uml: convert libc layer to call read and write

This patch converts calls in the os layer to os_{read,write}_file to calls
directly to libc read() and write() where it is clear that the I/O buffer is
in the kernel.

We can do that here instead of calling os_{read,write}_file_k since we are in
libc code and can call libc directly.

With the change in the calls, error handling needs to be changed to refer to
errno directly rather than the return value of the call.

CATCH_EINTR wrappers were also added where needed.

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/arch/um/os-Linux/helper.c b/arch/um/os-Linux/helper.c
index 8a4c9e4..97bed16 100644
--- a/arch/um/os-Linux/helper.c
+++ b/arch/um/os-Linux/helper.c
@@ -36,7 +36,7 @@ static int helper_child(void *arg)
 	errval = execvp_noalloc(data->buf, argv[0], argv);
 	printk("helper_child - execvp of '%s' failed - errno = %d\n", argv[0],
 	       -errval);
-	os_write_file(data->fd, &errval, sizeof(errval));
+	write(data->fd, &errval, sizeof(errval));
 	kill(os_getpid(), SIGKILL);
 	return 0;
 }
@@ -92,11 +92,12 @@ int run_helper(void (*pre_exec)(void *), void *pre_data, char **argv,
 	 * Read the errno value from the child, if the exec failed, or get 0 if
 	 * the exec succeeded because the pipe fd was set as close-on-exec.
 	 */
-	n = os_read_file(fds[0], &ret, sizeof(ret));
+	n = read(fds[0], &ret, sizeof(ret));
 	if (n == 0) {
 		ret = pid;
 	} else {
 		if (n < 0) {
+			n = -errno;
 			printk("run_helper : read on pipe failed, ret = %d\n",
 			       -n);
 			ret = n;