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lib/vsprintf.c: update documentation 

%n is no longer just ignored; it results in early return from vsnprintf.
Also add a request to add test cases for future %p extensions.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Rasmus Villemoes 2015-11-06 16:30:35 -08:00 committed by Linus Torvalds
parent 317dc34ab7
commit d7ec9a05d6
2 changed files with 10 additions and 9 deletions
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12
Documentation/printk-formats.txt
View File

@ -23,6 +23,10 @@ Example:
Reminder: sizeof() result is of type size_t.
The kernel's printf does not support %n. For obvious reasons, floating
point formats (%e, %f, %g, %a) are also not recognized. Use of any
unsupported specifier or length qualifier results in a WARN and early
return from vsnprintf.
Raw pointer value SHOULD be printed with %p. The kernel supports
the following extended format specifiers for pointer types:
@ -305,13 +309,9 @@ Command from struct task_struct
Passed by reference.
Ignored argument:
If you add other %p extensions, please extend lib/test_printf.c with
one or more test cases, if at all feasible.
%n %n
The argument passed will be ignored. In other words, literal "%n" will
be in the output and the argument will be considered for next format
specifier.
Thank you for your cooperation and attention.

7
lib/vsprintf.c
View File

@ -1448,7 +1448,6 @@ int kptr_restrict __read_mostly;
* - 'Cn' For a clock, it prints the name (Common Clock Framework) or address
* (legacy clock framework) of the clock
* - 'Cr' For a clock, it prints the current rate of the clock
* - 'n' For ignored argument
*
* ** Please update also Documentation/printk-formats.txt when making changes **
*
@ -1814,8 +1813,10 @@ int format_decode(const char *fmt, struct printf_spec *spec)
* @fmt: The format string to use
* @args: Arguments for the format string
*
* This function follows C99 vsnprintf, but has some extensions:
* %n is ignored
* This function generally follows C99 vsnprintf, but has some
* extensions and a few limitations:
*
* %n is unsupported
* %p* is handled by pointer()
*
* See pointer() or Documentation/printk-formats.txt for more