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@xxxxxxxxxxx>
(according to sign-off history). I reworked the driver a little bit,
and ported it to pstore.
Signed-off-by: Anton Vorontsov <anton.vorontsov@xxxxxxxxxx>
---
fs/pstore/Kconfig | 12 +++++
fs/pstore/Makefile | 6 +++
fs/pstore/ftrace.c | 122 ++++++++++++++++++++++++++++++++++++++++++++++++
fs/pstore/inode.c | 111 +++++++++++++++++++++++++++++++++++++++++--
fs/pstore/internal.h | 49 +++++++++++++++++++
fs/pstore/platform.c | 3 +-
include/linux/pstore.h | 1 +
7 files changed, 299 insertions(+), 5 deletions(-)
create mode 100644 fs/pstore/ftrace.c
diff --git a/fs/pstore/Kconfig b/fs/pstore/Kconfig
index d044de6..d39bb5c 100644
--- a/fs/pstore/Kconfig
+++ b/fs/pstore/Kconfig
@@ -19,6 +19,18 @@ config PSTORE_CONSOLE
When the option is enabled, pstore will log all kernel
messages, even if no oops or panic happened.
+config PSTORE_FTRACE
+ bool "Persistent function tracer"
+ depends on PSTORE
+ depends on FUNCTION_TRACER
+ help
+ With this option kernel traces function calls 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.
+
+ If unsure, say N.
+
config PSTORE_RAM
tristate "Log panic/oops to a RAM buffer"
depends on PSTORE
diff --git a/fs/pstore/Makefile b/fs/pstore/Makefile
index 278a44e..cc6aa3d 100644
--- a/fs/pstore/Makefile
+++ b/fs/pstore/Makefile
@@ -7,4 +7,10 @@ obj-y += pstore.o
pstore-objs += inode.o platform.o
ramoops-objs += ram.o ram_core.o
+
+ifeq ($(CONFIG_PSTORE_FTRACE),y)
+ramoops-objs += ftrace.o
+CFLAGS_REMOVE_ftrace.o = -pg
+endif
+
obj-$(CONFIG_PSTORE_RAM) += ramoops.o
diff --git a/fs/pstore/ftrace.c b/fs/pstore/ftrace.c
new file mode 100644
index 0000000..eb16773
--- /dev/null
+++ b/fs/pstore/ftrace.c
@@ -0,0 +1,122 @@
+/*
+ * Copyright 2012 Google, Inc.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/compiler.h>
+#include <linux/irqflags.h>
+#include <linux/smp.h>
+#include <linux/atomic.h>
+#include <asm/barrier.h>
+#include "../../../kernel/trace/trace.h"
+#include "internal.h"
+
+static int pstore_ftrace_enabled;
+static struct trace_array *pstore_ftrace_array;
+
+static void pstore_ftrace_call(unsigned long ip, unsigned long parent_ip)
+{
+ struct trace_array *tr = pstore_ftrace_array;
+ struct trace_array_cpu *data;
+ unsigned long flags;
+ long disabled;
+ int cpu;
+
+ smp_rmb();
+ if (unlikely(!pstore_ftrace_enabled))
+ return;
+
+ if (unlikely(oops_in_progress))
+ return;
+
+ /*
+ * Need to use raw, since this must be called before the
+ * recursive protection is performed.
