pstore: Add persistent function tracing
With this support kernel can save function call chain log into a
persistent ram buffer that can be decoded and dumped after reboot
through pstore filesystem. It can be used to determine what function
was last called before a reset or panic.
We store the log in a binary format and then decode it at read time.
p.s.
Mostly the code comes from trace_persistent.c driver found in the
Android git tree, written by Colin Cross <ccross@android.com>
(according to sign-off history). I reworked the driver a little bit,
and ported it to pstore.
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c
index 45bff54..4ab572e 100644
--- a/fs/pstore/inode.c
+++ b/fs/pstore/inode.c
@@ -27,6 +27,7 @@
#include <linux/list.h>
#include <linux/string.h>
#include <linux/mount.h>
+#include <linux/seq_file.h>
#include <linux/ramfs.h>
#include <linux/parser.h>
#include <linux/sched.h>
@@ -52,18 +53,117 @@
char data[];
};
+struct pstore_ftrace_seq_data {
+ const void *ptr;
+ size_t off;
+ size_t size;
+};
+
+#define REC_SIZE sizeof(struct pstore_ftrace_record)
+
+static void *pstore_ftrace_seq_start(struct seq_file *s, loff_t *pos)
+{
+ struct pstore_private *ps = s->private;
+ struct pstore_ftrace_seq_data *data;
+
+ data = kzalloc(sizeof(*data), GFP_KERNEL);
+ if (!data)
+ return NULL;
+
+ data->off = ps->size % REC_SIZE;
+ data->off += *pos * REC_SIZE;
+ if (data->off + REC_SIZE > ps->size) {
+ kfree(data);
+ return NULL;
+ }
+
+ return data;
+
+}
+
+static void pstore_ftrace_seq_stop(struct seq_file *s, void *v)
+{
+ kfree(v);
+}
+
+static void *pstore_ftrace_seq_next(struct seq_file *s, void *v, loff_t *pos)
+{
+ struct pstore_private *ps = s->private;
+ struct pstore_ftrace_seq_data *data = v;
+
+ data->off += REC_SIZE;
+ if (data->off + REC_SIZE > ps->size)
+ return NULL;
+
+ (*pos)++;
+ return data;
+}
+
+static int pstore_ftrace_seq_show(struct seq_file *s, void *v)
+{
+ struct pstore_private *ps = s->private;
+ struct pstore_ftrace_seq_data *data = v;
+ struct pstore_ftrace_record *rec = (void *)(ps->data + data->off);
+
+ seq_printf(s, "%d %08lx %08lx %pf <- %pF\n",
+ pstore_ftrace_decode_cpu(rec), rec->ip, rec->parent_ip,
+ (void *)rec->ip, (void *)rec->parent_ip);
+
+ return 0;
+}
+
+static const struct seq_operations pstore_ftrace_seq_ops = {
+ .start = pstore_ftrace_seq_start,
+ .next = pstore_ftrace_seq_next,
+ .stop = pstore_ftrace_seq_stop,
+ .show = pstore_ftrace_seq_show,
+};
+
static ssize_t pstore_file_read(struct file *file, char __user *userbuf,
size_t count, loff_t *ppos)
{
- struct pstore_private *ps = file->private_data;
+ struct seq_file *sf = file->private_data;
+ struct pstore_private *ps = sf->private;
+ if (ps->type == PSTORE_TYPE_FTRACE)
+ return seq_read(file, userbuf, count, ppos);
return simple_read_from_buffer(userbuf, count, ppos, ps->data, ps->size);
}
+static int pstore_file_open(struct inode *inode, struct file *file)
+{
+ struct pstore_private *ps = inode->i_private;
+ struct seq_file *sf;
+ int err;
+ const struct seq_operations *sops = NULL;
+
+ if (ps->type == PSTORE_TYPE_FTRACE)
+ sops = &pstore_ftrace_seq_ops;
+
+ err = seq_open(file, sops);
+ if (err < 0)
+ return err;
+
+ sf = file->private_data;
+ sf->private = ps;
+
+ return 0;
+}
+
+static loff_t pstore_file_llseek(struct file *file, loff_t off, int origin)
+{
+ struct seq_file *sf = file->private_data;
+
+ if (sf->op)
+ return seq_lseek(file, off, origin);
+ return default_llseek(file, off, origin);
+}
+
static const struct file_operations pstore_file_operations = {
- .open = simple_open,
- .read = pstore_file_read,
- .llseek = default_llseek,
+ .open = pstore_file_open,
+ .read = pstore_file_read,
+ .llseek = pstore_file_llseek,
+ .release = seq_release,
};
/*
@@ -215,6 +315,9 @@
case PSTORE_TYPE_CONSOLE:
sprintf(name, "console-%s", psname);
break;
+ case PSTORE_TYPE_FTRACE:
+ sprintf(name, "ftrace-%s", psname);
+ break;
case PSTORE_TYPE_MCE:
sprintf(name, "mce-%s-%lld", psname, id);
break;