1 files changed, 69 insertions, 10 deletions

diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
index d39a1eeb080e..638b143ee60f 100644
--- a/scripts/kallsyms.c
+++ b/scripts/kallsyms.c
@@ -22,6 +22,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <ctype.h>
+#include <limits.h>
 
 #ifndef ARRAY_SIZE
 #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(arr[0]))
@@ -43,6 +44,7 @@ struct addr_range {
 };
 
 static unsigned long long _text;
+static unsigned long long relative_base;
 static struct addr_range text_ranges[] = {
         { "_stext",     "_etext"     },
         { "_sinittext", "_einittext" },
@@ -62,6 +64,7 @@ static int all_symbols = 0;
 static int absolute_percpu = 0;
 static char symbol_prefix_char = '\0';
 static unsigned long long kernel_start_addr = 0;
+static int base_relative = 0;
 
 int token_profit[0x10000];
 
@@ -75,7 +78,7 @@ static void usage(void)
         fprintf(stderr, "Usage: kallsyms [--all-symbols] "
                         "[--symbol-prefix=<prefix char>] "
                         "[--page-offset=<CONFIG_PAGE_OFFSET>] "
-                        "< in.map > out.S\n");
+                        "[--base-relative] < in.map > out.S\n");
         exit(1);
 }
 
@@ -205,6 +208,8 @@ static int symbol_valid(struct sym_entry *s)
          */
         static char *special_symbols[] = {
                 "kallsyms_addresses",
+                "kallsyms_offsets",
+                "kallsyms_relative_base",
                 "kallsyms_num_syms",
                 "kallsyms_names",
                 "kallsyms_markers",
@@ -349,16 +354,48 @@ static void write_src(void)
 
         printf("\t.section .rodata, \"a\"\n");
 
-        /* Provide proper symbols relocatability by their '_text'
-         * relativeness.  The symbol names cannot be used to construct
-         * normal symbol references as the list of symbols contains
-         * symbols that are declared static and are private to their
-         * .o files.  This prevents .tmp_kallsyms.o or any other
-         * object from referencing them.
+        /* Provide proper symbols relocatability by their relativeness
+         * to a fixed anchor point in the runtime image, either '_text'
+         * for absolute address tables, in which case the linker will
+         * emit the final addresses at build time. Otherwise, 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.
+         *
+         * The symbol names cannot be used to construct normal symbol
+         * references as the list of symbols contains symbols that are
+         * declared static and are private to their .o files.  This prevents
+         * .tmp_kallsyms.o or any other object from referencing them.
          */
-        output_label("kallsyms_addresses");
+        if (!base_relative)
+                output_label("kallsyms_addresses");
+        else
+                output_label("kallsyms_offsets");
+
         for (i = 0; i < table_cnt; i++) {
-                if (!symbol_absolute(&table[i])) {
+                if (base_relative) {
+                        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\n", (int)offset);
+                } else if (!symbol_absolute(&table[i])) {
                         if (_text <= table[i].addr)
                                 printf("\tPTR\t_text + %#llx\n",
                                         table[i].addr - _text);
@@ -371,6 +408,12 @@ static void write_src(void)
         }
         printf("\n");
 
+        if (base_relative) {
+                output_label("kallsyms_relative_base");
+                printf("\tPTR\t_text - %#llx\n", _text - relative_base);
+                printf("\n");
+        }
+
         output_label("kallsyms_num_syms");
         printf("\tPTR\t%d\n", table_cnt);
         printf("\n");
@@ -695,6 +738,18 @@ static void make_percpus_absolute(void)
                 }
 }
 
+/* find the minimum non-absolute symbol address */
+static void record_relative_base(void)
+{
+        unsigned int i;
+
+        relative_base = -1ULL;
+        for (i = 0; i < table_cnt; i++)
+                if (!symbol_absolute(&table[i]) &&
+                    table[i].addr < relative_base)
+                        relative_base = table[i].addr;
+}
+
 int main(int argc, char **argv)
 {
         if (argc >= 2) {
@@ -713,7 +768,9 @@ int main(int argc, char **argv)
                         } else if (strncmp(argv[i], "--page-offset=", 14) == 0) {
                                 const char *p = &argv[i][14];
                                 kernel_start_addr = strtoull(p, NULL, 16);
-                        } else
+                        } else if (strcmp(argv[i], "--base-relative") == 0)
+                                base_relative = 1;
+                        else
                                 usage();
                 }
         } else if (argc != 1)
@@ -722,6 +779,8 @@ int main(int argc, char **argv)
         read_map(stdin);
         if (absolute_percpu)
                 make_percpus_absolute();
+        if (base_relative)
+                record_relative_base();
         sort_symbols();
         optimize_token_table();
         write_src();