
-	if (v == 0)
+	if (v == 0 || is_compat_task())
 		len = 1;
 	else
 		len = (sizeof(v) * 8 - __builtin_clzll(v) + 3) / 4;
+#else
+	/* On 32-bit kernel always use provided width */
+	len = 1;
+#endif
 
 	if (len < width)
 		len = width;

Re: [PATCH] procfs: Fix /proc/self/maps output for 32-bit kernel and compat tasks

[Vegard Nossum]

On 8/19/23 11:21, Helge Deller wrote:
> On a 32-bit kernel addresses should be shown with 8 hex digits, e.g.:
> 
> root@debian:~# cat /proc/self/maps
> 00010000-00019000 r-xp 00000000 08:05 787324     /usr/bin/cat
> 00019000-0001a000 rwxp 00009000 08:05 787324     /usr/bin/cat
> 0001a000-0003b000 rwxp 00000000 00:00 0          [heap]
> f7551000-f770d000 r-xp 00000000 08:05 794765     /usr/lib/hppa-linux-gnu/libc.so.6
> f770d000-f770f000 r--p 001bc000 08:05 794765     /usr/lib/hppa-linux-gnu/libc.so.6
> f770f000-f7714000 rwxp 001be000 08:05 794765     /usr/lib/hppa-linux-gnu/libc.so.6
> f7d39000-f7d68000 r-xp 00000000 08:05 794759     /usr/lib/hppa-linux-gnu/ld.so.1
> f7d68000-f7d69000 r--p 0002f000 08:05 794759     /usr/lib/hppa-linux-gnu/ld.so.1
> f7d69000-f7d6d000 rwxp 00030000 08:05 794759     /usr/lib/hppa-linux-gnu/ld.so.1
> f7ea9000-f7eaa000 r-xp 00000000 00:00 0          [vdso]
> f8565000-f8587000 rwxp 00000000 00:00 0          [stack]
> 
> But since commmit 0e3dc0191431 ("procfs: add seq_put_hex_ll to speed up
> /proc/pid/maps") even on native 32-bit kernels the output looks like this:
> 
> root@debian:~# cat /proc/self/maps
> 0000000010000-0000000019000 r-xp 00000000 000000008:000000005 787324  /usr/bin/cat
> 0000000019000-000000001a000 rwxp 000000009000 000000008:000000005 787324  /usr/bin/cat
> 000000001a000-000000003b000 rwxp 00000000 00:00 0  [heap]
> 00000000f73d1000-00000000f758d000 r-xp 00000000 000000008:000000005 794765  /usr/lib/hppa-linux-gnu/libc.so.6
> 00000000f758d000-00000000f758f000 r--p 000000001bc000 000000008:000000005 794765  /usr/lib/hppa-linux-gnu/libc.so.6
> 00000000f758f000-00000000f7594000 rwxp 000000001be000 000000008:000000005 794765  /usr/lib/hppa-linux-gnu/libc.so.6
> 00000000f7af9000-00000000f7b28000 r-xp 00000000 000000008:000000005 794759  /usr/lib/hppa-linux-gnu/ld.so.1
> 00000000f7b28000-00000000f7b29000 r--p 000000002f000 000000008:000000005 794759  /usr/lib/hppa-linux-gnu/ld.so.1
> 00000000f7b29000-00000000f7b2d000 rwxp 0000000030000 000000008:000000005 794759  /usr/lib/hppa-linux-gnu/ld.so.1
> 00000000f7e0c000-00000000f7e0d000 r-xp 00000000 00:00 0  [vdso]
> 00000000f9061000-00000000f9083000 rwxp 00000000 00:00 0  [stack]
> 
> This patch brings back the old default 8-hex digit output for
> 32-bit kernels and compat tasks.
> 
> Signed-off-by: Helge Deller <deller@gmx.de>
> Fixes: 0e3dc0191431 ("procfs: add seq_put_hex_ll to speed up /proc/pid/maps")
> Cc: Andrei Vagin <avagin@openvz.org>
> 
> diff --git a/fs/seq_file.c b/fs/seq_file.c
> index f5fdaf3b1572..1a15b531aede 100644
> --- a/fs/seq_file.c
> +++ b/fs/seq_file.c
> @@ -19,6 +19,7 @@
>   #include <linux/printk.h>
>   #include <linux/string_helpers.h>
>   #include <linux/uio.h>
> +#include <linux/compat.h>
>   
>   #include <linux/uaccess.h>
>   #include <asm/page.h>
> @@ -759,11 +760,16 @@ void seq_put_hex_ll(struct seq_file *m, const char *delimiter,
>   			seq_puts(m, delimiter);
>   	}
>   
> +#ifdef CONFIG_64BIT
>   	/* If x is 0, the result of __builtin_clzll is undefined */
> -	if (v == 0)
> +	if (v == 0 || is_compat_task())
>   		len = 1;
>   	else
>   		len = (sizeof(v) * 8 - __builtin_clzll(v) + 3) / 4;
> +#else
> +	/* On 32-bit kernel always use provided width */
> +	len = 1;
> +#endif
>   
>   	if (len < width)
>   		len = width;

