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Linux/kernel/trace/trace_printk.c

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  1 /*
  2  * trace binary printk
  3  *
  4  * Copyright (C) 2008 Lai Jiangshan <laijs@cn.fujitsu.com>
  5  *
  6  */
  7 #include <linux/seq_file.h>
  8 #include <linux/debugfs.h>
  9 #include <linux/uaccess.h>
 10 #include <linux/kernel.h>
 11 #include <linux/ftrace.h>
 12 #include <linux/string.h>
 13 #include <linux/module.h>
 14 #include <linux/mutex.h>
 15 #include <linux/ctype.h>
 16 #include <linux/list.h>
 17 #include <linux/slab.h>
 18 #include <linux/fs.h>
 19 
 20 #include "trace.h"
 21 
 22 #ifdef CONFIG_MODULES
 23 
 24 /*
 25  * modules trace_printk()'s formats are autosaved in struct trace_bprintk_fmt
 26  * which are queued on trace_bprintk_fmt_list.
 27  */
 28 static LIST_HEAD(trace_bprintk_fmt_list);
 29 
 30 /* serialize accesses to trace_bprintk_fmt_list */
 31 static DEFINE_MUTEX(btrace_mutex);
 32 
 33 struct trace_bprintk_fmt {
 34         struct list_head list;
 35         char fmt[0];
 36 };
 37 
 38 static inline struct trace_bprintk_fmt *lookup_format(const char *fmt)
 39 {
 40         struct trace_bprintk_fmt *pos;
 41         list_for_each_entry(pos, &trace_bprintk_fmt_list, list) {
 42                 if (!strcmp(pos->fmt, fmt))
 43                         return pos;
 44         }
 45         return NULL;
 46 }
 47 
 48 static
 49 void hold_module_trace_bprintk_format(const char **start, const char **end)
 50 {
 51         const char **iter;
 52 
 53         mutex_lock(&btrace_mutex);
 54         for (iter = start; iter < end; iter++) {
 55                 struct trace_bprintk_fmt *tb_fmt = lookup_format(*iter);
 56                 if (tb_fmt) {
 57                         *iter = tb_fmt->fmt;
 58                         continue;
 59                 }
 60 
 61                 tb_fmt = kmalloc(offsetof(struct trace_bprintk_fmt, fmt)
 62                                 + strlen(*iter) + 1, GFP_KERNEL);
 63                 if (tb_fmt) {
 64                         list_add_tail(&tb_fmt->list, &trace_bprintk_fmt_list);
 65                         strcpy(tb_fmt->fmt, *iter);
 66                         *iter = tb_fmt->fmt;
 67                 } else
 68                         *iter = NULL;
 69         }
 70         mutex_unlock(&btrace_mutex);
 71 }
 72 
 73 static int module_trace_bprintk_format_notify(struct notifier_block *self,
 74                 unsigned long val, void *data)
 75 {
 76         struct module *mod = data;
 77         if (mod->num_trace_bprintk_fmt) {
 78                 const char **start = mod->trace_bprintk_fmt_start;
 79                 const char **end = start + mod->num_trace_bprintk_fmt;
 80 
 81                 if (val == MODULE_STATE_COMING)
 82                         hold_module_trace_bprintk_format(start, end);
 83         }
 84         return 0;
 85 }
 86 
 87 #else /* !CONFIG_MODULES */
 88 __init static int
 89 module_trace_bprintk_format_notify(struct notifier_block *self,
 90                 unsigned long val, void *data)
 91 {
 92         return 0;
 93 }
 94 #endif /* CONFIG_MODULES */
 95 
 96 
 97 __initdata_or_module static
 98 struct notifier_block module_trace_bprintk_format_nb = {
 99         .notifier_call = module_trace_bprintk_format_notify,
100 };
101 
102 int __trace_bprintk(unsigned long ip, const char *fmt, ...)
