semihosting: support fileio operation

This patch adds support for bridging semihosting to GDB's File-I/O
remote protocol extension. For the most part operations match up 1:1,
however some require a working area to complete successfully, namely
operations that devolve to read, stat, and gettimeofday.

A new command was added to enable support for fileio named `arm
semihosting_fileio`, which ensures that the default behavior remains
intact for those that prefer it.

Finally, redundant logging was removed from the target_arch_state
function; this permits ARM targets to quiesce log output when polling
for a fileio reply. This prevents filling the logs with halt/resume
messages when using semihosting fileio.

Change-Id: Ifbb864fc2373336a501cc0332675b887b552e1ee
Signed-off-by: Steven Stallion <stallion@squareup.com>
Reviewed-on: http://openocd.zylin.com/3566
Tested-by: jenkins
Reviewed-by: Steven Stallion <sstallion@gmail.com>
Reviewed-by: Paul Fertser <fercerpav@gmail.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/doc/openocd.texi b/doc/openocd.texi
index 372683a..1cca4ab 100644
--- a/doc/openocd.texi
+++ b/doc/openocd.texi
@@ -7404,6 +7404,17 @@ requests by using a special SVC instruction that is trapped at the
 Supervisor Call vector by OpenOCD.
 @end deffn
 
+@deffn Command {arm semihosting_fileio} [@option{enable}|@option{disable}]
+@cindex ARM semihosting
+Display status of semihosting fileio, after optionally changing that
+status.
+
+Enabling this option forwards semihosting I/O to GDB process using the
+File-I/O remote protocol extension. This is especially useful for
+interacting with remote files or displaying console messages in the
+debugger.
+@end deffn
+
 @section ARMv4 and ARMv5 Architecture
 @cindex ARMv4
 @cindex ARMv5