Add weak symbol support. Also fix a bug caused by a typo.
This commit is contained in:
Doug Kwan
parent
f1729553e3
commit
e823807dc2
@ -68,7 +68,6 @@
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*
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* open issues / todo:
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*
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* - should we do anything special for STB_WEAK symbols?
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* - are we doing everything we should for ARM_COPY relocations?
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* - cleaner error reporting
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* - after linking, set as much stuff as possible to READONLY
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@ -406,13 +405,13 @@ static Elf32_Sym *_elf_lookup(soinfo *si, unsigned hash, const char *name)
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s = symtab + n;
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if(strcmp(strtab + s->st_name, name)) continue;
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/* only concern ourselves with global symbols */
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/* only concern ourselves with global and weak symbol definitions */
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switch(ELF32_ST_BIND(s->st_info)){
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case STB_GLOBAL:
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case STB_WEAK:
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/* no section == undefined */
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if(s->st_shndx == 0) continue;
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case STB_WEAK:
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TRACE_TYPE(LOOKUP, "%5d FOUND %s in %s (%08x) %d\n", pid,
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name, si->name, s->st_value, s->st_size);
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return s;
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@ -446,7 +445,13 @@ _do_lookup(soinfo *si, const char *name, unsigned *base)
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/* Look for symbols in the local scope first (the object who is
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* searching). This happens with C++ templates on i386 for some
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* reason. */
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* reason.
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*
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* Notes on weak symbols:
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* The ELF specs are ambigious about treatment of weak definitions in
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* dynamic linking. Some systems return the first definition found
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* and some the first non-weak definition. This is system dependent.
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* Here we return the first definition found for simplicity. */
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s = _elf_lookup(si, elf_hash, name);
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if(s != NULL)
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goto done;
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@ -513,7 +518,7 @@ Elf32_Sym *lookup(const char *name, soinfo **found)
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{
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if(si->flags & FLAG_ERROR)
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continue;
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s = _elf_lookup(si, elfhash, name);
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s = _elf_lookup(si, elf_hash, name);
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if (s != NULL) {
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*found = si;
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break;
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@ -1232,10 +1237,64 @@ static int reloc_library(soinfo *si, Elf32_Rel *rel, unsigned count)
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if(sym != 0) {
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sym_name = (char *)(strtab + symtab[sym].st_name);
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s = _do_lookup(si, sym_name, &base);
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if(s == 0) {
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DL_ERR("%5d cannot locate '%s'...", pid, sym_name);
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return -1;
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}
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if(s == NULL) {
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/* We only allow an undefined symbol if this is a weak
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reference.. */
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s = &symtab[sym];
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if (ELF32_ST_BIND(s->st_info) != STB_WEAK) {
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DL_ERR("%5d cannot locate '%s'...\n", pid, sym_name);
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return -1;
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}
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/* IHI0044C AAELF 4.5.1.1:
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Libraries are not searched to resolve weak references.
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It is not an error for a weak reference to remain
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unsatisfied.
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During linking, the value of an undefined weak reference is:
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- Zero if the relocation type is absolute
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- The address of the place if the relocation is pc-relative
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- The address of nominial base address if the relocation
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type is base-relative.
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*/
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switch (type) {
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#if defined(ANDROID_ARM_LINKER)
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case R_ARM_JUMP_SLOT:
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case R_ARM_GLOB_DAT:
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case R_ARM_ABS32:
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case R_ARM_RELATIVE: /* Don't care. */
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case R_ARM_NONE: /* Don't care. */
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#elif defined(ANDROID_X86_LINKER)
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case R_386_JUMP_SLOT:
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case R_386_GLOB_DAT:
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case R_386_32:
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case R_386_RELATIVE: /* Dont' care. */
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#endif /* ANDROID_*_LINKER */
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/* sym_addr was initialized to be zero above or relocation
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code below does not care about value of sym_addr.
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No need to do anything. */
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break;
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#if defined(ANDROID_X86_LINKER)
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case R_386_PC32:
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sym_addr = reloc;
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break;
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#endif /* ANDROID_X86_LINKER */
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#if defined(ANDROID_ARM_LINKER)
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case R_ARM_COPY:
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/* Fall through. Can't really copy if weak symbol is
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not found in run-time. */
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#endif /* ANDROID_ARM_LINKER */
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default:
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DL_ERR("%5d unknown weak reloc type %d @ %p (%d)\n",
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pid, type, rel, (int) (rel - start));
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return -1;
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}
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} else {
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/* We got a definition. */
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#if 0
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if((base == 0) && (si->base != 0)){
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/* linking from libraries to main image is bad */
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@ -1244,20 +1303,11 @@ static int reloc_library(soinfo *si, Elf32_Rel *rel, unsigned count)
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return -1;
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}
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#endif
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// st_shndx==SHN_UNDEF means an undefined symbol.
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// st_value should be 0 then, except that the low bit of st_value is
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// used to indicate whether the symbol points to an ARM or thumb function,
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// and should be ignored in the following check.
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if ((s->st_shndx == SHN_UNDEF) && ((s->st_value & ~1) != 0)) {
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DL_ERR("%5d In '%s', symbol=%s shndx=%d && value=0x%08x. We do not "
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"handle this yet", pid, si->name, sym_name, s->st_shndx,
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s->st_value);
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return -1;
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}
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sym_addr = (unsigned)(s->st_value + base);
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sym_addr = (unsigned)(s->st_value + base);
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}
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COUNT_RELOC(RELOC_SYMBOL);
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} else {
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s = 0;
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s = NULL;
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}
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/* TODO: This is ugly. Split up the relocations by arch into
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