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2213e9a66b
Similar to how relative extables are implemented, it is possible to emit the kallsyms table in such a way that it contains offsets relative to some anchor point in the kernel image rather than absolute addresses. On 64-bit architectures, it cuts the size of the kallsyms address table in half, since offsets between kernel symbols can typically be expressed in 32 bits. This saves several hundreds of kilobytes of permanent .rodata on average. In addition, the kallsyms address table is no longer subject to dynamic relocation when CONFIG_RELOCATABLE is in effect, so the relocation work done after decompression now doesn't have to do relocation updates for all these values. This saves up to 24 bytes (i.e., the size of a ELF64 RELA relocation table entry) per value, which easily adds up to a couple of megabytes of uncompressed __init data on ppc64 or arm64. Even if these relocation entries typically compress well, the combined size reduction of 2.8 MB uncompressed for a ppc64_defconfig build (of which 2.4 MB is __init data) results in a ~500 KB space saving in the compressed image. Since it is useful for some architectures (like x86) to retain the ability to emit absolute values as well, this patch also adds support for capturing both absolute and relative values when KALLSYMS_ABSOLUTE_PERCPU is in effect, by emitting absolute per-cpu addresses as positive 32-bit values, and addresses relative to the lowest encountered relative symbol as negative values, which are subtracted from the runtime address of this base symbol to produce the actual address. Support for the above is enabled by default for all architectures except IA-64 and Tile-GX, whose symbols are too far apart to capture in this manner. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Tested-by: Guenter Roeck <linux@roeck-us.net> Reviewed-by: Kees Cook <keescook@chromium.org> Tested-by: Kees Cook <keescook@chromium.org> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Ingo Molnar <mingo@kernel.org> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Michal Marek <mmarek@suse.cz> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
633 lines
16 KiB
C
633 lines
16 KiB
C
/*
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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/module.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/mm.h>
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#include <linux/ctype.h>
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#include <linux/slab.h>
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#include <linux/compiler.h>
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#include <asm/sections.h>
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#ifdef CONFIG_KALLSYMS_ALL
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#define all_var 1
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#else
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#define all_var 0
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#endif
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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 long kallsyms_num_syms
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__attribute__((weak, section(".rodata")));
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extern const unsigned long kallsyms_relative_base
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__attribute__((weak, section(".rodata")));
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extern const u8 kallsyms_token_table[] __weak;
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extern const u16 kallsyms_token_index[] __weak;
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extern const unsigned long kallsyms_markers[] __weak;
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static inline int is_kernel_inittext(unsigned long addr)
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{
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if (addr >= (unsigned long)_sinittext
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&& addr <= (unsigned long)_einittext)
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return 1;
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return 0;
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}
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static inline int is_kernel_text(unsigned long addr)
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{
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if ((addr >= (unsigned long)_stext && addr <= (unsigned long)_etext) ||
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arch_is_kernel_text(addr))
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return 1;
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return in_gate_area_no_mm(addr);
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}
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static inline int is_kernel(unsigned long addr)
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{
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if (addr >= (unsigned long)_stext && addr <= (unsigned long)_end)
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return 1;
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return in_gate_area_no_mm(addr);
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}
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static int is_ksym_addr(unsigned long addr)
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{
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if (all_var)
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return is_kernel(addr);
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return is_kernel_text(addr) || is_kernel_inittext(addr);
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}
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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 u8 *tptr, *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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EXPORT_SYMBOL_GPL(kallsyms_lookup_name);
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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 module_kallsyms_on_each_symbol(fn, data);
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}
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EXPORT_SYMBOL_GPL(kallsyms_on_each_symbol);
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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 (all_var)
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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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return !!get_symbol_pos(addr, symbolsize, offset);
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return !!module_address_lookup(addr, symbolsize, offset, NULL, 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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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. */
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return module_address_lookup(addr, symbolsize, offset, modname,
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namebuf);
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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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/* Look up a kernel symbol and print it to the kernel messages. */
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void __print_symbol(const char *fmt, unsigned long address)
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{
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char buffer[KSYM_SYMBOL_LEN];
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sprint_symbol(buffer, address);
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printk(fmt, buffer);
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}
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EXPORT_SYMBOL(__print_symbol);
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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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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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};
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static int get_ksymbol_mod(struct kallsym_iter *iter)
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{
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if (module_get_kallsym(iter->pos - kallsyms_num_syms, &iter->value,
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&iter->type, iter->name, iter->module_name,
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&iter->exported) < 0)
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return 0;
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return 1;
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}
|
|
|
|
/* 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;
|
|
}
|
|
|
|
/* 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, "%pK %c %s\t[%s]\n", (void *)iter->value,
|
|
type, iter->name, iter->module_name);
|
|
} else
|
|
seq_printf(m, "%pK %c %s\n", (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;
|
|
iter = __seq_open_private(file, &kallsyms_op, sizeof(*iter));
|
|
if (!iter)
|
|
return -ENOMEM;
|
|
reset_iter(iter, 0);
|
|
|
|
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);
|