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kallsyms_on_each_symbol and module_kallsyms_on_each_symbol are only used by the livepatching code, so don't build them if livepatching is not enabled. Reviewed-by: Miroslav Benes <mbenes@suse.cz> Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jessica Yu <jeyu@kernel.org>
757 lines
19 KiB
C
757 lines
19 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* kallsyms.c: in-kernel printing of symbolic oopses and stack traces.
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*
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* Rewritten and vastly simplified by Rusty Russell for in-kernel
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* module loader:
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* Copyright 2002 Rusty Russell <rusty@rustcorp.com.au> IBM Corporation
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*
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* ChangeLog:
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*
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* (25/Aug/2004) Paulo Marques <pmarques@grupopie.com>
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* Changed the compression method from stem compression to "table lookup"
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* compression (see scripts/kallsyms.c for a more complete description)
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*/
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#include <linux/kallsyms.h>
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#include <linux/init.h>
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#include <linux/seq_file.h>
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#include <linux/fs.h>
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#include <linux/kdb.h>
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#include <linux/err.h>
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#include <linux/proc_fs.h>
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#include <linux/sched.h> /* for cond_resched */
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#include <linux/ctype.h>
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#include <linux/slab.h>
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#include <linux/filter.h>
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#include <linux/ftrace.h>
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#include <linux/kprobes.h>
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#include <linux/compiler.h>
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/*
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* These will be re-linked against their real values
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* during the second link stage.
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*/
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extern const unsigned long kallsyms_addresses[] __weak;
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extern const int kallsyms_offsets[] __weak;
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extern const u8 kallsyms_names[] __weak;
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/*
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* Tell the compiler that the count isn't in the small data section if the arch
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* has one (eg: FRV).
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*/
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extern const unsigned int kallsyms_num_syms
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__section(".rodata") __attribute__((weak));
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extern const unsigned long kallsyms_relative_base
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__section(".rodata") __attribute__((weak));
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extern const char kallsyms_token_table[] __weak;
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extern const u16 kallsyms_token_index[] __weak;
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extern const unsigned int kallsyms_markers[] __weak;
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/*
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* Expand a compressed symbol data into the resulting uncompressed string,
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* if uncompressed string is too long (>= maxlen), it will be truncated,
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* given the offset to where the symbol is in the compressed stream.
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*/
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static unsigned int kallsyms_expand_symbol(unsigned int off,
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char *result, size_t maxlen)
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{
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int len, skipped_first = 0;
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const char *tptr;
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const u8 *data;
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/* Get the compressed symbol length from the first symbol byte. */
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data = &kallsyms_names[off];
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len = *data;
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data++;
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/*
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* Update the offset to return the offset for the next symbol on
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* the compressed stream.
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*/
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off += len + 1;
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/*
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* For every byte on the compressed symbol data, copy the table
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* entry for that byte.
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*/
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while (len) {
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tptr = &kallsyms_token_table[kallsyms_token_index[*data]];
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data++;
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len--;
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while (*tptr) {
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if (skipped_first) {
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if (maxlen <= 1)
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goto tail;
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*result = *tptr;
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result++;
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maxlen--;
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} else
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skipped_first = 1;
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tptr++;
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}
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}
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tail:
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if (maxlen)
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*result = '\0';
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/* Return to offset to the next symbol. */
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return off;
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}
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/*
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* Get symbol type information. This is encoded as a single char at the
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* beginning of the symbol name.
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*/
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static char kallsyms_get_symbol_type(unsigned int off)
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{
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/*
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* Get just the first code, look it up in the token table,
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* and return the first char from this token.
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*/
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return kallsyms_token_table[kallsyms_token_index[kallsyms_names[off + 1]]];
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}
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/*
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* Find the offset on the compressed stream given and index in the
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* kallsyms array.
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*/
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static unsigned int get_symbol_offset(unsigned long pos)
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{
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const u8 *name;
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int i;
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/*
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* Use the closest marker we have. We have markers every 256 positions,
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* so that should be close enough.
