Merge remote-tracking branch 'remotes/stsquad/tags/pull-testing-and-gdbstub-100719-1' into staging

Testing and gdbstub fixes:

  - fix diff-out pass in check-tcg
  - ensure generation of fprem reference
  - fix gdb set_reg fallback

# gpg: Signature made Wed 10 Jul 2019 11:24:28 BST
# gpg:                using RSA key 6685AE99E75167BCAFC8DF35FBD0DB095A9E2A44
# gpg: Good signature from "Alex Bennée (Master Work Key) <alex.bennee@linaro.org>" [full]
# Primary key fingerprint: 6685 AE99 E751 67BC AFC8  DF35 FBD0 DB09 5A9E 2A44

* remotes/stsquad/tags/pull-testing-and-gdbstub-100719-1:
  gdbstub: revert to previous set_reg behaviour
  gdbstub: add some notes to the header comment
  tests/tcg: fix diff-out pass to properly report failure
  tests/tcg: fix up test-i386-fprem.ref generation

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

3 files changed, 25 insertions, 9 deletions

diff --git a/gdbstub.c b/gdbstub.c
index 687c02e..b470aec 100644
--- a/gdbstub.c
+++ b/gdbstub.c
@@ -1,6 +1,10 @@
 /*
  * gdb server stub
  *
+ * This implements a subset of the remote protocol as described in:
+ *
+ *   https://sourceware.org/gdb/onlinedocs/gdb/Remote-Protocol.html
+ *
  * Copyright (c) 2003-2005 Fabrice Bellard
  *
  * This library is free software; you can redistribute it and/or
@@ -15,6 +19,8 @@
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ *
+ * SPDX-License-Identifier: LGPL-2.0+
  */
 
 #include "qemu/osdep.h"
@@ -1667,12 +1673,23 @@ static void handle_remove_bp(GdbCmdContext *gdb_ctx, void *user_ctx)
     put_packet(gdb_ctx->s, "E22");
 }
 
+/*
+ * handle_set/get_reg
+ *
+ * Older gdb are really dumb, and don't use 'G/g' if 'P/p' is available.
+ * This works, but can be very slow. Anything new enough to understand
+ * XML also knows how to use this properly. However to use this we
+ * need to define a local XML file as well as be talking to a
+ * reasonably modern gdb. Responding with an empty packet will cause
+ * the remote gdb to fallback to older methods.
+ */
+
 static void handle_set_reg(GdbCmdContext *gdb_ctx, void *user_ctx)
 {
     int reg_size;
 
     if (!gdb_has_xml) {
-        put_packet(gdb_ctx->s, "E00");
+        put_packet(gdb_ctx->s, "");
         return;
     }
 
@@ -1692,11 +1709,6 @@ static void handle_get_reg(GdbCmdContext *gdb_ctx, void *user_ctx)
 {
     int reg_size;
 
-    /*
-     * Older gdb are really dumb, and don't use 'g' if 'p' is avaialable.
-     * This works, but can be very slow.  Anything new enough to
-     * understand XML also knows how to use this properly.
-     */
     if (!gdb_has_xml) {
         put_packet(gdb_ctx->s, "");
         return;
diff --git a/tests/tcg/Makefile b/tests/tcg/Makefile
index 6fa63cc..9f56768 100644
--- a/tests/tcg/Makefile
+++ b/tests/tcg/Makefile
@@ -45,7 +45,11 @@ run-test = $(call quiet-command, timeout $(TIMEOUT) $2,"TEST",$3)
 endif
 
 # $1 = test name, $2 = reference
-diff-out = $(call quiet-command, diff -u $1.out $2 | head -n 10,"DIFF","$1.out with $2")
+# to work around the pipe squashing the status we only pipe the result if
+# we know it failed and then force failure at the end.
+diff-out = $(call quiet-command, diff -q $1.out $2 || \
+                                 (diff -u $1.out $2 | head -n 10 && false), \
+                                 "DIFF","$1.out with $2")
 
 # $1 = test name, $2 = reason
 skip-test = @printf "  SKIPPED %s on $(TARGET_NAME) because %s\n" $1 $2
diff --git a/tests/tcg/i386/Makefile.target b/tests/tcg/i386/Makefile.target
index b4033ba..d0eb702 100644
--- a/tests/tcg/i386/Makefile.target
+++ b/tests/tcg/i386/Makefile.target
@@ -35,9 +35,9 @@ test-i386-fprem.ref: test-i386-fprem
 	$(call quiet-command, ./$< > $@,"GENREF","generating $@")
 
 run-test-i386-fprem: TIMEOUT=60
-run-test-i386-fprem: test-i386-fprem
+run-test-i386-fprem: test-i386-fprem test-i386-fprem.ref
 	$(call run-test,test-i386-fprem, $(QEMU) $<,"$< on $(TARGET_NAME)")
-	$(call diff-out,test-i386-fprem, $(I386_SRC)/$<.ref)
+	$(call diff-out,test-i386-fprem, test-i386-fprem.ref)
 else
 run-test-i386-fprem: test-i386-fprem
 	$(call skip-test, $<, "SLOW")