new file mode 100644
@@ -0,0 +1,388 @@
+/*
+ * Control Flow plugin
+ *
+ * This plugin will track changes to control flow and detect where
+ * instructions fault.
+ *
+ * Copyright (c) 2024 Linaro Ltd
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+#include <glib.h>
+#include <inttypes.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <qemu-plugin.h>
+
+QEMU_PLUGIN_EXPORT int qemu_plugin_version = QEMU_PLUGIN_VERSION;
+
+typedef enum {
+ SORT_HOTTEST, /* hottest branch insn */
+ SORT_EXCEPTION, /* most early exits */
+ SORT_POPDEST, /* most destinations (usually ret's) */
+} ReportType;
+
+ReportType report = SORT_HOTTEST;
+int topn = 10;
+
+typedef struct {
+ uint64_t daddr;
+ uint64_t dcount;
+} DestData;
+
+/* A node is an address where we can go to multiple places */
+typedef struct {
+ GMutex lock;
+ /* address of the branch point */
+ uint64_t addr;
+ /* array of DestData */
+ GArray *dests;
+ /* early exit/fault count */
+ uint64_t early_exit;
+ /* jump destination count */
+ uint64_t dest_count;
+ /* instruction data */
+ char *insn_disas;
+ /* symbol? */
+ const char *symbol;
+ /* times translated as last in block? */
+ int last_count;
+ /* times translated in the middle of block? */
+ int mid_count;
+} NodeData;
+
+typedef enum {
+ /* last insn in block, expected flow control */
+ LAST_INSN = (1 << 0),
+ /* mid-block insn, can only be an exception */
+ EXCP_INSN = (1 << 1),
+ /* multiple disassembly, may have changed */
+ MULT_INSN = (1 << 2),
+} InsnTypes;
+
+typedef struct {
+ /* address of the branch point */
+ uint64_t addr;
+ /* disassembly */
+ char *insn_disas;
+ /* symbol? */
+ const char *symbol;
+ /* types */
+ InsnTypes type_flag;
+} InsnData;
+
+/* We use this to track the current execution state */
+typedef struct {
+ /* address of end of block */
+ uint64_t end_block;
+ /* next pc after end of block */
+ uint64_t pc_after_block;
+ /* address of last executed PC */
+ uint64_t last_pc;
+} VCPUScoreBoard;
+
+/* descriptors for accessing the above scoreboard */
+static qemu_plugin_u64 end_block;
+static qemu_plugin_u64 pc_after_block;
+static qemu_plugin_u64 last_pc;
+
+
+static GMutex node_lock;
+static GHashTable *nodes;
+struct qemu_plugin_scoreboard *state;
+
+/* SORT_HOTTEST */
+static gint hottest(gconstpointer a, gconstpointer b)
+{
+ NodeData *na = (NodeData *) a;
+ NodeData *nb = (NodeData *) b;
+
+ return na->dest_count > nb->dest_count ? -1 :
+ na->dest_count == nb->dest_count ? 0 : 1;
+}
+
+static gint exception(gconstpointer a, gconstpointer b)
+{
+ NodeData *na = (NodeData *) a;
+ NodeData *nb = (NodeData *) b;
+
+ return na->early_exit > nb->early_exit ? -1 :
+ na->early_exit == nb->early_exit ? 0 : 1;
+}
+
+static gint popular(gconstpointer a, gconstpointer b)
+{
+ NodeData *na = (NodeData *) a;
+ NodeData *nb = (NodeData *) b;
+
+ return na->dests->len > nb->dests->len ? -1 :
+ na->dests->len == nb->dests->len ? 0 : 1;
+}
+
+/* Filter out non-branches - returns true to remove entry */
+static gboolean filter_non_branches(gpointer key, gpointer value,
+ gpointer user_data)
+{
+ NodeData *node = (NodeData *) value;
+
+ return node->dest_count == 0;
+}
+
+static void plugin_exit(qemu_plugin_id_t id, void *p)
+{
+ g_autoptr(GString) result = g_string_new("collected ");
+ GList *data;
+ GCompareFunc sort = &hottest;
+ int n = 0;
+
+ g_mutex_lock(&node_lock);
+ g_string_append_printf(result, "%d control flow nodes in the hash table\n",
+ g_hash_table_size(nodes));
+
+ /* remove all nodes that didn't branch */
+ g_hash_table_foreach_remove(nodes, filter_non_branches, NULL);
+
+ data = g_hash_table_get_values(nodes);
+
+ switch (report) {
+ case SORT_HOTTEST:
+ sort = &hottest;
+ break;
+ case SORT_EXCEPTION:
+ sort = &exception;
+ break;
