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Subject[PATCH] Add parse_integer() (replacement for simple_strto*())
kstrto*() and kstrto*_from_user() family of functions were added
help with parsing one integer written as string to proc/sysfs/debugfs
files and pass it elsewhere. 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:
parse "%u.%u".

Currently the only way to parse everything is simple_strto*() family of
functions. But they are suboptimal:
* they do not detect overflow,
* there are only 2(4) of them -- long and "long long" version.
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().

int parse_integer(const char *s, unsigned int base, T *val);

Rationale:

* parse_integer() is exactly 1 (one) interface not 2 or many,
one for each type.
* parse_integer() reports -E errors reliably in a canonical kernel way:

rv = parse_integer(str, 10, &val);
if (rv < 0)
return rv;

* parse_integer() writes result only if there were no errors, at least
one digit was consumed.
* parse_integer doesn't mix error reporting channel and value channel,
it does mix error and number-of-character-consumed channel, though.

* parse_integer() reports number of characters consumed, makes parsing
multiple values easy:

rv = parse_integer(str, 0, &val1);
if (rv < 0)
return rv;
s += rv;
if (s != '.')
return -EINVAL;
rv = parse_integer(str, 0, &val2);
if (rv < 0)
return rv;
if (str[rv] != '\0')
return -EINVAL;

There are several deficiencies in parse_integer() compared to strto*():
* can't be used in initializers:

const T x = strtoul();

* can't be used with bitfields,
* can't be used in experessions:

x = strtol() * 1024;
x = y = strtol() * 1024;
x += strtol();

In defense of parse_integer() all I can say, is that using strtol() in
expression or initializer promotes no error checking and thus probably
should not be encouraged in C, language with no built-in error checking
anyway.

The amount of "x = y = strtol()" expressions in kernel is very small.
The amount of direct usage in expression is not small, but can be
counted as an acceptable loss.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---

include/linux/kernel.h | 72 +++++++++++++++++++
lib/Makefile | 1
lib/kstrtox.c | 27 +------
lib/parse-integer.c | 180 +++++++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 257 insertions(+), 23 deletions(-)

--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -251,6 +251,78 @@ void do_exit(long error_code)
void complete_and_exit(struct completion *, long)
__noreturn;

+/*
+ * int parse_integer(const char *s, unsigned int base, T *val);
+ *
+ * Convert integer string representation to an integer.
+ * If an integer doesn't fit into specified type, -E is returned.
+ *
+ * Conversion to signed integer accepts sign "-".
+ * Conversion to an unsigned integer doesn't accept sign "-".
+ *
+ * Radix 0 means autodetection: leading "0x" implies radix 16,
+ * leading "0" implies radix 8, otherwise radix is 10.
+ * Autodetection hints work after optional sign, but not before.
+ *
+ * If -E is returned, result is not touched.
+ *
+ * "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) _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 *) && BITS_PER_LONG == 32,\
+ _parse_integer_i(_s, _base, (void *)_val), \
+ __builtin_choose_expr( \
+ __builtin_types_compatible_p(typeof(_val), long *) && BITS_PER_LONG == 64,\
+ _parse_integer_ll(_s, _base, (void *)_val), \
+ __builtin_choose_expr( \
+ __builtin_types_compatible_p(typeof(_val), unsigned long *) && BITS_PER_LONG == 32,\
+ _parse_integer_u(_s, _base, (void *)_val), \
+ __builtin_choose_expr( \
+ __builtin_types_compatible_p(typeof(_val), unsigned long *) && BITS_PER_LONG == 64,\
+ _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())))))))))))); \
+})
+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);
+void _parse_integer_link_time_error(void);
+
/* Internal, do not use. */
int __must_check _kstrtoul(const char *s, unsigned int base, unsigned long *res);
int __must_check _kstrtol(const char *s, unsigned int base, long *res);
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -32,6 +32,7 @@ obj-$(CONFIG_TEST_STRING_HELPERS) += test-string_helpers.o
obj-y += hexdump.o
obj-$(CONFIG_TEST_HEXDUMP) += test-hexdump.o
obj-y += kstrtox.o
+obj-y += parse-integer.o
obj-$(CONFIG_TEST_BPF) += test_bpf.o
obj-$(CONFIG_TEST_FIRMWARE) += test_firmware.o
obj-$(CONFIG_TEST_KASAN) += test_kasan.o
--- a/lib/kstrtox.c
+++ b/lib/kstrtox.c
@@ -20,22 +20,6 @@
#include <asm/uaccess.h>
#include "kstrtox.h"

-const char *_parse_integer_fixup_radix(const char *s, unsigned int *base)
-{
- if (*base == 0) {
- if (s[0] == '0') {
- if (_tolower(s[1]) == 'x' && isxdigit(s[2]))
- *base = 16;
- else
- *base = 8;
- } else
- *base = 10;
- }
- if (*base == 16 && s[0] == '0' && _tolower(s[1]) == 'x')
- s += 2;
- return s;
-}
-
/*
* Convert non-negative integer string representation in explicitly given radix
* to an integer.
@@ -86,14 +70,11 @@ unsigned int _parse_integer(const char *s, unsigned int base, unsigned long long
static int _kstrtoull(const char *s, unsigned int base, unsigned long long *res)
{
unsigned long long _res;
- unsigned int rv;
+ int rv;

