sysprof-user-sampler: implement await for FDs

This allows us to not need libdex 0.9+ for use by the sampler.

src/libsysprof/meson.build

@@ -144,6 +144,7 @@ libsysprof_private_sources = [
   'sysprof-document-symbols.c',
   'sysprof-elf-loader.c',
   'sysprof-elf.c',
+  'sysprof-fd.c',
   'sysprof-leak-detector.c',
   'sysprof-maps-parser.c',
   'sysprof-mount-device.c',

src/libsysprof/sysprof-fd-private.h

@@ -0,0 +1,39 @@
+/* sysprof-fd-private.h
+ *
+ * Copyright 2024 Christian Hergert <chergert@redhat.com>
+ *
+ * This library is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation; either version 2.1 of the
+ * License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ */
+
+#pragma once
+
+#include <glib-object.h>
+
+G_BEGIN_DECLS
+
+#define SYSPROF_TYPE_FD (sysprof_fd_get_type())
+
+typedef struct _SysprofFD SysprofFD;
+
+GType      sysprof_fd_get_type (void) G_GNUC_CONST;
+int        sysprof_fd_peek     (const SysprofFD *fd);
+int        sysprof_fd_steal    (SysprofFD       *fd);
+SysprofFD *sysprof_fd_dup      (const SysprofFD *fd);
+void       sysprof_fd_free     (SysprofFD       *fd);
+
+G_DEFINE_AUTOPTR_CLEANUP_FUNC (SysprofFD, sysprof_fd_free)
+
+G_END_DECLS

src/libsysprof/sysprof-fd.c

@@ -0,0 +1,67 @@
+/* sysprof-fd.c
+ *
+ * Copyright 2024 Christian Hergert <chergert@redhat.com>
+ *
+ * This library is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation; either version 2.1 of the
+ * License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ */
+
+#include "config.h"
+
+#include <unistd.h>
+
+#include "sysprof-fd-private.h"
+
+int
+sysprof_fd_peek (const SysprofFD *fd)
+{
+  if (fd == NULL)
+    return -1;
+
+  return *(int *)fd;
+}
+
+int
+sysprof_fd_steal (SysprofFD *fd)
+{
+  if (fd == NULL)
+    return -1;
+
+  return g_steal_fd ((int *)fd);
+}
+
+void
+sysprof_fd_free (SysprofFD *fd)
+{
+  int real = sysprof_fd_steal (fd);
+  if (real != -1)
+    close (real);
+  g_free (fd);
+}
+
+SysprofFD *
+sysprof_fd_dup (const SysprofFD *fd)
+{
+  int real = sysprof_fd_peek (fd);
+
+  if (real == -1)
+    return NULL;
+
+  real = dup (real);
+
+  return g_memdup2 (&real, sizeof real);
+}
+
+G_DEFINE_BOXED_TYPE (SysprofFD, sysprof_fd, sysprof_fd_dup, sysprof_fd_free)

src/libsysprof/sysprof-user-sampler.c

@@ -32,6 +32,7 @@
 #include "sysprof-recording-private.h"
 #include "sysprof-user-sampler.h"
 #include "sysprof-muxer-source.h"
+#include "sysprof-fd-private.h"
 
 #include "ipc-unwinder.h"
 
@@ -85,6 +86,30 @@ close_fd (gpointer data)
     }
 }
 
+static void
+promise_resolve_fd (DexPromise *promise,
+                    int         fd)
+{
+  GValue gvalue = {SYSPROF_TYPE_FD, {{.v_pointer = &fd}, {.v_int = 0}}};
+  dex_promise_resolve (promise, &gvalue);
+}
+
+static int
+await_fd (DexFuture  *future,
+          GError    **error)
+{
+  SysprofFD *fd = dex_await_boxed (future, error);
+  int ret = -1;
+
+  if (fd != NULL)
+    {
+      ret = sysprof_fd_steal (fd);
+      sysprof_fd_free (fd);
+    }
+
+  return ret;
+}
+
 static void
 sysprof_user_sampler_ioctl (SysprofUserSampler *self,
                             gboolean            enable)
@@ -149,7 +174,7 @@ _perf_event_open_cb (GObject      *object,
       if (-1 == (fd = g_unix_fd_list_get (fd_list, handle, &error)))
         goto failure;
 
-      dex_promise_resolve_fd (promise, g_steal_fd (&fd));
+      promise_resolve_fd (promise, g_steal_fd (&fd));
       return;
     }
 
@@ -234,7 +259,7 @@ try_again:
                                             _perf_event_open_cb,
                                             dex_ref (promise));
 
-  if (-1 == (perf_fd = dex_await_fd (dex_ref (promise), error)))
+  if (-1 == (perf_fd = await_fd (dex_ref (promise), error)))
     {
       g_clear_pointer (&options, g_variant_unref);
 
@@ -274,7 +299,7 @@ call_unwind_cb (GObject      *object,
 
   if (ipc_unwinder_call_unwind_finish (IPC_UNWINDER (object), &out_capture_fd, &out_fd_list, result, &error) &&
       -1 != (capture_fd = g_unix_fd_list_get (out_fd_list, g_variant_get_handle (out_capture_fd), &error)))
-    dex_promise_resolve_fd (promise, g_steal_fd (&capture_fd));
+    promise_resolve_fd (promise, g_steal_fd (&capture_fd));
   else
     dex_promise_reject (promise, error);
 }
@@ -406,7 +431,7 @@ sysprof_user_sampler_prepare_fiber (gpointer user_data)
                                     call_unwind_cb,
                                     dex_ref (promise));
 
-          fd = dex_await_fd (dex_ref (promise), &error);
+          fd = await_fd (dex_ref (promise), &error);
 
           if (fd == -1)
             {