[U-Boot] [PATCH v4 3/5] Add safe vsnprintf and snprintf library functions
Simon Glass
sjg at chromium.org
Wed Oct 19 01:36:24 CEST 2011
From: Sonny Rao <sonnyrao at chromium.org>
From: Sonny Rao <sonnyrao at 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 at chromium.org> modified this commit a little)
Signed-off-by: Sonny Rao <sonnyrao at chromium.org>
---
Changes in v3:
- Add CONFIG_SYS_VSNPRINT option to enable vsnprintf() functions
- Update README with CONFIG_SYS_VSNPRINT docs
- Use ADDCH macro to support checking/not checking end pointer
Changes in v4:
- Add these changes in unless CONFIG_NO_SYS_VSNPRINT is defined
- Reduce code size overhead if disabled to only 4 bytes on ARM
- Remove the ugly #ifdef patch from series since it only saves 4 bytes
README | 7 ++
include/vsprintf.h | 19 ++++
lib/vsprintf.c | 263 +++++++++++++++++++++++++++++++++++++++++----------
3 files changed, 237 insertions(+), 52 deletions(-)
diff --git a/README b/README
index eb9ade9..d4074b2 100644
--- a/README
+++ b/README
@@ -634,6 +634,13 @@ The following options need to be configured:
'Sane' compilers will generate smaller code if
CONFIG_PRE_CON_BUF_SZ is a power of 2
+- Safe printf() functions
+ Define CONFIG_SYS_NO_VSNPRINT to avoiding compilinf in
+ safe versions of the printf() functions. These are defined
+ in include/vsprintf.h and include snprintf(), vsnprintf()
+ and so on. Code size reduction is approximately 300-500
+ bytes.
+
- Boot Delay: CONFIG_BOOTDELAY - in seconds
Delay before automatically booting the default image;
set to -1 to disable autoboot.
diff --git a/include/vsprintf.h b/include/vsprintf.h
index 5d57d5f..8f26923 100644
--- a/include/vsprintf.h
+++ b/include/vsprintf.h
@@ -35,4 +35,23 @@ int sprintf(char *buf, const char *fmt, ...)
__attribute__ ((format (__printf__, 2, 3)));
int vsprintf(char *buf, const char *fmt, va_list args);
+#ifdef CONFIG_SYS_NO_VSNPRINT
+/*
+ * 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_VSNPRINT
+ */
+#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)
+#else
+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);
+#endif
+
#endif
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 79dead3..245cbaf 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -16,6 +16,7 @@
#include <errno.h>
#include <common.h>
+#include <limits.h>
#if !defined (CONFIG_PANIC_HANG)
#include <command.h>
#endif
@@ -289,7 +290,22 @@ 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_NO_VSNPRINT
+#define ADDCH(str, ch) (*(str)++ = (ch))
+#else
+/*
+ * 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)
+#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"; */
@@ -351,37 +367,40 @@ 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;
@@ -392,16 +411,16 @@ 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 */
@@ -415,10 +434,11 @@ 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 */
@@ -433,10 +453,11 @@ 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 */
@@ -454,7 +475,8 @@ 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
@@ -476,10 +498,12 @@ 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) {
@@ -487,15 +511,18 @@ 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;
}
@@ -505,27 +532,31 @@ 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;
@@ -540,12 +571,20 @@ 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;
+#ifndef CONFIG_SYS_NO_VSNPRINT
+ /* 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;
}
@@ -607,20 +646,22 @@ 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 */
@@ -639,7 +680,7 @@ 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" */
@@ -660,9 +701,9 @@ 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;
@@ -686,17 +727,135 @@ 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_NO_VSNPRINT
*str = '\0';
+#else
+ if (size > 0) {
+ ADDCH(str, '\0');
+ if (str > end)
+ end[-1] = '\0';
+ }
+#endif
+ /* the trailing null byte doesn't count towards the total */
return str-buf;
}
+#ifndef CONFIG_SYS_NO_VSNPRINT
+int vsnprintf(char *buf, size_t size, const char *fmt,
+ va_list args)
+{
+ return vsnprintf_internal(buf, size, fmt, args);
+}
+
+/**
+ * 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;
+}
+
/**
- * 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
+ *
+ * @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 /* nCONFIG_SYS_NO_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.
--
1.7.3.1
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