arch/x86/boot/string.c

Source file repositories/reference/linux-study-clean/arch/x86/boot/string.c

File Facts

System
Linux kernel
Corpus path
arch/x86/boot/string.c
Extension
.c
Size
7531 bytes
Lines
351
Domain
Architecture Layer
Bucket
arch/x86
Inferred role
Architecture Layer: implementation source
Status
source implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

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.
 * Return number of characters consumed maybe or-ed with overflow bit.
 * If overflow occurs, result integer (incorrect) is still returned.
 *
 * Don't you dare use this function.
 */
static unsigned int _parse_integer(const char *s,
				   unsigned int base,
				   unsigned long long *p)
{
	unsigned long long res;
	unsigned int rv;

	res = 0;
	rv = 0;
	while (1) {
		unsigned int c = *s;
		unsigned int lc = c | 0x20; /* don't tolower() this line */
		unsigned int val;

		if ('0' <= c && c <= '9')
			val = c - '0';
		else if ('a' <= lc && lc <= 'f')
			val = lc - 'a' + 10;
		else
			break;

		if (val >= base)
			break;
		/*
		 * Check for overflow only if we are within range of
		 * it in the max base we support (16)
		 */
		if (unlikely(res & (~0ull << 60))) {
			if (res > __div_u64(ULLONG_MAX - val, base))
				rv |= KSTRTOX_OVERFLOW;
		}
		res = res * base + val;
		rv++;
		s++;
	}
	*p = res;
	return rv;
}

static int _kstrtoull(const char *s, unsigned int base, unsigned long long *res)
{
	unsigned long long _res;
	unsigned int rv;

	if (s[0] == '+')
		s++;

	s = _parse_integer_fixup_radix(s, &base);
	rv = _parse_integer(s, base, &_res);
	if (rv & KSTRTOX_OVERFLOW)
		return -ERANGE;
	if (rv == 0)
		return -EINVAL;
	s += rv;
	if (*s == '\n')
		s++;
	if (*s)
		return -EINVAL;
	*res = _res;
	return 0;
}

static int _kstrtoul(const char *s, unsigned int base, unsigned long *res)
{
	unsigned long long tmp;
	int rv;

	rv = _kstrtoull(s, base, &tmp);
	if (rv < 0)

Annotation

Implementation Notes