[PATCH 08/21] qapi: add 'tldr-dump' command for on-demand data recorder output

["Daniel P. Berrangé" <berrange@redhat.com>]

While the data recorder is designed to dump its contents in
response to various signals that result in a QEMU crash, it
is also interesting to explicitly request dump.

This could be simply as an adhoc debugging activity, or could
be in response to a specific event like a guest OS panic
notification.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 MAINTAINERS           |  1 +
 qapi/meson.build      |  1 +
 qapi/qapi-schema.json |  1 +
 qapi/tldr.json        | 28 ++++++++++++++++++++++++++++
 qemu-options.hx       |  2 ++
 util/tldr.c           | 32 ++++++++++++++++++++++++++++++++
 6 files changed, 65 insertions(+)
 create mode 100644 qapi/tldr.json

diff --git a/MAINTAINERS b/MAINTAINERS
index 4fa68810c1e..54265d987cb 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4780,3 +4780,4 @@ F: util/tldr.c
 F: util/tldr-internal.h
 F: include/qemu/tldr.h
 F: tests/unit/test-util-tldr.c
+F: qapi/tldr.json
diff --git a/qapi/meson.build b/qapi/meson.build
index a46269b5a0c..f8aecb61284 100644
--- a/qapi/meson.build
+++ b/qapi/meson.build
@@ -49,6 +49,7 @@ qapi_all_modules = [
   'run-state',
   'sockets',
   'stats',
+  'tldr',
   'trace',
   'transaction',
   'vfio',
diff --git a/qapi/qapi-schema.json b/qapi/qapi-schema.json
index b93dd68d94c..b36777970d1 100644
--- a/qapi/qapi-schema.json
+++ b/qapi/qapi-schema.json
@@ -76,3 +76,4 @@
 { 'include': 'cryptodev.json' }
 { 'include': 'cxl.json' }
 { 'include': 'uefi.json' }
+{ 'include': 'tldr.json' }
diff --git a/qapi/tldr.json b/qapi/tldr.json
new file mode 100644
index 00000000000..8e2b7cda324
--- /dev/null
+++ b/qapi/tldr.json
@@ -0,0 +1,28 @@
+# -*- Mode: Python -*-
+# vim: filetype=python
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+##
+# @QTLDRDumpOptions:
+#     Options for `tldr-dump`.
+#
+# @target: the fully qualified file path to dump
+#     the data recorder to
+#
+# Since: 11.2.0
+##
+{ 'struct': 'QTLDRDumpOptions',
+  'data': { 'target': 'str' } }
+
+##
+# @tldr-dump:
+#     Dump the data recorder to a file
+#
+# Since: 11.2.0
+#
+# .. qmp-example::
+#
+#     -> { "execute": "tldr-dump", "arguments": { "target": "/tmp/qemu.txt" } }
+#     <- { "return": {} }
+##
+{ 'command': 'tldr-dump', 'data': 'QTLDRDumpOptions' }
diff --git a/qemu-options.hx b/qemu-options.hx
index 2f63d86b635..5f96257cef0 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -6692,6 +6692,8 @@ SRST
         recorder will be dumped to the stderr stream. If the
         ``crash-target`` parameter was given, that specifies a fully
         qualified file path to write the dump to instead of stderr.
+        The ``tldr-dump`` QMP command can also be used at any time to
+        save the captured data to an arbitrary file.
 
         The ``tldr-config`` object can be added at initial startup
         or via QMP at runtime. Once created, however, it is not
diff --git a/util/tldr.c b/util/tldr.c
index 13e9881bc9b..ea7c26b8e9b 100644
--- a/util/tldr.c
+++ b/util/tldr.c
@@ -12,6 +12,7 @@
 #include "qom/object.h"
 #include "qom/object_interfaces.h"
 #include "qapi/error.h"
+#include "qapi/qapi-commands-tldr.h"
 
 struct QTLDRConfig {
     Object parent;
@@ -436,3 +437,34 @@ qtldr_crash_dump_signal(siginfo_t *si)
         close(fd);
     }
 }
+
+
+/*
+ * WARNING: Code below this marker provides a QMP handler
+ * WARNING: for use in normal execution. It calls into
+ * WARNING: the common crash report outputting APIs, but
+ * WARNING: this specific method is not restricted to async
+ * WARNING: signal safe POSIX functions.
+ */
+
+
+void
+qmp_tldr_dump(const char *target, Error **errp)
+{
+    int fd;
+
+    if (!qatomic_read(&qtldr_active)) {
+        error_setg(errp, "No 'tldr-config' object has been creted");
+        return;
+    }
+
+    fd = qemu_create(target, O_WRONLY | O_TRUNC, 0600, errp);
+    if (fd < 0) {
+        return;
+    }
+
+    qtldr_crash_dump_internal(fd, NULL);
+
+    qemu_fdatasync(fd);
+    close(fd);
+}
-- 
2.56.0