[libc] Rewrite string functions

Some of the C library string functions have an unknown provenance.
Reimplement all such functions to avoid potential licensing
uncertainty.

Remove the inline-assembler versions of strlen(), memswap(), and
strncmp(); these save a minimal amount of space (around 40 bytes in
total) and are not performance-critical.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

1 files changed, 0 insertions, 84 deletions

diff --git a/src/arch/x86/core/x86_string.c b/src/arch/x86/core/x86_string.c
index d48347c96..59e0eaae1 100644
--- a/src/arch/x86/core/x86_string.c
+++ b/src/arch/x86/core/x86_string.c
@@ -104,87 +104,3 @@ void * __memmove ( void *dest, const void *src, size_t len ) {
 		return __memcpy_reverse ( dest, src, len );
 	}
 }
-
-/**
- * Swap memory areas
- *
- * @v dest		Destination address
- * @v src		Source address
- * @v len		Length
- * @ret dest		Destination address
- */
-void * memswap ( void *dest, void *src, size_t len ) {
-	size_t discard_c;
-	int discard;
-
-	__asm__ __volatile__ ( "\n1:\n\t"
-			       "dec %2\n\t"
-			       "js 2f\n\t"
-			       "movb (%0,%2), %b3\n\t"
-			       "xchgb (%1,%2), %b3\n\t"
-			       "movb %b3, (%0,%2)\n\t"
-			       "jmp 1b\n\t"
-			       "2:\n\t"
-			       : "=r" ( src ), "=r" ( dest ),
-				 "=&c" ( discard_c ), "=&q" ( discard )
-			       : "0" ( src ), "1" ( dest ), "2" ( len )
-			       : "memory" );
-
-	return dest;
-}
-
-/**
- * Calculate length of string
- *
- * @v string		String
- * @ret len		Length (excluding NUL)
- */
-size_t strlen ( const char *string ) {
-	const char *discard_D;
-	size_t len_plus_one;
-
-	__asm__ __volatile__ ( "repne scasb\n\t"
-			       "not %1\n\t"
-			       : "=&D" ( discard_D ), "=&c" ( len_plus_one )
-			       : "0" ( string ), "1" ( -1UL ), "a" ( 0 ) );
-
-	return ( len_plus_one - 1 );
-}
-
-/**
- * Compare strings (up to a specified length)
- *
- * @v str1		First string
- * @v str2		Second string
- * @v len		Maximum length
- * @ret diff		Difference
- */
-int strncmp ( const char *str1, const char *str2, size_t len ) {
-	const void *discard_S;
-	const void *discard_D;
-	size_t discard_c;
-	int diff;
-
-	__asm__ __volatile__ ( "\n1:\n\t"
-			       "dec %2\n\t"
-			       "js 2f\n\t"
-			       "lodsb\n\t"
-			       "scasb\n\t"
-			       "jne 3f\n\t"
-			       "testb %b3, %b3\n\t"
-			       "jnz 1b\n\t"
-			       /* Equal */
-			       "\n2:\n\t"
-			       "xor %3, %3\n\t"
-			       "jmp 4f\n\t"
-			       /* Not equal; CF indicates difference */
-			       "\n3:\n\t"
-			       "sbb %3, %3\n\t"
-			       "orb $1, %b3\n\t"
-			       "\n4:\n\t"
-			       : "=&S" ( discard_S ), "=&D" ( discard_D ),
-				 "=&c" ( discard_c ), "=&a" ( diff )
-			       : "0" ( str1 ), "1" ( str2 ), "2" ( len ) );
-
-	return diff;
-}