util/nvmutil: make EINTR configurable in prw()

Signed-off-by: Leah Rowe <leah@libreboot.org>

util/nvmutil/nvmutil.c

@@ -330,15 +330,16 @@ static off_t gbe_x_offset(size_t part, const char *f_op,
 static ssize_t rw_gbe_file_exact(int fd, u8 *mem, size_t nrw,
     off_t off, int rw_type);
 static ssize_t rw_file_exact(int fd, u8 *mem, size_t len,
-    off_t off, int rw_type, int loop_eagain);
+    off_t off, int rw_type, int loop_eagain, int loop_eintr);
 static ssize_t rw_file_once(int fd, u8 *mem, size_t len,
-    off_t off, int rw_type, size_t rc, int loop_eagain);
+    off_t off, int rw_type, size_t rc, int loop_eagain,
+    int loop_eintr);
 static ssize_t prw(int fd, void *mem, size_t nrw,
-    off_t off, int rw_type, int loop_eagain);
+    off_t off, int rw_type, int loop_eagain, int loop_eintr);
 static int rw_over_nrw(ssize_t r, size_t nrw);
 static off_t lseek_eintr(int fd, off_t off,
-    int whence, int loop_eagain);
+    int whence, int loop_eagain, int loop_eintr);
-static int err_eagain(int loop_eagain);
+static int err_eagain(int loop_err, int errval);
 
 /*
  * Error handling and cleanup
@@ -1153,7 +1154,7 @@ rhex(void)
 
 	if (!n) {
 		n = sizeof(rnum);
-		if (rw_file_exact(urandom_fd, rnum, n, 0, IO_READ, 0) == -1)
+		if (rw_file_exact(urandom_fd, rnum, n, 0, IO_READ, 0, 1) == -1)
 			err(errno, "Randomisation failed");
 	}
 
@@ -1322,7 +1323,7 @@ static void
 gbe_cat_buf(u8 *b)
 {
 	if (rw_file_exact(STDOUT_FILENO, b,
-	    GBE_PART_SIZE, 0, IO_WRITE, 1) < 0)
+	    GBE_PART_SIZE, 0, IO_WRITE, 1, 1) < 0)
 		err(errno, "stdout: cat");
 }
 
@@ -1576,7 +1577,7 @@ rw_gbe_file_exact(int fd, u8 *mem, size_t nrw,
 	if (nrw > GBE_PART_SIZE)
 		goto err_rw_gbe_file_exact;
 
-	return rw_file_exact(fd, mem, nrw, off, rw_type, 0);
+	return rw_file_exact(fd, mem, nrw, off, rw_type, 0, 1);
 
 err_rw_gbe_file_exact:
 	errno = EIO;
@@ -1602,14 +1603,15 @@ err_rw_gbe_file_exact:
  */
 static ssize_t
 rw_file_exact(int fd, u8 *mem, size_t nrw,
-    off_t off, int rw_type, int loop_eagain)
+    off_t off, int rw_type, int loop_eagain,
+    int loop_eintr)
 {
 	ssize_t rv;
 	size_t rc;
 
 	for (rc = 0, rv = 0; rc < nrw; ) {
 		if ((rv = rw_file_once(fd, mem, nrw, off, rw_type, rc,
-		    loop_eagain)) <= 0)
+		    loop_eagain, loop_eintr)) <= 0)
 			return -1;
 
 		rc += (size_t)rv;
@@ -1629,7 +1631,7 @@ rw_file_exact(int fd, u8 *mem, size_t nrw,
 static ssize_t
 rw_file_once(int fd, u8 *mem, size_t nrw,
     off_t off, int rw_type, size_t rc,
-    int loop_eagain)
+    int loop_eagain, int loop_eintr)
 {
 	ssize_t rv;
 	size_t retries_on_zero = 0;
@@ -1639,7 +1641,8 @@ rw_file_once(int fd, u8 *mem, size_t nrw,
 		goto err_rw_file_once;
 
