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kallsyms: get rid of code for absolute kallsyms

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Commit cf8e865810 ("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>
This commit is contained in:
Jann Horn 2024-02-21 21:26:53 +01:00 committed by Masahiro Yamada
parent 7efcb39e0d
commit 64e166099b
7 changed files with 32 additions and 77 deletions
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18
init/Kconfig
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@ -1789,24 +1789,6 @@ config KALLSYMS_ABSOLUTE_PERCPU
depends on KALLSYMS
default X86_64 && SMP
config KALLSYMS_BASE_RELATIVE
bool
depends on KALLSYMS
default y
help
Instead of emitting them as absolute values in the native word size,
emit the symbol references in the kallsyms table as 32-bit entries,
each containing a relative value in the range [base, base + U32_MAX]
or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
an absolute value in the range [0, S32_MAX] or a relative value in the
range [base, base + S32_MAX], where base is the lowest relative symbol
address encountered in the image.
On 64-bit builds, this reduces the size of the address table by 50%,
but more importantly, it results in entries whose values are build
time constants, and no relocation pass is required at runtime to fix
up the entries based on the runtime load address of the kernel.
# end of the "standard kernel features (expert users)" menu
config ARCH_HAS_MEMBARRIER_CALLBACKS

5
kernel/kallsyms.c
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@ -148,9 +148,6 @@ static unsigned int get_symbol_offset(unsigned long pos)
unsigned long kallsyms_sym_address(int idx)
{
if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
return kallsyms_addresses[idx];
/* values are unsigned offsets if --absolute-percpu is not in effect */
if (!IS_ENABLED(CONFIG_KALLSYMS_ABSOLUTE_PERCPU))
return kallsyms_relative_base + (u32)kallsyms_offsets[idx];
@ -325,7 +322,7 @@ static unsigned long get_symbol_pos(unsigned long addr,
unsigned long symbol_start = 0, symbol_end = 0;
unsigned long i, low, high, mid;
/* Do a binary search on the sorted kallsyms_addresses array. */
/* Do a binary search on the sorted kallsyms_offsets array. */
low = 0;
high = kallsyms_num_syms;

1
kernel/kallsyms_internal.h
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@ -4,7 +4,6 @@
#include <linux/types.h>
extern const unsigned long kallsyms_addresses[];
extern const int kallsyms_offsets[];
extern const u8 kallsyms_names[];

4
kernel/vmcore_info.c
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@ -216,12 +216,8 @@ static int __init crash_save_vmcoreinfo_init(void)
VMCOREINFO_SYMBOL(kallsyms_num_syms);
VMCOREINFO_SYMBOL(kallsyms_token_table);
VMCOREINFO_SYMBOL(kallsyms_token_index);
#ifdef CONFIG_KALLSYMS_BASE_RELATIVE
VMCOREINFO_SYMBOL(kallsyms_offsets);
VMCOREINFO_SYMBOL(kallsyms_relative_base);
#else
VMCOREINFO_SYMBOL(kallsyms_addresses);
#endif /* CONFIG_KALLSYMS_BASE_RELATIVE */
#endif /* CONFIG_KALLSYMS */
arch_crash_save_vmcoreinfo();

