kernel/kallsyms.c - kernel/msm-4.9 - Gitiles

 /*
  * 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/module.h>
 #include <linux/init.h>
 #include <linux/seq_file.h>
 #include <linux/fs.h>
 #include <linux/err.h>
 #include <linux/proc_fs.h>
 #include <linux/sched.h>	/* for cond_resched */
 #include <linux/mm.h>
 #include <linux/ctype.h>

 #include <asm/sections.h>

 #ifdef CONFIG_KALLSYMS_ALL
 #define all_var 1
 #else
 #define all_var 0
 #endif

 /*
  * These will be re-linked against their real values
  * during the second link stage.
  */
 extern const unsigned long kallsyms_addresses[] __attribute__((weak));
 extern const u8 kallsyms_names[] __attribute__((weak));

 /*
  * Tell the compiler that the count isn't in the small data section if the arch
  * has one (eg: FRV).
  */
 extern const unsigned long kallsyms_num_syms
 __attribute__((weak, section(".rodata")));

 extern const u8 kallsyms_token_table[] __attribute__((weak));
 extern const u16 kallsyms_token_index[] __attribute__((weak));

 extern const unsigned long kallsyms_markers[] __attribute__((weak));

 static inline int is_kernel_inittext(unsigned long addr)
 {
 	if (addr >= (unsigned long)_sinittext
 	    && addr <= (unsigned long)_einittext)
 		return 1;
 	return 0;
 }

 static inline int is_kernel_text(unsigned long addr)
 {
 	if (addr >= (unsigned long)_stext && addr <= (unsigned long)_etext)
 		return 1;
 	return in_gate_area_no_task(addr);
 }

 static inline int is_kernel(unsigned long addr)
 {
 	if (addr >= (unsigned long)_stext && addr <= (unsigned long)_end)
 		return 1;
 	return in_gate_area_no_task(addr);
 }

 static int is_ksym_addr(unsigned long addr)
 {
 	if (all_var)
 		return is_kernel(addr);

 	return is_kernel_text(addr) || is_kernel_inittext(addr);
 }

 /*
  * Expand a compressed symbol data into the resulting uncompressed string,
  * given the offset to where the symbol is in the compressed stream.
  */
 static unsigned int kallsyms_expand_symbol(unsigned int off, char *result)
 {
 	int len, skipped_first = 0;
 	const u8 *tptr, *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) {
 				*result = *tptr;
 				result++;
 			} else
 				skipped_first = 1;
 			tptr++;
 		}
 	}

 	*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;
 }

 /* 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);

 		if (strcmp(namebuf, name) == 0)
 			return kallsyms_addresses[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);
 		ret = fn(data, namebuf, NULL, kallsyms_addresses[i]);
 		if (ret != 0)
 			return ret;
 	}
 	return module_kallsyms_on_each_symbol(fn, data);
 }
 EXPORT_SYMBOL_GPL(kallsyms_on_each_symbol);

 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. */
 	BUG_ON(!kallsyms_addresses);

 	/* 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_addresses[mid] <= addr)
 			low = mid;
 		else
 			high = mid;
 	}

 	/*
 	 * Search for the first aliased symbol. Aliased
 	 * symbols are symbols with the same address.
 	 */
 	while (low && kallsyms_addresses[low-1] == kallsyms_addresses[low])
 		--low;

 	symbol_start = kallsyms_addresses[low];

 	/* Search for next non-aliased symbol. */
 	for (i = low + 1; i < kallsyms_num_syms; i++) {
 		if (kallsyms_addresses[i] > symbol_start) {
 			symbol_end = kallsyms_addresses[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 (all_var)
 			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))
 		return !!get_symbol_pos(addr, symbolsize, offset);

 	return !!module_address_lookup(addr, symbolsize, offset, NULL, 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)
 {
 	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);
 		if (modname)
 			*modname = NULL;
 		return namebuf;
 	}

 	/* See if it's in a module. */
 	return module_address_lookup(addr, symbolsize, offset, modname,
 				     namebuf);
 }

 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);
 		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);
 		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. */
 int sprint_symbol(char *buffer, unsigned long address)
 {
 	char *modname;
 	const char *name;
 	unsigned long offset, size;
 	int len;

 	name = kallsyms_lookup(address, &size, &offset, &modname, buffer);
 	if (!name)
 		return sprintf(buffer, "0x%lx", address);

