dtrace: use _stext in dtrace_relocs.

Read and use the _stext value for adding to relative relocation
info to make it absolute.
This works for my 4 test cases.  It was derived by examination
and discovery.  There could be cases where it does not work,
e.g. in other text sections.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>

diff --git a/scripts/dtrace_relocs.c b/scripts/dtrace_relocs.c
index a220d7b270704b76c9ea74c666f58cb552e89005..05742bde11066acbc2c90ac4f028dd41e950f0c9 100644 (file)
--- a/scripts/dtrace_relocs.c
+++ b/scripts/dtrace_relocs.c
@@ -16,6 +16,9 @@
 #include <ctype.h>
 #include <elf.h>
 
+//#define INFO 1
+//#define SCANF        1
+
 struct sym_entry {
        unsigned long long addr;
        unsigned char is_section;
@@ -31,7 +34,7 @@ struct text_range {
        unsigned long long start, end;
 };
 
-static unsigned long long _text; // TBD: need this from System.map
+static unsigned long long _text, _stext;       // from System.map
 
 static struct sym_entry *table;
 static unsigned int table_size, table_cnt;
@@ -210,6 +213,35 @@ static int get_symbol_info(char buf[500], struct sym_entry *s)
        return 0;
 }
 
+static void get_text_addr(char buf[500], char *str_match,
+                       unsigned long long *_adr)
+{
+       int rc;
+       unsigned long long adr;
+       char relo_type[100];
+       char symbol_name[200];
+
+       rc = sscanf(buf, "%llx %s %s\n",
+               &adr, (char *)&relo_type,
+               (char *)&symbol_name);
+#ifdef SCANF
+       fprintf(stderr, "%s: sscanf.1 rc= %d\n", __func__, rc);
+#endif
+       if (rc != 3)
+               return;
+
+       if (strcmp(relo_type, "T"))
+               return;
+       if (strcmp(symbol_name, str_match))
+               return;
+
+       *_adr = adr;
+#ifdef INFO
+       fprintf(stderr, "found '%s':_addr/offset=0x%llx, type=%s, name=%s\n",
+               str_match, adr, relo_type, symbol_name);
+#endif
+}
+
 static void read_info(FILE *fin)
 {
        char buf[500];
@@ -251,9 +283,14 @@ static void read_info(FILE *fin)
                        continue;
                }
 
-               if (in_symbols)
+               if (in_symbols) {
                        if (get_symbol_info(buf, &table[table_cnt]) == 0)
                                table_cnt++;
+                       else if (_text == 0)
+                               get_text_addr(buf, "_text", &_text);
+                       else if (_stext == 0)
+                               get_text_addr(buf, "_stext", &_stext);
+               }
        }
 }
 
@@ -285,6 +322,10 @@ static void write_relocs(FILE *fout)
        fprintf(fout, "\tPTR\t%d\n", relocs_count);
        fprintf(fout, "\n");
 
+       fprintf(fout, "_text_\t= 0x%llx\n", _text);
+       fprintf(fout, "_stext_\t= 0x%llx\n", _stext);
+       fprintf(fout, "\n");
+
        /*
         * Provide proper symbols relocatability by their '_text'
         * relativeness.  The symbol names cannot be used to construct
@@ -295,20 +336,11 @@ static void write_relocs(FILE *fout)
         */
        output_label(fout, "dtrace_relocs");
        for (i = 0; i < table_cnt; i++) {
-#if 0
-               if (_text <= table[i].addr)
-                       fprintf(fout, "\tPTR\t_text + %#llx\n",
-                               table[i].addr - _text);
-               else
-                       fprintf(fout, "\tPTR\t_text - %#llx\n",
-                               _text - table[i].addr);
-#endif
                // for reloc symbols (not sections):
                // print symbol relative address, section base address,
                // call target string length, call target string/name;
-               // TBD: figure out how to find the next 4-tuple;
                if (!table[i].is_section) {
-                       fprintf(fout, "\tPTR\t%#llx\n", table[i].addr);
+                       fprintf(fout, "\tPTR\t%#llx\n", _stext + table[i].addr);
                        fprintf(fout, "\tPTR\t%#llx\n", table[i].section_base);
                        fprintf(fout, "\tPTR\t%d\n", table[i].len);
                        fprintf(fout, "\t.asciz\t\"%s\"\n", table[i].sym);
@@ -326,43 +358,6 @@ static void write_relocs(FILE *fout)
        }
 }
 
-#if 0
-/* guess for "linker script provide" symbol */
-static int may_be_linker_script_provide_symbol(const struct sym_entry *se)
-{
-       const char *symbol = (char *)se->sym + 1;
-       int len = se->len - 1;
-
-       if (len < 8)
-               return 0;
-
-       if (symbol[0] != '_' || symbol[1] != '_')
-               return 0;
-
-       /* __start_XXXXX */
-       if (!memcmp(symbol + 2, "start_", 6))
-               return 1;
-
-       /* __stop_XXXXX */
-       if (!memcmp(symbol + 2, "stop_", 5))
-               return 1;
-
-       /* __end_XXXXX */
-       if (!memcmp(symbol + 2, "end_", 4))
-               return 1;
-
-       /* __XXXXX_start */
-       if (!memcmp(symbol + len - 6, "_start", 6))
-               return 1;
-
-       /* __XXXXX_end */
-       if (!memcmp(symbol + len - 4, "_end", 4))
-               return 1;
-
-       return 0;
-}
-#endif
-
 int main(int argc, char *argv[])
 {
        char *infile, *outfile;