 read_again:
-	rv = prw(fd, mem + rc, nrw - rc, off + rc, rw_type, loop_eagain);
+	rv = prw(fd, mem + rc, nrw - rc, off + rc, rw_type,
+	    loop_eagain, loop_eintr);
 
 	if (rv < 0)
 		return -1;
@@ -1672,10 +1675,21 @@ err_rw_file_once:
  * A fallback is provided for regular read/write.
  * rw_type can be IO_READ, IO_WRITE, IO_PREAD
  * or IO_PWRITE
+ *
+ * loop_eagain does a retry loop on EAGAIN if set
+ * loop_eintr does a retry loop on EINTR if set
+ *
+ * Unlike the bare syscalls, prw() does security
+ * checks e.g. checks NULL strings, checks bounds,
+ * also mitigates a few theoretical libc bugs.
+ * It is designed for extremely safe single-threaded
+ * I/O on applications that need it.
  */
+
 static ssize_t
 prw(int fd, void *mem, size_t nrw,
-    off_t off, int rw_type, int loop_eagain)
+    off_t off, int rw_type,
+    int loop_eagain, int loop_eintr)
 {
 	off_t off_orig;
 	ssize_t r;
@@ -1708,8 +1722,8 @@ try_rw_again:
 		else if (rw_type == IO_READ)
 			r = read(fd, mem, nrw);
 
-		if (r == -1 && (errno == EINTR
+		if (r == -1 && (errno == err_eagain(loop_eintr, EINTR)
-		    || errno == err_eagain(loop_eagain)))
+		    || errno == err_eagain(loop_eagain, EAGAIN)))
 			goto try_rw_again;
 
 		return rw_over_nrw(r, nrw);
@@ -1729,9 +1743,10 @@ try_rw_again:
 		goto err_prw;
 
 	if ((off_orig = lseek_eintr(fd, (off_t)0, SEEK_CUR,
-	    loop_eagain)) == (off_t)-1)
+	    loop_eagain, loop_eintr)) == (off_t)-1)
 		r = -1;
-	else if (lseek_eintr(fd, off, SEEK_SET, loop_eagain) == (off_t)-1)
+	else if (lseek_eintr(fd, off, SEEK_SET,
+	    loop_eagain, loop_eintr) == (off_t)-1)
 		r = -1;
 
 	do {
@@ -1741,12 +1756,13 @@ try_rw_again:
 			r = write(fd, mem, nrw);
 
 		r = rw_over_nrw(r, nrw);
-	} while (r == -1 && (errno == EINTR
+	} while (r == -1 &&
-	    || errno == err_eagain(loop_eagain)));
+	    (errno == err_eagain(loop_eintr, EINTR)
+	    || errno == err_eagain(loop_eagain, EAGAIN)));
 
 	saved_errno = errno;
 	if (lseek_eintr(fd, off_orig, SEEK_SET,
-	    loop_eagain) == (off_t)-1) {
+	    loop_eagain, loop_eintr) == (off_t)-1) {
 		if (r < 0)
 			errno = saved_errno;
 		return -1;
@@ -1803,23 +1819,26 @@ err_rw_over_nrw:
 }
 
 static off_t
-lseek_eintr(int fd, off_t off, int whence, int loop_eagain)
+lseek_eintr(int fd, off_t off, int whence,
+    int loop_eagain, int loop_eintr)
 {
 	off_t old;
 
 	do {
 		old = lseek(fd, off, whence);
 	} while (old == (off_t)-1
-	    && (!(errno == EINTR || errno == err_eagain(loop_eagain))));
+	    && (!(
+	    errno == err_eagain(loop_eintr, EINTR) ||
+	    errno == err_eagain(loop_eagain, EAGAIN))));
 
 	return old;
 }
 
 static int
-err_eagain(int loop_eagain)
+err_eagain(int loop_err, int errval)
 {
-	if (loop_eagain)
+	if (loop_err)
-		return EAGAIN;
+		return errval;
 
 	/* errno is never negative,
 	   so functions checking it