gdbstub: fixes cases where wrong threads were reported to GDB on SIGINT

This fix is implemented by having the vCont handler set the value of
`gdbserver_state.c_cpu` if any threads are to be resumed. The specific
CPU picked is arbitrarily from the ones to be resumed, but it should
be okay, as all GDB cares about is that it is a resumed thread.

Signed-off-by: Matheus Branco Borella <dark.ryu.550@gmail.com>
Message-Id: <20230804182633.47300-2-dark.ryu.550@gmail.com>
[AJB: style and whitespace fixes]
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1725
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20230829161528.2707696-9-alex.bennee@linaro.org>

1 files changed, 28 insertions, 0 deletions

diff --git a/tests/tcg/multiarch/system/interrupt.c b/tests/tcg/multiarch/system/interrupt.c
new file mode 100644
index 0000000000..98d4f2eff9
--- /dev/null
+++ b/tests/tcg/multiarch/system/interrupt.c
@@ -0,0 +1,28 @@
+/*
+ * External interruption test. This test is structured in such a way that it
+ * passes the cases that require it to exit, but we can make it enter an
+ * infinite loop from GDB.
+ *
+ * We don't have the benefit of libc, just builtin C primitives and
+ * whatever is in minilib.
+ */
+
+#include <minilib.h>
+
+void loop(void)
+{
+    do {
+        /*
+         * Loop forever. Just make sure the condition is always a constant
+         * expression, so that this loop is not UB, as per the C
+         * standard.
+         */
+    } while (1);
+}
+
+int main(void)
+{
+    return 0;
+}
+
+