Hi,

I think this is fixing the wrong thing.

seq_put_hex_ll() is a generic routine so the #ifdef/is_compat_task()
doesn't seem to belong there.

Moreover, the kerneldoc comment on this function states:

  * seq_put_hex_ll(m, "", v, 8) is equal to seq_printf(m, "%08llx", v)

The seq_put_hex_ll() call from show_vma_header_prefix() is calling this
with the last argument (minimum padding length) being 8, so why is it
padding to more than that in the first place?

Look at your example:

 > root@debian:~# cat /proc/self/maps
 > 0000000010000-0000000019000 r-xp 00000000 000000008:000000005 787324 
/usr/bin/cat

that's padded to... 13 hex characters? Huh?

Even on my x86_64, short addresses are only padded to 8 bytes, as they
should be in all cases. Could there possibly be a bug in parisc
__builtin_clzll()...?


Vegard

Re: [PATCH] procfs: Fix /proc/self/maps output for 32-bit kernel and compat tasks

[kernel test robot]

Hi Helge,

kernel test robot noticed the following build errors:

[auto build test ERROR on linus/master]
[also build test ERROR on v6.5-rc7 next-20230821]
[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/Helge-Deller/procfs-Fix-proc-self-maps-output-for-32-bit-kernel-and-compat-tasks/20230821-100823
base:   linus/master
patch link:    https://lore.kernel.org/r/ZOCJltW%2FeufPUc%2BT%40p100
patch subject: [PATCH] procfs: Fix /proc/self/maps output for 32-bit kernel and compat tasks
config: x86_64-buildonly-randconfig-006-20230822 (https://download.01.org/0day-ci/archive/20230822/202308220747.XMKc32Kz-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce: (https://download.01.org/0day-ci/archive/20230822/202308220747.XMKc32Kz-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/202308220747.XMKc32Kz-lkp@intel.com/

All errors (new ones prefixed by >>):

   fs/seq_file.c: In function 'seq_put_hex_ll':
>> fs/seq_file.c:765:23: error: implicit declaration of function 'is_compat_task' [-Werror=implicit-function-declaration]
     765 |         if (v == 0 || is_compat_task())
         |                       ^~~~~~~~~~~~~~
   cc1: some warnings being treated as errors


