[PATCH v4 02/10] tracing/boot: Add per-event histogram action options

Masami Hiramatsu
2021-08-10T02:07:41Z

Add a hist-trigger action syntax support to boot-time tracing.
Currently, boot-time tracing supports per-event actions as option
strings. However, for the histogram action, it has a special syntax
and usually needs a long action definition.
To make it readable and fit to the bootconfig syntax, this introduces
a new options for histogram.

Here are the histogram action options for boot-time tracing.

ftrace.[instance.INSTANCE.]event.GROUP.EVENT.hist {
keys = <KEY>[,...]
values = <VAL>[,...]
sort = <SORT-KEY>[,...]
size = <ENTRIES>
name = <HISTNAME>
var { <VAR> = <EXPR> ... }
pause|continue|clear
onmax|onchange { var = <VAR>; <ACTION> [= <PARAM>] }
onmatch { event = <EVENT>; <ACTION> [= <PARAM>] }
filter = <FILTER>
}

Where <ACTION> is one of below;

trace = <EVENT>, <ARG1>[, ...]
save = <ARG1>[, ...]
snapshot

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
Changes in v4:
- Add 'const' qualifier for @str parameter of append_str_nospace().
Changes in v3:
- Allow var expression includes spaces, since it is natural that
user write an expression with space in bootconfig.
(e.g. "var.lat = common_timestamp.usecs - $ts0")
Changes in v2:
- Cleanup code to add ':' as a prefix for each element
instead of fixup the last ':'.
- Fix syntax typo for handler actions.
- Make pause|continue|clear mutual exclusive.
- Add __printf() attribute to the append_printf().
---
kernel/trace/trace_boot.c | 231 +++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 231 insertions(+)

diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c
index d713714cba67..3d0e51368f51 100644
--- a/kernel/trace/trace_boot.c
+++ b/kernel/trace/trace_boot.c
@@ -171,6 +171,231 @@ trace_boot_add_synth_event(struct xbc_node *node, const char *event)
}
#endif

