[PATCH v3] plugins/syscall: Added a table-like summary output

[Mahmoud Mandour <ma.mandourr@gmail.com>]

Added a table-like output which contains the total number of calls
for each used syscall along with the number of errors that occurred.

Per-call tracing is still available through supplying the argument
``print`` to the plugin.

Signed-off-by: Mahmoud Mandour <ma.mandourr@gmail.com>
---
v2 -> v3: * Locked shared hash-table to protect access across multiple
          callback invocations.
          * Used better variable names for the hash table and entries.
          * Factored the creation and looking-up for hash table entries.
          * Eliminated the usage of a global boolean and checked against
          the existence of the ``statistics`` hash-table. (it's allocated
          only if the plugin in the summary(default) mode.
          * Removed the function ``free_entry`` and passed ``g_free``
          directly to ``g_hash_table_new_full()``.

 tests/plugin/syscall.c | 98 +++++++++++++++++++++++++++++++++++++++---
 1 file changed, 93 insertions(+), 5 deletions(-)

diff --git a/tests/plugin/syscall.c b/tests/plugin/syscall.c
index 53ee2ab6c4..7b856f2fe2 100644
--- a/tests/plugin/syscall.c
+++ b/tests/plugin/syscall.c
@@ -16,32 +16,120 @@
 
 QEMU_PLUGIN_EXPORT int qemu_plugin_version = QEMU_PLUGIN_VERSION;
 
+typedef struct {
+    int64_t num;
+    int64_t calls;
+    int64_t errors;
+} SyscallStats;
+
+static GMutex lock;
+static GHashTable *statistics;
+
+static SyscallStats *get_or_create_entry(int64_t num)
+{
+    SyscallStats *entry =
+        (SyscallStats *) g_hash_table_lookup(statistics, GINT_TO_POINTER(num));
+
+    if (!entry) {
+        entry = g_new0(SyscallStats, 1);
+        entry->num = num;
+        g_hash_table_insert(statistics, GINT_TO_POINTER(num), (gpointer) entry);
+    }
+
+    return entry;
+}
+
 static void vcpu_syscall(qemu_plugin_id_t id, unsigned int vcpu_index,
                          int64_t num, uint64_t a1, uint64_t a2,
                          uint64_t a3, uint64_t a4, uint64_t a5,
                          uint64_t a6, uint64_t a7, uint64_t a8)
 {
-    g_autofree gchar *out = g_strdup_printf("syscall #%" PRIi64 "\n", num);
-    qemu_plugin_outs(out);
+    if (statistics) {
+        SyscallStats *entry;
+        g_mutex_lock(&lock);
+        entry = get_or_create_entry(num);
+        entry->calls++;
+        g_mutex_unlock(&lock);
+    } else {
+        g_autofree gchar *out = g_strdup_printf("syscall #%" PRIi64 "\n", num);
+        qemu_plugin_outs(out);
+    }
 }
 
 static void vcpu_syscall_ret(qemu_plugin_id_t id, unsigned int vcpu_idx,
                              int64_t num, int64_t ret)
+{
+    if (statistics) {
+        SyscallStats *entry;
+
+        g_mutex_lock(&lock);
+        /* Should always return an existent entry. */
+        entry = get_or_create_entry(num);
+        if (ret < 0) {
+            entry->errors++;
+        }
+        g_mutex_unlock(&lock);
+    } else {
+        g_autofree gchar *out;
+        out = g_strdup_printf("syscall #%" PRIi64 " returned -> %" PRIi64 "\n",
+                num, ret);
+        qemu_plugin_outs(out);
+    }
+}
+
+void print_entry(gpointer val, gpointer user_data)
 {
     g_autofree gchar *out;
-    out = g_strdup_printf("syscall #%" PRIi64 " returned -> %" PRIi64 "\n",
-            num, ret);
+    SyscallStats *entry = (SyscallStats *) val;
+    int64_t syscall_num = entry->num;
+    out = g_strdup_printf(
+        "%-13" PRIi64 "%-6" PRIi64 " %" PRIi64 "\n",
+        syscall_num, entry->calls, entry->errors);
     qemu_plugin_outs(out);
 }
 
+static gint comp_func(gconstpointer ea, gconstpointer eb)
+{
+    SyscallStats *ent_a = (SyscallStats *) ea;
+    SyscallStats *ent_b = (SyscallStats *) eb;
+
+    return ent_a->calls > ent_b->calls ? -1 : 1;
+}
+
 /* ************************************************************************* */
+static void plugin_exit(qemu_plugin_id_t id, void *p)
+{
+    if (!statistics) {
+        return;
+    }
+
+    g_mutex_lock(&lock);
+    GList *entries = g_hash_table_get_values(statistics);
+    entries = g_list_sort(entries, comp_func);
+    qemu_plugin_outs("syscall no.  calls  errors\n");
 
-static void plugin_exit(qemu_plugin_id_t id, void *p) {}
+    g_list_foreach(entries, print_entry, NULL);
+
+    g_list_free(entries);
+    g_hash_table_destroy(statistics);
+    g_mutex_unlock(&lock);
+}
 
 QEMU_PLUGIN_EXPORT int qemu_plugin_install(qemu_plugin_id_t id,
                                            const qemu_info_t *info,
                                            int argc, char **argv)
 {
+    if (argc == 0) {
+        statistics = g_hash_table_new_full(NULL, g_direct_equal, NULL, g_free);
+    } else {
+        for (int i = 0; i < argc; i++) {
+            if (g_strcmp0(argv[i], "print") != 0) {
+                fprintf(stderr, "unsupported argument: %s\n", argv[i]);
+                return -1;
+            }
+        }
+    }
+
     qemu_plugin_register_vcpu_syscall_cb(id, vcpu_syscall);
     qemu_plugin_register_vcpu_syscall_ret_cb(id, vcpu_syscall_ret);
     qemu_plugin_register_atexit_cb(id, plugin_exit, NULL);
-- 
2.25.1