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Add safe vsnprintf and snprintf library functions

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From: Sonny Rao <sonnyrao@chromium.org>

These functions are useful in U-Boot because they allow a graceful failure
rather than an unpredictable stack overflow when printf() buffers are
exceeded.

Mostly copied from the Linux kernel. I copied vscnprintf and
scnprintf so we can change printf and vprintf to use the safe
implementation but still return the correct values.

(Simon Glass <sjg@chromium.org> modified this commit a little)

Signed-off-by: Sonny Rao <sonnyrao@chromium.org>
This commit is contained in:
Sonny Rao 2011-11-02 09:52:08 +00:00 committed by Wolfgang Denk
parent 9785c905cf
commit 046a37bd53
3 changed files with 241 additions and 52 deletions
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9
README
View file

@ -655,6 +655,15 @@ The following options need to be configured:
to get the character out. Baud rates will need to default
to something sensible.
- Safe printf() functions
Define CONFIG_SYS_VSNPRINTF to compile in safe versions of
the printf() functions. These are defined in
include/vsprintf.h and include snprintf(), vsnprintf() and
so on. Code size increase is approximately 300-500 bytes.
If this option is not given then these functions will
silently discard their buffer size argument - this means
you are not getting any overflow checking in this case.
- Boot Delay: CONFIG_BOOTDELAY - in seconds
Delay before automatically booting the default image;
set to -1 to disable autoboot.

19
include/vsprintf.h
View file

@ -36,4 +36,23 @@ int sprintf(char *buf, const char *fmt, ...)
int vsprintf(char *buf, const char *fmt, va_list args);
char *simple_itoa(ulong i);
#ifdef CONFIG_SYS_VSNPRINTF
int snprintf(char *buf, size_t size, const char *fmt, ...)
__attribute__ ((format (__printf__, 3, 4)));
int scnprintf(char *buf, size_t size, const char *fmt, ...)
__attribute__ ((format (__printf__, 3, 4)));
int vsnprintf(char *buf, size_t size, const char *fmt, va_list args);
int vscnprintf(char *buf, size_t size, const char *fmt, va_list args);
#else
/*
* Use macros to silently drop the size parameter. Note that the 'cn'
* versions are the same as the 'n' versions since the functions assume
* there is always enough buffer space when !CONFIG_SYS_VSNPRINTF
*/
#define snprintf(buf, size, fmt, args...) sprintf(buf, fmt, ##args)
#define scnprintf(buf, size, fmt, args...) sprintf(buf, fmt, ##args)
#define vsnprintf(buf, size, fmt, args...) vsprintf(buf, fmt, ##args)
#define vscnprintf(buf, size, fmt, args...) vsprintf(buf, fmt, ##args)
#endif /* CONFIG_SYS_VSNPRINTF */
#endif

