These are symmetric to write_remainder() and write_all_buf() and
almost a copy and paste of them, with the most notable differences
being reversed reads/writes and a couple of better-safe-than-sorry
asserts to keep Coverity happy.
I'll use them in the next patch. At least for the moment, they're
going to be used for vhost-user mode only, so I'm not unconditionally
enabling readv() in the seccomp profile: the caller has to ensure it's
there.
Signed-off-by: Stefano Brivio <sbrivio(a)redhat.com>
---
util.c | 83 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
util.h | 2 ++
2 files changed, 85 insertions(+)
diff --git a/util.c b/util.c
index c7b09f0..f2eef93 100644
--- a/util.c
+++ b/util.c
@@ -606,6 +606,89 @@ int write_remainder(int fd, const struct iovec *iov, size_t iovcnt,
size_t skip)
return 0;
}
+/**
+ * read_all_buf() - Fill a whole buffer from a file descriptor
+ * @fd: File descriptor
+ * @buf: Pointer to base of buffer
+ * @len: Length of buffer
+ *
+ * Return: 0 on success, -1 on error (with errno set)
+ *
+ * #syscalls read
+ */
+int read_all_buf(int fd, void *buf, size_t len)
+{
+ size_t left = len;
+ char *p = buf;
+
+ while (left) {
+ ssize_t rc;
+
+ ASSERT(left <= len);
+
+ do
+ rc = read(fd, p, left);
+ while ((rc < 0) && errno == EINTR);
+
+ if (rc < 0)
+ return -1;
+
+ if (rc == 0) {
+ errno = ENODATA;
+ return -1;
+ }
+
+ p += rc;
+ left -= rc;
+ }
+ return 0;
+}
+
+/**
+ * read_remainder() - Read the tail of an IO vector from a file descriptor
+ * @fd: File descriptor
+ * @iov: IO vector
+ * @cnt: Number of entries in @iov
+ * @skip: Number of bytes of the vector to skip reading
+ *
+ * Return: 0 on success, -1 on error (with errno set)
+ *
+ * Note: mode-specific seccomp profiles need to enable readv() to use this.
+ */
+int read_remainder(int fd, struct iovec *iov, size_t cnt, size_t skip)
+{
+ size_t i = 0, offset;
+
+ while ((i += iov_skip_bytes(iov + i, cnt - i, skip, &offset)) < cnt) {
+ ssize_t rc;
+
+ if (offset) {
+ ASSERT(offset < iov[i].iov_len);
+ /* Read the remainder of the partially read buffer */
+ if (read_all_buf(fd, (char *)iov[i].iov_base + offset,
+ iov[i].iov_len - offset) < 0)
+ return -1;
+ i++;
+ }
+
+ if (cnt == i)
+ break;
+
+ /* Fill as many of the remaining buffers as we can */
+ rc = readv(fd, &iov[i], cnt - i);
+ if (rc < 0)
+ return -1;
+
+ if (rc == 0) {
+ errno = ENODATA;
+ return -1;
+ }
+
+ skip = rc;
+ }
+ return 0;
+}
+
/** sockaddr_ntop() - Convert a socket address to text format
* @sa: Socket address
* @dst: output buffer, minimum SOCKADDR_STRLEN bytes
diff --git a/util.h b/util.h
index 800a28b..6ae8588 100644
--- a/util.h
+++ b/util.h
@@ -203,6 +203,8 @@ int fls(unsigned long x);
int write_file(const char *path, const char *buf);
int write_all_buf(int fd, const void *buf, size_t len);
int write_remainder(int fd, const struct iovec *iov, size_t iovcnt, size_t skip);
+int read_all_buf(int fd, void *buf, size_t len);
+int read_remainder(int fd, struct iovec *iov, size_t cnt, size_t skip);
void close_open_files(int argc, char **argv);
bool snprintf_check(char *str, size_t size, const char *format, ...);
--
2.43.0