| // 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/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 |
| __attribute__((weak, section(".rodata"))); |
| |
| extern const unsigned long kallsyms_relative_base |
| __attribute__((weak, section(".rodata"))); |
| |
| extern const u8 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 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) { |
| 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); |
| } |
| EXPORT_SYMBOL_GPL(kallsyms_lookup_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); |
| } |
| 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. */ |
| 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; |
| 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; |
| } |
| |
| 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) |
| { |
| strlcpy(iter->module_name, "bpf", MODULE_NAME_LEN); |
| iter->exported = 0; |
| return bpf_get_kallsym(iter->pos - iter->pos_ftrace_mod_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; |
| } |
| } |
| |
| /* |
| * 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; |
| |
| return get_ksymbol_bpf(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 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); |