[coreboot-gerrit] New patch to review for coreboot: 9f872cc console/vsprintf: Implement snprintf

[Vladimir Serbinenko]

Vladimir Serbinenko ([e-mail]) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/4278

-gerrit

commit 9f872cccfd6fe85552a9a3e2ccb3b99dfa137957
Author: Vladimir Serbinenko 
Date:   Tue Nov 26 02:20:32 2013 +0100

console/vsprintf: Implement snprintf

snprintf is a safe variant of sprintf. To avoid buffer overflows we shouldn't
    use sprintf at all. But for now let's start by implementing snprintf in first
    place.

Change-Id: Ic17d94b8cd91b72f66b84b0589a06b8abef5e5c9
    Signed-off-by: Vladimir Serbinenko 
---
 src/console/vsprintf.c | 30 +++++++++++++++++++++++++-----
 src/include/string.h   |  1 +
 2 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/src/console/vsprintf.c b/src/console/vsprintf.c
index 435401b..3d085e9 100644
--- a/src/console/vsprintf.c
+++ b/src/console/vsprintf.c
@@ -27,14 +27,18 @@
 DECLARE_SPIN_LOCK(vsprintf_lock)

static char *str_buf;
+static size_t buf_limit;

static void str_tx_byte(unsigned char byte)
 {
-	*str_buf = byte;
-	str_buf++;
+	if (buf_limit) {
+		*str_buf = byte;
+		str_buf++;
+		buf_limit--;
+	}
 }

-static int vsprintf(char *buf, const char *fmt, va_list args)
+static int vsnprintf(char *buf, size_t size, const char *fmt, va_list args)
 {
    int i;

@@ -42,8 +46,10 @@ static int vsprintf(char *buf, const char *fmt, va_list args)
    spin_lock(&vsprintf_lock);

str_buf = buf;
+	buf_limit = size ? size - 1 : 0;
    i = vtxprintf(str_tx_byte, fmt, args);
-	*str_buf = '\0';
+	if (size)
+		*str_buf = '\0';

spin_unlock(&vsprintf_lock);
    ENABLE_TRACE;
@@ -57,7 +63,21 @@ int sprintf(char *buf, const char *fmt, ...)
    int i;

va_start(args, fmt);
-	i = vsprintf(buf, fmt, args);
+	/* A trick: we have at most (size_t)-1 adressable space anyway, so
+	   if we output so much we'll crash anyway.  */
+	i = vsnprintf(buf, -1, fmt, args);
+	va_end(args);
+
+	return i;
+}
+
+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;
diff --git a/src/include/string.h b/src/include/string.h
index 77985e1..dc125e1 100644
--- a/src/include/string.h
+++ b/src/include/string.h
@@ -17,6 +17,7 @@ int memcmp(const void *s1, const void *s2, size_t n);
 void *memchr(const void *s, int c, size_t n);
 #if !defined(__PRE_RAM__)
 int sprintf(char * buf, const char *fmt, ...);
+int snprintf(char * buf, size_t size, const char *fmt, ...);
 #endif

// simple string functions