Re: [PATCH 02/12] Add parse_integer() (replacement for simple_strto*())

[Andrew Morton <akpm@linux-foundation.org>]

On Fri, 8 May 2015 21:30:29 +0300 Alexey Dobriyan <adobriyan@gmail.com> wrote:

> kstrto*() and kstrto*_from_user() family of functions were added
> to help with parsing one integer written as string to proc/sysfs/debugfs
> files. But they have a limitation: string passed must end with \0 or \n\0.
> There are enough places where kstrto*() functions can't be used because of
> this limitation. Trivial example: major:minor "%u:%u".
> 
> Currently the only way to parse everything is simple_strto*() functions.
> But they are suboptimal:
> * they do not detect overflow (can be fixed, but no one bothered since ~0.99.11),
> * there are only 4 of them -- long and "long long" versions,
>   This leads to silent truncation in the most simple case:
> 
> 	val = strtoul(s, NULL, 0);
> 
> * half of the people think that "char **endp" argument is necessary and
>   add unnecessary variable.
> 
> OpenBSD people, fed up with how complex correct integer parsing is, added
> strtonum(3) to fixup for deficiencies of libc-style integer parsing:
> http://www.openbsd.org/cgi-bin/man.cgi/OpenBSD-current/man3/strtonum.3?query=strtonum&arch=i386
> 
> It'd be OK to copy that but it relies on "errno" and fixed strings as
> error reporting channel which I think is not OK for kernel.
> strtonum() also doesn't report number of characted consumed.
> 
> What to do?
> 
> Enter parse_integer().

 fs/binfmt_misc.c               |   12 
 fs/cachefiles/daemon.c         |   84 ++--
 fs/dcache.c                    |    2 
 fs/ext2/super.c                |    6 
 fs/ext3/super.c                |    7 
 fs/ext4/super.c                |   15 
 fs/inode.c                     |    2 
 fs/libfs.c                     |   26 -
 fs/namespace.c                 |    4 
 fs/ocfs2/cluster/heartbeat.c   |   54 +-
 fs/ocfs2/cluster/nodemanager.c |   50 +-
 fs/ocfs2/stack_user.c          |   52 +-
 include/linux/kernel.h         |  129 -------
 include/linux/parse-integer.h  |  188 ++++++++++
 lib/Kconfig.debug              |    3 
 lib/Makefile                   |    2 
 lib/cmdline.c                  |   42 +-
 lib/kstrtox.c                  |  254 -------------
 lib/kstrtox.h                  |    1 
 lib/parse-integer.c            |  222 ++++++++++++
 lib/parser.c                   |   33 -
 lib/swiotlb.c                  |    2 
 lib/test-kstrtox.c             |    6 
 lib/test-parse-integer.c       |  563 +++++++++++++++++++++++++++++++
 lib/vsprintf.c                 |   81 ++--
 mm/memcontrol.c                |   19 -
 mm/memtest.c                   |    2 
 mm/page_alloc.c                |    2 
 mm/shmem.c                     |   14 
 29 files changed, 1242 insertions(+), 635 deletions(-)

So not counting lib/test-parse-integer.c, it's a net addition of 44
lines.  That's OK.

My overall reaction to this is "oh god, not again".  Is it really worth
it?


