// SPDX-License-Identifier: GPL-2.0-only

  /*
   * kallsyms.c: in-kernel printing of symbolic oopses and stack traces.
   *
   * Rewritten and vastly simplified by Rusty Russell for in-kernel
   * module loader:
   *   Copyright 2002 Rusty Russell <rusty@rustcorp.com.au> IBM Corporation
   *
   * ChangeLog:
   *
   * (25/Aug/2004) Paulo Marques <pmarques@grupopie.com>
   *      Changed the compression method from stem compression to "table lookup"
   *      compression (see scripts/kallsyms.c for a more complete description)
   */
  #include <linux/kallsyms.h>

  #include <linux/init.h>
  #include <linux/seq_file.h>
  #include <linux/fs.h>

  #include <linux/kdb.h>

  #include <linux/err.h>
  #include <linux/proc_fs.h>

  #include <linux/sched.h>	/* for cond_resched */

  #include <linux/ctype.h>

  #include <linux/slab.h>

  #include <linux/filter.h>

  #include <linux/ftrace.h>

  #include <linux/kprobes.h>

  #include <linux/compiler.h>

  /*
   * These will be re-linked against their real values
   * during the second link stage.
   */

  extern const unsigned long kallsyms_addresses[] __weak;

  extern const int kallsyms_offsets[] __weak;

  extern const u8 kallsyms_names[] __weak;

  /*
   * Tell the compiler that the count isn't in the small data section if the arch
   * has one (eg: FRV).

   */

  extern const unsigned int kallsyms_num_syms

  __section(".rodata") __attribute__((weak));

  extern const unsigned long kallsyms_relative_base

  __section(".rodata") __attribute__((weak));

  extern const char kallsyms_token_table[] __weak;

  extern const u16 kallsyms_token_index[] __weak;

  extern const unsigned int kallsyms_markers[] __weak;

  /*
   * Expand a compressed symbol data into the resulting uncompressed string,

   * if uncompressed string is too long (>= maxlen), it will be truncated,

   * given the offset to where the symbol is in the compressed stream.
   */

  static unsigned int kallsyms_expand_symbol(unsigned int off,
  					   char *result, size_t maxlen)

  {
  	int len, skipped_first = 0;

  	const char *tptr;
  	const u8 *data;

  	/* Get the compressed symbol length from the first symbol byte. */

  	data = &kallsyms_names[off];
  	len = *data;
  	data++;

  	/*
  	 * Update the offset to return the offset for the next symbol on
  	 * the compressed stream.
  	 */

  	off += len + 1;

  	/*
  	 * For every byte on the compressed symbol data, copy the table
  	 * entry for that byte.
  	 */
  	while (len) {
  		tptr = &kallsyms_token_table[kallsyms_token_index[*data]];

  		data++;
  		len--;
  
  		while (*tptr) {

  			if (skipped_first) {

  				if (maxlen <= 1)
  					goto tail;

  				*result = *tptr;
  				result++;

  				maxlen--;

  			} else
  				skipped_first = 1;
  			tptr++;
  		}
  	}

  tail:
  	if (maxlen)
  		*result = '\0';

  	/* Return to offset to the next symbol. */

  	return off;
  }

  /*
   * Get symbol type information. This is encoded as a single char at the
   * beginning of the symbol name.
   */

  static char kallsyms_get_symbol_type(unsigned int off)
  {

  	/*
  	 * Get just the first code, look it up in the token table,
  	 * and return the first char from this token.
  	 */
  	return kallsyms_token_table[kallsyms_token_index[kallsyms_names[off + 1]]];

  }

  /*
   * Find the offset on the compressed stream given and index in the
   * kallsyms array.
   */

  static unsigned int get_symbol_offset(unsigned long pos)
  {

  	const u8 *name;

  	int i;

  	/*
  	 * Use the closest marker we have. We have markers every 256 positions,
  	 * so that should be close enough.
  	 */
  	name = &kallsyms_names[kallsyms_markers[pos >> 8]];

