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Message-Id: <20211130205549.116673-6-brgerst@gmail.com>
Date: Tue, 30 Nov 2021 15:55:48 -0500
From: Brian Gerst <brgerst@...il.com>
To: linux-kernel@...r.kernel.org, x86@...nel.org
Cc: Andy Lutomirski <luto@...nel.org>, Borislav Petkov <bp@...en8.de>,
Thomas Gleixner <tglx@...utronix.de>,
"H . Peter Anvin" <hpa@...or.com>,
Peter Zijlstra <peterz@...radead.org>,
Brian Gerst <brgerst@...il.com>
Subject: [PATCH v2 5/6] kallsyms: Remove KALLSYMS_ABSOLUTE_PERCPU
x86-64 was the only user.
Signed-off-by: Brian Gerst <brgerst@...il.com>
---
init/Kconfig | 10 +-----
kernel/kallsyms.c | 12 ++------
scripts/kallsyms.c | 68 ++++++-----------------------------------
scripts/link-vmlinux.sh | 4 ---
4 files changed, 12 insertions(+), 82 deletions(-)
diff --git a/init/Kconfig b/init/Kconfig
index 943552dc9c19..981621f658a9 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1711,10 +1711,6 @@ config KALLSYMS_ALL
Say N unless you really need all symbols.
-config KALLSYMS_ABSOLUTE_PERCPU
- bool
- depends on KALLSYMS
-
config KALLSYMS_BASE_RELATIVE
bool
depends on KALLSYMS
@@ -1722,11 +1718,7 @@ 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 3011bc33a5ba..bea1cfc5cacd 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -152,16 +152,8 @@ static 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 bool cleanup_symbol_name(char *s)
diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
index 54ad86d13784..f6419efc2c54 100644
--- a/scripts/kallsyms.c
+++ b/scripts/kallsyms.c
@@ -33,7 +33,6 @@ struct sym_entry {
unsigned long long addr;
unsigned int len;
unsigned int start_pos;
- unsigned int percpu_absolute;
unsigned char sym[];
};
@@ -51,14 +50,9 @@ 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 token_profit[0x10000];
@@ -224,7 +218,6 @@ static struct sym_entry *read_symbol(FILE *in)
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 */
@@ -241,7 +234,6 @@ static struct sym_entry *read_symbol(FILE *in)
sym->len = len;
sym->sym[0] = type;
strcpy(sym_name(sym), name);
- sym->percpu_absolute = 0;
return sym;
}
@@ -379,11 +371,6 @@ 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 write_src(void)
{
unsigned int i, k, off;
@@ -419,28 +406,17 @@ 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);
- }
+ offset = table[i]->addr - relative_base;
+ overflow = (offset < 0 || offset > UINT_MAX);
if (overflow) {
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\n", (int)offset);
- } 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");
@@ -730,36 +706,14 @@ 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 */
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.
+ */
+ relative_base = table[0]->addr;
}
int main(int argc, char **argv)
@@ -769,8 +723,6 @@ int main(int argc, char **argv)
for (i = 1; i < argc; i++) {
if(strcmp(argv[i], "--all-symbols") == 0)
all_symbols = 1;
- else if (strcmp(argv[i], "--absolute-percpu") == 0)
- absolute_percpu = 1;
else if (strcmp(argv[i], "--base-relative") == 0)
base_relative = 1;
else
@@ -781,8 +733,6 @@ int main(int argc, char **argv)
read_map(stdin);
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 5cdd9bc5c385..797b177cc181 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -243,10 +243,6 @@ kallsyms()
kallsymopt="${kallsymopt} --all-symbols"
fi
- if [ -n "${CONFIG_KALLSYMS_ABSOLUTE_PERCPU}" ]; then
- kallsymopt="${kallsymopt} --absolute-percpu"
- fi
-
if [ -n "${CONFIG_KALLSYMS_BASE_RELATIVE}" ]; then
kallsymopt="${kallsymopt} --base-relative"
fi
--
2.31.1
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