Add weak symbol support. Also fix a bug caused by a typo.
diff --git a/linker/linker.c b/linker/linker.c
index 5f93bd3..6e42145 100644
--- a/linker/linker.c
+++ b/linker/linker.c
@@ -68,7 +68,6 @@
*
* open issues / todo:
*
- * - should we do anything special for STB_WEAK symbols?
* - are we doing everything we should for ARM_COPY relocations?
* - cleaner error reporting
* - after linking, set as much stuff as possible to READONLY
@@ -406,13 +405,13 @@
s = symtab + n;
if(strcmp(strtab + s->st_name, name)) continue;
- /* only concern ourselves with global symbols */
+ /* only concern ourselves with global and weak symbol definitions */
switch(ELF32_ST_BIND(s->st_info)){
case STB_GLOBAL:
+ case STB_WEAK:
/* no section == undefined */
if(s->st_shndx == 0) continue;
- case STB_WEAK:
TRACE_TYPE(LOOKUP, "%5d FOUND %s in %s (%08x) %d\n", pid,
name, si->name, s->st_value, s->st_size);
return s;
@@ -446,7 +445,13 @@
/* Look for symbols in the local scope first (the object who is
* searching). This happens with C++ templates on i386 for some
- * reason. */
+ * reason.
+ *
+ * Notes on weak symbols:
+ * The ELF specs are ambigious about treatment of weak definitions in
+ * dynamic linking. Some systems return the first definition found
+ * and some the first non-weak definition. This is system dependent.
+ * Here we return the first definition found for simplicity. */
s = _elf_lookup(si, elf_hash, name);
if(s != NULL)
goto done;
@@ -513,7 +518,7 @@
{
if(si->flags & FLAG_ERROR)
continue;
- s = _elf_lookup(si, elfhash, name);
+ s = _elf_lookup(si, elf_hash, name);
if (s != NULL) {
*found = si;
break;
@@ -1232,10 +1237,64 @@
if(sym != 0) {
sym_name = (char *)(strtab + symtab[sym].st_name);
s = _do_lookup(si, sym_name, &base);
- if(s == 0) {
- DL_ERR("%5d cannot locate '%s'...", pid, sym_name);
- return -1;
- }
+ if(s == NULL) {
+ /* We only allow an undefined symbol if this is a weak
+ reference.. */
+ s = &symtab[sym];
+ if (ELF32_ST_BIND(s->st_info) != STB_WEAK) {
+ DL_ERR("%5d cannot locate '%s'...\n", pid, sym_name);
+ return -1;
+ }
+
+ /* IHI0044C AAELF 4.5.1.1:
+
+ Libraries are not searched to resolve weak references.
+ It is not an error for a weak reference to remain
+ unsatisfied.
+
+ During linking, the value of an undefined weak reference is:
+ - Zero if the relocation type is absolute
+ - The address of the place if the relocation is pc-relative
+ - The address of nominial base address if the relocation
+ type is base-relative.
+ */
+
+ switch (type) {
+#if defined(ANDROID_ARM_LINKER)
+ case R_ARM_JUMP_SLOT:
+ case R_ARM_GLOB_DAT:
+ case R_ARM_ABS32:
+ case R_ARM_RELATIVE: /* Don't care. */
+ case R_ARM_NONE: /* Don't care. */
+#elif defined(ANDROID_X86_LINKER)
+ case R_386_JUMP_SLOT:
+ case R_386_GLOB_DAT:
+ case R_386_32:
+ case R_386_RELATIVE: /* Dont' care. */
+#endif /* ANDROID_*_LINKER */
+ /* sym_addr was initialized to be zero above or relocation
+ code below does not care about value of sym_addr.
+ No need to do anything. */
+ break;
+
+#if defined(ANDROID_X86_LINKER)
+ case R_386_PC32:
+ sym_addr = reloc;
+ break;
+#endif /* ANDROID_X86_LINKER */
+
+#if defined(ANDROID_ARM_LINKER)
+ case R_ARM_COPY:
+ /* Fall through. Can't really copy if weak symbol is
+ not found in run-time. */
+#endif /* ANDROID_ARM_LINKER */
+ default:
+ DL_ERR("%5d unknown weak reloc type %d @ %p (%d)\n",
+ pid, type, rel, (int) (rel - start));
+ return -1;
+ }
+ } else {
+ /* We got a definition. */
#if 0
if((base == 0) && (si->base != 0)){
/* linking from libraries to main image is bad */
@@ -1244,20 +1303,11 @@
return -1;
}
#endif
- // st_shndx==SHN_UNDEF means an undefined symbol.
- // st_value should be 0 then, except that the low bit of st_value is
- // used to indicate whether the symbol points to an ARM or thumb function,
- // and should be ignored in the following check.
- if ((s->st_shndx == SHN_UNDEF) && ((s->st_value & ~1) != 0)) {
- DL_ERR("%5d In '%s', symbol=%s shndx=%d && value=0x%08x. We do not "
- "handle this yet", pid, si->name, sym_name, s->st_shndx,
- s->st_value);
- return -1;
- }
- sym_addr = (unsigned)(s->st_value + base);
+ sym_addr = (unsigned)(s->st_value + base);
+ }
COUNT_RELOC(RELOC_SYMBOL);
} else {
- s = 0;
+ s = NULL;
}
/* TODO: This is ugly. Split up the relocations by arch into