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@xxxxxx>
Fixes: 0e3dc0191431 ("procfs: add seq_put_hex_ll to speed up /proc/pid/maps")
Cc: Andrei Vagin <avagin@xxxxxxxxxx>
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