76
scripts/kallsyms.c
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@ -6,7 +6,7 @@
* of the GNU General Public License, incorporated herein by reference.
*
* Usage: kallsyms [--all-symbols] [--absolute-percpu]
* [--base-relative] [--lto-clang] in.map > out.S
* [--lto-clang] in.map > out.S
*
* Table compression uses all the unused char codes on the symbols and
* maps these to the most used substrings (tokens). For instance, it might
@ -63,7 +63,6 @@ static struct sym_entry **table;
static unsigned int table_size, table_cnt;
static int all_symbols;
static int absolute_percpu;
static int base_relative;
static int lto_clang;
static int token_profit[0x10000];
@ -76,7 +75,7 @@ static unsigned char best_table_len[256];
static void usage(void)
{
fprintf(stderr, "Usage: kallsyms [--all-symbols] [--absolute-percpu] "
"[--base-relative] [--lto-clang] in.map > out.S\n");
"[--lto-clang] in.map > out.S\n");
exit(1);
}
@ -491,54 +490,43 @@ static void write_src(void)
printf("\t.short\t%d\n", best_idx[i]);
printf("\n");
if (!base_relative)
output_label("kallsyms_addresses");
else
output_label("kallsyms_offsets");
output_label("kallsyms_offsets");
for (i = 0; i < table_cnt; i++) {
if (base_relative) {
/*
* Use the offset relative to the lowest value
* encountered of all relative symbols, and emit
* non-relocatable fixed offsets that will be fixed
* up at runtime.
*/
/*
* Use the offset relative to the lowest value
* encountered of all relative symbols, and emit
* non-relocatable fixed offsets that will be fixed
* up at runtime.
*/
long long offset;
int overflow;
long long offset;
int overflow;
if (!absolute_percpu) {
offset = table[i]->addr - relative_base;
overflow = (offset < 0 || offset > UINT_MAX);
} else if (symbol_absolute(table[i])) {
offset = table[i]->addr;
overflow = (offset < 0 || offset > INT_MAX);
} else {
offset = relative_base - table[i]->addr - 1;
overflow = (offset < INT_MIN || offset >= 0);
}
if (overflow) {
fprintf(stderr, "kallsyms failure: "
"%s symbol value %#llx out of range in relative mode\n",
symbol_absolute(table[i]) ? "absolute" : "relative",
table[i]->addr);
exit(EXIT_FAILURE);
}
printf("\t.long\t%#x /* %s */\n", (int)offset, table[i]->sym);
} else if (!symbol_absolute(table[i])) {
output_address(table[i]->addr);
if (!absolute_percpu) {
offset = table[i]->addr - relative_base;
overflow = (offset < 0 || offset > UINT_MAX);
} else if (symbol_absolute(table[i])) {
offset = table[i]->addr;
overflow = (offset < 0 || offset > INT_MAX);
} else {
printf("\tPTR\t%#llx\n", table[i]->addr);
offset = relative_base - table[i]->addr - 1;
overflow = (offset < INT_MIN || offset >= 0);
}
if (overflow) {
fprintf(stderr, "kallsyms failure: "
"%s symbol value %#llx out of range in relative mode\n",
symbol_absolute(table[i]) ? "absolute" : "relative",
table[i]->addr);
exit(EXIT_FAILURE);
}
printf("\t.long\t%#x /* %s */\n", (int)offset, table[i]->sym);
}
printf("\n");
if (base_relative) {
output_label("kallsyms_relative_base");
output_address(relative_base);
printf("\n");
}
output_label("kallsyms_relative_base");
output_address(relative_base);
printf("\n");
if (lto_clang)
for (i = 0; i < table_cnt; i++)
@ -820,7 +808,6 @@ int main(int argc, char **argv)
static const struct option long_options[] = {
{"all-symbols", no_argument, &all_symbols, 1},
{"absolute-percpu", no_argument, &absolute_percpu, 1},
{"base-relative", no_argument, &base_relative, 1},
{"lto-clang", no_argument, &lto_clang, 1},
{},
};
@ -841,8 +828,7 @@ int main(int argc, char **argv)
if (absolute_percpu)
make_percpus_absolute();
sort_symbols();
if (base_relative)
record_relative_base();
record_relative_base();
optimize_token_table();
write_src();

4
scripts/link-vmlinux.sh
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@ -156,10 +156,6 @@ kallsyms()
kallsymopt="${kallsymopt} --absolute-percpu"
fi
if is_enabled CONFIG_KALLSYMS_BASE_RELATIVE; then
kallsymopt="${kallsymopt} --base-relative"
fi
if is_enabled CONFIG_LTO_CLANG; then
kallsymopt="${kallsymopt} --lto-clang"
fi

1
tools/perf/tests/vmlinux-kallsyms.c
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@ -26,7 +26,6 @@ static bool is_ignored_symbol(const char *name, char type)
* when --all-symbols is specified so exclude them to get a
* stable symbol list.
*/
"kallsyms_addresses",
"kallsyms_offsets",
"kallsyms_relative_base",
"kallsyms_num_syms",