tests/tcg: Add late gdbstub attach test

Add a small test to prevent regressions.
Make sure that host_interrupt_signal is not visible to the guest.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Message-Id: <20250117001542.8290-9-iii@linux.ibm.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20250207153112.3939799-18-alex.bennee@linaro.org>

3 files changed, 77 insertions, 1 deletions

diff --git a/tests/tcg/multiarch/Makefile.target b/tests/tcg/multiarch/Makefile.target
index 18d3cf4..688a6be 100644
--- a/tests/tcg/multiarch/Makefile.target
+++ b/tests/tcg/multiarch/Makefile.target
@@ -130,6 +130,13 @@ run-gdbstub-follow-fork-mode-parent: follow-fork-mode
 		--bin $< --test $(MULTIARCH_SRC)/gdbstub/follow-fork-mode-parent.py, \
 	following parents on fork)
 
+run-gdbstub-late-attach: late-attach
+	$(call run-test, $@, env LATE_ATTACH_PY=1 $(GDB_SCRIPT) \
+		--gdb $(GDB) \
+		--qemu $(QEMU) --qargs "$(QEMU_OPTS)" --no-suspend \
+		--bin $< --test $(MULTIARCH_SRC)/gdbstub/late-attach.py, \
+	attaching to a running process)
+
 else
 run-gdbstub-%:
 	$(call skip-test, "gdbstub test $*", "need working gdb with $(patsubst -%,,$(TARGET_NAME)) support")
@@ -139,7 +146,7 @@ EXTRA_RUNS += run-gdbstub-sha1 run-gdbstub-qxfer-auxv-read \
 	      run-gdbstub-registers run-gdbstub-prot-none \
 	      run-gdbstub-catch-syscalls run-gdbstub-follow-fork-mode-child \
 	      run-gdbstub-follow-fork-mode-parent \
-	      run-gdbstub-qxfer-siginfo-read
+	      run-gdbstub-qxfer-siginfo-read run-gdbstub-late-attach
 
 # ARM Compatible Semi Hosting Tests
 #
diff --git a/tests/tcg/multiarch/gdbstub/late-attach.py b/tests/tcg/multiarch/gdbstub/late-attach.py
new file mode 100644
index 0000000..1d40efb
--- /dev/null
+++ b/tests/tcg/multiarch/gdbstub/late-attach.py
@@ -0,0 +1,28 @@
+"""Test attaching GDB to a running process.
+
+SPDX-License-Identifier: GPL-2.0-or-later
+"""
+from test_gdbstub import main, report
+
+
+def run_test():
+    """Run through the tests one by one"""
+    try:
+        phase = gdb.parse_and_eval("phase").string()
+    except gdb.error:
+        # Assume the guest did not reach main().
+        phase = "start"
+
+    if phase == "start":
+        gdb.execute("break sigwait")
+        gdb.execute("continue")
+        phase = gdb.parse_and_eval("phase").string()
+    report(phase == "sigwait", "{} == \"sigwait\"".format(phase))
+
+    gdb.execute("signal SIGUSR1")
+
+    exitcode = int(gdb.parse_and_eval("$_exitcode"))
+    report(exitcode == 0, "{} == 0".format(exitcode))
+
+
+main(run_test)
diff --git a/tests/tcg/multiarch/late-attach.c b/tests/tcg/multiarch/late-attach.c
new file mode 100644
index 0000000..20a3640
--- /dev/null
+++ b/tests/tcg/multiarch/late-attach.c
@@ -0,0 +1,41 @@
+/*
+ * Test attaching GDB to a running process.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+#include <assert.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+static const char *phase = "start";
+
+int main(void)
+{
+    sigset_t set;
+    int sig;
+
+    assert(sigfillset(&set) == 0);
+    assert(sigprocmask(SIG_BLOCK, &set, NULL) == 0);
+
+    /* Let GDB know it can send SIGUSR1. */
+    phase = "sigwait";
+    if (getenv("LATE_ATTACH_PY")) {
+        assert(sigwait(&set, &sig) == 0);
+        if (sig != SIGUSR1) {
+            fprintf(stderr, "Unexpected signal %d\n", sig);
+            return EXIT_FAILURE;
+        }
+    }
+
+    /* Check that the guest does not see host_interrupt_signal. */
+    assert(sigpending(&set) == 0);
+    for (sig = 1; sig < NSIG; sig++) {
+        if (sigismember(&set, sig)) {
+            fprintf(stderr, "Unexpected signal %d\n", sig);
+            return EXIT_FAILURE;
+        }
+    }
+
+    return EXIT_SUCCESS;
+}