  	/*
  	 * Sequentially scan all the symbols up to the point we're searching
  	 * for. Every symbol is stored in a [<len>][<len> bytes of data] format,
  	 * so we just need to add the len to the current pointer for every
  	 * symbol we wish to skip.
  	 */
  	for (i = 0; i < (pos & 0xFF); i++)

  		name = name + (*name) + 1;
  
  	return name - kallsyms_names;
  }

  static unsigned long kallsyms_sym_address(int idx)
  {
  	if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
  		return kallsyms_addresses[idx];
  
  	/* values are unsigned offsets if --absolute-percpu is not in effect */
  	if (!IS_ENABLED(CONFIG_KALLSYMS_ABSOLUTE_PERCPU))
  		return kallsyms_relative_base + (u32)kallsyms_offsets[idx];
  
  	/* ...otherwise, positive offsets are absolute values */
  	if (kallsyms_offsets[idx] >= 0)
  		return kallsyms_offsets[idx];
  
  	/* ...and negative offsets are relative to kallsyms_relative_base - 1 */
  	return kallsyms_relative_base - 1 - kallsyms_offsets[idx];
  }

  /* Lookup the address for this symbol. Returns 0 if not found. */
  unsigned long kallsyms_lookup_name(const char *name)
  {

  	char namebuf[KSYM_NAME_LEN];

  	unsigned long i;
  	unsigned int off;
  
  	for (i = 0, off = 0; i < kallsyms_num_syms; i++) {

  		off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));

  
  		if (strcmp(namebuf, name) == 0)

  			return kallsyms_sym_address(i);

  	}
  	return module_kallsyms_lookup_name(name);
  }

  int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
  				      unsigned long),
  			    void *data)
  {
  	char namebuf[KSYM_NAME_LEN];
  	unsigned long i;
  	unsigned int off;
  	int ret;
  
  	for (i = 0, off = 0; i < kallsyms_num_syms; i++) {

  		off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));

  		ret = fn(data, namebuf, NULL, kallsyms_sym_address(i));

  		if (ret != 0)
  			return ret;
  	}
  	return module_kallsyms_on_each_symbol(fn, data);
  }

  static unsigned long get_symbol_pos(unsigned long addr,
  				    unsigned long *symbolsize,
  				    unsigned long *offset)
  {
  	unsigned long symbol_start = 0, symbol_end = 0;
  	unsigned long i, low, high, mid;

  	/* This kernel should never had been booted. */

  	if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
  		BUG_ON(!kallsyms_addresses);
  	else
  		BUG_ON(!kallsyms_offsets);

  	/* Do a binary search on the sorted kallsyms_addresses array. */

  	low = 0;
  	high = kallsyms_num_syms;
  
  	while (high - low > 1) {

  		mid = low + (high - low) / 2;

  		if (kallsyms_sym_address(mid) <= addr)

  			low = mid;
  		else
  			high = mid;
  	}
  
  	/*

  	 * Search for the first aliased symbol. Aliased
  	 * symbols are symbols with the same address.

  	 */

  	while (low && kallsyms_sym_address(low-1) == kallsyms_sym_address(low))

  		--low;

  	symbol_start = kallsyms_sym_address(low);

  	/* Search for next non-aliased symbol. */

  	for (i = low + 1; i < kallsyms_num_syms; i++) {

  		if (kallsyms_sym_address(i) > symbol_start) {
  			symbol_end = kallsyms_sym_address(i);

  			break;
  		}
  	}

  	/* If we found no next symbol, we use the end of the section. */

  	if (!symbol_end) {
  		if (is_kernel_inittext(addr))
  			symbol_end = (unsigned long)_einittext;

  		else if (IS_ENABLED(CONFIG_KALLSYMS_ALL))

  			symbol_end = (unsigned long)_end;
  		else
  			symbol_end = (unsigned long)_etext;
  	}

  	if (symbolsize)
  		*symbolsize = symbol_end - symbol_start;
  	if (offset)
  		*offset = addr - symbol_start;

  
  	return low;
  }
  
  /*
   * Lookup an address but don't bother to find any names.
   */
  int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
  				unsigned long *offset)
  {

  	char namebuf[KSYM_NAME_LEN];

  	if (is_ksym_addr(addr)) {
  		get_symbol_pos(addr, symbolsize, offset);
  		return 1;
  	}

  	return !!module_address_lookup(addr, symbolsize, offset, NULL, namebuf) ||
  	       !!__bpf_address_lookup(addr, symbolsize, offset, namebuf);