- s = _parse_integer_fixup_radix(s, &base);
- rv = _parse_integer(s, base, &_res);
- if (rv & KSTRTOX_OVERFLOW)
- return -ERANGE;
- if (rv == 0)
- return -EINVAL;
+ rv = parse_integer(s, base, &_res);
+ if (rv < 0)
+ return rv;
s += rv;
if (*s == '\n')
s++;
--- /dev/null
+++ b/lib/parse-integer.c
@@ -0,0 +1,180 @@
+/*
+ * See parse_integer().
+ *
+ * Individual dispatch functions in this file aren't supposed to be used
+ * directly and thus aren't advertised and documented despited being exported.
+ *
+ * Do not use any function in this file for any reason.
+ */
+#include <linux/ctype.h>
+#include <linux/errno.h>
+#include <linux/export.h>
+#include <linux/kernel.h>
+#include <linux/math64.h>
+#include <asm/bug.h>
+#include "kstrtox.h"
+
+const char *_parse_integer_fixup_radix(const char *s, unsigned int *base)
+{
+ if (*base == 0) {
+ if (s[0] == '0') {
+ if (_tolower(s[1]) == 'x' && isxdigit(s[2]))
+ *base = 16;
+ else
+ *base = 8;
+ } else
+ *base = 10;
+ }
+ if (*base == 16 && s[0] == '0' && _tolower(s[1]) == 'x')
+ s += 2;
+ BUG_ON(*base < 2 || *base > 16);
+ return s;
+}
+
+int _parse_integer_ull(const char *s, unsigned int base, unsigned long long *val)
+{
+ const char *s0 = s, *sd;
+ unsigned long long acc;
+
+ s = sd = _parse_integer_fixup_radix(s0, &base);
+ acc = 0;
+ while (*s != '\0') {
+ unsigned int d;
+
+ if ('0' <= *s && *s <= '9')
+ d = *s - '0';
+ else if ('a' <= _tolower(*s) && _tolower(*s) <= 'f')
+ d = _tolower(*s) - 'a' + 10;
+ else
+ break;
+ if (d >= base)
+ break;
+ /* Overflow can't happen early enough. */
+ if ((acc >> 60) && acc > div_u64(ULLONG_MAX - d, base))
+ return -ERANGE;
+ acc = acc * base + d;
+ s++;
+ }
+ /* At least one digit has to be converted. */
+ if (s == sd)
+ return -EINVAL;
+ *val = acc;
+ /* Radix 1 is not supported otherwise returned length can overflow. */
+ return s - s0;
+}
+EXPORT_SYMBOL(_parse_integer_ull);
+
+int _parse_integer_ll(const char *s, unsigned int base, long long *val)
+{
+ unsigned long long tmp;
+ int rv;
+
+ if (*s == '-') {
+ rv = _parse_integer_ull(s + 1, base, &tmp);
+ if (rv < 0)
+ return rv;
+ if ((long long)-tmp >= 0)
+ return -ERANGE;
+ *val = -tmp;
+ return rv + 1;
+ } else {
+ rv = _parse_integer_ull(s, base, &tmp);
+ if (rv < 0)
+ return rv;
+ if ((long long)tmp < 0)
+ return -ERANGE;
+ *val = tmp;
+ return rv;
+ }
+}
+EXPORT_SYMBOL(_parse_integer_ll);
+
+int _parse_integer_u(const char *s, unsigned int base, unsigned int *val)
+{
+ unsigned long long tmp;
+ int rv;
+
+ rv = _parse_integer_ull(s, base, &tmp);
+ if (rv < 0)
+ return rv;
+ if (tmp != (unsigned int)tmp)
+ return -ERANGE;
+ *val = tmp;
+ return rv;
+}
+EXPORT_SYMBOL(_parse_integer_u);
+
+int _parse_integer_i(const char *s, unsigned int base, int *val)
+{
+ long long tmp;
+ int rv;
+
+ rv = _parse_integer_ll(s, base, &tmp);
+ if (rv < 0)
+ return rv;
+ if (tmp != (int)tmp)
+ return -ERANGE;
+ *val = tmp;
+ return rv;
+}
+EXPORT_SYMBOL(_parse_integer_i);
+
+int _parse_integer_us(const char *s, unsigned int base, unsigned short *val)
+{
+ unsigned long long tmp;
+ int rv;
+
+ rv = _parse_integer_ull(s, base, &tmp);
+ if (rv < 0)
+ return rv;
+ if (tmp != (unsigned short)tmp)
+ return -ERANGE;
+ *val = tmp;
+ return rv;
+}
+EXPORT_SYMBOL(_parse_integer_us);
+
+int _parse_integer_s(const char *s, unsigned int base, short *val)
+{
+ long long tmp;
+ int rv;
+
+ rv = _parse_integer_ll(s, base, &tmp);
+ if (rv < 0)
+ return rv;
+ if (tmp != (short)tmp)
+ return -ERANGE;
+ *val = tmp;
+ return rv;
+}
+EXPORT_SYMBOL(_parse_integer_s);
+
+int _parse_integer_uc(const char *s, unsigned int base, unsigned char *val)
+{
+ unsigned long long tmp;
+ int rv;
+
+ rv = _parse_integer_ull(s, base, &tmp);
+ if (rv < 0)
+ return rv;
+ if (tmp != (unsigned char)tmp)
+ return -ERANGE;
+ *val = tmp;
+ return rv;
+}
+EXPORT_SYMBOL(_parse_integer_uc);
+
+int _parse_integer_sc(const char *s, unsigned int base, signed char *val)
+{
+ long long tmp;
+ int rv;
+
+ rv = _parse_integer_ll(s, base, &tmp);
+ if (rv < 0)
+ return rv;
+ if (tmp != (signed char)tmp)
+ return -ERANGE;
+ *val = tmp;
+ return rv;
+}
+EXPORT_SYMBOL(_parse_integer_sc);

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