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*/
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name = &kallsyms_names[kallsyms_markers[pos >> 8]];
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/*
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* Sequentially scan all the symbols up to the point we're searching
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* for. Every symbol is stored in a [<len>][<len> bytes of data] format,
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* so we just need to add the len to the current pointer for every
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* symbol we wish to skip.
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*/
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for (i = 0; i < (pos & 0xFF); i++)
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name = name + (*name) + 1;
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return name - kallsyms_names;
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}
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static unsigned long kallsyms_sym_address(int idx)
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{
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if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
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return kallsyms_addresses[idx];
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/* values are unsigned offsets if --absolute-percpu is not in effect */
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if (!IS_ENABLED(CONFIG_KALLSYMS_ABSOLUTE_PERCPU))
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return kallsyms_relative_base + (u32)kallsyms_offsets[idx];
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/* ...otherwise, positive offsets are absolute values */
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if (kallsyms_offsets[idx] >= 0)
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return kallsyms_offsets[idx];
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/* ...and negative offsets are relative to kallsyms_relative_base - 1 */
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return kallsyms_relative_base - 1 - kallsyms_offsets[idx];
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}
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/* Lookup the address for this symbol. Returns 0 if not found. */
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unsigned long kallsyms_lookup_name(const char *name)
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{
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char namebuf[KSYM_NAME_LEN];
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unsigned long i;
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unsigned int off;
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for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
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off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
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if (strcmp(namebuf, name) == 0)
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return kallsyms_sym_address(i);
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}
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return module_kallsyms_lookup_name(name);
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}
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#ifdef CONFIG_LIVEPATCH
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/*
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* Iterate over all symbols in vmlinux. For symbols from modules use
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* module_kallsyms_on_each_symbol instead.
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*/
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int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
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unsigned long),
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void *data)
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{
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char namebuf[KSYM_NAME_LEN];
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unsigned long i;
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unsigned int off;
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int ret;
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for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
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off = kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
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ret = fn(data, namebuf, NULL, kallsyms_sym_address(i));
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if (ret != 0)
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return ret;
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}
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return 0;
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}
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#endif /* CONFIG_LIVEPATCH */
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static unsigned long get_symbol_pos(unsigned long addr,
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unsigned long *symbolsize,
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unsigned long *offset)
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{
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unsigned long symbol_start = 0, symbol_end = 0;
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unsigned long i, low, high, mid;
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/* This kernel should never had been booted. */
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if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
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BUG_ON(!kallsyms_addresses);
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else
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BUG_ON(!kallsyms_offsets);
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/* Do a binary search on the sorted kallsyms_addresses array. */
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low = 0;
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high = kallsyms_num_syms;
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while (high - low > 1) {
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mid = low + (high - low) / 2;
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if (kallsyms_sym_address(mid) <= addr)
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low = mid;
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else
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high = mid;
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}
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/*
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* Search for the first aliased symbol. Aliased
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* symbols are symbols with the same address.
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*/
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while (low && kallsyms_sym_address(low-1) == kallsyms_sym_address(low))
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--low;
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symbol_start = kallsyms_sym_address(low);
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/* Search for next non-aliased symbol. */
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for (i = low + 1; i < kallsyms_num_syms; i++) {
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if (kallsyms_sym_address(i) > symbol_start) {
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symbol_end = kallsyms_sym_address(i);
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break;
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}
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}
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/* If we found no next symbol, we use the end of the section. */
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if (!symbol_end) {
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if (is_kernel_inittext(addr))
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symbol_end = (unsigned long)_einittext;
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else if (IS_ENABLED(CONFIG_KALLSYMS_ALL))
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symbol_end = (unsigned long)_end;
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else
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symbol_end = (unsigned long)_etext;
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}
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if (symbolsize)
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*symbolsize = symbol_end - symbol_start;
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if (offset)
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*offset = addr - symbol_start;
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return low;
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}
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/*
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* Lookup an address but don't bother to find any names.