  }

  /*
   * Lookup an address

   * - modname is set to NULL if it's in the kernel.
   * - We guarantee that the returned name is valid until we reschedule even if.
   *   It resides in a module.
   * - We also guarantee that modname will be valid until rescheduled.

   */
  const char *kallsyms_lookup(unsigned long addr,
  			    unsigned long *symbolsize,
  			    unsigned long *offset,
  			    char **modname, char *namebuf)
  {

  	const char *ret;

  	namebuf[KSYM_NAME_LEN - 1] = 0;

  	namebuf[0] = 0;

  	if (is_ksym_addr(addr)) {
  		unsigned long pos;

  		pos = get_symbol_pos(addr, symbolsize, offset);

  		/* Grab name */

  		kallsyms_expand_symbol(get_symbol_offset(pos),
  				       namebuf, KSYM_NAME_LEN);

  		if (modname)
  			*modname = NULL;

  		return namebuf;
  	}

  	/* See if it's in a module or a BPF JITed image. */
  	ret = module_address_lookup(addr, symbolsize, offset,
  				    modname, namebuf);
  	if (!ret)
  		ret = bpf_address_lookup(addr, symbolsize,
  					 offset, modname, namebuf);

  
  	if (!ret)
  		ret = ftrace_mod_address_lookup(addr, symbolsize,
  						offset, modname, namebuf);

  	return ret;

  }

  int lookup_symbol_name(unsigned long addr, char *symname)
  {
  	symname[0] = '\0';

  	symname[KSYM_NAME_LEN - 1] = '\0';

  
  	if (is_ksym_addr(addr)) {
  		unsigned long pos;
  
  		pos = get_symbol_pos(addr, NULL, NULL);
  		/* Grab name */

  		kallsyms_expand_symbol(get_symbol_offset(pos),
  				       symname, KSYM_NAME_LEN);

  		return 0;
  	}

  	/* See if it's in a module. */

  	return lookup_module_symbol_name(addr, symname);
  }

  int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
  			unsigned long *offset, char *modname, char *name)
  {
  	name[0] = '\0';

  	name[KSYM_NAME_LEN - 1] = '\0';

  
  	if (is_ksym_addr(addr)) {
  		unsigned long pos;
  
  		pos = get_symbol_pos(addr, size, offset);
  		/* Grab name */

  		kallsyms_expand_symbol(get_symbol_offset(pos),
  				       name, KSYM_NAME_LEN);

  		modname[0] = '\0';
  		return 0;
  	}

  	/* See if it's in a module. */

  	return lookup_module_symbol_attrs(addr, size, offset, modname, name);
  }

  /* Look up a kernel symbol and return it in a text buffer. */

  static int __sprint_symbol(char *buffer, unsigned long address,

  			   int symbol_offset, int add_offset)

  {
  	char *modname;
  	const char *name;
  	unsigned long offset, size;

  	int len;

  	address += symbol_offset;

  	name = kallsyms_lookup(address, &size, &offset, &modname, buffer);

  	if (!name)

  		return sprintf(buffer, "0x%lx", address - symbol_offset);

  	if (name != buffer)
  		strcpy(buffer, name);
  	len = strlen(buffer);

  	offset -= symbol_offset;

  	if (add_offset)
  		len += sprintf(buffer + len, "+%#lx/%#lx", offset, size);

  	if (modname)

  		len += sprintf(buffer + len, " [%s]", modname);

  
  	return len;

