// 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/build_bug.h>

#include <linux/compiler.h>

#include <linux/module.h>

#include <linux/kernel.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];

}

static bool cleanup_symbol_name(char *s)

{

char *res;

if (!IS_ENABLED(CONFIG_LTO_CLANG))

return false;

/*

* LLVM appends various suffixes for local functions and variables that

* must be promoted to global scope as part of LTO. This can break

* hooking of static functions with kprobes. '.' is not a valid

* character in an identifier in C. Suffixes observed:

* - foo.llvm.[0-9a-f]+

* - foo.[0-9a-f]+

* - foo.[0-9a-f]+.cfi_jt

*/

res = strchr(s, '.');

if (res) {

*res = '\0';

return true;

}

if (!IS_ENABLED(CONFIG_CFI_CLANG) ||

!IS_ENABLED(CONFIG_LTO_CLANG_THIN) ||

CONFIG_CLANG_VERSION >= 130000)

return false;

/*

* Prior to LLVM 13, the following suffixes were observed when thinLTO

* and CFI are both enabled:

* - foo$[0-9]+

*/

res = strrchr(s, '$');

if (res) {

*res = '\0';

return true;

}

return false;

}

/* 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);

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

return kallsyms_sym_address(i);

}

return module_kallsyms_lookup_name(name);

}

#ifdef CONFIG_LIVEPATCH

/*

* Iterate over all symbols in vmlinux. For symbols from modules use

* module_kallsyms_on_each_symbol instead.

*/

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;

cond_resched();

}

return 0;

}

#endif /* CONFIG_LIVEPATCH */

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, NULL, namebuf) ||

!!__bpf_address_lookup(addr, symbolsize, offset, namebuf);

}

static const char *kallsyms_lookup_buildid(unsigned long addr,

unsigned long *symbolsize,

unsigned long *offset, char **modname,

const unsigned char **modbuildid, 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;

if (modbuildid)

*modbuildid = NULL;

ret = namebuf;

goto found;

}

/* See if it's in a module or a BPF JITed image. */

ret = module_address_lookup(addr, symbolsize, offset,

modname, modbuildid, namebuf);

if (!ret)

ret = bpf_address_lookup(addr, symbolsize,

offset, modname, namebuf);

if (!ret)

ret = ftrace_mod_address_lookup(addr, symbolsize,

offset, modname, namebuf);

found:

cleanup_symbol_name(namebuf);

return ret;

}

/*

* 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)

{

return kallsyms_lookup_buildid(addr, symbolsize, offset, modname,

NULL, namebuf);

}

int lookup_symbol_name(unsigned long addr, char *symname)

{

int res;

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);

goto found;

}

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

res = lookup_module_symbol_name(addr, symname);

if (res)

return res;

found:

cleanup_symbol_name(symname);

return 0;

}

int lookup_symbol_attrs(unsigned long addr, unsigned long *size,

unsigned long *offset, char *modname, char *name)

{

int res;

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';

goto found;

}

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

res = lookup_module_symbol_attrs(addr, size, offset, modname, name);

if (res)

return res;

found:

cleanup_symbol_name(name);

return 0;

}

/* 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, int add_buildid)

{

char *modname;

const unsigned char *buildid;

const char *name;

unsigned long offset, size;

int len;

address += symbol_offset;

name = kallsyms_lookup_buildid(address, &size, &offset, &modname, &buildid,

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);

#if IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID)

if (add_buildid && buildid) {

/* build ID should match length of sprintf */

#if IS_ENABLED(CONFIG_MODULES)

static_assert(sizeof(typeof_member(struct module, build_id)) == 20);

#endif

len += sprintf(buffer + len, " %20phN", buildid);

}

#endif

len += sprintf(buffer + len, "]");

}

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, 0);

}

EXPORT_SYMBOL_GPL(sprint_symbol);

/**

* sprint_symbol_build_id - 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, module name and module build ID 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_build_id(char *buffer, unsigned long address)

{

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

}

EXPORT_SYMBOL_GPL(sprint_symbol_build_id);

/**

* 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, 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, 0);

}

/**

* sprint_backtrace_build_id - 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 also appends the module build ID to

* the @buffer if @address is within a kernel module.

*

* This function returns the number of bytes stored in @buffer.

*/

int sprint_backtrace_build_id(char *buffer, unsigned long address)

{

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

}

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

struct kallsym_iter {

};

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]\n", value,

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

} else

seq_printf(m, "%px %c %s\n", 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);