> --- /dev/null
> +++ b/include/linux/parse-integer.h
> @@ -0,0 +1,79 @@
> +#ifndef _PARSE_INTEGER_H
> +#define _PARSE_INTEGER_H
> +#include <linux/compiler.h>
> +#include <linux/types.h>
> +
> +/*
> + * int parse_integer(const char *s, unsigned int base, T *val);
> + *
> + * Convert integer string representation to an integer.
> + * Range of accepted values equals to that of type T.
> + *
> + * Conversion to unsigned integer accepts sign "+".
> + * Conversion to signed integer accepts sign "+" and sign "-".
> + *
> + * Radix 0 means autodetection: leading "0x" implies radix 16,
> + * leading "0" implies radix 8, otherwise radix is 10.
> + * Autodetection hint works after optional sign, but not before.
> + *
> + * Return number of characters parsed or -E.
> + *
> + * "T=char" case is not supported because -f{un,}signed-char can silently
> + * change range of accepted values.
> + */
> +#define parse_integer(s, base, val)	\
> +({					\
> +	const char *_s = (s);		\
> +	unsigned int _base = (base);	\
> +	typeof(&(val)[0]) _val = (val);	\
> +					\
> +	__builtin_choose_expr(						\
> +	__builtin_types_compatible_p(typeof(_val), signed char *),	\
> +	_parse_integer_sc(_s, _base, (void *)_val),			\
> +	__builtin_choose_expr(						\
> +	__builtin_types_compatible_p(typeof(_val), unsigned char *),	\
> +	_parse_integer_uc(_s, _base, (void *)_val),			\
> +	__builtin_choose_expr(						\
> +	__builtin_types_compatible_p(typeof(_val), short *),		\
> +	_parse_integer_s(_s, _base, (void *)_val),			\
> +	__builtin_choose_expr(						\
> +	__builtin_types_compatible_p(typeof(_val), unsigned short *),	\
> +	_parse_integer_us(_s, _base, (void *)_val),			\
> +	__builtin_choose_expr(						\
> +	__builtin_types_compatible_p(typeof(_val), int *),		\
> +	_parse_integer_i(_s, _base, (void *)_val),			\
> +	__builtin_choose_expr(						\
> +	__builtin_types_compatible_p(typeof(_val), unsigned int *),	\
> +	_parse_integer_u(_s, _base, (void *)_val),			\
> +	__builtin_choose_expr(						\
> +	__builtin_types_compatible_p(typeof(_val), long *) && sizeof(long) == 4,\
> +	_parse_integer_i(_s, _base, (void *)_val),			\
> +	__builtin_choose_expr(						\
> +	__builtin_types_compatible_p(typeof(_val), long *) && sizeof(long) == 8,\
> +	_parse_integer_ll(_s, _base, (void *)_val),			\
> +	__builtin_choose_expr(						\
> +	__builtin_types_compatible_p(typeof(_val), unsigned long *) && sizeof(unsigned long) == 4,\
> +	_parse_integer_u(_s, _base, (void *)_val),			\
> +	__builtin_choose_expr(						\
> +	__builtin_types_compatible_p(typeof(_val), unsigned long *) && sizeof(unsigned long) == 8,\
> +	_parse_integer_ull(_s, _base, (void *)_val),			\
> +	__builtin_choose_expr(						\
> +	__builtin_types_compatible_p(typeof(_val), long long *),	\
> +	_parse_integer_ll(_s, _base, (void *)_val),			\
> +	__builtin_choose_expr(						\
> +	__builtin_types_compatible_p(typeof(_val), unsigned long long *),\
> +	_parse_integer_ull(_s, _base, (void *)_val),			\
> +	_parse_integer_link_time_error()))))))))))));	\
> +})

Wow.

> +/* internal, do not use */
> +int _parse_integer_sc(const char *s, unsigned int base, signed char *val);
> +int _parse_integer_uc(const char *s, unsigned int base, unsigned char *val);
> +int _parse_integer_s(const char *s, unsigned int base, short *val);
> +int _parse_integer_us(const char *s, unsigned int base, unsigned short *val);
> +int _parse_integer_i(const char *s, unsigned int base, int *val);
> +int _parse_integer_u(const char *s, unsigned int base, unsigned int *val);
> +int _parse_integer_ll(const char *s, unsigned int base, long long *val);
> +int _parse_integer_ull(const char *s, unsigned int base, unsigned long long *val);

These all have fairly lengthy implementations.  Could it all be done
with a single function?

int __parse_integer(const char *s, unsigned int base, unsigned int size, void *val);

Where "size" is 1,2,4,8 with the top bit set if signed?