sandbox: Add a function to read a host file

Add a way to read a file from the host filesystem. This can be useful for
reading test data, for example. Also fix up the writing function which was
not the right version, and drop the debugging lines.

Signed-off-by: Simon Glass <sjg@chromium.org>

arch/sandbox/cpu/os.c

@@ -98,9 +98,8 @@ void os_exit(int exit_code)
 	exit(exit_code);
 }
 
-int os_write_file(const char *name, const void *buf, int size)
+int os_write_file(const char *fname, const void *buf, int size)
 {
-	char fname[256];
 	int fd;
 
 	fd = os_open(fname, OS_O_WRONLY | OS_O_CREAT | OS_O_TRUNC);
@@ -110,14 +109,53 @@ int os_write_file(const char *name, const void *buf, int size)
 	}
 	if (os_write(fd, buf, size) != size) {
 		printf("Cannot write to file '%s'\n", fname);
+		os_close(fd);
 		return -EIO;
 	}
 	os_close(fd);
-	printf("Write '%s', size %#x (%d)\n", name, size, size);
 
 	return 0;
 }
 
+int os_read_file(const char *fname, void **bufp, int *sizep)
+{
+	off_t size;
+	int ret = -EIO;
+	int fd;
+
+	fd = os_open(fname, OS_O_RDONLY);
+	if (fd < 0) {
+		printf("Cannot open file '%s'\n", fname);
+		goto err;
+	}
+	size = os_lseek(fd, 0, OS_SEEK_END);
+	if (size < 0) {
+		printf("Cannot seek to end of file '%s'\n", fname);
+		goto err;
+	}
+	if (os_lseek(fd, 0, OS_SEEK_SET) < 0) {
+		printf("Cannot seek to start of file '%s'\n", fname);
+		goto err;
+	}
+	*bufp = os_malloc(size);
+	if (!*bufp) {
+		printf("Not enough memory to read file '%s'\n", fname);
+		ret = -ENOMEM;
+		goto err;
+	}
+	if (os_read(fd, *bufp, size) != size) {
+		printf("Cannot read from file '%s'\n", fname);
+		goto err;
+	}
+	os_close(fd);
+	*sizep = size;
+
+	return 0;
+err:
+	os_close(fd);
+	return ret;
+}
+
 /* Restore tty state when we exit */
 static struct termios orig_term;
 static bool term_setup;

include/os.h

@@ -350,4 +350,18 @@ int os_mprotect_allow(void *start, size_t len);
  */
 int os_write_file(const char *name, const void *buf, int size);
 
+/**
+ * os_read_file() - Read a file from the host filesystem
+ *
+ * This can be useful when reading test data into sandbox for use by test
+ * routines. The data is allocated using os_malloc() and should be freed by
+ * the caller.
+ *
+ * @name:	File path to read from
+ * @bufp:	Returns buffer containing data read
+ * @sizep:	Returns size of data
+ * @return 0 if OK, -ve on error
+ */
+int os_read_file(const char *name, void **bufp, int *sizep);
+
 #endif