// SPDX-License-Identifier: GPL-2.0
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/*
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* trace binary printk
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*
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* Copyright (C) 2008 Lai Jiangshan <laijs@cn.fujitsu.com>
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*
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*/
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#include <linux/seq_file.h>
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#include <linux/security.h>
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#include <linux/uaccess.h>
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#include <linux/kernel.h>
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#include <linux/ftrace.h>
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#include <linux/string.h>
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#include <linux/module.h>
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#include <linux/mutex.h>
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#include <linux/ctype.h>
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#include <linux/list.h>
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#include <linux/slab.h>
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#include "trace.h"
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#ifdef CONFIG_MODULES
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/*
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* modules trace_printk()'s formats are autosaved in struct trace_bprintk_fmt
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* which are queued on trace_bprintk_fmt_list.
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*/
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static LIST_HEAD(trace_bprintk_fmt_list);
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/* serialize accesses to trace_bprintk_fmt_list */
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static DEFINE_MUTEX(btrace_mutex);
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struct trace_bprintk_fmt {
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struct list_head list;
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const char *fmt;
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};
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static inline struct trace_bprintk_fmt *lookup_format(const char *fmt)
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{
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struct trace_bprintk_fmt *pos;
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if (!fmt)
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return ERR_PTR(-EINVAL);
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list_for_each_entry(pos, &trace_bprintk_fmt_list, list) {
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if (!strcmp(pos->fmt, fmt))
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return pos;
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}
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return NULL;
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}
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static
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void hold_module_trace_bprintk_format(const char **start, const char **end)
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{
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const char **iter;
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char *fmt;
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/* allocate the trace_printk per cpu buffers */
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if (start != end)
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trace_printk_init_buffers();
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mutex_lock(&btrace_mutex);
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for (iter = start; iter < end; iter++) {
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struct trace_bprintk_fmt *tb_fmt = lookup_format(*iter);
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if (tb_fmt) {
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if (!IS_ERR(tb_fmt))
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*iter = tb_fmt->fmt;
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continue;
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}
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fmt = NULL;
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tb_fmt = kmalloc(sizeof(*tb_fmt), GFP_KERNEL);
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if (tb_fmt) {
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fmt = kmalloc(strlen(*iter) + 1, GFP_KERNEL);
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if (fmt) {
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list_add_tail(&tb_fmt->list, &trace_bprintk_fmt_list);
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strcpy(fmt, *iter);
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tb_fmt->fmt = fmt;
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} else
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kfree(tb_fmt);
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}
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*iter = fmt;
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}
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mutex_unlock(&btrace_mutex);
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}
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static int module_trace_bprintk_format_notify(struct notifier_block *self,
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unsigned long val, void *data)
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{
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struct module *mod = data;
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if (mod->num_trace_bprintk_fmt) {
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const char **start = mod->trace_bprintk_fmt_start;
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const char **end = start + mod->num_trace_bprintk_fmt;
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if (val == MODULE_STATE_COMING)
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hold_module_trace_bprintk_format(start, end);
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}
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return NOTIFY_OK;
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}
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/*
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* The debugfs/tracing/printk_formats file maps the addresses with
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* the ASCII formats that are used in the bprintk events in the
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* buffer. For userspace tools to be able to decode the events from
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* the buffer, they need to be able to map the address with the format.
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*
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* The addresses of the bprintk formats are in their own section
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* __trace_printk_fmt. But for modules we copy them into a link list.
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* The code to print the formats and their addresses passes around the
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* address of the fmt string. If the fmt address passed into the seq
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* functions is within the kernel core __trace_printk_fmt section, then
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* it simply uses the next pointer in the list.
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*
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* When the fmt pointer is outside the kernel core __trace_printk_fmt
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* section, then we need to read the link list pointers. The trick is
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* we pass the address of the string to the seq function just like
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* we do for the kernel core formats. To get back the structure that
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* holds the format, we simply use container_of() and then go to the
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* next format in the list.
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*/
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static const char **
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find_next_mod_format(int start_index, void *v, const char **fmt, loff_t *pos)
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{
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struct trace_bprintk_fmt *mod_fmt;
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if (list_empty(&trace_bprintk_fmt_list))
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return NULL;
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/*
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* v will point to the address of the fmt record from t_next
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* v will be NULL from t_start.
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* If this is the first pointer or called from start
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* then we need to walk the list.
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*/
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if (!v || start_index == *pos) {
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struct trace_bprintk_fmt *p;
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/* search the module list */
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list_for_each_entry(p, &trace_bprintk_fmt_list, list) {
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if (start_index == *pos)
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return &p->fmt;
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start_index++;
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}
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/* pos > index */
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return NULL;
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}
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/*
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* v points to the address of the fmt field in the mod list
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* structure that holds the module print format.
