[PATCH] kallsyms: get rid of code for absolute kallsyms

From: Masahiro Yamada
Date: Tue Jul 16 2024 - 04:50:00 EST

From: Jann Horn <jannh@xxxxxxxxxx>

Commit cf8e8658100d ("arch: Remove Itanium (IA-64) architecture")
removed the last use of the absolute kallsyms.

Signed-off-by: Jann Horn <jannh@xxxxxxxxxx>
Acked-by: Arnd Bergmann <arnd@xxxxxxxx>
Link: https://lore.kernel.org/all/20240221202655.2423854-1-jannh@xxxxxxxxxx/
[masahiroy@xxxxxxxxxx: rebase the code and reword the commit description]
Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
---

init/Kconfig | 18 -------
kernel/kallsyms.c | 5 +-
kernel/kallsyms_internal.h | 1 -
kernel/vmcore_info.c | 4 --
scripts/kallsyms.c | 76 ++++++++++++-----------------
scripts/link-vmlinux.sh | 4 --
tools/perf/tests/vmlinux-kallsyms.c | 1 -
7 files changed, 32 insertions(+), 77 deletions(-)

diff --git a/init/Kconfig b/init/Kconfig
index febdea2afc3b..8e21ce38dee6 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -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
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 98b9622d372e..fb2c77368d18 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -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;

diff --git a/kernel/kallsyms_internal.h b/kernel/kallsyms_internal.h
index 925f2ab22639..9633782f8250 100644
--- a/kernel/kallsyms_internal.h
+++ b/kernel/kallsyms_internal.h
@@ -4,7 +4,6 @@

#include <linux/types.h>

-extern const unsigned long kallsyms_addresses[];
extern const int kallsyms_offsets[];
extern const u8 kallsyms_names[];

diff --git a/kernel/vmcore_info.c b/kernel/vmcore_info.c
index 1d5eadd9dd61..8b4f8cc2e0ec 100644
--- a/kernel/vmcore_info.c
+++ b/kernel/vmcore_info.c
@@ -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();
diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
index fa53b5eef553..55a423519f2e 100644
--- a/scripts/kallsyms.c
+++ b/scripts/kallsyms.c
@@ -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();

diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index c64158a04f82..f7b2503cdba9 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -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
diff --git a/tools/perf/tests/vmlinux-kallsyms.c b/tools/perf/tests/vmlinux-kallsyms.c
index e30fd55f8e51..cd3b480d20bd 100644
--- a/tools/perf/tests/vmlinux-kallsyms.c
+++ b/tools/perf/tests/vmlinux-kallsyms.c
@@ -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",
--
2.43.0