+#ifdef CONFIG_HIST_TRIGGERS
+static int __init __printf(3, 4)
+append_printf(char **bufp, char *end, const char *fmt, ...)
+{
+ va_list args;
+ int ret;
+
+ if (*bufp == end)
+ return -ENOSPC;
+
+ va_start(args, fmt);
+ ret = vsnprintf(*bufp, end - *bufp, fmt, args);
+ if (ret < end - *bufp) {
+ *bufp += ret;
+ } else {
+ *bufp = end;
+ ret = -ERANGE;
+ }
+ va_end(args);
+
+ return ret;
+}
+
+static int __init
+append_str_nospace(char **bufp, char *end, const char *str)
+{
+ char *p = *bufp;
+ int len;
+
+ while (p < end - 1 && *str != '\0') {
+ if (!isspace(*str))
+ *(p++) = *str;
+ str++;
+ }
+ *p = '\0';
+ if (p == end - 1) {
+ *bufp = end;
+ return -ENOSPC;
+ }
+ len = p - *bufp;
+ *bufp = p;
+ return (int)len;
+}
+
+static int __init
+trace_boot_hist_add_array(struct xbc_node *hnode, char **bufp,
+ char *end, const char *key)
+{
+ struct xbc_node *knode, *anode;
+ const char *p;
+ char sep;
+
+ knode = xbc_node_find_child(hnode, key);
+ if (knode) {
+ anode = xbc_node_get_child(knode);
+ if (!anode) {
+ pr_err("hist.%s requires value(s).\n", key);
+ return -EINVAL;
+ }
+
+ append_printf(bufp, end, ":%s", key);
+ sep = '=';
+ xbc_array_for_each_value(anode, p) {
+ append_printf(bufp, end, "%c%s", sep, p);
+ if (sep == '=')
+ sep = ',';
+ }
+ } else
+ return -ENOENT;
+
+ return 0;
+}
+
+static int __init
+trace_boot_hist_add_handler(struct xbc_node *hnode, char **bufp,
+ char *end, const char *param)
+{
+ struct xbc_node *knode, *anode;
+ const char *p;
+ char sep;
+
+ /* Compose 'handler' parameter */
+ p = xbc_node_find_value(hnode, param, NULL);
+ if (!p) {
+ pr_err("hist.%s requires '%s' option.\n",
+ xbc_node_get_data(hnode), param);
+ return -EINVAL;
+ }
+ append_printf(bufp, end, ":%s(%s)", xbc_node_get_data(hnode), p);
+
+ /* Compose 'action' parameter */
+ knode = xbc_node_find_child(hnode, "trace");
+ if (!knode)
+ knode = xbc_node_find_child(hnode, "save");
+
+ if (knode) {
+ anode = xbc_node_get_child(knode);
+ if (!anode || !xbc_node_is_value(anode)) {
+ pr_err("hist.%s.%s requires value(s).\n",
+ xbc_node_get_data(hnode),
+ xbc_node_get_data(knode));
+ return -EINVAL;
+ }
+
+ append_printf(bufp, end, ".%s", xbc_node_get_data(knode));
+ sep = '(';
+ xbc_array_for_each_value(anode, p) {
+ append_printf(bufp, end, "%c%s", sep, p);
+ if (sep == '(')
+ sep = ',';
+ }
+ append_printf(bufp, end, ")");
+ } else if (xbc_node_find_child(hnode, "snapshot")) {
+ append_printf(bufp, end, ".snapshot()");
+ } else {
+ pr_err("hist.%s requires an action.\n",
+ xbc_node_get_data(hnode));
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+/*
+ * Histogram boottime tracing syntax.
+ *
+ * ftrace.[instance.INSTANCE.]event.GROUP.EVENT.hist {
+ * keys = <KEY>[,...]
+ * values = <VAL>[,...]
+ * sort = <SORT-KEY>[,...]
+ * size = <ENTRIES>
+ * name = <HISTNAME>
+ * var { <VAR> = <EXPR> ... }
+ * pause|continue|clear
+ * onmax|onchange { var = <VAR>; <ACTION> [= <PARAM>] }
+ * onmatch { event = <EVENT>; <ACTION> [= <PARAM>] }
+ * filter = <FILTER>
+ * }
+ *
+ * Where <ACTION> are;
+ *
+ * trace = <EVENT>, <ARG1>[, ...]
+ * save = <ARG1>[, ...]
+ * snapshot
+ */
+static int __init
+trace_boot_compose_hist_cmd(struct xbc_node *hnode, char *buf, size_t size)
+{
+ struct xbc_node *node, *knode;
+ char *end = buf + size;
+ const char *p;
+ int ret = 0;
+
+ append_printf(&buf, end, "hist");
+
+ ret = trace_boot_hist_add_array(hnode, &buf, end, "keys");
+ if (ret < 0) {
+ if (ret == -ENOENT)
+ pr_err("hist requires keys.\n");
+ return -EINVAL;
+ }
+
+ ret = trace_boot_hist_add_array(hnode, &buf, end, "values");
+ if (ret == -EINVAL)
+ return ret;
+ ret = trace_boot_hist_add_array(hnode, &buf, end, "sort");
+ if (ret == -EINVAL)
+ return ret;
+
+ p = xbc_node_find_value(hnode, "size", NULL);
+ if (p)
+ append_printf(&buf, end, ":size=%s", p);
+
+ p = xbc_node_find_value(hnode, "name", NULL);
+ if (p)
+ append_printf(&buf, end, ":name=%s", p);
+
+ node = xbc_node_find_child(hnode, "var");
+ if (node) {
+ xbc_node_for_each_key_value(node, knode, p) {
+ /* Expression must not include spaces. */
+ append_printf(&buf, end, ":%s=",
+ xbc_node_get_data(knode));
+ append_str_nospace(&buf, end, p);
+ }
+ }
+
+ /* Histogram control attributes (mutual exclusive) */
+ if (xbc_node_find_child(hnode, "pause"))
+ append_printf(&buf, end, ":pause");
+ else if (xbc_node_find_child(hnode, "continue"))
+ append_printf(&buf, end, ":continue");
+ else if (xbc_node_find_child(hnode, "clear"))
+ append_printf(&buf, end, ":clear");
+
+ /* Histogram handler and actions */
+ node = xbc_node_find_child(hnode, "onmax");
+ if (node && trace_boot_hist_add_handler(node, &buf, end, "var") < 0)
+ return -EINVAL;
+ node = xbc_node_find_child(hnode, "onchange");
+ if (node && trace_boot_hist_add_handler(node, &buf, end, "var") < 0)
+ return -EINVAL;
+ node = xbc_node_find_child(hnode, "onmatch");
+ if (node && trace_boot_hist_add_handler(node, &buf, end, "event") < 0)
+ return -EINVAL;
+
+ p = xbc_node_find_value(hnode, "filter", NULL);
+ if (p)
+ append_printf(&buf, end, " if %s", p);
+
+ if (buf == end) {
+ pr_err("hist exceeds the max command length.\n");
+ return -E2BIG;
+ }
+
+ return 0;
+}
+#else
+static int __init
+trace_boot_compose_hist_cmd(struct xbc_node *hnode, char *buf, size_t size)
+{
+ return -EOPNOTSUPP;
+}
+#endif
+
static void __init
trace_boot_init_one_event(struct trace_array *tr, struct xbc_node *gnode,
struct xbc_node *enode)
@@ -212,6 +437,12 @@ trace_boot_init_one_event(struct trace_array *tr, struct xbc_node *gnode,
else if (trigger_process_regex(file, buf) < 0)
pr_err("Failed to apply an action: %s\n", buf);
}
+ anode = xbc_node_find_child(enode, "hist");
+ if (anode &&
+ trace_boot_compose_hist_cmd(anode, buf, ARRAY_SIZE(buf)) == 0) {
+ if (trigger_process_regex(file, buf) < 0)
+ pr_err("Failed to apply hist trigger: %s\n", buf);
+ }
} else if (xbc_node_find_value(enode, "actions", NULL))
pr_err("Failed to apply event actions because CONFIG_HIST_TRIGGERS is not set.\n");