kernel/printk/index.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Userspace indexing of printk formats
   4  */
   5
   6 #include <linux/debugfs.h>
   7 #include <linux/module.h>
   8 #include <linux/printk.h>
   9 #include <linux/slab.h>
  10 #include <linux/string_helpers.h>
  11
  12 #include "internal.h"
  13
  14 extern struct pi_entry *__start_printk_index[];
  15 extern struct pi_entry *__stop_printk_index[];
  16
  17 /* The base dir for module formats, typically debugfs/printk/index/ */
  18 static struct dentry *dfs_index;
  19
  20 static struct pi_entry *pi_get_entry(const struct module *mod, loff_t pos)
  21 {
  22         struct pi_entry **entries;
  23         unsigned int nr_entries;
  24
  25 #ifdef CONFIG_MODULES
  26         if (mod) {
  27                 entries = mod->printk_index_start;
  28                 nr_entries = mod->printk_index_size;
  29         } else
  30 #endif
  31         {
  32                 /* vmlinux, comes from linker symbols */
  33                 entries = __start_printk_index;
  34                 nr_entries = __stop_printk_index - __start_printk_index;
  35         }
  36
  37         if (pos >= nr_entries)
  38                 return NULL;
  39
  40         return entries[pos];
  41 }
  42
  43 static void *pi_next(struct seq_file *s, void *v, loff_t *pos)
  44 {
  45         const struct module *mod = s->file->f_inode->i_private;
  46         struct pi_entry *entry = pi_get_entry(mod, *pos);
  47
  48         (*pos)++;
  49
  50         return entry;
  51 }
  52
  53 static void *pi_start(struct seq_file *s, loff_t *pos)
  54 {
  55         /*
  56          * Make show() print the header line. Do not update *pos because
  57          * pi_next() still has to return the entry at index 0 later.
  58          */
  59         if (*pos == 0)
  60                 return SEQ_START_TOKEN;
  61
  62         return pi_next(s, NULL, pos);
  63 }
  64
  65 /*
  66  * We need both ESCAPE_ANY and explicit characters from ESCAPE_SPECIAL in @only
  67  * because otherwise ESCAPE_NAP will cause double quotes and backslashes to be
  68  * ignored for quoting.
  69  */
  70 #define seq_escape_printf_format(s, src) \
  71         seq_escape_str(s, src, ESCAPE_ANY | ESCAPE_NAP | ESCAPE_APPEND, "\"\\")
  72
  73 static int pi_show(struct seq_file *s, void *v)
  74 {
  75         const struct pi_entry *entry = v;
  76         int level = LOGLEVEL_DEFAULT;
  77         enum printk_info_flags flags = 0;
  78         u16 prefix_len = 0;
  79
  80         if (v == SEQ_START_TOKEN) {
  81                 seq_puts(s, "# <level/flags> filename:line function \"format\"\n");
  82                 return 0;
  83         }
  84
  85         if (!entry->fmt)
  86                 return 0;
  87
  88         if (entry->level)
  89                 printk_parse_prefix(entry->level, &level, &flags);
  90         else
  91                 prefix_len = printk_parse_prefix(entry->fmt, &level, &flags);
  92
  93
  94         if (flags & LOG_CONT) {
  95                 /*
  96                  * LOGLEVEL_DEFAULT here means "use the same level as the
  97                  * message we're continuing from", not the default message
  98                  * loglevel, so don't display it as such.
  99                  */
 100                 if (level == LOGLEVEL_DEFAULT)
 101                         seq_puts(s, "<c>");
 102                 else
 103                         seq_printf(s, "<%d,c>", level);
 104         } else
 105                 seq_printf(s, "<%d>", level);
 106
 107         seq_printf(s, " %s:%d %s \"", entry->file, entry->line, entry->func);
 108         if (entry->subsys_fmt_prefix)
 109                 seq_escape_printf_format(s, entry->subsys_fmt_prefix);
 110         seq_escape_printf_format(s, entry->fmt + prefix_len);
 111         seq_puts(s, "\"\n");
 112
 113         return 0;
 114 }
 115
 116 static void pi_stop(struct seq_file *p, void *v) { }
 117
 118 static const struct seq_operations dfs_index_sops = {
 119         .start = pi_start,
 120         .next  = pi_next,
 121         .show  = pi_show,
 122         .stop  = pi_stop,
 123 };
 124
 125 DEFINE_SEQ_ATTRIBUTE(dfs_index);
 126
 127 #ifdef CONFIG_MODULES
 128 static const char *pi_get_module_name(struct module *mod)
 129 {
 130         return mod ? mod->name : "vmlinux";
 131 }
 132 #else
 133 static const char *pi_get_module_name(struct module *mod)
 134 {
 135         return "vmlinux";
 136 }
 137 #endif
 138
 139 static void pi_create_file(struct module *mod)
 140 {
 141         debugfs_create_file(pi_get_module_name(mod), 0444, dfs_index,
 142                                        mod, &dfs_index_fops);
 143 }
 144
 145 #ifdef CONFIG_MODULES
 146 static void pi_remove_file(struct module *mod)
 147 {
 148         debugfs_lookup_and_remove(pi_get_module_name(mod), dfs_index);
 149 }
 150
 151 static int pi_module_notify(struct notifier_block *nb, unsigned long op,
 152                             void *data)
 153 {
 154         struct module *mod = data;
 155
 156         switch (op) {
 157         case MODULE_STATE_COMING:
 158                 pi_create_file(mod);
 159                 break;
 160         case MODULE_STATE_GOING:
 161                 pi_remove_file(mod);
 162                 break;
 163         default: /* we don't care about other module states */
 164                 break;
 165         }
 166
 167         return NOTIFY_OK;
 168 }
 169
 170 static struct notifier_block module_printk_fmts_nb = {
 171         .notifier_call = pi_module_notify,
 172 };
 173
 174 static void __init pi_setup_module_notifier(void)
 175 {
 176         register_module_notifier(&module_printk_fmts_nb);
 177 }
 178 #else
 179 static inline void __init pi_setup_module_notifier(void) { }
 180 #endif
 181
 182 static int __init pi_init(void)
 183 {
 184         struct dentry *dfs_root = debugfs_create_dir("printk", NULL);
 185
 186         dfs_index = debugfs_create_dir("index", dfs_root);
 187         pi_setup_module_notifier();
 188         pi_create_file(NULL);
 189
 190         return 0;
 191 }
 192
 193 /* debugfs comes up on core and must be initialised first */
 194 postcore_initcall(pi_init);