265
lib/vsprintf.c
View file

@ -26,6 +26,9 @@
# define NUM_TYPE long long
#define noinline __attribute__((noinline))
/* some reluctance to put this into a new limits.h, so it is here */
#define INT_MAX ((int)(~0U>>1))
const char hex_asc[] = "0123456789abcdef";
#define hex_asc_lo(x) hex_asc[((x) & 0x0f)]
#define hex_asc_hi(x) hex_asc[((x) & 0xf0) >> 4]
@ -291,7 +294,22 @@ static noinline char* put_dec(char *buf, unsigned NUM_TYPE num)
#define SMALL 32 /* Must be 32 == 0x20 */
#define SPECIAL 64 /* 0x */
static char *number(char *buf, unsigned NUM_TYPE num, int base, int size, int precision, int type)
#ifdef CONFIG_SYS_VSNPRINTF
/*
* Macro to add a new character to our output string, but only if it will
* fit. The macro moves to the next character position in the output string.
*/
#define ADDCH(str, ch) do { \
if ((str) < end) \
*(str) = (ch); \
++str; \
} while (0)
#else
#define ADDCH(str, ch) (*(str)++ = (ch))
#endif
static char *number(char *buf, char *end, unsigned NUM_TYPE num,
int base, int size, int precision, int type)
{
/* we are called with base 8, 10 or 16, only, thus don't need "G..." */
static const char digits[16] = "0123456789ABCDEF"; /* "GHIJKLMNOPQRSTUVWXYZ"; */
@ -353,37 +371,40 @@ static char *number(char *buf, unsigned NUM_TYPE num, int base, int size, int pr
precision = i;
/* leading space padding */
size -= precision;
if (!(type & (ZEROPAD+LEFT)))
while(--size >= 0)
*buf++ = ' ';
if (!(type & (ZEROPAD + LEFT))) {
while (--size >= 0)
ADDCH(buf, ' ');
}
/* sign */
if (sign)
*buf++ = sign;
ADDCH(buf, sign);
/* "0x" / "0" prefix */
if (need_pfx) {
*buf++ = '0';
ADDCH(buf, '0');
if (base == 16)
*buf++ = ('X' | locase);
ADDCH(buf, 'X' | locase);
}
/* zero or space padding */
if (!(type & LEFT)) {
char c = (type & ZEROPAD) ? '0' : ' ';
while (--size >= 0)
*buf++ = c;
ADDCH(buf, c);
}
/* hmm even more zero padding? */
while (i <= --precision)
*buf++ = '0';
ADDCH(buf, '0');
/* actual digits of result */
while (--i >= 0)
*buf++ = tmp[i];
ADDCH(buf, tmp[i]);
/* trailing space padding */
while (--size >= 0)
*buf++ = ' ';
ADDCH(buf, ' ');
return buf;
}
static char *string(char *buf, char *s, int field_width, int precision, int flags)
static char *string(char *buf, char *end, char *s, int field_width,
int precision, int flags)
{
int len, i;
@ -394,16 +415,16 @@ static char *string(char *buf, char *s, int field_width, int precision, int flag
if (!(flags & LEFT))
while (len < field_width--)
*buf++ = ' ';
ADDCH(buf, ' ');
for (i = 0; i < len; ++i)
*buf++ = *s++;
ADDCH(buf, *s++);
while (len < field_width--)
*buf++ = ' ';
ADDCH(buf, ' ');
return buf;
}
#ifdef CONFIG_CMD_NET
static char *mac_address_string(char *buf, u8 *addr, int field_width,
static char *mac_address_string(char *buf, char *end, u8 *addr, int field_width,
int precision, int flags)
{
char mac_addr[6 * 3]; /* (6 * 2 hex digits), 5 colons and trailing zero */
@ -417,10 +438,11 @@ static char *mac_address_string(char *buf, u8 *addr, int field_width,
}
*p = '\0';
return string(buf, mac_addr, field_width, precision, flags & ~SPECIAL);
return string(buf, end, mac_addr, field_width, precision,
flags & ~SPECIAL);
}
static char *ip6_addr_string(char *buf, u8 *addr, int field_width,
static char *ip6_addr_string(char *buf, char *end, u8 *addr, int field_width,
int precision, int flags)
{
char ip6_addr[8 * 5]; /* (8 * 4 hex digits), 7 colons and trailing zero */
@ -435,10 +457,11 @@ static char *ip6_addr_string(char *buf, u8 *addr, int field_width,
}
*p = '\0';
return string(buf, ip6_addr, field_width, precision, flags & ~SPECIAL);
return string(buf, end, ip6_addr, field_width, precision,
flags & ~SPECIAL);
}
static char *ip4_addr_string(char *buf, u8 *addr, int field_width,
static char *ip4_addr_string(char *buf, char *end, u8 *addr, int field_width,
int precision, int flags)
{
char ip4_addr[4 * 4]; /* (4 * 3 decimal digits), 3 dots and trailing zero */
@ -456,7 +479,8 @@ static char *ip4_addr_string(char *buf, u8 *addr, int field_width,
}
*p = '\0';
return string(buf, ip4_addr, field_width, precision, flags & ~SPECIAL);
return string(buf, end, ip4_addr, field_width, precision,
