ARM semihosting: fix writing to stdout

SYS_FLEN would be called before a write on a descriptor to check its size.
Currently lseek would fail with -1 when given the stdout/stderr descriptor.
Changing to use fstat seems to be the standard way of handling this.

Signed-off-by: Spencer Oliver <ntfreak@users.sourceforge.net>

2 files changed, 6 insertions, 8 deletions

diff --git a/src/helper/system.h b/src/helper/system.h
index 169df1cb..af19d018 100644
--- a/src/helper/system.h
+++ b/src/helper/system.h
@@ -50,6 +50,8 @@
 #ifdef _WIN32
 #include <winsock2.h>
 #include <ws2tcpip.h>
+#include <sys/types.h>
+#include <sys/stat.h>
 #endif
 // --- platform specific headers ---
 
diff --git a/src/target/arm_semihosting.c b/src/target/arm_semihosting.c
index f4244c84..1d0acd63 100644
--- a/src/target/arm_semihosting.c
+++ b/src/target/arm_semihosting.c
@@ -230,18 +230,14 @@ static int do_semihosting(struct target *target)
 			return retval;
 		else {
 			int fd = target_buffer_get_u32(target, params+0);
-			off_t cur = lseek(fd, 0, SEEK_CUR);
-			if (cur == (off_t)-1) {
+			struct stat buf;
+			result = fstat(fd, &buf);
+			if (result == -1) {
 				armv4_5->semihosting_errno = errno;
 				result = -1;
 				break;
 			}
-			result = lseek(fd, 0, SEEK_END);
-			armv4_5->semihosting_errno = errno;
-			if (lseek(fd, cur, SEEK_SET) == (off_t)-1) {
-				armv4_5->semihosting_errno = errno;
-				result = -1;
-			}
+			result = buf.st_size;
 		}
 		break;