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




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