libbb: add a function to make a copy of a region of memory

Introduce a library routine to package the idiom:

    p = xmalloc(b, n);
    memcpy(p, b, n);

and use it where possible.  The example in traceroute used xzalloc
but it didn't need to.

function                                             old     new   delta
xmemdup                                                -      32     +32
last_main                                            834     826      -8
make_device                                         2321    2311     -10
common_traceroute_main                              3698    3685     -13
readtoken1                                          3182    3168     -14
procps_scan                                         1222    1206     -16
forkchild                                            655     638     -17
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 0/6 up/down: 32/-78)            Total: -46 bytes

Signed-off-by: Ron Yorston <rmy@frippery.org>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

include/libbb.h

@@ -673,6 +673,7 @@ uint16_t inet_cksum(uint16_t *addr, int len) FAST_FUNC;
 
 char *xstrdup(const char *s) FAST_FUNC RETURNS_MALLOC;
 char *xstrndup(const char *s, int n) FAST_FUNC RETURNS_MALLOC;
+void *xmemdup(const void *s, int n) FAST_FUNC RETURNS_MALLOC;
 void overlapping_strcpy(char *dst, const char *src) FAST_FUNC;
 char *safe_strncpy(char *dst, const char *src, size_t size) FAST_FUNC;
 char *strncpy_IFNAMSIZ(char *dst, const char *src) FAST_FUNC;

libbb/procps.c

@@ -554,8 +554,7 @@ procps_status_t* FAST_FUNC procps_scan(procps_status_t* sp, int flags)
 				break;
 			if (flags & PSSCAN_ARGVN) {
 				sp->argv_len = n;
-				sp->argv0 = xmalloc(n + 1);
-				memcpy(sp->argv0, buf, n + 1);
+				sp->argv0 = xmemdup(buf, n + 1);
 				/* sp->argv0[n] = '\0'; - buf has it */
 			} else {
 				sp->argv_len = 0;

libbb/xfuncs_printf.c

@@ -112,6 +112,11 @@ char* FAST_FUNC xstrndup(const char *s, int n)
 	return memcpy(t, s, n);
 }
 
+void* FAST_FUNC xmemdup(const void *s, int n)
+{
+	return memcpy(xmalloc(n), s, n);
+}
+
 // Die if we can't open a file and return a FILE* to it.
 // Notice we haven't got xfread(), This is for use with fscanf() and friends.
 FILE* FAST_FUNC xfopen(const char *path, const char *mode)

miscutils/last_fancy.c

@@ -233,7 +233,7 @@ int last_main(int argc UNUSED_PARAM, char **argv)
 				break;
 			}
 			/* add_entry */
-			llist_add_to(&zlist, memcpy(xmalloc(sizeof(ut)), &ut, sizeof(ut)));
+			llist_add_to(&zlist, xmemdup(&ut, sizeof(ut)));
 			break;
 		case USER_PROCESS: {
 			int show;
@@ -275,7 +275,7 @@ int last_main(int argc UNUSED_PARAM, char **argv)
 				show_entry(&ut, state, boot_time);
 			}
 			/* add_entry */
-			llist_add_to(&zlist, memcpy(xmalloc(sizeof(ut)), &ut, sizeof(ut)));
+			llist_add_to(&zlist, xmemdup(&ut, sizeof(ut)));
 			break;
 		}
 		}

networking/traceroute.c

@@ -387,15 +387,6 @@ struct globals {
 #define outudp  ((struct udphdr *)(outip + 1))
 
 
-/* libbb candidate? tftp uses this idiom too */
-static len_and_sockaddr* dup_sockaddr(const len_and_sockaddr *lsa)
-{
-	len_and_sockaddr *new_lsa = xzalloc(LSA_LEN_SIZE + lsa->len);
-	memcpy(new_lsa, lsa, LSA_LEN_SIZE + lsa->len);
-	return new_lsa;
-}
-
-
 static int
 wait_for_reply(len_and_sockaddr *from_lsa, struct sockaddr *to, unsigned *timestamp_us, int *left_ms)
 {
@@ -1074,7 +1065,7 @@ common_traceroute_main(int op, char **argv)
 		printf(" from %s", source);
 	printf(", %d hops max, %d byte packets\n", max_ttl, packlen);
 
-	from_lsa = dup_sockaddr(dest_lsa);
+	from_lsa = xmemdup(dest_lsa, LSA_LEN_SIZE + dest_lsa->len);
 	lastaddr = xzalloc(dest_lsa->len);
 	to = xzalloc(dest_lsa->len);
 	seq = 0;

networking/udhcp/d6_dhcpc.c

@@ -118,7 +118,7 @@ static void *d6_copy_option(uint8_t *option, uint8_t *option_end, unsigned code)
 	uint8_t *opt = d6_find_option(option, option_end, code);
 	if (!opt)
 		return opt;
-	return memcpy(xmalloc(opt[3] + 4), opt, opt[3] + 4);
+	return xmemdup(opt, opt[3] + 4);
 }
 
 static void *d6_store_blob(void *dst, const void *src, unsigned len)

shell/ash.c

@@ -4751,7 +4751,7 @@ forkchild(struct job *jp, union node *n, int mode)
 		 * Our solution: ONLY bare $(trap) or `trap` is special.
 		 */
 		/* Save trap handler strings for trap builtin to print */
-		trap_ptr = memcpy(xmalloc(sizeof(trap)), trap, sizeof(trap));
+		trap_ptr = xmemdup(trap, sizeof(trap));
 		/* Fall through into clearing traps */
 	}
 	clear_traps();

util-linux/mdev.c

@@ -471,7 +471,7 @@ static const struct rule *next_rule(void)
 	if (G.parser) {
 		parse_next_rule();
 		if (G.rule_vec) { /* mdev -s */
-			rule = memcpy(xmalloc(sizeof(G.cur_rule)), &G.cur_rule, sizeof(G.cur_rule));
+			rule = xmemdup(&G.cur_rule, sizeof(G.cur_rule));
 			G.rule_vec = xrealloc_vector(G.rule_vec, 4, G.rule_idx);
 			G.rule_vec[G.rule_idx++] = rule;
 			dbg3("> G.rule_vec[G.rule_idx:%d]=%p", G.rule_idx, G.rule_vec[G.rule_idx]);