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Diffstat (limited to 'contrib/plugins/cflow.c')
| -rw-r--r-- | contrib/plugins/cflow.c | 393 |
1 files changed, 393 insertions, 0 deletions
diff --git a/contrib/plugins/cflow.c b/contrib/plugins/cflow.c new file mode 100644 index 0000000..b5e33f2 --- /dev/null +++ b/contrib/plugins/cflow.c @@ -0,0 +1,393 @@ +/* + * 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 current translated block */ + uint64_t tb_pc; + /* 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 tb_pc; +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, gpointer d) +{ + 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, gpointer d) +{ + 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, gpointer d) +{ + 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; + GCompareDataFunc sort = &hottest; + int i = 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_with_data(data, sort, NULL); + + for (GList *l = data; + l != NULL && i < topn; + l = l->next, i++) { + 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(g_int64_hash, g_int64_equal); + state = qemu_plugin_scoreboard_new(sizeof(VCPUScoreBoard)); + + /* score board declarations */ + tb_pc = qemu_plugin_scoreboard_u64_in_struct(state, VCPUScoreBoard, tb_pc); + 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, &addr); + if (!node && create_if_not_found) { + node = create_node(addr); + g_hash_table_insert(nodes, &node->addr, 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 = qemu_plugin_u64_get(tb_pc, cpu_index); + + /* 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. + */ + qemu_plugin_register_vcpu_tb_exec_inline_per_vcpu( + tb, QEMU_PLUGIN_INLINE_STORE_U64, tb_pc, 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, NULL); + + /* + * 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; +} |