flags & ~SPECIAL);
}
#endif
@ -478,10 +502,12 @@ static char *ip4_addr_string(char *buf, u8 *addr, int field_width,
* function pointers are really function descriptors, which contain a
* pointer to the real address.
*/
static char *pointer(const char *fmt, char *buf, void *ptr, int field_width, int precision, int flags)
static char *pointer(const char *fmt, char *buf, char *end, void *ptr,
int field_width, int precision, int flags)
{
if (!ptr)
return string(buf, "(null)", field_width, precision, flags);
return string(buf, end, "(null)", field_width, precision,
flags);
#ifdef CONFIG_CMD_NET
switch (*fmt) {
@ -489,15 +515,18 @@ static char *pointer(const char *fmt, char *buf, void *ptr, int field_width, int
flags |= SPECIAL;
/* Fallthrough */
case 'M':
return mac_address_string(buf, ptr, field_width, precision, flags);
return mac_address_string(buf, end, ptr, field_width,
precision, flags);
case 'i':
flags |= SPECIAL;
/* Fallthrough */
case 'I':
if (fmt[1] == '6')
return ip6_addr_string(buf, ptr, field_width, precision, flags);
return ip6_addr_string(buf, end, ptr, field_width,
precision, flags);
if (fmt[1] == '4')
return ip4_addr_string(buf, ptr, field_width, precision, flags);
return ip4_addr_string(buf, end, ptr, field_width,
precision, flags);
flags &= ~SPECIAL;
break;
}
@ -507,27 +536,31 @@ static char *pointer(const char *fmt, char *buf, void *ptr, int field_width, int
field_width = 2*sizeof(void *);
flags |= ZEROPAD;
}
return number(buf, (unsigned long) ptr, 16, field_width, precision, flags);
return number(buf, end, (unsigned long)ptr, 16, field_width,
precision, flags);
}
/**
* vsprintf - Format a string and place it in a buffer
* @buf: The buffer to place the result into
* @fmt: The format string to use
* @args: Arguments for the format string
* Format a string and place it in a buffer (base function)
*
* This function follows C99 vsprintf, but has some extensions:
* @param buf The buffer to place the result into
* @param size The size of the buffer, including the trailing null space
* @param fmt The format string to use
* @param args Arguments for the format string
* @return The number characters which would be generated for the given
* input, excluding the trailing '\0', as per ISO C99. Note that fewer
* characters may be written if this number of characters is >= size.
*
* This function follows C99 vsnprintf, but has some extensions:
* %pS output the name of a text symbol
* %pF output the name of a function pointer
* %pR output the address range in a struct resource
*
* The function returns the number of characters written
* into @buf.
*
* Call this function if you are already dealing with a va_list.
* You probably want sprintf() instead.
* You probably want snprintf() instead.
*/
int vsprintf(char *buf, const char *fmt, va_list args)
static int vsnprintf_internal(char *buf, size_t size, const char *fmt,
va_list args)
{
unsigned NUM_TYPE num;
int base;
@ -542,12 +575,20 @@ int vsprintf(char *buf, const char *fmt, va_list args)
/* 'z' support added 23/7/1999 S.H. */
/* 'z' changed to 'Z' --davidm 1/25/99 */
/* 't' added for ptrdiff_t */
char *end = buf + size;
#ifdef CONFIG_SYS_VSNPRINTF
/* Make sure end is always >= buf - do we want this in U-Boot? */
if (end < buf) {
end = ((void *)-1);
size = end - buf;
}
#endif
str = buf;
for (; *fmt ; ++fmt) {
if (*fmt != '%') {
*str++ = *fmt;
ADDCH(str, *fmt);
continue;
}
@ -609,20 +650,22 @@ int vsprintf(char *buf, const char *fmt, va_list args)
switch (*fmt) {
case 'c':
if (!(flags & LEFT))
if (!(flags & LEFT)) {
while (--field_width > 0)
*str++ = ' ';
*str++ = (unsigned char) va_arg(args, int);
ADDCH(str, ' ');
}
ADDCH(str, (unsigned char) va_arg(args, int));
while (--field_width > 0)
*str++ = ' ';
ADDCH(str, ' ');
continue;
case 's':
str = string(str, va_arg(args, char *), field_width, precision, flags);
str = string(str, end, va_arg(args, char *),
field_width, precision, flags);
continue;
case 'p':
str = pointer(fmt+1, str,
str = pointer(fmt+1, str, end,
va_arg(args, void *),
field_width, precision, flags);
/* Skip all alphanumeric pointer suffixes */