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*/
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int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
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unsigned long *offset)
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{
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char namebuf[KSYM_NAME_LEN];
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if (is_ksym_addr(addr)) {
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get_symbol_pos(addr, symbolsize, offset);
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return 1;
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}
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return !!module_address_lookup(addr, symbolsize, offset, NULL, namebuf) ||
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!!__bpf_address_lookup(addr, symbolsize, offset, namebuf);
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}
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/*
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* Lookup an address
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* - modname is set to NULL if it's in the kernel.
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* - We guarantee that the returned name is valid until we reschedule even if.
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* It resides in a module.
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* - We also guarantee that modname will be valid until rescheduled.
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*/
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const char *kallsyms_lookup(unsigned long addr,
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unsigned long *symbolsize,
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unsigned long *offset,
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char **modname, char *namebuf)
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{
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const char *ret;
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namebuf[KSYM_NAME_LEN - 1] = 0;
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namebuf[0] = 0;
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if (is_ksym_addr(addr)) {
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unsigned long pos;
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pos = get_symbol_pos(addr, symbolsize, offset);
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/* Grab name */
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kallsyms_expand_symbol(get_symbol_offset(pos),
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namebuf, KSYM_NAME_LEN);
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if (modname)
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*modname = NULL;
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return namebuf;
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}
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/* See if it's in a module or a BPF JITed image. */
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ret = module_address_lookup(addr, symbolsize, offset,
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modname, namebuf);
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if (!ret)
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ret = bpf_address_lookup(addr, symbolsize,
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offset, modname, namebuf);
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if (!ret)
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ret = ftrace_mod_address_lookup(addr, symbolsize,
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offset, modname, namebuf);
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return ret;
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}
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int lookup_symbol_name(unsigned long addr, char *symname)
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{
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symname[0] = '\0';
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symname[KSYM_NAME_LEN - 1] = '\0';
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if (is_ksym_addr(addr)) {
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unsigned long pos;
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pos = get_symbol_pos(addr, NULL, NULL);
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/* Grab name */
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kallsyms_expand_symbol(get_symbol_offset(pos),
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symname, KSYM_NAME_LEN);
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return 0;
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}
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/* See if it's in a module. */
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return lookup_module_symbol_name(addr, symname);
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}
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int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
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unsigned long *offset, char *modname, char *name)
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{
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name[0] = '\0';
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name[KSYM_NAME_LEN - 1] = '\0';
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if (is_ksym_addr(addr)) {
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unsigned long pos;
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pos = get_symbol_pos(addr, size, offset);
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/* Grab name */
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kallsyms_expand_symbol(get_symbol_offset(pos),
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name, KSYM_NAME_LEN);
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modname[0] = '\0';
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return 0;
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}
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/* See if it's in a module. */
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return lookup_module_symbol_attrs(addr, size, offset, modname, name);
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}
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/* Look up a kernel symbol and return it in a text buffer. */
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static int __sprint_symbol(char *buffer, unsigned long address,
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int symbol_offset, int add_offset)
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{
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char *modname;
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const char *name;
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unsigned long offset, size;
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int len;
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address += symbol_offset;
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name = kallsyms_lookup(address, &size, &offset, &modname, buffer);
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if (!name)
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return sprintf(buffer, "0x%lx", address - symbol_offset);
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if (name != buffer)
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strcpy(buffer, name);
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len = strlen(buffer);
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offset -= symbol_offset;
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if (add_offset)
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len += sprintf(buffer + len, "+%#lx/%#lx", offset, size);
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if (modname)
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len += sprintf(buffer + len, " [%s]", modname);
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return len;
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}
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/**
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* sprint_symbol - Look up a kernel symbol and return it in a text buffer
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* @buffer: buffer to be stored
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* @address: address to lookup
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*
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* This function looks up a kernel symbol with @address and stores its name,
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* offset, size and module name to @buffer if possible. If no symbol was found,
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* just saves its @address as is.