+ case SORT_POPDEST:
+ sort = &popular;
+ break;
+ }
+
+ data = g_list_sort(data, sort);
+
+ for (GList *l = data;
+ l != NULL && n < topn;
+ l = l->next, n++) {
+ NodeData *n = l->data;
+ const char *type = n->mid_count ? "sync fault" : "branch";
+ g_string_append_printf(result, " addr: 0x%"PRIx64 " %s: %s (%s)\n",
+ n->addr, n->symbol, n->insn_disas, type);
+ if (n->early_exit) {
+ g_string_append_printf(result, " early exits %"PRId64"\n",
+ n->early_exit);
+ }
+ g_string_append_printf(result, " branches %"PRId64"\n",
+ n->dest_count);
+ for (int j = 0; j < n->dests->len; j++) {
+ DestData *dd = &g_array_index(n->dests, DestData, j);
+ g_string_append_printf(result, " to 0x%"PRIx64" (%"PRId64")\n",
+ dd->daddr, dd->dcount);
+ }
+ }
+
+ qemu_plugin_outs(result->str);
+
+ g_mutex_unlock(&node_lock);
+}
+
+static void plugin_init(void)
+{
+ g_mutex_init(&node_lock);
+ nodes = g_hash_table_new(NULL, g_direct_equal);
+ state = qemu_plugin_scoreboard_new(sizeof(VCPUScoreBoard));
+
+ /* score board declarations */
+ end_block = qemu_plugin_scoreboard_u64_in_struct(state, VCPUScoreBoard,
+ end_block);
+ pc_after_block = qemu_plugin_scoreboard_u64_in_struct(state, VCPUScoreBoard,
+ pc_after_block);
+ last_pc = qemu_plugin_scoreboard_u64_in_struct(state, VCPUScoreBoard,
+ last_pc);
+}
+
+static NodeData *create_node(uint64_t addr)
+{
+ NodeData *node = g_new0(NodeData, 1);
+ g_mutex_init(&node->lock);
+ node->addr = addr;
+ node->dests = g_array_new(true, true, sizeof(DestData));
+ return node;
+}
+
+static NodeData *fetch_node(uint64_t addr, bool create_if_not_found)
+{
+ NodeData *node = NULL;
+
+ g_mutex_lock(&node_lock);
+ node = (NodeData *) g_hash_table_lookup(nodes, (gconstpointer) addr);
+ if (!node && create_if_not_found) {
+ node = create_node(addr);
+ g_hash_table_insert(nodes, (gpointer) addr, (gpointer) node);
+ }
+ g_mutex_unlock(&node_lock);
+ return node;
+}
+
+/*
+ * Called when we detect a non-linear execution (pc !=
+ * pc_after_block). This could be due to a fault causing some sort of
+ * exit exception (if last_pc != block_end) or just a taken branch.
+ */
+static void vcpu_tb_branched_exec(unsigned int cpu_index, void *udata)
+{
+ uint64_t lpc = qemu_plugin_u64_get(last_pc, cpu_index);
+ uint64_t ebpc = qemu_plugin_u64_get(end_block, cpu_index);
+ uint64_t npc = qemu_plugin_u64_get(pc_after_block, cpu_index);
+ uint64_t pc = GPOINTER_TO_UINT(udata);
+
+ /* return early for address 0 */
+ if (!lpc) {
+ return;
+ }
+
+ NodeData *node = fetch_node(lpc, true);
+ DestData *data = NULL;
+ bool early_exit = (lpc != ebpc);
+ GArray *dests;
+
+ /* the condition should never hit */
+ g_assert(pc != npc);
+
+ g_mutex_lock(&node->lock);
+
+ if (early_exit) {
+ fprintf(stderr, "%s: pc=%"PRIx64", epbc=%"PRIx64
+ " npc=%"PRIx64", lpc=%"PRIx64"\n",
+ __func__, pc, ebpc, npc, lpc);
+ node->early_exit++;
+ if (!node->mid_count) {
+ /* count now as we've only just allocated */
+ node->mid_count++;
+ }
+ }
+
+ dests = node->dests;
+ for (int i = 0; i < dests->len; i++) {
+ if (g_array_index(dests, DestData, i).daddr == pc) {
+ data = &g_array_index(dests, DestData, i);
+ }
+ }
+
+ /* we've never seen this before, allocate a new entry */
+ if (!data) {
+ DestData new_entry = { .daddr = pc };
+ g_array_append_val(dests, new_entry);
+ data = &g_array_index(dests, DestData, dests->len - 1);
+ g_assert(data->daddr == pc);
+ }
+
+ data->dcount++;
+ node->dest_count++;
+
+ g_mutex_unlock(&node->lock);
+}
+
+/*
+ * At the start of each block we need to resolve two things:
+ *
+ * - is last_pc == block_end, if not we had an early exit
+ * - is start of block last_pc + insn width, if not we jumped
+ *
+ * Once those are dealt with we can instrument the rest of the
+ * instructions for their execution.