@ -641,7 +684,7 @@ int vsprintf(char *buf, const char *fmt, va_list args)
continue;
case '%':
*str++ = '%';
ADDCH(str, '%');
continue;
/* integer number formats - set up the flags and "break" */
@ -662,9 +705,9 @@ int vsprintf(char *buf, const char *fmt, va_list args)
break;
default:
*str++ = '%';
ADDCH(str, '%');
if (*fmt)
*str++ = *fmt;
ADDCH(str, *fmt);
else
--fmt;
continue;
@ -688,17 +731,135 @@ int vsprintf(char *buf, const char *fmt, va_list args)
if (flags & SIGN)
num = (signed int) num;
}
str = number(str, num, base, field_width, precision, flags);
str = number(str, end, num, base, field_width, precision,
flags);
}
#ifdef CONFIG_SYS_VSNPRINTF
if (size > 0) {
ADDCH(str, '\0');
if (str > end)
end[-1] = '\0';
}
#else
*str = '\0';
#endif
/* the trailing null byte doesn't count towards the total */
return str-buf;
}
#ifdef CONFIG_SYS_VSNPRINTF
int vsnprintf(char *buf, size_t size, const char *fmt,
va_list args)
{
return vsnprintf_internal(buf, size, fmt, args);
}
/**
* sprintf - Format a string and place it in a buffer
* @buf: The buffer to place the result into
* @fmt: The format string to use
* @...: Arguments for the format string
* Format a string and place it in a buffer (va_list version)
*
* @param buf The buffer to place the result into
* @param size The size of the buffer, including the trailing null space
* @param fmt The format string to use
* @param args Arguments for the format string
* @return the number of characters which have been written into
* the @buf not including the trailing '\0'. If @size is == 0 the function
* returns 0.
*
* If you're not already dealing with a va_list consider using scnprintf().
*
* See the vsprintf() documentation for format string extensions over C99.
*/
int vscnprintf(char *buf, size_t size, const char *fmt, va_list args)
{
int i;
i = vsnprintf(buf, size, fmt, args);
if (likely(i < size))
return i;
if (size != 0)
return size - 1;
return 0;
}
/**
* Format a string and place it in a buffer
*
* @param buf The buffer to place the result into
* @param size The size of the buffer, including the trailing null space
* @param fmt The format string to use
* @param ... Arguments for the format string
* @return the number of characters which would be
* generated for the given input, excluding the trailing null,
* as per ISO C99. If the return is greater than or equal to
* @size, the resulting string is truncated.
*
* See the vsprintf() documentation for format string extensions over C99.
*/
int snprintf(char *buf, size_t size, const char *fmt, ...)
{
va_list args;
int i;
va_start(args, fmt);
i = vsnprintf(buf, size, fmt, args);
va_end(args);
return i;
}
/**
* Format a string and place it in a buffer
*
* @param buf The buffer to place the result into
* @param size The size of the buffer, including the trailing null space
* @param fmt The format string to use
* @param ... Arguments for the format string
*
* The return value is the number of characters written into @buf not including
* the trailing '\0'. If @size is == 0 the function returns 0.
*
* See the vsprintf() documentation for format string extensions over C99.
*/
int scnprintf(char *buf, size_t size, const char *fmt, ...)
{
va_list args;
int i;
va_start(args, fmt);
i = vscnprintf(buf, size, fmt, args);
va_end(args);
return i;
}
#endif /* CONFIG_SYS_VSNPRINT */
/**
* Format a string and place it in a buffer (va_list version)
*
* @param buf The buffer to place the result into
* @param fmt The format string to use
* @param args Arguments for the format string
*
* The function returns the number of characters written
* into @buf. Use vsnprintf() or vscnprintf() in order to avoid
* buffer overflows.
*
* If you're not already dealing with a va_list consider using sprintf().
*/
int vsprintf(char *buf, const char *fmt, va_list args)
{
return vsnprintf_internal(buf, INT_MAX, fmt, args);
}
/**
* Format a string and place it in a buffer
*
* @param buf The buffer to place the result into
* @param fmt The format string to use
* @param ... Arguments for the format string
*
* The function returns the number of characters written
* into @buf.