v4.19.13 snapshot.
diff --git a/tools/perf/util/help-unknown-cmd.c b/tools/perf/util/help-unknown-cmd.c
new file mode 100644
index 0000000..4f07a5b
--- /dev/null
+++ b/tools/perf/util/help-unknown-cmd.c
@@ -0,0 +1,116 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "cache.h"
+#include "config.h"
+#include <poll.h>
+#include <stdio.h>
+#include <subcmd/help.h>
+#include "../builtin.h"
+#include "levenshtein.h"
+
+static int autocorrect;
+
+static int perf_unknown_cmd_config(const char *var, const char *value,
+ void *cb __maybe_unused)
+{
+ if (!strcmp(var, "help.autocorrect"))
+ return perf_config_int(&autocorrect, var,value);
+
+ return 0;
+}
+
+static int levenshtein_compare(const void *p1, const void *p2)
+{
+ const struct cmdname *const *c1 = p1, *const *c2 = p2;
+ const char *s1 = (*c1)->name, *s2 = (*c2)->name;
+ int l1 = (*c1)->len;
+ int l2 = (*c2)->len;
+ return l1 != l2 ? l1 - l2 : strcmp(s1, s2);
+}
+
+static int add_cmd_list(struct cmdnames *cmds, struct cmdnames *old)
+{
+ unsigned int i, nr = cmds->cnt + old->cnt;
+ void *tmp;
+
+ if (nr > cmds->alloc) {
+ /* Choose bigger one to alloc */
+ if (alloc_nr(cmds->alloc) < nr)
+ cmds->alloc = nr;
+ else
+ cmds->alloc = alloc_nr(cmds->alloc);
+ tmp = realloc(cmds->names, cmds->alloc * sizeof(*cmds->names));
+ if (!tmp)
+ return -1;
+ cmds->names = tmp;
+ }
+ for (i = 0; i < old->cnt; i++)
+ cmds->names[cmds->cnt++] = old->names[i];
+ zfree(&old->names);
+ old->cnt = 0;
+ return 0;
+}
+
+const char *help_unknown_cmd(const char *cmd)
+{
+ unsigned int i, n = 0, best_similarity = 0;
+ struct cmdnames main_cmds, other_cmds;
+
+ memset(&main_cmds, 0, sizeof(main_cmds));
+ memset(&other_cmds, 0, sizeof(main_cmds));
+
+ perf_config(perf_unknown_cmd_config, NULL);
+
+ load_command_list("perf-", &main_cmds, &other_cmds);
+
+ if (add_cmd_list(&main_cmds, &other_cmds) < 0) {
+ fprintf(stderr, "ERROR: Failed to allocate command list for unknown command.\n");
+ goto end;
+ }
+ qsort(main_cmds.names, main_cmds.cnt,
+ sizeof(main_cmds.names), cmdname_compare);
+ uniq(&main_cmds);
+
+ if (main_cmds.cnt) {
+ /* This reuses cmdname->len for similarity index */
+ for (i = 0; i < main_cmds.cnt; ++i)
+ main_cmds.names[i]->len =
+ levenshtein(cmd, main_cmds.names[i]->name, 0, 2, 1, 4);
+
+ qsort(main_cmds.names, main_cmds.cnt,
+ sizeof(*main_cmds.names), levenshtein_compare);
+
+ best_similarity = main_cmds.names[0]->len;
+ n = 1;
+ while (n < main_cmds.cnt && best_similarity == main_cmds.names[n]->len)
+ ++n;
+ }
+
+ if (autocorrect && n == 1) {
+ const char *assumed = main_cmds.names[0]->name;
+
+ main_cmds.names[0] = NULL;
+ clean_cmdnames(&main_cmds);
+ fprintf(stderr, "WARNING: You called a perf program named '%s', "
+ "which does not exist.\n"
+ "Continuing under the assumption that you meant '%s'\n",
+ cmd, assumed);
+ if (autocorrect > 0) {
+ fprintf(stderr, "in %0.1f seconds automatically...\n",
+ (float)autocorrect/10.0);
+ poll(NULL, 0, autocorrect * 100);
+ }
+ return assumed;
+ }
+
+ fprintf(stderr, "perf: '%s' is not a perf-command. See 'perf --help'.\n", cmd);
+
+ if (main_cmds.cnt && best_similarity < 6) {
+ fprintf(stderr, "\nDid you mean %s?\n",
+ n < 2 ? "this": "one of these");
+
+ for (i = 0; i < n; i++)
+ fprintf(stderr, "\t%s\n", main_cmds.names[i]->name);
+ }
+end:
+ exit(1);
+}