+ *
+ */
+static void vcpu_tb_trans(qemu_plugin_id_t id, struct qemu_plugin_tb *tb)
+{
+ uint64_t pc = qemu_plugin_tb_vaddr(tb);
+ size_t insns = qemu_plugin_tb_n_insns(tb);
+ struct qemu_plugin_insn *first_insn = qemu_plugin_tb_get_insn(tb, 0);
+ struct qemu_plugin_insn *last_insn = qemu_plugin_tb_get_insn(tb, insns - 1);
+
+ /*
+ * check if we are executing linearly after the last block. We can
+ * handle both early block exits and normal branches in the
+ * callback if we hit it.
+ */
+ gpointer udata = GUINT_TO_POINTER(pc);
+ qemu_plugin_register_vcpu_tb_exec_cond_cb(
+ tb, vcpu_tb_branched_exec, QEMU_PLUGIN_CB_NO_REGS,
+ QEMU_PLUGIN_COND_NE, pc_after_block, pc, udata);
+
+ /*
+ * Now we can set start/end for this block so the next block can
+ * check where we are at. Do this on the first instruction and not
+ * the TB so we don't get mixed up with above.
+ */
+ qemu_plugin_register_vcpu_insn_exec_inline_per_vcpu(first_insn,
+ QEMU_PLUGIN_INLINE_STORE_U64,
+ end_block, qemu_plugin_insn_vaddr(last_insn));
+ qemu_plugin_register_vcpu_insn_exec_inline_per_vcpu(first_insn,
+ QEMU_PLUGIN_INLINE_STORE_U64,
+ pc_after_block,
+ qemu_plugin_insn_vaddr(last_insn) +
+ qemu_plugin_insn_size(last_insn));
+
+ for (int idx = 0; idx < qemu_plugin_tb_n_insns(tb); ++idx) {
+ struct qemu_plugin_insn *insn = qemu_plugin_tb_get_insn(tb, idx);
+ uint64_t ipc = qemu_plugin_insn_vaddr(insn);
+ /*
+ * If this is a potential branch point check if we could grab
+ * the disassembly for it. If it is the last instruction
+ * always create an entry.
+ */
+ NodeData *node = fetch_node(ipc, last_insn);
+ if (node) {
+ g_mutex_lock(&node->lock);
+ if (!node->insn_disas) {
+ node->insn_disas = qemu_plugin_insn_disas(insn);
+ }
+ if (!node->symbol) {
+ node->symbol = qemu_plugin_insn_symbol(insn);
+ }
+ if (last_insn == insn) {
+ node->last_count++;
+ } else {
+ node->mid_count++;
+ }
+ g_mutex_unlock(&node->lock);
+ }
+
+ /* Store the PC of what we are about to execute */
+ qemu_plugin_register_vcpu_insn_exec_inline_per_vcpu(insn,
+ QEMU_PLUGIN_INLINE_STORE_U64,
+ last_pc, ipc);
+ }
+}
+
+QEMU_PLUGIN_EXPORT
+int qemu_plugin_install(qemu_plugin_id_t id, const qemu_info_t *info,
+ int argc, char **argv)
+{
+ for (int i = 0; i < argc; i++) {
+ char *opt = argv[i];
+ g_auto(GStrv) tokens = g_strsplit(opt, "=", 2);
+ if (g_strcmp0(tokens[0], "sort") == 0) {
+ if (g_strcmp0(tokens[1], "hottest") == 0) {
+ report = SORT_HOTTEST;
+ } else if (g_strcmp0(tokens[1], "early") == 0) {
+ report = SORT_EXCEPTION;
+ } else if (g_strcmp0(tokens[1], "exceptions") == 0) {
+ report = SORT_POPDEST;
+ } else {
+ fprintf(stderr, "failed to parse: %s\n", tokens[1]);
+ return -1;
+ }
+ } else {
+ fprintf(stderr, "option parsing failed: %s\n", opt);
+ return -1;
+ }
+ }
+
+ plugin_init();
+
+ qemu_plugin_register_vcpu_tb_trans_cb(id, vcpu_tb_trans);
+ qemu_plugin_register_atexit_cb(id, plugin_exit, NULL);
+ return 0;
+}
@@ -29,6 +29,7 @@ NAMES += cache
NAMES += drcov
NAMES += ips
NAMES += stoptrigger
+NAMES += cflow
ifeq ($(CONFIG_WIN32),y)
SO_SUFFIX := .dll