[coreboot-gerrit] Patch set updated for coreboot: 00dba6d 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 00dba6da719d2804572a25ba6643eb2179d66fba
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 6210d01..f055d61 100644
--- a/src/console/vsprintf.c
+++ b/src/console/vsprintf.c
@@ -26,16 +26,20 @@
 struct context
 {
    char *str_buf;
+	size_t buf_limit;
 };

static void str_tx_byte(unsigned char byte, void *data)
 {
    struct context *ctx = data;
-	*ctx->str_buf = byte;
-	ctx->str_buf++;
+	if (ctx->buf_limit) {
+		*ctx->str_buf = byte;
+		ctx->str_buf++;
+		ctx->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;
    struct context ctx;
@@ -43,8 +47,10 @@ static int vsprintf(char *buf, const char *fmt, va_list args)
    DISABLE_TRACE;

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

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