libsysprof: add simple preload source

This source is useful to quickly add an LD_PRELOAD to a profiler.

src/libsysprof/meson.build

@@ -20,6 +20,7 @@ libsysprof_public_sources = [
   'sysprof-memprof-profile.c',
   'sysprof-memprof-source.c',
   'sysprof-netdev-source.c',
+  'sysprof-preload-source.c',
   'sysprof-process-model.c',
   'sysprof-process-model-item.c',
   'sysprof-profile.c',
@@ -51,6 +52,7 @@ libsysprof_public_headers = [
   'sysprof-local-profiler.h',
   'sysprof-memprof-profile.h',
   'sysprof-memprof-source.h',
+  'sysprof-preload-source.h',
   'sysprof-process-model.h',
   'sysprof-process-model-item.h',
   'sysprof-profile.h',

src/libsysprof/sysprof-preload-source.c

@@ -0,0 +1,153 @@
+/* sysprof-preload-source.c
+ *
+ * Copyright 2020 Christian Hergert <chergert@redhat.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 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: GPL-3.0-or-later
+ */
+
+#define G_LOG_DOMAIN "sysprof-preload-source.h"
+
+#include "config.h"
+
+#include "sysprof-preload-source.h"
+
+struct _SysprofPreloadSource
+{
+  GObject parent_instance;
+  gchar *preload;
+};
+
+enum {
+  PROP_0,
+  PROP_PRELOAD,
+  N_PROPS
+};
+
+static void
+sysprof_preload_source_modify_spawn (SysprofSource    *source,
+                                     SysprofSpawnable *spawnable)
+{
+  SysprofPreloadSource *self = (SysprofPreloadSource *)source;
+
+  g_assert (SYSPROF_IS_SOURCE (self));
+  g_assert (SYSPROF_IS_SPAWNABLE (spawnable));
+
+#ifdef __linux__
+  if (self->preload)
+    {
+      g_autofree gchar *freeme = NULL;
+      const gchar *ld_preload;
+
+      if (!(ld_preload = sysprof_spawnable_getenv (spawnable, "LD_PRELOAD")))
+        sysprof_spawnable_setenv (spawnable, "LD_PRELOAD", self->preload);
+      else
+        sysprof_spawnable_setenv (spawnable,
+                                  "LD_PRELOAD",
+                                  (freeme = g_strdup_printf ("%s,%s", self->preload, ld_preload)));
+    }
+#endif
+}
+
+static void
+sysprof_preload_source_stop (SysprofSource *source)
+{
+  sysprof_source_emit_finished (source);
+}
+
+static void
+source_iface_init (SysprofSourceInterface *iface)
+{
+  iface->modify_spawn = sysprof_preload_source_modify_spawn;
+  iface->stop = sysprof_preload_source_stop;
+}
+
+G_DEFINE_TYPE_WITH_CODE (SysprofPreloadSource, sysprof_preload_source, G_TYPE_OBJECT,
+                         G_IMPLEMENT_INTERFACE (SYSPROF_TYPE_SOURCE, source_iface_init))
+
+static GParamSpec *properties [N_PROPS];
+
+static void
+sysprof_preload_source_finalize (GObject *object)
+{
+  SysprofPreloadSource *self = (SysprofPreloadSource *)object;
+
+  g_clear_pointer (&self->preload, g_free);
+
+  G_OBJECT_CLASS (sysprof_preload_source_parent_class)->finalize (object);
+}
+
+static void
+sysprof_preload_source_get_property (GObject    *object,
+                                     guint       prop_id,
+                                     GValue     *value,
+                                     GParamSpec *pspec)
+{
+  SysprofPreloadSource *self = SYSPROF_PRELOAD_SOURCE (object);
+
+  switch (prop_id)
+    {
+    case PROP_PRELOAD:
+      g_value_set_string (value, self->preload);
+      break;
+
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+    }
+}
+
+static void
+sysprof_preload_source_set_property (GObject      *object,
+                                     guint         prop_id,
+                                     const GValue *value,
+                                     GParamSpec   *pspec)
+{
+  SysprofPreloadSource *self = SYSPROF_PRELOAD_SOURCE (object);
+
+  switch (prop_id)
+    {
+    case PROP_PRELOAD:
+      g_free (self->preload);
+      self->preload = g_value_dup_string (value);
+      break;
+
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+    }
+}
+
+static void
+sysprof_preload_source_class_init (SysprofPreloadSourceClass *klass)
+{
+  GObjectClass *object_class = G_OBJECT_CLASS (klass);
+
+  object_class->finalize = sysprof_preload_source_finalize;
+  object_class->get_property = sysprof_preload_source_get_property;
+  object_class->set_property = sysprof_preload_source_set_property;
+
+  properties [PROP_PRELOAD] =
+    g_param_spec_string ("preload",
+                         "Preload",
+                         "The preload to load into the process",
+                         NULL,
+                         (G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
+  
+  g_object_class_install_properties (object_class, N_PROPS, properties);
+}
+
+static void
+sysprof_preload_source_init (SysprofPreloadSource *self)
+{
+}

src/libsysprof/sysprof-preload-source.h

@@ -0,0 +1,32 @@
+/* sysprof-preload-source.h
+ *
+ * Copyright 2020 Christian Hergert <chergert@redhat.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 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: GPL-3.0-or-later
+ */
+
+#pragma once
+
+#include "sysprof-source.h"
+
+G_BEGIN_DECLS
+
+#define SYSPROF_TYPE_PRELOAD_SOURCE (sysprof_preload_source_get_type())
+
+SYSPROF_AVAILABLE_IN_3_38
+G_DECLARE_FINAL_TYPE (SysprofPreloadSource, sysprof_preload_source, SYSPROF, PRELOAD_SOURCE, GObject)
+
+G_END_DECLS

src/libsysprof/sysprof.h

@@ -40,6 +40,7 @@ G_BEGIN_DECLS
 # include "sysprof-memprof-profile.h"
 # include "sysprof-memprof-source.h"
 # include "sysprof-netdev-source.h"
+# include "sysprof-preload-source.h"
 # include "sysprof-process-model-item.h"
 # include "sysprof-process-model.h"
 # include "sysprof-profile.h"