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*/
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mod_fmt = container_of(v, typeof(*mod_fmt), fmt);
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if (mod_fmt->list.next == &trace_bprintk_fmt_list)
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return NULL;
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mod_fmt = container_of(mod_fmt->list.next, typeof(*mod_fmt), list);
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return &mod_fmt->fmt;
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}
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static void format_mod_start(void)
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{
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mutex_lock(&btrace_mutex);
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}
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static void format_mod_stop(void)
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{
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mutex_unlock(&btrace_mutex);
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}
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#else /* !CONFIG_MODULES */
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__init static int
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module_trace_bprintk_format_notify(struct notifier_block *self,
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unsigned long val, void *data)
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{
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return NOTIFY_OK;
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}
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static inline const char **
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find_next_mod_format(int start_index, void *v, const char **fmt, loff_t *pos)
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{
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return NULL;
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}
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static inline void format_mod_start(void) { }
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static inline void format_mod_stop(void) { }
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#endif /* CONFIG_MODULES */
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static bool __read_mostly trace_printk_enabled = true;
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void trace_printk_control(bool enabled)
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{
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trace_printk_enabled = enabled;
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}
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__initdata_or_module static
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struct notifier_block module_trace_bprintk_format_nb = {
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.notifier_call = module_trace_bprintk_format_notify,
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};
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int __trace_bprintk(unsigned long ip, const char *fmt, ...)
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{
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int ret;
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va_list ap;
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if (unlikely(!fmt))
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return 0;
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if (!trace_printk_enabled)
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return 0;
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va_start(ap, fmt);
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ret = trace_vbprintk(ip, fmt, ap);
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va_end(ap);
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return ret;
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}
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EXPORT_SYMBOL_GPL(__trace_bprintk);
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int __ftrace_vbprintk(unsigned long ip, const char *fmt, va_list ap)
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{
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if (unlikely(!fmt))
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return 0;
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if (!trace_printk_enabled)
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return 0;
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return trace_vbprintk(ip, fmt, ap);
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}
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EXPORT_SYMBOL_GPL(__ftrace_vbprintk);
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int __trace_printk(unsigned long ip, const char *fmt, ...)
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{
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int ret;
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va_list ap;
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if (!trace_printk_enabled)
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return 0;
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va_start(ap, fmt);
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ret = trace_vprintk(ip, fmt, ap);
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va_end(ap);
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return ret;
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}
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EXPORT_SYMBOL_GPL(__trace_printk);
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int __ftrace_vprintk(unsigned long ip, const char *fmt, va_list ap)
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{
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if (!trace_printk_enabled)
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return 0;
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return trace_vprintk(ip, fmt, ap);
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}
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EXPORT_SYMBOL_GPL(__ftrace_vprintk);
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static const char **find_next(void *v, loff_t *pos)
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{
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const char **fmt = v;
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int start_index;
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int last_index;
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start_index = __stop___trace_bprintk_fmt - __start___trace_bprintk_fmt;
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if (*pos < start_index)
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return __start___trace_bprintk_fmt + *pos;
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/*
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* The __tracepoint_str section is treated the same as the
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* __trace_printk_fmt section. The difference is that the
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* __trace_printk_fmt section should only be used by trace_printk()
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* in a debugging environment, as if anything exists in that section
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* the trace_prink() helper buffers are allocated, which would just
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* waste space in a production environment.
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*
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* The __tracepoint_str sections on the other hand are used by
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* tracepoints which need to map pointers to their strings to
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* the ASCII text for userspace.
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*/
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last_index = start_index;
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start_index = __stop___tracepoint_str - __start___tracepoint_str;
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if (*pos < last_index + start_index)
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return __start___tracepoint_str + (*pos - last_index);
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start_index += last_index;
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return find_next_mod_format(start_index, v, fmt, pos);
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}
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static void *
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t_start(struct seq_file *m, loff_t *pos)
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{
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format_mod_start();
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return find_next(NULL, pos);
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}
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static void *t_next(struct seq_file *m, void * v, loff_t *pos)
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{
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(*pos)++;
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return find_next(v, pos);
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}
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static int t_show(struct seq_file *m, void *v)
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{
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const char **fmt = v;
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const char *str = *fmt;
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int i;
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if (!*fmt)
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return 0;
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seq_printf(m, "0x%lx : \"", *(unsigned long *)fmt);
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/*
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* Tabs and new lines need to be converted.
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*/
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for (i = 0; str[i]; i++) {
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switch (str[i]) {
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case '\n':
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seq_puts(m, "\\n");
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break;
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case '\t':
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seq_puts(m, "\\t");
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break;
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case '\\':
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seq_putc(m, '\\');
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break;
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case '"':
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seq_puts(m, "\\\"");
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break;
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default:
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seq_putc(m, str[i]);
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}
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}
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seq_puts(m, "\"\n");
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return 0;
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}
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static void t_stop(struct seq_file *m, void *p)
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{
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format_mod_stop();
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}
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static const struct seq_operations show_format_seq_ops = {
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.start = t_start,
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.next = t_next,
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.show = t_show,
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.stop = t_stop,
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};
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static int
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ftrace_formats_open(struct inode *inode, struct file *file)
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{
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int ret;
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ret = security_locked_down(LOCKDOWN_TRACEFS);
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if (ret)
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return ret;
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return seq_open(file, &show_format_seq_ops);
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}
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static const struct file_operations ftrace_formats_fops = {
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.open = ftrace_formats_open,
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.read = seq_read,
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.llseek = seq_lseek,
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.release = seq_release,
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};
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static __init int init_trace_printk_function_export(void)
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{
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int ret;
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ret = tracing_init_dentry();
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if (ret)
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return 0;
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trace_create_file("printk_formats", 0444, NULL,
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NULL, &ftrace_formats_fops);
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return 0;
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}
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fs_initcall(init_trace_printk_function_export);
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static __init int init_trace_printk(void)
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{
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return register_module_notifier(&module_trace_bprintk_format_nb);
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}
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early_initcall(init_trace_printk);
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