[PATCH V2 3/5] sys_info: add help to translate sys_info string to bitmap

[Feng Tang <feng.tang@linux.alibaba.com>]

Bitmap definition is hard to remember and decode. Add sysctl interface
to translate human readable string like "tasks,mem,timer,lock,ftrace,..."
to bitmap.

Suggested-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Feng Tang <feng.tang@linux.alibaba.com>
---
 include/linux/sys_info.h |  7 +++
 lib/sys_info.c           | 97 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 104 insertions(+)

diff --git a/include/linux/sys_info.h b/include/linux/sys_info.h
index 79bf4a942e5f..0b49863cd414 100644
--- a/include/linux/sys_info.h
+++ b/include/linux/sys_info.h
@@ -16,5 +16,12 @@
 #define SYS_SHOW_BLOCKED_TASKS		0x00000080
 
 extern void sys_show_info(unsigned long info_mask);
+extern unsigned long sys_info_parse_param(char *str);
 
+#ifdef CONFIG_SYSCTL
+struct ctl_table;
+extern int sysctl_sys_info_handler(const struct ctl_table *ro_table, int write,
+					  void *buffer, size_t *lenp,
+					  loff_t *ppos);
+#endif
 #endif	/* _LINUX_SYS_INFO_H */
diff --git a/lib/sys_info.c b/lib/sys_info.c
index 90a79b5164c9..9693542435ba 100644
--- a/lib/sys_info.c
+++ b/lib/sys_info.c
@@ -5,6 +5,103 @@
 #include <linux/console.h>
 #include <linux/nmi.h>
 
+struct sys_info_name {
+	unsigned long bit;
+	const char *name;
+};
+
+static const char sys_info_avail[] = "tasks,mem,timer,lock,ftrace,all_bt,blocked_tasks";
+
+static const struct sys_info_name  si_names[] = {
+	{ SYS_SHOW_TASK_INFO,	"tasks" },
+	{ SYS_SHOW_MEM_INFO,	"mem" },
+	{ SYS_SHOW_TIMER_INFO,	"timer" },
+	{ SYS_SHOW_LOCK_INFO,	"lock" },
+	{ SYS_SHOW_FTRACE_INFO, "ftrace" },
+	{ SYS_SHOW_ALL_CPU_BT,	"all_bt" },
+	{ SYS_SHOW_BLOCKED_TASKS, "blocked_tasks" },
+};
+
+/* Expecting string like "xxx_sys_info=tasks,mem,timer,lock,ftrace,..." */
+unsigned long sys_info_parse_param(char *str)
+{
+	unsigned long si_bits = 0;
+	char *s, *name;
+	int i;
+
+	s = str;
+	while ((name = strsep(&s, ",")) && *name) {
+		for (i = 0; i < ARRAY_SIZE(si_names); i++) {
+			if (!strcmp(name, si_names[i].name)) {
+				si_bits |= si_names[i].bit;
+				break;
+			}
+		}
+	}
+
+	return si_bits;
+}
+
+#ifdef CONFIG_SYSCTL
+int sysctl_sys_info_handler(const struct ctl_table *ro_table, int write,
+					  void *buffer, size_t *lenp,
+					  loff_t *ppos)
+{
+	char names[sizeof(sys_info_avail) + 1];
+	struct ctl_table table;
+	unsigned long *si_bits_global;
+	int i, ret, len;
+
+	si_bits_global = ro_table->data;
+
+	if (write) {
+		unsigned long si_bits;
+
+		table = *ro_table;
+		table.data = names;
+		table.maxlen = sizeof(names);
+		ret = proc_dostring(&table, write, buffer, lenp, ppos);
+		if (ret)
+			return ret;
+
+		si_bits = sys_info_parse_param(names);
+		/*
+		 * The access to the global value is not synchronized.
+		 */
+		WRITE_ONCE(*si_bits_global, si_bits);
+		return 0;
+	} else {
+		/* for 'read' operation */
+		bool first = true;
+		char *buf;
+
+		buf = names;
+		for (i = 0; i < ARRAY_SIZE(si_names); i++) {
+			if (*si_bits_global & si_names[i].bit) {
+
+				if (first) {
+					first = false;
+				} else {
+					*buf = ',';
+					buf++;
+				}
+
+				len = strlen(si_names[i].name);
+				strncpy(buf, si_names[i].name, len);
+				buf += len;
+			}
+
+		}
+		*buf = '\0';
+
+		table = *ro_table;
+		table.data = names;
+		table.maxlen = sizeof(names);
+		return proc_dostring(&table, write, buffer, lenp, ppos);
+	}
+}
+#endif
+
 void sys_show_info(unsigned long info_flag)
 {
 	if (info_flag & SYS_SHOW_TASK_INFO)
-- 
2.39.5 (Apple Git-154)