+ */
+ local_irq_save(flags);
+ cpu = raw_smp_processor_id();
+ data = tr->data[cpu];
+ disabled = atomic_inc_return(&data->disabled);
+
+ if (likely(disabled == 1)) {
+ struct pstore_ftrace_record rec = {};
+
+ rec.ip = ip;
+ rec.parent_ip = parent_ip;
+ pstore_ftrace_encode_cpu(&rec, cpu);
+ psinfo->write_buf(PSTORE_TYPE_FTRACE, 0, NULL, 0, (void *)&rec,
+ sizeof(rec), psinfo);
+ }
+
+ atomic_dec(&data->disabled);
+ local_irq_restore(flags);
+}
+
+static struct ftrace_ops pstore_ftrace_ops __read_mostly = {
+ .func = pstore_ftrace_call,
+ .flags = FTRACE_OPS_FL_GLOBAL,
+};
+
+static int pstore_ftracer_init(struct trace_array *tr)
+{
+ if (!psinfo->write_buf) {
+ pr_info("%s: write_buf required, fix your backend\n", __func__);
+ return -ENOSYS;
+ }
+
+ pstore_ftrace_array = tr;
+ tr->cpu = get_cpu();
+ put_cpu();
+
+ tracing_start_cmdline_record();
+
+ pstore_ftrace_enabled = 0;
+ smp_wmb();
+
+ register_ftrace_function(&pstore_ftrace_ops);
+
+ smp_wmb();
+ pstore_ftrace_enabled = 1;
+ return 0;
+}
+
+static void pstore_ftrace_reset(struct trace_array *tr)
+{
+ pstore_ftrace_enabled = 0;
+ smp_wmb();
+
+ unregister_ftrace_function(&pstore_ftrace_ops);
+
+ tracing_stop_cmdline_record();
+}
+
+static void pstore_ftrace_start(struct trace_array *tr)
+{
+ tracing_reset_online_cpus(tr);
+}
+
+static struct tracer pstore_ftracer __read_mostly = {
+ .name = "persistent",
+ .init = pstore_ftracer_init,
+ .reset = pstore_ftrace_reset,
+ .start = pstore_ftrace_start,
+ .wait_pipe = poll_wait_pipe,
+};
+
+void pstore_register_ftrace(void)
+{
+ int err;
+
+ err = register_tracer(&pstore_ftracer);
+ if (err)
+ pr_err("%s: failed to register tracer: %d\n", __func__, err);
+}
diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c
index fda1331..5368b6d 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 @@ struct pstore_private {
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 @@ int pstore_mkfile(enum pstore_type_id type, char *psname, u64 id,
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;
diff --git a/fs/pstore/internal.h b/fs/pstore/internal.h
index 3bde461..6e09673 100644
--- a/fs/pstore/internal.h
+++ b/fs/pstore/internal.h
@@ -1,6 +1,55 @@
+#ifndef __PSTORE_INTERNAL_H__
+#define __PSTORE_INTERNAL_H__
+
+#include <linux/pstore.h>
+
+#if NR_CPUS <= 2 && defined(CONFIG_ARM_THUMB)
+#define PSTORE_CPU_IN_IP 0x1
+#elif NR_CPUS <= 4 && defined(CONFIG_ARM)
+#define PSTORE_CPU_IN_IP 0x3
+#endif
+
+struct pstore_ftrace_record {
+ unsigned long ip;
+ unsigned long parent_ip;
+#ifndef PSTORE_CPU_IN_IP
+ unsigned int cpu;
+#endif
+};
+
+static inline void
+pstore_ftrace_encode_cpu(struct pstore_ftrace_record *rec, unsigned int cpu)
+{
+#ifndef PSTORE_CPU_IN_IP
+ rec->cpu = cpu;
+#else
+ rec->ip |= cpu;
+#endif
+}
+
+static inline unsigned int
+pstore_ftrace_decode_cpu(struct pstore_ftrace_record *rec)
+{
+#ifndef PSTORE_CPU_IN_IP
+ return rec->cpu;
+#else
+ return rec->ip & PSTORE_CPU_IN_IP;
+#endif
+}
+
+#ifdef CONFIG_PSTORE_FTRACE
+extern void pstore_register_ftrace(void);
+#else
+static inline void pstore_register_ftrace(void) {}
+#endif
+
+extern struct pstore_info *psinfo;
+
extern void pstore_set_kmsg_bytes(int);
extern void pstore_get_records(int);
extern int pstore_mkfile(enum pstore_type_id, char *psname, u64 id,
char *data, size_t size,
struct timespec time, struct pstore_info *psi);
extern int pstore_is_mounted(void);
+
+#endif
diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index e7c0a52..89995da 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -61,7 +61,7 @@ static DECLARE_WORK(pstore_work, pstore_dowork);
* calls to pstore_register()
*/
static DEFINE_SPINLOCK(pstore_lock);
-static struct pstore_info *psinfo;
+struct pstore_info *psinfo;
static char *backend;
@@ -246,6 +246,7 @@ int pstore_register(struct pstore_info *psi)
kmsg_dump_register(&pstore_dumper);
pstore_register_console();
+ pstore_register_ftrace();
if (pstore_update_ms >= 0) {
pstore_timer.expires = jiffies +
diff --git a/include/linux/pstore.h b/include/linux/pstore.h
index b107484..23afffe 100644
--- a/include/linux/pstore.h
+++ b/include/linux/pstore.h
@@ -30,6 +30,7 @@ enum pstore_type_id {
PSTORE_TYPE_DMESG = 0,
PSTORE_TYPE_MCE = 1,
PSTORE_TYPE_CONSOLE = 2,
+ PSTORE_TYPE_FTRACE = 3,
PSTORE_TYPE_UNKNOWN = 255
};
--
1.7.9.2
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