  }

  
  /**
   * sprint_symbol - Look up a kernel symbol and return it in a text buffer
   * @buffer: buffer to be stored
   * @address: address to lookup
   *
   * This function looks up a kernel symbol with @address and stores its name,
   * offset, size and module name to @buffer if possible. If no symbol was found,
   * just saves its @address as is.
   *
   * This function returns the number of bytes stored in @buffer.
   */
  int sprint_symbol(char *buffer, unsigned long address)
  {

  	return __sprint_symbol(buffer, address, 0, 1);

  }

  EXPORT_SYMBOL_GPL(sprint_symbol);

  /**

   * sprint_symbol_no_offset - Look up a kernel symbol and return it in a text buffer
   * @buffer: buffer to be stored
   * @address: address to lookup
   *
   * This function looks up a kernel symbol with @address and stores its name
   * and module name to @buffer if possible. If no symbol was found, just saves
   * its @address as is.
   *
   * This function returns the number of bytes stored in @buffer.
   */
  int sprint_symbol_no_offset(char *buffer, unsigned long address)
  {
  	return __sprint_symbol(buffer, address, 0, 0);
  }
  EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);
  
  /**

   * sprint_backtrace - Look up a backtrace symbol and return it in a text buffer
   * @buffer: buffer to be stored
   * @address: address to lookup
   *
   * This function is for stack backtrace and does the same thing as
   * sprint_symbol() but with modified/decreased @address. If there is a
   * tail-call to the function marked "noreturn", gcc optimized out code after
   * the call so that the stack-saved return address could point outside of the
   * caller. This function ensures that kallsyms will find the original caller
   * by decreasing @address.
   *
   * This function returns the number of bytes stored in @buffer.
   */
  int sprint_backtrace(char *buffer, unsigned long address)
  {

  	return __sprint_symbol(buffer, address, -1, 1);

  }

  /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */

  struct kallsym_iter {

  	loff_t pos;

  	loff_t pos_arch_end;

  	loff_t pos_mod_end;

  	loff_t pos_ftrace_mod_end;

  	loff_t pos_bpf_end;

  	unsigned long value;

  	unsigned int nameoff; /* If iterating in core kernel symbols. */

  	char type;

  	char name[KSYM_NAME_LEN];
  	char module_name[MODULE_NAME_LEN];

  	int exported;

  	int show_value;

  };

  int __weak arch_get_kallsym(unsigned int symnum, unsigned long *value,
  			    char *type, char *name)
  {
  	return -EINVAL;
  }
  
  static int get_ksymbol_arch(struct kallsym_iter *iter)
  {
  	int ret = arch_get_kallsym(iter->pos - kallsyms_num_syms,
  				   &iter->value, &iter->type,
  				   iter->name);
  
  	if (ret < 0) {
  		iter->pos_arch_end = iter->pos;
  		return 0;
  	}
  
  	return 1;
  }

  static int get_ksymbol_mod(struct kallsym_iter *iter)
  {

  	int ret = module_get_kallsym(iter->pos - iter->pos_arch_end,

  				     &iter->value, &iter->type,
  				     iter->name, iter->module_name,
  				     &iter->exported);
  	if (ret < 0) {
  		iter->pos_mod_end = iter->pos;

  		return 0;

  	}

  	return 1;
  }

  /*
   * ftrace_mod_get_kallsym() may also get symbols for pages allocated for ftrace
   * purposes. In that case "__builtin__ftrace" is used as a module name, even
   * though "__builtin__ftrace" is not a module.
   */

  static int get_ksymbol_ftrace_mod(struct kallsym_iter *iter)
  {
  	int ret = ftrace_mod_get_kallsym(iter->pos - iter->pos_mod_end,
  					 &iter->value, &iter->type,
  					 iter->name, iter->module_name,
  					 &iter->exported);
  	if (ret < 0) {
  		iter->pos_ftrace_mod_end = iter->pos;
  		return 0;
  	}
  
