pstore/ftrace: Convert to its own enable/disable debugfs knob
With this patch we no longer reuse function tracer infrastructure, now we register our own tracer back-end via a debugfs knob. It's a bit more code, but that is the only downside. On the bright side we have: - Ability to make persistent_ram module removable (when needed, we can move ftrace_ops struct into a module). Note that persistent_ram is still not removable for other reasons, but with this patch it's just one thing less to worry about; - Pstore part is more isolated from the generic function tracer. We tried it already by registering our own tracer in available_tracers, but that way we're loosing ability to see the traces while we record them to pstore. This solution is somewhere in the middle: we only register "internal ftracer" back-end, but not the "front-end"; - When there is only pstore tracing enabled, the kernel will only write to the pstore buffer, omitting function tracer buffer (which, of course, still can be enabled via 'echo function > current_tracer'). Suggested-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
This commit is contained in:
parent
b4a871bce6
commit
65f8c95e46
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@ -102,9 +102,7 @@ related hangs. The functions call chain log is stored in a "ftrace-ramoops"
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file. Here is an example of usage:
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file. Here is an example of usage:
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# mount -t debugfs debugfs /sys/kernel/debug/
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# mount -t debugfs debugfs /sys/kernel/debug/
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# cd /sys/kernel/debug/tracing
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# echo 1 > /sys/kernel/debug/pstore/record_ftrace
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# echo function > current_tracer
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# echo 1 > options/func_pstore
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# reboot -f
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# reboot -f
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[...]
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[...]
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# mount -t pstore pstore /mnt/
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# mount -t pstore pstore /mnt/
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@ -23,6 +23,7 @@ config PSTORE_FTRACE
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bool "Persistent function tracer"
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bool "Persistent function tracer"
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depends on PSTORE
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depends on PSTORE
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depends on FUNCTION_TRACER
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depends on FUNCTION_TRACER
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depends on DEBUG_FS
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help
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help
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With this option kernel traces function calls into a persistent
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With this option kernel traces function calls into a persistent
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ram buffer that can be decoded and dumped after reboot through
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ram buffer that can be decoded and dumped after reboot through
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@ -17,19 +17,113 @@
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#include <linux/percpu.h>
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#include <linux/percpu.h>
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#include <linux/smp.h>
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#include <linux/smp.h>
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#include <linux/atomic.h>
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#include <linux/atomic.h>
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#include <linux/types.h>
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#include <linux/mutex.h>
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#include <linux/ftrace.h>
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#include <linux/fs.h>
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#include <linux/debugfs.h>
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#include <linux/err.h>
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#include <linux/cache.h>
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#include <asm/barrier.h>
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#include <asm/barrier.h>
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#include "internal.h"
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#include "internal.h"
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void notrace pstore_ftrace_call(unsigned long ip, unsigned long parent_ip)
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static void notrace pstore_ftrace_call(unsigned long ip,
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unsigned long parent_ip)
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{
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{
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unsigned long flags;
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struct pstore_ftrace_record rec = {};
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struct pstore_ftrace_record rec = {};
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if (unlikely(oops_in_progress))
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if (unlikely(oops_in_progress))
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return;
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return;
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local_irq_save(flags);
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rec.ip = ip;
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rec.ip = ip;
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rec.parent_ip = parent_ip;
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rec.parent_ip = parent_ip;
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pstore_ftrace_encode_cpu(&rec, raw_smp_processor_id());
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pstore_ftrace_encode_cpu(&rec, raw_smp_processor_id());
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psinfo->write_buf(PSTORE_TYPE_FTRACE, 0, NULL, 0, (void *)&rec,
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psinfo->write_buf(PSTORE_TYPE_FTRACE, 0, NULL, 0, (void *)&rec,
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sizeof(rec), psinfo);
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sizeof(rec), psinfo);
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local_irq_restore(flags);
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}
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static struct ftrace_ops pstore_ftrace_ops __read_mostly = {
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.func = pstore_ftrace_call,
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};
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static DEFINE_MUTEX(pstore_ftrace_lock);
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static bool pstore_ftrace_enabled;
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static ssize_t pstore_ftrace_knob_write(struct file *f, const char __user *buf,
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size_t count, loff_t *ppos)
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{
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u8 on;
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ssize_t ret;
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ret = kstrtou8_from_user(buf, count, 2, &on);
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if (ret)
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return ret;
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mutex_lock(&pstore_ftrace_lock);
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if (!on ^ pstore_ftrace_enabled)
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goto out;
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if (on)
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ret = register_ftrace_function(&pstore_ftrace_ops);
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else
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ret = unregister_ftrace_function(&pstore_ftrace_ops);
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if (ret) {
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pr_err("%s: unable to %sregister ftrace ops: %zd\n",
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__func__, on ? "" : "un", ret);
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goto err;
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}
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pstore_ftrace_enabled = on;
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out:
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ret = count;
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err:
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mutex_unlock(&pstore_ftrace_lock);
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return ret;
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}
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static ssize_t pstore_ftrace_knob_read(struct file *f, char __user *buf,
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size_t count, loff_t *ppos)
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{
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char val[] = { '0' + pstore_ftrace_enabled, '\n' };
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return simple_read_from_buffer(buf, count, ppos, val, sizeof(val));
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}
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static const struct file_operations pstore_knob_fops = {
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.open = simple_open,
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.read = pstore_ftrace_knob_read,
