[PATCH v6 1/5] x86/boot: Add strlcat() and strscpy() to compressed kernel

[Evgeniy Baskov]

These functions simplify the code of command line concatenation
helper and reduce the probability of mistakes.

Use simpler implementation of strscpy than used in it kernel itself
to avoid code bloat in compressed kernel.

Signed-off-by: Evgeniy Baskov <baskov@xxxxxxxxx>
---
 arch/x86/boot/compressed/string.c | 50 +++++++++++++++++++++++++++++++
 arch/x86/purgatory/purgatory.c    |  1 +
 2 files changed, 51 insertions(+)

diff --git a/arch/x86/boot/compressed/string.c b/arch/x86/boot/compressed/string.c
index 81fc1eaa3229..5c193fa0a09b 100644
--- a/arch/x86/boot/compressed/string.c
+++ b/arch/x86/boot/compressed/string.c
@@ -40,6 +40,56 @@ static void *____memcpy(void *dest, const void *src, size_t n)
 }
 #endif
 
+size_t strlcat(char *dest, const char *src, size_t count)
+{
+	size_t dsize = strlen(dest);
+	size_t len = strlen(src);
+	size_t res = dsize + len;
+
+	/* This would be a bug */
+	if (dsize >= count)
+		error("strlcat(): destination too big\n");
+
+	dest += dsize;
+	count -= dsize;
+	if (len >= count)
+		len = count-1;
+	memcpy(dest, src, len);
+	dest[len] = 0;
+	return res;
+}
+
+/* Don't include word-at-a-time code path in compressed kernel for simplicity */
+size_t strscpy(char *dest, const char *src, size_t count)
+{
+	long res = 0;
+
+	if (count == 0)
+		return -E2BIG;
+
+	if (count > INT_MAX) {
+		warn("strscpy(): Count is too big");
+		return -E2BIG;
+	}
+
+	while (count) {
+		char c;
+
+		c = src[res];
+		dest[res] = c;
+		if (!c)
+			return res;
+		res++;
+		count--;
+	}
+
+	/* Hit buffer length without finding a NUL; force NUL-termination. */
+	if (res)
+		dest[res-1] = '\0';
+
+	return -E2BIG;
+}
+
 void *memset(void *s, int c, size_t n)
 {
 	int i;
diff --git a/arch/x86/purgatory/purgatory.c b/arch/x86/purgatory/purgatory.c
index 7558139920f8..65f0cedb65ae 100644
--- a/arch/x86/purgatory/purgatory.c
+++ b/arch/x86/purgatory/purgatory.c
@@ -57,3 +57,4 @@ void purgatory(void)
  * arch/x86/boot/compressed/string.c
  */
 void warn(const char *msg) {}
+void error(char *m) {}
-- 
2.37.2