  	return 1;
  }

  static int get_ksymbol_bpf(struct kallsym_iter *iter)
  {

  	int ret;

  	strlcpy(iter->module_name, "bpf", MODULE_NAME_LEN);

  	iter->exported = 0;

  	ret = bpf_get_kallsym(iter->pos - iter->pos_ftrace_mod_end,
  			      &iter->value, &iter->type,
  			      iter->name);
  	if (ret < 0) {
  		iter->pos_bpf_end = iter->pos;
  		return 0;
  	}
  
  	return 1;
  }
  
  /*
   * This uses "__builtin__kprobes" as a module name for symbols for pages
   * allocated for kprobes' purposes, even though "__builtin__kprobes" is not a
   * module.
   */
  static int get_ksymbol_kprobe(struct kallsym_iter *iter)
  {
  	strlcpy(iter->module_name, "__builtin__kprobes", MODULE_NAME_LEN);
  	iter->exported = 0;
  	return kprobe_get_kallsym(iter->pos - iter->pos_bpf_end,
  				  &iter->value, &iter->type,
  				  iter->name) < 0 ? 0 : 1;

  }

  /* Returns space to next name. */
  static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
  {
  	unsigned off = iter->nameoff;

  	iter->module_name[0] = '\0';

  	iter->value = kallsyms_sym_address(iter->pos);

  
  	iter->type = kallsyms_get_symbol_type(off);

  	off = kallsyms_expand_symbol(off, iter->name, ARRAY_SIZE(iter->name));

  
  	return off - iter->nameoff;
  }
  
  static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
  {
  	iter->name[0] = '\0';
  	iter->nameoff = get_symbol_offset(new_pos);
  	iter->pos = new_pos;

  	if (new_pos == 0) {

  		iter->pos_arch_end = 0;

  		iter->pos_mod_end = 0;

  		iter->pos_ftrace_mod_end = 0;

  		iter->pos_bpf_end = 0;

  	}

  }

  /*
   * The end position (last + 1) of each additional kallsyms section is recorded
   * in iter->pos_..._end as each section is added, and so can be used to
   * determine which get_ksymbol_...() function to call next.
   */

  static int update_iter_mod(struct kallsym_iter *iter, loff_t pos)
  {
  	iter->pos = pos;

  	if ((!iter->pos_arch_end || iter->pos_arch_end > pos) &&
  	    get_ksymbol_arch(iter))
  		return 1;

  	if ((!iter->pos_mod_end || iter->pos_mod_end > pos) &&
  	    get_ksymbol_mod(iter))

  		return 1;

  	if ((!iter->pos_ftrace_mod_end || iter->pos_ftrace_mod_end > pos) &&
  	    get_ksymbol_ftrace_mod(iter))
  		return 1;

  	if ((!iter->pos_bpf_end || iter->pos_bpf_end > pos) &&
  	    get_ksymbol_bpf(iter))
  		return 1;
  
  	return get_ksymbol_kprobe(iter);

  }
  
  /* Returns false if pos at or past end of file. */
  static int update_iter(struct kallsym_iter *iter, loff_t pos)
  {
  	/* Module symbols can be accessed randomly. */

  	if (pos >= kallsyms_num_syms)
  		return update_iter_mod(iter, pos);

  	/* If we're not on the desired position, reset to new position. */
  	if (pos != iter->pos)
  		reset_iter(iter, pos);
  
  	iter->nameoff += get_ksymbol_core(iter);
  	iter->pos++;
  
  	return 1;
  }
  
  static void *s_next(struct seq_file *m, void *p, loff_t *pos)
  {
  	(*pos)++;
  
  	if (!update_iter(m->private, *pos))
  		return NULL;
  	return p;
  }
  
  static void *s_start(struct seq_file *m, loff_t *pos)
  {
  	if (!update_iter(m->private, *pos))
  		return NULL;
  	return m->private;
  }
  
  static void s_stop(struct seq_file *m, void *p)
  {
  }
  
  static int s_show(struct seq_file *m, void *p)
  {

  	void *value;

  	struct kallsym_iter *iter = m->private;