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.write = pstore_ftrace_knob_write,
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};
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void pstore_register_ftrace(void)
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{
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struct dentry *dir;
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struct dentry *file;
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if (!psinfo->write_buf)
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return;
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dir = debugfs_create_dir("pstore", NULL);
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if (!dir) {
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pr_err("%s: unable to create pstore directory\n", __func__);
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return;
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}
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file = debugfs_create_file("record_ftrace", 0600, dir, NULL,
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&pstore_knob_fops);
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if (!file) {
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pr_err("%s: unable to create record_ftrace file\n", __func__);
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goto err_file;
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}
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return;
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err_file:
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debugfs_remove(dir);
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}
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}
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@ -39,6 +39,12 @@ pstore_ftrace_decode_cpu(struct pstore_ftrace_record *rec)
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#endif
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#endif
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}
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}
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#ifdef CONFIG_PSTORE_FTRACE
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extern void pstore_register_ftrace(void);
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#else
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static inline void pstore_register_ftrace(void) {}
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#endif
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extern struct pstore_info *psinfo;
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extern struct pstore_info *psinfo;
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extern void pstore_set_kmsg_bytes(int);
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extern void pstore_set_kmsg_bytes(int);
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@ -236,6 +236,7 @@ int pstore_register(struct pstore_info *psi)
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kmsg_dump_register(&pstore_dumper);
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kmsg_dump_register(&pstore_dumper);
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pstore_register_console();
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pstore_register_console();
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pstore_register_ftrace();
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if (pstore_update_ms >= 0) {
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if (pstore_update_ms >= 0) {
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pstore_timer.expires = jiffies +
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pstore_timer.expires = jiffies +
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void *data;
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void *data;
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};
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};
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#ifdef CONFIG_PSTORE_FTRACE
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extern void pstore_ftrace_call(unsigned long ip, unsigned long parent_ip);
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#else
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static inline void pstore_ftrace_call(unsigned long ip, unsigned long parent_ip)
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{ }
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#endif
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#ifdef CONFIG_PSTORE
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#ifdef CONFIG_PSTORE
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extern int pstore_register(struct pstore_info *);
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extern int pstore_register(struct pstore_info *);
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#else
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#else
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@ -13,7 +13,6 @@
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#include <linux/debugfs.h>
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#include <linux/debugfs.h>
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#include <linux/uaccess.h>
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#include <linux/uaccess.h>
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#include <linux/ftrace.h>
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#include <linux/ftrace.h>
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#include <linux/pstore.h>
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#include <linux/fs.h>
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#include <linux/fs.h>
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#include "trace.h"
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#include "trace.h"
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preempt_enable_notrace();
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preempt_enable_notrace();
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}
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}
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/* Our two options */
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/* Our option */
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enum {
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enum {
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TRACE_FUNC_OPT_STACK = 0x1,
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TRACE_FUNC_OPT_STACK = 0x1,
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TRACE_FUNC_OPT_PSTORE = 0x2,
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};
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};
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static struct tracer_flags func_flags;
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static struct tracer_flags func_flags;
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disabled = atomic_inc_return(&data->disabled);
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disabled = atomic_inc_return(&data->disabled);
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if (likely(disabled == 1)) {
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if (likely(disabled == 1)) {
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/*
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* So far tracing doesn't support multiple buffers, so
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* we make an explicit call for now.
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*/
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if (unlikely(func_flags.val & TRACE_FUNC_OPT_PSTORE))
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pstore_ftrace_call(ip, parent_ip);
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pc = preempt_count();
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pc = preempt_count();
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trace_function(tr, ip, parent_ip, flags, pc);
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trace_function(tr, ip, parent_ip, flags, pc);
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}
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}
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static struct tracer_opt func_opts[] = {
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static struct tracer_opt func_opts[] = {
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#ifdef CONFIG_STACKTRACE
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#ifdef CONFIG_STACKTRACE
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{ TRACER_OPT(func_stack_trace, TRACE_FUNC_OPT_STACK) },
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{ TRACER_OPT(func_stack_trace, TRACE_FUNC_OPT_STACK) },
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#endif
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#ifdef CONFIG_PSTORE_FTRACE
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{ TRACER_OPT(func_pstore, TRACE_FUNC_OPT_PSTORE) },
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#endif
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#endif
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{ } /* Always set a last empty entry */
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{ } /* Always set a last empty entry */
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};
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};
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register_ftrace_function(&trace_ops);
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register_ftrace_function(&trace_ops);
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}
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}
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break;
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case TRACE_FUNC_OPT_PSTORE:
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break;
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break;
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default:
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default:
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return -EINVAL;
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return -EINVAL;
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