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*
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* This function returns the number of bytes stored in @buffer.
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*/
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int sprint_symbol(char *buffer, unsigned long address)
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{
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return __sprint_symbol(buffer, address, 0, 1);
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}
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EXPORT_SYMBOL_GPL(sprint_symbol);
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/**
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* sprint_symbol_no_offset - Look up a kernel symbol and return it in a text buffer
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* @buffer: buffer to be stored
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* @address: address to lookup
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*
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* This function looks up a kernel symbol with @address and stores its name
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* and module name to @buffer if possible. If no symbol was found, just saves
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* its @address as is.
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*
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* This function returns the number of bytes stored in @buffer.
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*/
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int sprint_symbol_no_offset(char *buffer, unsigned long address)
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{
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return __sprint_symbol(buffer, address, 0, 0);
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}
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EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);
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/**
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* sprint_backtrace - Look up a backtrace symbol and return it in a text buffer
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* @buffer: buffer to be stored
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* @address: address to lookup
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*
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* This function is for stack backtrace and does the same thing as
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* sprint_symbol() but with modified/decreased @address. If there is a
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* tail-call to the function marked "noreturn", gcc optimized out code after
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* the call so that the stack-saved return address could point outside of the
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* caller. This function ensures that kallsyms will find the original caller
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* by decreasing @address.
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*
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* This function returns the number of bytes stored in @buffer.
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*/
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int sprint_backtrace(char *buffer, unsigned long address)
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{
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return __sprint_symbol(buffer, address, -1, 1);
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}
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/* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
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struct kallsym_iter {
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loff_t pos;
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loff_t pos_arch_end;
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loff_t pos_mod_end;
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loff_t pos_ftrace_mod_end;
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loff_t pos_bpf_end;
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unsigned long value;
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unsigned int nameoff; /* If iterating in core kernel symbols. */
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char type;
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char name[KSYM_NAME_LEN];
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char module_name[MODULE_NAME_LEN];
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int exported;
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int show_value;
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};
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int __weak arch_get_kallsym(unsigned int symnum, unsigned long *value,
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char *type, char *name)
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{
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return -EINVAL;
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}
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static int get_ksymbol_arch(struct kallsym_iter *iter)
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{
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int ret = arch_get_kallsym(iter->pos - kallsyms_num_syms,
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&iter->value, &iter->type,
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iter->name);
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if (ret < 0) {
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iter->pos_arch_end = iter->pos;
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return 0;
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}
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return 1;
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}
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static int get_ksymbol_mod(struct kallsym_iter *iter)
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{
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int ret = module_get_kallsym(iter->pos - iter->pos_arch_end,
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&iter->value, &iter->type,
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iter->name, iter->module_name,
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&iter->exported);
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if (ret < 0) {
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iter->pos_mod_end = iter->pos;
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return 0;
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}
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return 1;
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}
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/*
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* ftrace_mod_get_kallsym() may also get symbols for pages allocated for ftrace
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* purposes. In that case "__builtin__ftrace" is used as a module name, even
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* though "__builtin__ftrace" is not a module.
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*/
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static int get_ksymbol_ftrace_mod(struct kallsym_iter *iter)
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{
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int ret = ftrace_mod_get_kallsym(iter->pos - iter->pos_mod_end,
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&iter->value, &iter->type,
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iter->name, iter->module_name,
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&iter->exported);
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if (ret < 0) {
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iter->pos_ftrace_mod_end = iter->pos;
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return 0;
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}
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return 1;
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}
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static int get_ksymbol_bpf(struct kallsym_iter *iter)
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{
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int ret;
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strlcpy(iter->module_name, "bpf", MODULE_NAME_LEN);
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iter->exported = 0;
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ret = bpf_get_kallsym(iter->pos - iter->pos_ftrace_mod_end,
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&iter->value, &iter->type,
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iter->name);
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if (ret < 0) {
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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);
|