  	/* Some debugging symbols have no name.  Ignore them. */

  	if (!iter->name[0])
  		return 0;

  	value = iter->show_value ? (void *)iter->value : NULL;

  	if (iter->module_name[0]) {
  		char type;

  		/*
  		 * Label it "global" if it is exported,
  		 * "local" if not exported.
  		 */

  		type = iter->exported ? toupper(iter->type) :
  					tolower(iter->type);

  		seq_printf(m, "%px %c %s\t[%s]
  ", value,

  			   type, iter->name, iter->module_name);

  	} else

  		seq_printf(m, "%px %c %s
  ", value,

  			   iter->type, iter->name);

  	return 0;
  }

  static const struct seq_operations kallsyms_op = {

  	.start = s_start,
  	.next = s_next,
  	.stop = s_stop,
  	.show = s_show
  };

  static inline int kallsyms_for_perf(void)
  {
  #ifdef CONFIG_PERF_EVENTS
  	extern int sysctl_perf_event_paranoid;
  	if (sysctl_perf_event_paranoid <= 1)
  		return 1;
  #endif
  	return 0;
  }
  
  /*
   * We show kallsyms information even to normal users if we've enabled
   * kernel profiling and are explicitly not paranoid (so kptr_restrict
   * is clear, and sysctl_perf_event_paranoid isn't set).
   *
   * Otherwise, require CAP_SYSLOG (assuming kptr_restrict isn't set to
   * block even that).
   */

  bool kallsyms_show_value(const struct cred *cred)

  {
  	switch (kptr_restrict) {
  	case 0:
  		if (kallsyms_for_perf())

  			return true;

  		fallthrough;

  	case 1:

  		if (security_capable(cred, &init_user_ns, CAP_SYSLOG,
  				     CAP_OPT_NOAUDIT) == 0)
  			return true;

  		fallthrough;

  	default:

  		return false;

  	}
  }

  static int kallsyms_open(struct inode *inode, struct file *file)
  {

  	/*
  	 * We keep iterator in m->private, since normal case is to

  	 * s_start from where we left off, so we avoid doing

  	 * using get_symbol_offset for every symbol.
  	 */

  	struct kallsym_iter *iter;

  	iter = __seq_open_private(file, &kallsyms_op, sizeof(*iter));

  	if (!iter)
  		return -ENOMEM;
  	reset_iter(iter, 0);

  	/*
  	 * Instead of checking this on every s_show() call, cache
  	 * the result here at open time.
  	 */
  	iter->show_value = kallsyms_show_value(file->f_cred);

  	return 0;

  }

  #ifdef	CONFIG_KGDB_KDB
  const char *kdb_walk_kallsyms(loff_t *pos)
  {
  	static struct kallsym_iter kdb_walk_kallsyms_iter;
  	if (*pos == 0) {
  		memset(&kdb_walk_kallsyms_iter, 0,
  		       sizeof(kdb_walk_kallsyms_iter));
  		reset_iter(&kdb_walk_kallsyms_iter, 0);
  	}
  	while (1) {
  		if (!update_iter(&kdb_walk_kallsyms_iter, *pos))
  			return NULL;
  		++*pos;
  		/* Some debugging symbols have no name.  Ignore them. */
  		if (kdb_walk_kallsyms_iter.name[0])
  			return kdb_walk_kallsyms_iter.name;
  	}
  }
  #endif	/* CONFIG_KGDB_KDB */

  static const struct proc_ops kallsyms_proc_ops = {
  	.proc_open	= kallsyms_open,
  	.proc_read	= seq_read,
  	.proc_lseek	= seq_lseek,
  	.proc_release	= seq_release_private,

  };
  
  static int __init kallsyms_init(void)
  {

  	proc_create("kallsyms", 0444, NULL, &kallsyms_proc_ops);

  	return 0;
  }

  device_initcall(kallsyms_init);