vim +/is_compat_task +765 fs/seq_file.c

   737	
   738	/**
   739	 * seq_put_hex_ll - put a number in hexadecimal notation
   740	 * @m: seq_file identifying the buffer to which data should be written
   741	 * @delimiter: a string which is printed before the number
   742	 * @v: the number
   743	 * @width: a minimum field width
   744	 *
   745	 * seq_put_hex_ll(m, "", v, 8) is equal to seq_printf(m, "%08llx", v)
   746	 *
   747	 * This routine is very quick when you show lots of numbers.
   748	 * In usual cases, it will be better to use seq_printf(). It's easier to read.
   749	 */
   750	void seq_put_hex_ll(struct seq_file *m, const char *delimiter,
   751					unsigned long long v, unsigned int width)
   752	{
   753		unsigned int len;
   754		int i;
   755	
   756		if (delimiter && delimiter[0]) {
   757			if (delimiter[1] == 0)
   758				seq_putc(m, delimiter[0]);
   759			else
   760				seq_puts(m, delimiter);
   761		}
   762	
   763	#ifdef CONFIG_64BIT
   764		/* If x is 0, the result of __builtin_clzll is undefined */
 > 765		if (v == 0 || is_compat_task())
   766			len = 1;
   767		else
   768			len = (sizeof(v) * 8 - __builtin_clzll(v) + 3) / 4;
   769	#else
   770		/* On 32-bit kernel always use provided width */
   771		len = 1;
   772	#endif
   773	
   774		if (len < width)
   775			len = width;
   776	
   777		if (m->count + len > m->size) {
   778			seq_set_overflow(m);
   779			return;
   780		}
   781	
   782		for (i = len - 1; i >= 0; i--) {
   783			m->buf[m->count + i] = hex_asc[0xf & v];
   784			v = v >> 4;
   785		}
   786		m->count += len;
   787	}
   788	

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

Re: [PATCH] procfs: Fix /proc/self/maps output for 32-bit kernel and compat tasks

[kernel test robot]

Hi Helge,

kernel test robot noticed the following build errors:

[auto build test ERROR on linus/master]
[also build test ERROR on v6.5-rc7 next-20230821]
[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/Helge-Deller/procfs-Fix-proc-self-maps-output-for-32-bit-kernel-and-compat-tasks/20230821-100823
base:   linus/master
patch link:    https://lore.kernel.org/r/ZOCJltW%2FeufPUc%2BT%40p100
patch subject: [PATCH] procfs: Fix /proc/self/maps output for 32-bit kernel and compat tasks
config: x86_64-randconfig-013-20230821 (https://download.01.org/0day-ci/archive/20230822/202308221231.B7yBmSQV-lkp@intel.com/config)
compiler: clang version 16.0.4 (https://github.com/llvm/llvm-project.git ae42196bc493ffe877a7e3dff8be32035dea4d07)
reproduce: (https://download.01.org/0day-ci/archive/20230822/202308221231.B7yBmSQV-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/202308221231.B7yBmSQV-lkp@intel.com/

All errors (new ones prefixed by >>):

>> fs/seq_file.c:765:16: error: call to undeclared function 'is_compat_task'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
           if (v == 0 || is_compat_task())
                         ^
   1 error generated.


vim +/is_compat_task +765 fs/seq_file.c

   737	
   738	/**
   739	 * seq_put_hex_ll - put a number in hexadecimal notation
   740	 * @m: seq_file identifying the buffer to which data should be written
   741	 * @delimiter: a string which is printed before the number
   742	 * @v: the number
   743	 * @width: a minimum field width
   744	 *
   745	 * seq_put_hex_ll(m, "", v, 8) is equal to seq_printf(m, "%08llx", v)
   746	 *
   747	 * This routine is very quick when you show lots of numbers.
   748	 * In usual cases, it will be better to use seq_printf(). It's easier to read.
   749	 */
   750	void seq_put_hex_ll(struct seq_file *m, const char *delimiter,
   751					unsigned long long v, unsigned int width)
   752	{
   753		unsigned int len;
   754		int i;
   755	
   756		if (delimiter && delimiter[0]) {
   757			if (delimiter[1] == 0)
   758				seq_putc(m, delimiter[0]);
   759			else
   760				seq_puts(m, delimiter);
   761		}
   762	
   763	#ifdef CONFIG_64BIT
   764		/* If x is 0, the result of __builtin_clzll is undefined */
 > 765		if (v == 0 || is_compat_task())
   766			len = 1;
   767		else
   768			len = (sizeof(v) * 8 - __builtin_clzll(v) + 3) / 4;
   769	#else
   770		/* On 32-bit kernel always use provided width */
   771		len = 1;
   772	#endif
   773	
   774		if (len < width)
   775			len = width;
   776	
   777		if (m->count + len > m->size) {
   778			seq_set_overflow(m);
   779			return;
   780		}
   781	
   782		for (i = len - 1; i >= 0; i--) {
   783			m->buf[m->count + i] = hex_asc[0xf & v];
   784			v = v >> 4;
   785		}
   786		m->count += len;
   787	}
   788	

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