[PATCH v4 16/16] kallsyms: Remove KALLSYMS_ABSOLUTE_PERCPU

Brian Gerst
2024-03-22T16:53:08Z

x86-64 was the only user.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
---
init/Kconfig | 11 +-----
kernel/kallsyms.c | 12 ++-----
scripts/kallsyms.c | 80 ++++++++---------------------------------
scripts/link-vmlinux.sh | 4 ---
4 files changed, 18 insertions(+), 89 deletions(-)

diff --git a/init/Kconfig b/init/Kconfig
index 0f928f82dc7a..0622599ce503 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1781,11 +1781,6 @@ config KALLSYMS_ALL

Say N unless you really need all symbols, or kernel live patching.

-config KALLSYMS_ABSOLUTE_PERCPU
- bool
- depends on KALLSYMS
- default n
-
config KALLSYMS_BASE_RELATIVE
bool
depends on KALLSYMS
@@ -1793,11 +1788,7 @@ config KALLSYMS_BASE_RELATIVE
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.
+ each containing a relative value in the range [base, base + U32_MAX].

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
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 18edd57b5fe8..f4e8e531052a 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -151,16 +151,8 @@ 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];
-
- /* ...otherwise, positive offsets are absolute values */
- if (kallsyms_offsets[idx] >= 0)
- return kallsyms_offsets[idx];
-
- /* ...and negative offsets are relative to kallsyms_relative_base - 1 */
- return kallsyms_relative_base - 1 - kallsyms_offsets[idx];
+ /* values are unsigned offsets */
+ return kallsyms_relative_base + (u32)kallsyms_offsets[idx];
}

static void cleanup_symbol_name(char *s)
diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
index 653b92f6d4c8..501f978abf4b 100644
--- a/scripts/kallsyms.c
+++ b/scripts/kallsyms.c
@@ -5,8 +5,8 @@
* This software may be used and distributed according to the terms
* of the GNU General Public License, incorporated herein by reference.
*
- * Usage: kallsyms [--all-symbols] [--absolute-percpu]
- * [--base-relative] [--lto-clang] in.map > out.S
+ * Usage: kallsyms [--all-symbols] [--base-relative] [--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
@@ -37,7 +37,6 @@ struct sym_entry {
unsigned int len;
unsigned int seq;
unsigned int start_pos;
- unsigned int percpu_absolute;
unsigned char sym[];
};

@@ -55,14 +54,9 @@ static struct addr_range text_ranges[] = {
#define text_range_text (&text_ranges[0])
#define text_range_inittext (&text_ranges[1])

-static struct addr_range percpu_range = {
- "__per_cpu_start", "__per_cpu_end", -1ULL, 0
-};
-
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;

@@ -75,7 +69,7 @@ static unsigned char best_table_len[256];

static void usage(void)
{
- fprintf(stderr, "Usage: kallsyms [--all-symbols] [--absolute-percpu] "
+ fprintf(stderr, "Usage: kallsyms [--all-symbols] "
"[--base-relative] [--lto-clang] in.map > out.S\n");
exit(1);
}
@@ -167,7 +161,6 @@ static struct sym_entry *read_symbol(FILE *in, char **buf, size_t *buf_len)
return NULL;

check_symbol_range(name, addr, text_ranges, ARRAY_SIZE(text_ranges));
- check_symbol_range(name, addr, &percpu_range, 1);

/* include the type field in the symbol name, so that it gets
* compressed together */
@@ -183,7 +176,6 @@ static struct sym_entry *read_symbol(FILE *in, char **buf, size_t *buf_len)
sym->len = len;
sym->sym[0] = type;
strcpy(sym_name(sym), name);
- sym->percpu_absolute = 0;

return sym;
}
@@ -334,11 +326,6 @@ static int expand_symbol(const unsigned char *data, int len, char *result)
return total;
}

-static int symbol_absolute(const struct sym_entry *s)
-{
- return s->percpu_absolute;
-}
-
static void cleanup_symbol_name(char *s)
{
char *p;
@@ -499,30 +486,17 @@ static void write_src(void)
*/

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) {
+
+ offset = table[i]->addr - relative_base;
+ if (offset < 0 || offset > UINT_MAX) {
fprintf(stderr, "kallsyms failure: "
- "%s symbol value %#llx out of range in relative mode\n",
- symbol_absolute(table[i]) ? "absolute" : "relative",
+ "symbol value %#llx out of range in relative mode\n",
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);
} else {
- printf("\tPTR\t%#llx\n", table[i]->addr);
+ output_address(table[i]->addr);
}
}
printf("\n");
@@ -775,36 +749,15 @@ static void sort_symbols(void)
qsort(table, table_cnt, sizeof(table[0]), compare_symbols);
}

-static void make_percpus_absolute(void)
-{
- unsigned int i;
-
- for (i = 0; i < table_cnt; i++)
- if (symbol_in_range(table[i], &percpu_range, 1)) {
- /*
- * Keep the 'A' override for percpu symbols to
- * ensure consistent behavior compared to older
- * versions of this tool.
- */
- table[i]->sym[0] = 'A';
- table[i]->percpu_absolute = 1;
- }
-}
-
-/* find the minimum non-absolute symbol address */
+/* find the minimum symbol address */
static void record_relative_base(void)
{
- unsigned int i;
-
- for (i = 0; i < table_cnt; i++)
- if (!symbol_absolute(table[i])) {
- /*
- * The table is sorted by address.
- * Take the first non-absolute symbol value.
- */
- relative_base = table[i]->addr;
- return;
- }
+ /*
+ * The table is sorted by address.
+ * Take the first symbol value.
+ */
+ if (table_cnt)
+ relative_base = table[0]->addr;
}

int main(int argc, char **argv)
@@ -812,7 +765,6 @@ int main(int argc, char **argv)
while (1) {
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},
{},
@@ -831,8 +783,6 @@ int main(int argc, char **argv)

read_map(argv[optind]);
shrink_table();
- if (absolute_percpu)
- make_percpus_absolute();
sort_symbols();
if (base_relative)
record_relative_base();
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index 7862a8101747..7b0596cd5a80 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -153,10 +153,6 @@ kallsyms()
kallsymopt="${kallsymopt} --all-symbols"
fi

- if is_enabled CONFIG_KALLSYMS_ABSOLUTE_PERCPU; then
- kallsymopt="${kallsymopt} --absolute-percpu"
- fi
-
if is_enabled CONFIG_KALLSYMS_BASE_RELATIVE; then
kallsymopt="${kallsymopt} --base-relative"
fi
--
2.44.0