Merge pull request torvalds#221 from andreas-abel/kallsyms_rodata

lkl: Add a config option to select section for kallsyms

arch/lkl/defconfig

@@ -1,6 +1,7 @@
 # CONFIG_LOCALVERSION_AUTO is not set
 CONFIG_NO_HZ_IDLE=y
 # CONFIG_SYSFS_SYSCALL is not set
+CONFIG_KALLSYMS_USE_DATA_SECTION=y
 CONFIG_KALLSYMS_ALL=y
 # CONFIG_BASE_FULL is not set
 # CONFIG_FUTEX is not set

init/Kconfig

@@ -1443,6 +1443,18 @@ config KALLSYMS_BASE_RELATIVE
 	  time constants, and no relocation pass is required at runtime to fix
 	  up the entries based on the runtime load address of the kernel.
 
+config KALLSYMS_USE_DATA_SECTION
+	bool "Use .data instead of .rodata section for kallsyms"
+	depends on KALLSYMS
+	default n
+	help
+	  Enabling this option will put the kallsyms data in the .data section
+	  instead of the .rodata section.
+
+	  This is useful when building the kernel as a library, as it avoids
+	  relocations in the text segment that could otherwise occur if the
+	  .rodata section is in the same segment as the .text section.
+
 config PRINTK
 	default y
 	bool "Enable support for printk" if EXPERT

scripts/kallsyms.c

@@ -60,11 +60,12 @@ static struct addr_range percpu_range = {
 
 static struct sym_entry *table;
 static unsigned int table_size, table_cnt;
-static int all_symbols = 0;
-static int absolute_percpu = 0;
+static int all_symbols;
+static int use_data_section;
+static int absolute_percpu;
 static char symbol_prefix_char = '\0';
-static unsigned long long kernel_start_addr = 0;
-static int base_relative = 0;
+static unsigned long long kernel_start_addr;
+static int base_relative;
 
 int token_profit[0x10000];
 
@@ -76,6 +77,7 @@ unsigned char best_table_len[256];
 static void usage(void)
 {
 	fprintf(stderr, "Usage: kallsyms [--all-symbols] "
+			"[--use-data-section] "
 			"[--symbol-prefix=<prefix char>] "
 			"[--page-offset=<CONFIG_PAGE_OFFSET>] "
 			"[--base-relative] < in.map > out.S\n");
@@ -352,7 +354,10 @@ static void write_src(void)
 	printf("#define ALGN .align 4\n");
 	printf("#endif\n");
 
-	printf("\t.section .rodata, \"a\"\n");
+	if (use_data_section)
+		printf("\t.section .data\n");
+	else
+		printf("\t.section .rodata, \"a\"\n");
 
 	/* Provide proper symbols relocatability by their relativeness
 	 * to a fixed anchor point in the runtime image, either '_text'
@@ -759,6 +764,8 @@ int main(int argc, char **argv)
 				all_symbols = 1;
 			else if (strcmp(argv[i], "--absolute-percpu") == 0)
 				absolute_percpu = 1;
+			else if (strcmp(argv[i], "--use-data-section") == 0)
+				use_data_section = 1;
 			else if (strncmp(argv[i], "--symbol-prefix=", 16) == 0) {
 				char *p = &argv[i][16];
 				/* skip quote */

scripts/link-vmlinux.sh

@@ -94,6 +94,10 @@ kallsyms()
 		kallsymopt="${kallsymopt} --base-relative"
 	fi
 
+	if [ -n "${CONFIG_KALLSYMS_USE_DATA_SECTION}" ]; then
+		kallsymopt="${kallsymopt} --use-data-section"
+	fi
+
 	local aflags="${KBUILD_AFLAGS} ${KBUILD_AFLAGS_KERNEL}               \
 		      ${NOSTDINC_FLAGS} ${LINUXINCLUDE} ${KBUILD_CPPFLAGS}"