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

 	if (modname)
 		len += sprintf(buffer, "+%#lx/%#lx [%s]",
 						offset, size, modname);
 	else
 		len += sprintf(buffer, "+%#lx/%#lx", offset, size);

 	return len;
 }
 EXPORT_SYMBOL_GPL(sprint_symbol);

 /* Look up a kernel symbol and print it to the kernel messages. */
 void __print_symbol(const char *fmt, unsigned long address)
 {
 	char buffer[KSYM_SYMBOL_LEN];

 	sprint_symbol(buffer, address);

 	printk(fmt, buffer);
 }
 EXPORT_SYMBOL(__print_symbol);

 /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
 struct kallsym_iter {
 	loff_t pos;
 	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;
 };

 static int get_ksymbol_mod(struct kallsym_iter *iter)
 {
 	if (module_get_kallsym(iter->pos - kallsyms_num_syms, &iter->value,
 				&iter->type, iter->name, iter->module_name,
 				&iter->exported) < 0)
 		return 0;
 	return 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_addresses[iter->pos];

 	iter->type = kallsyms_get_symbol_type(off);

 	off = kallsyms_expand_symbol(off, 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;
 }

 /* 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) {
 		iter->pos = pos;
 		return get_ksymbol_mod(iter);
 	}

 	/* 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)
 {
 	struct kallsym_iter *iter = m->private;

 	/* Some debugging symbols have no name.  Ignore them. */
 	if (!iter->name[0])
 		return 0;

 	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, "%0*lx %c %s\t[%s]\n",
 			   (int)(2 * sizeof(void *)),
 			   iter->value, type, iter->name, iter->module_name);
 	} else
 		seq_printf(m, "%0*lx %c %s\n",
 			   (int)(2 * sizeof(void *)),
 			   iter->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 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;
 	int ret;

 	iter = kmalloc(sizeof(*iter), GFP_KERNEL);
 	if (!iter)
 		return -ENOMEM;
 	reset_iter(iter, 0);

 	ret = seq_open(file, &kallsyms_op);
 	if (ret == 0)
 		((struct seq_file *)file->private_data)->private = iter;
 	else
 		kfree(iter);
 	return ret;
 }

 static const struct file_operations kallsyms_operations = {
 	.open = kallsyms_open,
 	.read = seq_read,
 	.llseek = seq_lseek,
 	.release = seq_release_private,
 };

 static int __init kallsyms_init(void)
 {
 	proc_create("kallsyms", 0444, NULL, &kallsyms_operations);
 	return 0;
 }
 device_initcall(kallsyms_init);
	/*
	* 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/module.h>
	#include <linux/init.h>
	#include <linux/seq_file.h>
	#include <linux/fs.h>
	#include <linux/err.h>
	#include <linux/proc_fs.h>
	#include <linux/sched.h> /* for cond_resched */
	#include <linux/mm.h>
	#include <linux/ctype.h>

	#include <asm/sections.h>

	#ifdef CONFIG_KALLSYMS_ALL
	#define all_var 1
	#else
	#define all_var 0
	#endif

	/*
	* These will be re-linked against their real values
	* during the second link stage.
	*/
	extern const unsigned long kallsyms_addresses[] __attribute__((weak));
	extern const u8 kallsyms_names[] __attribute__((weak));

	/*
	* Tell the compiler that the count isn't in the small data section if the arch
	* has one (eg: FRV).
	*/
	extern const unsigned long kallsyms_num_syms
	__attribute__((weak, section(".rodata")));

	extern const u8 kallsyms_token_table[] __attribute__((weak));
	extern const u16 kallsyms_token_index[] __attribute__((weak));

	extern const unsigned long kallsyms_markers[] __attribute__((weak));

	static inline int is_kernel_inittext(unsigned long addr)
	{
	if (addr >= (unsigned long)_sinittext
	&& addr <= (unsigned long)_einittext)
	return 1;
	return 0;
	}

	static inline int is_kernel_text(unsigned long addr)
	{
	if (addr >= (unsigned long)_stext && addr <= (unsigned long)_etext)
	return 1;
	return in_gate_area_no_task(addr);
	}

	static inline int is_kernel(unsigned long addr)
	{
	if (addr >= (unsigned long)_stext && addr <= (unsigned long)_end)
	return 1;
	return in_gate_area_no_task(addr);
	}

	static int is_ksym_addr(unsigned long addr)
	{
	if (all_var)
	return is_kernel(addr);

	return is_kernel_text(addr) \|\| is_kernel_inittext(addr);
	}

	/*
	* Expand a compressed symbol data into the resulting uncompressed string,
	* given the offset to where the symbol is in the compressed stream.
	*/
	static unsigned int kallsyms_expand_symbol(unsigned int off, char *result)
	{
	int len, skipped_first = 0;
	const u8 tptr, 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) {
	result = tptr;
	result++;
	} else
	skipped_first = 1;
	tptr++;
	}
	}

