kallsyms: get rid of code for absolute kallsyms

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>

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

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;
 

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[];
 

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();

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();
 

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

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",