RMIB: add support for vector copy-out

Change-Id: I9e9b4b8d6eed39fdb511c6bd2a375ddf898064a5

minix/include/minix/rmib.h

@@ -9,6 +9,12 @@
 
 #include <sys/sysctl.h>
 
+/*
+ * The maximum number of I/O vector elements that can be passed to the
+ * rmib_vcopyout function.
+ */
+#define RMIB_IOV_MAX	SCPVEC_NR
+
 /*
  * This structure contains a number of less heavily used parameters for handler
  * functions, mainly to provide extensibility while limiting argument clutter.
@@ -145,6 +151,8 @@ int rmib_inrange(struct rmib_oldp *, size_t);
 size_t rmib_getoldlen(struct rmib_oldp *);
 ssize_t rmib_copyout(struct rmib_oldp *, size_t, const void * __restrict,
 	size_t);
+ssize_t rmib_vcopyout(struct rmib_oldp *, size_t, const iovec_t *,
+	unsigned int);
 int rmib_copyin(struct rmib_newp * __restrict, void * __restrict, size_t);
 ssize_t rmib_readwrite(struct rmib_call *, struct rmib_node *,
 	struct rmib_oldp *, struct rmib_newp *);

minix/lib/libsys/rmib.c

@@ -110,6 +110,60 @@ rmib_copyout(struct rmib_oldp * __restrict oldp, size_t off,
 	return size;
 }
 
+/*
+ * Copy out (partial) data to the user, from a vector of up to RMIB_IOV_MAX
+ * local buffers.  The copy is automatically limited to the range of data
+ * requested by the user.  Return the total requested length on success or an
+ * error code on failure.
+ */
+ssize_t
+rmib_vcopyout(struct rmib_oldp * oldp, size_t off, const iovec_t * iov,
+	unsigned int iovcnt)
+{
+	static struct vscp_vec vec[RMIB_IOV_MAX];
+	size_t size, chunk;
+	unsigned int i;
+	ssize_t r;
+
+	assert(iov != NULL);
+	assert(iovcnt <= __arraycount(vec));
+
+	/* Take a shortcut for single-vector elements, saving a kernel copy. */
+	if (iovcnt == 1)
+		return rmib_copyout(oldp, off, (const void *)iov->iov_addr,
+		    iov->iov_size);
+
+	/*
+	 * Iterate through the full vector even if we cannot copy out all of
+	 * it, because we need to compute the total length.
+	 */
+	for (size = i = 0; iovcnt > 0; iov++, iovcnt--) {
+		if (oldp != NULL && off < oldp->oldp_len) {
+			chunk = oldp->oldp_len - off;
+			if (chunk > iov->iov_size)
+				chunk = iov->iov_size;
+
+			vec[i].v_from = SELF;
+			vec[i].v_to = MIB_PROC_NR;
+			vec[i].v_gid = oldp->oldp_grant;
+			vec[i].v_offset = off;
+			vec[i].v_addr = iov->iov_addr;
+			vec[i].v_bytes = chunk;
+
+			off += chunk;
+			i++;
+		}
+
+		size += iov->iov_size;
+	}
+
+	/* Perform the copy, if there is anything to copy, that is. */
+	if (i > 0 && (r = sys_vsafecopy(vec, i)) != OK)
+		return r;
+
+	return size;
+}
+
 /*
  * Copy in data from the user.  The given length must match exactly the length
  * given by the user.  Return OK or an error code.

minix/net/inet/rtinfo.c

@@ -26,32 +26,6 @@
 
 static const char padbuf[RT_ROUNDUP(0)] = { 0 };
 
-/*
- * Copy out a vector of data to the sysctl(2) caller.  TODO: decide what to do
- * with this.  We could implement this as a vectored-safecopy operation in
- * RMIB.  We could also copy everything into a single buffer first.  The
- * current implementation is probably the worst among the possibilities.
- */
-static ssize_t
-rmib_vcopyout(struct rmib_oldp * oldp, size_t off, const iovec_t * iov,
-	unsigned int iovcnt)
-{
-	unsigned int i;
-	ssize_t r, len;
-
-	len = 0;
-
-	for (i = 0; i < iovcnt; i++) {
-		if ((r = rmib_copyout(oldp, off + len,
-		    (const void *)iov[i].iov_addr, iov[i].iov_size)) < 0)
-			return r;
-
-		len += r;
-	}
-
-	return len;
-}
-
 /*
  * Compute the length for, and possibly copy out, an interface information or
  * interface address record with an associated set of zero or more routing

minix/net/lwip/rtinfo.c

@@ -23,32 +23,6 @@
 
 static const char padbuf[RT_ROUNDUP(0)] = { 0 };
 
-/*
- * Copy out a vector of data to the sysctl(2) caller.  TODO: decide what to do
- * with this.  We could implement this as a vectored-safecopy operation in
- * RMIB.  We could also copy everything into a single buffer first.  The
- * current implementation is probably the worst among the possibilities.
- */
-static ssize_t
-rmib_vcopyout(struct rmib_oldp * oldp, size_t off, const iovec_t * iov,
-	unsigned int iovcnt)
-{
-	unsigned int i;
-	ssize_t r, len;
-
-	len = 0;
-
-	for (i = 0; i < iovcnt; i++) {
-		if ((r = rmib_copyout(oldp, off + len,
-		    (const void *)iov[i].iov_addr, iov[i].iov_size)) < 0)
-			return r;
-
-		len += r;
-	}
-
-	return len;
-}
-
 /*
  * Compute the length for, and possibly copy out, an interface information or
  * interface address record with an associated set of zero or more routing