	*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;
	}

	/* 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);

	if (strcmp(namebuf, name) == 0)
	return kallsyms_addresses[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);
	ret = fn(data, namebuf, NULL, kallsyms_addresses[i]);
	if (ret != 0)
	return ret;
	}
	return module_kallsyms_on_each_symbol(fn, data);
	}
	EXPORT_SYMBOL_GPL(kallsyms_on_each_symbol);

	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. */
	BUG_ON(!kallsyms_addresses);

	/* 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_addresses[mid] <= addr)
	low = mid;
	else
	high = mid;
	}

	/*
	* Search for the first aliased symbol. Aliased
	* symbols are symbols with the same address.
	*/
	while (low && kallsyms_addresses[low-1] == kallsyms_addresses[low])
	--low;

	symbol_start = kallsyms_addresses[low];

	/* Search for next non-aliased symbol. */
	for (i = low + 1; i < kallsyms_num_syms; i++) {
	if (kallsyms_addresses[i] > symbol_start) {
	symbol_end = kallsyms_addresses[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 (all_var)
	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))
	return !!get_symbol_pos(addr, symbolsize, offset);

	return !!module_address_lookup(addr, symbolsize, offset, NULL, 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)
	{
	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);
	if (modname)
	*modname = NULL;
	return namebuf;
	}

	/* See if it's in a module. */
	return module_address_lookup(addr, symbolsize, offset, modname,
	namebuf);
	}

	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);
	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);
	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. */
	int sprint_symbol(char *buffer, unsigned long address)
	{
	char *modname;
	const char *name;
	unsigned long offset, size;
	int len;

	name = kallsyms_lookup(address, &size, &offset, &modname, buffer);
	if (!name)
	return sprintf(buffer, "0x%lx", address);

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

	if (modname)
	len += sprintf(buffer, "+%#lx/%#lx [%s]",
	offset, size, modname);
	else
	len += sprintf(buffer, "+%#lx/%#lx", offset, size);

	return len;
	}
	EXPORT_SYMBOL_GPL(sprint_symbol);

	/* Look up a kernel symbol and print it to the kernel messages. */
	void __print_symbol(const char *fmt, unsigned long address)
	{
	char buffer[KSYM_SYMBOL_LEN];

	sprint_symbol(buffer, address);

	printk(fmt, buffer);
	}
	EXPORT_SYMBOL(__print_symbol);

	/* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
	struct kallsym_iter {
	loff_t pos;
	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;
	};

	static int get_ksymbol_mod(struct kallsym_iter *iter)
	{
	if (module_get_kallsym(iter->pos - kallsyms_num_syms, &iter->value,
	&iter->type, iter->name, iter->module_name,
	&iter->exported) < 0)
	return 0;
	return 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_addresses[iter->pos];

	iter->type = kallsyms_get_symbol_type(off);

	off = kallsyms_expand_symbol(off, 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;
	}

	/* 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) {
	iter->pos = pos;
	return get_ksymbol_mod(iter);
	}

	/* 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)
	{
	struct kallsym_iter *iter = m->private;

	/* Some debugging symbols have no name. Ignore them. */
	if (!iter->name[0])
	return 0;

	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, "%0*lx %c %s\t[%s]\n",
	(int)(2 * sizeof(void *)),
	iter->value, type, iter->name, iter->module_name);
	} else
	seq_printf(m, "%0*lx %c %s\n",
	(int)(2 * sizeof(void *)),
	iter->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 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;
	int ret;

	iter = kmalloc(sizeof(*iter), GFP_KERNEL);
	if (!iter)
	return -ENOMEM;
	reset_iter(iter, 0);

	ret = seq_open(file, &kallsyms_op);
	if (ret == 0)
	((struct seq_file *)file->private_data)->private = iter;
	else
	kfree(iter);
	return ret;
	}

	static const struct file_operations kallsyms_operations = {
	.open = kallsyms_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = seq_release_private,
	};

	static int __init kallsyms_init(void)
	{
	proc_create("kallsyms", 0444, NULL, &kallsyms_operations);
	return 0;
	}
	device_initcall(kallsyms_init);