commit 6ee18643770b360da0c8ee44aa07708caa516fa9
author Peter Maydell <peter.maydell@linaro.org> Mon Sep 16 15:15:44 2019 +0100
committer Peter Maydell <peter.maydell@linaro.org> Tue Oct 15 18:09:04 2019 +0100
tree e33b9e6ca0683709473303cd26a3e3f5ea8ae2ab
parent 22a43bb9abf946a9e405e740cfd0ba887ccd4823

target/arm/arm-semi: Implement SH_EXT_STDOUT_STDERR extension

SH_EXT_STDOUT_STDERR is a v2.0 semihosting extension: the guest
can open ":tt" with a file mode requesting append access in
order to open stderr, in addition to the existing "open for
read for stdin or write for stdout". Implement this and
report it via the :semihosting-features data.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 20190916141544.17540-16-peter.maydell@linaro.org

target/arm/arm-semi.c

diff --git a/target/arm/arm-semi.c b/target/arm/arm-semi.c
index f65d8c9..6f7b6d8 100644
--- a/target/arm/arm-semi.c
+++ b/target/arm/arm-semi.c
@@ -516,13 +516,14 @@
 
 /* Feature bits reportable in feature byte 0 */
 #define SH_EXT_EXIT_EXTENDED (1 << 0)
+#define SH_EXT_STDOUT_STDERR (1 << 1)
 
 static const uint8_t featurefile_data[] = {
     SHFB_MAGIC_0,
     SHFB_MAGIC_1,
     SHFB_MAGIC_2,
     SHFB_MAGIC_3,
-    SH_EXT_EXIT_EXTENDED, /* Feature byte 0 */
+    SH_EXT_EXIT_EXTENDED | SH_EXT_STDOUT_STDERR, /* Feature byte 0 */
 };
 
 static void init_featurefile_guestfd(int guestfd)
@@ -710,7 +711,21 @@
         }
 
         if (strcmp(s, ":tt") == 0) {
-            int result_fileno = arg1 < 4 ? STDIN_FILENO : STDOUT_FILENO;
+            int result_fileno;
+
+            /*
+             * We implement SH_EXT_STDOUT_STDERR, so:
+             *  open for read == stdin
+             *  open for write == stdout
+             *  open for append == stderr
+             */
+            if (arg1 < 4) {
+                result_fileno = STDIN_FILENO;
+            } else if (arg1 < 8) {
+                result_fileno = STDOUT_FILENO;
+            } else {
+                result_fileno = STDERR_FILENO;
+            }
             associate_guestfd(guestfd, result_fileno);
             unlock_user(s, arg0, 0);
             return guestfd;