[RFC PATCH 1/2] livepatch: Extend the livepatch-sample patch

[Petr Mladek]

We are going to play with the livepatch API when fixing
the use of kobjects. This change makes the livepatch
more complex and better see the effects of the new API.
But it might be useful on its own.

Anyway, it adds alternative output also for:

   /proc/uptime
   /proc/consoles

and for the sysfs entries created by the module kobject_example:

    /sys/kernel/kobject_example/foo
    /sys/kernel/kobject_example/bar
    /sys/kernel/kobject_example/baz

Signed-off-by: Petr Mladek <pmladek@xxxxxxxx>
---
 samples/livepatch/livepatch-sample.c | 127 ++++++++++++++++++++++++++++++++++-
 1 file changed, 125 insertions(+), 2 deletions(-)

diff --git a/samples/livepatch/livepatch-sample.c b/samples/livepatch/livepatch-sample.c
index e34f871e69b1..b9bec5f8c725 100644
--- a/samples/livepatch/livepatch-sample.c
+++ b/samples/livepatch/livepatch-sample.c
@@ -22,8 +22,18 @@
 #include <linux/livepatch.h>
 
 /*
- * This (dumb) live patch overrides the function that prints the
- * kernel boot cmdline when /proc/cmdline is read.
+ * This (dumb) live patch overrides output from the following files
+ * that provide information about the system:
+ *
+ *	/proc/cmdline
+ *	/proc/uptime
+ *	/proc/consoles
+ *
+ * and also output from sysfs entries created by the module kobject_example:
+ *
+ *	/sys/kernel/kobject_example/foo
+ *	/sys/kernel/kobject_example/bar
+ *	/sys/kernel/kobject_example/baz
  *
  * Example:
  *
@@ -40,23 +50,136 @@
  */
 
 #include <linux/seq_file.h>
+#include <linux/kernel_stat.h>
+#include <linux/cputime.h>
+#include <linux/console.h>
+#include <linux/tty_driver.h>
+
 static int livepatch_cmdline_proc_show(struct seq_file *m, void *v)
 {
 	seq_printf(m, "%s\n", "this has been live patched");
 	return 0;
 }
 
+static int livepatch_uptime_proc_show(struct seq_file *m, void *v)
+{
+	struct timespec uptime;
+	struct timespec idle;
+	u64 idletime;
+	u64 nsec;
+	u32 rem;
+	int i;
+
+	idletime = 0;
+	for_each_possible_cpu(i)
+		idletime += (__force u64) kcpustat_cpu(i).cpustat[CPUTIME_IDLE];
+
+	get_monotonic_boottime(&uptime);
+	nsec = cputime64_to_jiffies64(idletime) * TICK_NSEC;
+	idle.tv_sec = div_u64_rem(nsec, NSEC_PER_SEC, &rem);
+	idle.tv_nsec = rem;
+	seq_printf(m, "%s\n", "this has been live patched");
+	seq_printf(m, "%lu.%02lu %lu.%02lu\n",
+			(unsigned long) uptime.tv_sec,
+			(uptime.tv_nsec / (NSEC_PER_SEC / 100)),
+			(unsigned long) idle.tv_sec,
+			(idle.tv_nsec / (NSEC_PER_SEC / 100)));
+	return 0;
+}
+
+static int livepatch_show_console_dev(struct seq_file *m, void *v)
+{
+	static const struct {
+		short flag;
+		char name;
+	} con_flags[] = {
+		{ CON_ENABLED,		'E' },
+		{ CON_CONSDEV,		'C' },
+		{ CON_BOOT,		'B' },
+		{ CON_PRINTBUFFER,	'p' },
+		{ CON_BRL,		'b' },
+		{ CON_ANYTIME,		'a' },
+	};
+	char flags[ARRAY_SIZE(con_flags) + 1];
+	struct console *con = v;
+	unsigned int a;
+	dev_t dev = 0;
+
+	seq_printf(m, "%s\n", "this has been live patched");
+
+	if (con->device) {
+		const struct tty_driver *driver;
+		int index;
+
+		driver = con->device(con, &index);
+		if (driver) {
+			dev = MKDEV(driver->major, driver->minor_start);
+			dev += index;
+		}
+	}
+
+	for (a = 0; a < ARRAY_SIZE(con_flags); a++)
+		flags[a] = (con->flags & con_flags[a].flag) ?
+			con_flags[a].name : ' ';
+	flags[a] = 0;
+
+	seq_setwidth(m, 21 - 1);
+	seq_printf(m, "%s%d", con->name, con->index);
+	seq_pad(m, ' ');
+	seq_printf(m, "%c%c%c (%s)", con->read ? 'R' : '-',
+			con->write ? 'W' : '-', con->unblank ? 'U' : '-',
+			flags);
+	if (dev)
+		seq_printf(m, " %4d:%d", MAJOR(dev), MINOR(dev));
+
+	seq_puts(m, "\n");
+
+	return 0;
+}
+
+static ssize_t livepatch_foo_show(struct kobject *kobj,
+				  struct kobj_attribute *attr, char *buf)
+{
+	return sprintf(buf, "foo: this has been livepatched\n");
+}
+
+static ssize_t livepatch_b_show(struct kobject *kobj,
+				struct kobj_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%s: this has been livepatched\n", attr->attr.name);
+}
+
 static struct klp_func funcs[] = {
 	{
 		.old_name = "cmdline_proc_show",
 		.new_func = livepatch_cmdline_proc_show,
+	}, {
+		.old_name = "uptime_proc_show",
+		.new_func = livepatch_uptime_proc_show,
+	}, {
+		.old_name = "show_console_dev",
+		.new_func = livepatch_show_console_dev,
+	}, { }
+};
+
+static struct klp_func kobject_example_funcs[] = {
+	{
+		.old_name = "foo_show",
+		.new_func = livepatch_foo_show,
+	}, {
+		.old_name = "b_show",
+		.new_func = livepatch_b_show,
 	}, { }
 };
 
+
 static struct klp_object objs[] = {
 	{
 		/* name being NULL means vmlinux */
 		.funcs = funcs,
+	}, {
+		.name = "kobject_example",
+		.funcs = kobject_example_funcs,
 	}, { }
 };
 
-- 
1.8.5.6