103  {
104         int ret;
105         va_list ap;
106 
107         if (unlikely(!fmt))
108                 return 0;
109 
110         if (!(trace_flags & TRACE_ITER_PRINTK))
111                 return 0;
112 
113         va_start(ap, fmt);
114         ret = trace_vbprintk(ip, fmt, ap);
115         va_end(ap);
116         return ret;
117 }
118 EXPORT_SYMBOL_GPL(__trace_bprintk);
119 
120 int __ftrace_vbprintk(unsigned long ip, const char *fmt, va_list ap)
121  {
122         if (unlikely(!fmt))
123                 return 0;
124 
125         if (!(trace_flags & TRACE_ITER_PRINTK))
126                 return 0;
127 
128         return trace_vbprintk(ip, fmt, ap);
129 }
130 EXPORT_SYMBOL_GPL(__ftrace_vbprintk);
131 
132 int __trace_printk(unsigned long ip, const char *fmt, ...)
133 {
134         int ret;
135         va_list ap;
136 
137         if (!(trace_flags & TRACE_ITER_PRINTK))
138                 return 0;
139 
140         va_start(ap, fmt);
141         ret = trace_vprintk(ip, fmt, ap);
142         va_end(ap);
143         return ret;
144 }
145 EXPORT_SYMBOL_GPL(__trace_printk);
146 
147 int __ftrace_vprintk(unsigned long ip, const char *fmt, va_list ap)
148 {
149         if (!(trace_flags & TRACE_ITER_PRINTK))
150                 return 0;
151 
152         return trace_vprintk(ip, fmt, ap);
153 }
154 EXPORT_SYMBOL_GPL(__ftrace_vprintk);
155 
156 static void *
157 t_start(struct seq_file *m, loff_t *pos)
158 {
159         const char **fmt = __start___trace_bprintk_fmt + *pos;
160 
161         if ((unsigned long)fmt >= (unsigned long)__stop___trace_bprintk_fmt)
162                 return NULL;
163         return fmt;
164 }
165 
166 static void *t_next(struct seq_file *m, void * v, loff_t *pos)
167 {
168         (*pos)++;
169         return t_start(m, pos);
170 }
171 
172 static int t_show(struct seq_file *m, void *v)
173 {
174         const char **fmt = v;
175         const char *str = *fmt;
176         int i;
177 
178         seq_printf(m, "0x%lx : \"", *(unsigned long *)fmt);
179 
180         /*
181          * Tabs and new lines need to be converted.
182          */
183         for (i = 0; str[i]; i++) {
184                 switch (str[i]) {
185                 case '\n':
186                         seq_puts(m, "\\n");
187                         break;
188                 case '\t':
189                         seq_puts(m, "\\t");
190                         break;
191                 case '\\':
192                         seq_puts(m, "\\");
193                         break;
194                 case '"':
195                         seq_puts(m, "\\\"");
196                         break;
197                 default:
198                         seq_putc(m, str[i]);
199                 }
200         }
201         seq_puts(m, "\"\n");
202 
203         return 0;
204 }
205 
206 static void t_stop(struct seq_file *m, void *p)
207 {
208 }
209 
210 static const struct seq_operations show_format_seq_ops = {
211         .start = t_start,
212         .next = t_next,
213         .show = t_show,
214         .stop = t_stop,
215 };
216 
217 static int
218 ftrace_formats_open(struct inode *inode, struct file *file)
219 {
220         return seq_open(file, &show_format_seq_ops);
221 }
222 
223 static const struct file_operations ftrace_formats_fops = {
224         .open = ftrace_formats_open,
225         .read = seq_read,
226         .llseek = seq_lseek,
227         .release = seq_release,
228 };
229 
230 static __init int init_trace_printk_function_export(void)
231 {
232         struct dentry *d_tracer;
233 
234         d_tracer = tracing_init_dentry();
235         if (!d_tracer)
236                 return 0;
237 
238         trace_create_file("printk_formats", 0444, d_tracer,
239                                     NULL, &ftrace_formats_fops);
240 
241         return 0;
242 }
243 
244 fs_initcall(init_trace_printk_function_export);
245 
246 static __init int init_trace_printk(void)
247 {
248         return register_module_notifier(&module_trace_bprintk_format_nb);
249 }
250 
251 early_initcall(init_trace_printk);
252 

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