[src/netbsd-1-5]: src/sys/ddb Pullup rev 1.12, approved by thorpej:

[jhawk <jhawk%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/86e3cbc53a16
branches:  netbsd-1-5
changeset: 488474:86e3cbc53a16
user:      jhawk <jhawk%NetBSD.org@localhost>
date:      Wed Jul 12 21:49:06 2000 +0000

description:
Pullup rev 1.12, approved by thorpej:
  Detect ELF sections (string and symbol tables) by looking them
  up by name (in .shstrtab) instead of guessing based on section
  type (and throwing away the small one). In addition to being cleaner,
  multiple symbol tables are no longer and error condition, so
  booting netbsd.gdb no longer results in ddb being unable to use
  *any* symbols.

diffstat:

 sys/ddb/db_elf.c |  54 ++++++++++++++----------------------------------------
 1 files changed, 14 insertions(+), 40 deletions(-)

diffs (102 lines):

diff -r d3ff13175664 -r 86e3cbc53a16 sys/ddb/db_elf.c
--- a/sys/ddb/db_elf.c  Wed Jul 12 21:48:09 2000 +0000
+++ b/sys/ddb/db_elf.c  Wed Jul 12 21:49:06 2000 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: db_elf.c,v 1.11 2000/05/22 14:49:10 jhawk Exp $        */
+/*     $NetBSD: db_elf.c,v 1.11.4.1 2000/07/12 21:49:06 jhawk Exp $    */
 
 /*-
  * Copyright (c) 1997 The NetBSD Foundation, Inc.
@@ -104,7 +104,7 @@
        Elf_Ehdr *elf;
        Elf_Shdr *shp;
        Elf_Sym *symp, *symtab_start, *symtab_end;
-       char *strtab_start, *strtab_end;
+       char *shstrtab, *strtab_start, *strtab_end;
        int i;
 
        if (ALIGNED_POINTER(symtab, long) == 0) {
@@ -147,44 +147,24 @@
        }
 
        /*
-        * We need to avoid the section header string table (small string
-        * table which names the sections).  We do this by assuming that
-        * the following two conditions will be true:
-        *
-        *      (1) .shstrtab will be smaller than one page.
-        *      (2) .strtab will be larger than one page.
-        *
-        * When we encounter what we think is the .shstrtab, we change
-        * its section type Elf_sht_null so that it will be ignored
-        * later.
+        * Find the section header string table (.shstrtab), and look up
+        * the symbol table (.symtab) and string table (.strtab) via their
+        * names in shstrtab, rather than by table type.
+        * This works in the presence of multiple string tables, such as
+        * stabs data found when booting netbsd.gdb.
         */
        shp = (Elf_Shdr *)((char *)symtab + elf->e_shoff);
+       shstrtab = (char*)symtab + shp[elf->e_shstrndx].sh_offset;
        for (i = 0; i < elf->e_shnum; i++) {
-               switch (shp[i].sh_type) {
-               case SHT_STRTAB:
-                       if (shp[i].sh_size < NBPG) {
-                               shp[i].sh_type = SHT_NULL;
-                               continue;
-                       }
-                       if (strtab_start != NULL)
-                               goto multiple_strtab;
+               if (strcmp(".strtab", shstrtab+shp[i].sh_name) == 0) {
                        strtab_start = (char *)symtab + shp[i].sh_offset;
                        strtab_end = (char *)symtab + shp[i].sh_offset +
                            shp[i].sh_size;
-                       break;
-               
-               case SHT_SYMTAB:
-                       if (symtab_start != NULL)
-                               goto multiple_symtab;
+               } else if (strcmp(".symtab", shstrtab+shp[i].sh_name) == 0) {
                        symtab_start = (Elf_Sym *)((char *)symtab + 
                            shp[i].sh_offset);
                        symtab_end = (Elf_Sym *)((char *)symtab + 
                            shp[i].sh_offset + shp[i].sh_size);
-                       break;
-
-               default:
-                       /* Ignore all other sections. */
-                       break;
                }
        }
 
@@ -215,14 +195,6 @@
  badheader:
        printf("[ %s ELF symbol table not valid ]\n", name);
        return (FALSE);
-
- multiple_strtab:
-       printf("[ %s has multiple ELF string tables ]\n", name);
-       return (FALSE);
-
- multiple_symtab:
-       printf("[ %s has multiple ELF symbol tables ]\n", name);
-       return (FALSE);
 }
 
 /*
@@ -235,11 +207,13 @@
 {
        Elf_Ehdr *elf = STAB_TO_EHDR(stab);
        Elf_Shdr *shp = STAB_TO_SHDR(stab, elf);
+       char *shstrtab;
        int i;
 
+       shstrtab = (char*)elf + shp[elf->e_shstrndx].sh_offset;
        for (i = 0; i < elf->e_shnum; i++) {
-               if (shp[i].sh_type == SHT_STRTAB)
-                       return (stab->private + shp[i].sh_offset);
+               if (strcmp(".strtab", shstrtab+shp[i].sh_name) == 0)
+                       return ((char*)elf + shp[i].sh_offset);
        }
 
        return (NULL);