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git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
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linux
kallsyms: get rid of code for absolute kallsyms
Commit cf8e8658100d ("arch: Remove Itanium (IA-64) architecture")
removed the last use of the absolute kallsyms.
Signed-off-by: Jann Horn <jannh@google.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/all/20240221202655.2423854-1-jannh@google.com/
[masahiroy@kernel.org: rebase the code and reword the commit description]
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
authored by
Jann Horn
and committed by
Masahiro Yamada
64e16609
7efcb39e
+32
-77
-18
init/Kconfig
-18
init/Kconfig
···
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depends on KALLSYMS
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default X86_64 && SMP
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config KALLSYMS_BASE_RELATIVE
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bool
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depends on KALLSYMS
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default y
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help
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Instead of emitting them as absolute values in the native word size,
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emit the symbol references in the kallsyms table as 32-bit entries,
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each containing a relative value in the range [base, base + U32_MAX]
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or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
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an absolute value in the range [0, S32_MAX] or a relative value in the
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range [base, base + S32_MAX], where base is the lowest relative symbol
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address encountered in the image.
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-
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On 64-bit builds, this reduces the size of the address table by 50%,
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but more importantly, it results in entries whose values are build
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time constants, and no relocation pass is required at runtime to fix
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up the entries based on the runtime load address of the kernel.
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-
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# end of the "standard kernel features (expert users)" menu
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config ARCH_HAS_MEMBARRIER_CALLBACKS
+1
-4
kernel/kallsyms.c
+1
-4
kernel/kallsyms.c
···
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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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-
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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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unsigned long symbol_start = 0, symbol_end = 0;
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unsigned long i, low, high, mid;
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-
/* Do a binary search on the sorted kallsyms_addresses array. */
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+
/* Do a binary search on the sorted kallsyms_offsets array. */
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low = 0;
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high = kallsyms_num_syms;
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-1
kernel/kallsyms_internal.h
-1
kernel/kallsyms_internal.h
-4
kernel/vmcore_info.c
-4
kernel/vmcore_info.c
···
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VMCOREINFO_SYMBOL(kallsyms_num_syms);
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VMCOREINFO_SYMBOL(kallsyms_token_table);
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VMCOREINFO_SYMBOL(kallsyms_token_index);
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-
#ifdef CONFIG_KALLSYMS_BASE_RELATIVE
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VMCOREINFO_SYMBOL(kallsyms_offsets);
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VMCOREINFO_SYMBOL(kallsyms_relative_base);
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#else
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VMCOREINFO_SYMBOL(kallsyms_addresses);
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#endif /* CONFIG_KALLSYMS_BASE_RELATIVE */
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#endif /* CONFIG_KALLSYMS */
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arch_crash_save_vmcoreinfo();
+31
-45
scripts/kallsyms.c
+31
-45
scripts/kallsyms.c
···
6
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* of the GNU General Public License, incorporated herein by reference.
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*
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* Usage: kallsyms [--all-symbols] [--absolute-percpu]
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-
* [--base-relative] [--lto-clang] in.map > out.S
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+
* [--lto-clang] in.map > out.S
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*
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* Table compression uses all the unused char codes on the symbols and
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* maps these to the most used substrings (tokens). For instance, it might
···
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static unsigned int table_size, table_cnt;
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static int all_symbols;
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static int absolute_percpu;
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static int base_relative;
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static int lto_clang;
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static int token_profit[0x10000];
···
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static void usage(void)
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{
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fprintf(stderr, "Usage: kallsyms [--all-symbols] [--absolute-percpu] "
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"[--base-relative] [--lto-clang] in.map > out.S\n");
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"[--lto-clang] in.map > out.S\n");
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exit(1);
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}
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···
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printf("\t.short\t%d\n", best_idx[i]);
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printf("\n");
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-
if (!base_relative)
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output_label("kallsyms_addresses");
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-
else
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-
output_label("kallsyms_offsets");
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+
output_label("kallsyms_offsets");
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for (i = 0; i < table_cnt; i++) {
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-
if (base_relative) {
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/*
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* Use the offset relative to the lowest value
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* encountered of all relative symbols, and emit
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* non-relocatable fixed offsets that will be fixed
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* up at runtime.
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*/
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+
/*
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* Use the offset relative to the lowest value
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+
* encountered of all relative symbols, and emit
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+
* non-relocatable fixed offsets that will be fixed
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+
* up at runtime.
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+
*/
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-
long long offset;
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int overflow;
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+
long long offset;
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+
int overflow;
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-
if (!absolute_percpu) {
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offset = table[i]->addr - relative_base;
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-
overflow = (offset < 0 || offset > UINT_MAX);
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-
} else if (symbol_absolute(table[i])) {
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-
offset = table[i]->addr;
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overflow = (offset < 0 || offset > INT_MAX);
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-
} else {
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offset = relative_base - table[i]->addr - 1;
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overflow = (offset < INT_MIN || offset >= 0);
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-
}
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if (overflow) {
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fprintf(stderr, "kallsyms failure: "
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"%s symbol value %#llx out of range in relative mode\n",
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symbol_absolute(table[i]) ? "absolute" : "relative",
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-
table[i]->addr);
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exit(EXIT_FAILURE);
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-
}
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printf("\t.long\t%#x /* %s */\n", (int)offset, table[i]->sym);
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-
} else if (!symbol_absolute(table[i])) {
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-
output_address(table[i]->addr);
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+
if (!absolute_percpu) {
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+
offset = table[i]->addr - relative_base;
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+
overflow = (offset < 0 || offset > UINT_MAX);
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+
} else if (symbol_absolute(table[i])) {
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+
offset = table[i]->addr;
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+
overflow = (offset < 0 || offset > INT_MAX);
530
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} else {
531
-
printf("\tPTR\t%#llx\n", table[i]->addr);
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+
offset = relative_base - table[i]->addr - 1;
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+
overflow = (offset < INT_MIN || offset >= 0);
532
516
}
517
+
if (overflow) {
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fprintf(stderr, "kallsyms failure: "
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+
"%s symbol value %#llx out of range in relative mode\n",
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symbol_absolute(table[i]) ? "absolute" : "relative",
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+
table[i]->addr);
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exit(EXIT_FAILURE);
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+
}
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printf("\t.long\t%#x /* %s */\n", (int)offset, table[i]->sym);
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}
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printf("\n");
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if (base_relative) {
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output_label("kallsyms_relative_base");
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output_address(relative_base);
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printf("\n");
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}
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+
output_label("kallsyms_relative_base");
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+
output_address(relative_base);
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+
printf("\n");
541
531
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if (lto_clang)
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for (i = 0; i < table_cnt; i++)
···
808
820
static const struct option long_options[] = {
809
821
{"all-symbols", no_argument, &all_symbols, 1},
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822
{"absolute-percpu", no_argument, &absolute_percpu, 1},
811
-
{"base-relative", no_argument, &base_relative, 1},
812
823
{"lto-clang", no_argument, <o_clang, 1},
813
824
{},
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};
···
828
841
if (absolute_percpu)
829
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make_percpus_absolute();
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sort_symbols();
831
-
if (base_relative)
832
-
record_relative_base();
844
+
record_relative_base();
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845
optimize_token_table();
834
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write_src();
835
847
-4
scripts/link-vmlinux.sh
-4
scripts/link-vmlinux.sh