Handle relocations for newer non-PIC MIPS ABI.
Newer binutils supports extensions to the MIPS ABI for non-PIC code that is used when compiling O32 binaries with clang 5 (but not used for N64 oddly enough). These extensions require support for R_MIPS_COPY relocations as well as a second PLT GOT using R_MIPS_JUMP_SLOT relocations. For R_MIPS_COPY, use the same approach as on other architectures where fixups are deferred to the MD do_copy_relocations. The additional PLT GOT for jump slots is located in a .got.plt section which is identified by a DT_MIPS_PLTGOT dynamic entry. This GOT also requires fixups for the first two GOT entries just as the normal GOT. However, the entry point for this second GOT uses a different calling convention. Rather than passing an offset into the GOT, it passes an offset into the .rel.plt section. This requires a second entry point (_rtld_pltbind_start) which calls the normal _rtld_bind() rather than _mips_rtld_bind(). This also means providing a real version of reloc_jmpslot() which is used by _rtld_bind(). In addition, add real implementions of reloc_plt() and reloc_jmpslots() which walk .rel.plt handling R_MIPS_JUMP_SLOT relocations. Reviewed by: kib Sponsored by: DARPA / AFRL Differential Revision: https://reviews.freebsd.org/D12326
This commit is contained in:
John Baldwin
parent
08d1c5b152
commit
b4e9a36bf7
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=323501
@ -67,29 +67,6 @@ __FBSDID("$FreeBSD$");
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#define GOT1_RESERVED_FOR_RTLD(got) ((got)[1] & GOT1_MASK)
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#endif
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void
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init_pltgot(Obj_Entry *obj)
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{
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if (obj->pltgot != NULL) {
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obj->pltgot[0] = (Elf_Addr) &_rtld_bind_start;
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if (GOT1_RESERVED_FOR_RTLD(obj->pltgot))
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obj->pltgot[1] = (Elf_Addr) obj | GOT1_MASK;
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}
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}
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int
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do_copy_relocations(Obj_Entry *dstobj)
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{
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/* Do nothing */
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return 0;
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}
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void _rtld_relocate_nonplt_self(Elf_Dyn *, Elf_Addr);
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/*
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* It is possible for the compiler to emit relocations for unaligned data.
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* We handle this situation with these inlines.
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*/
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#ifdef __mips_n64
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/*
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* ELF64 MIPS encodes the relocs uniquely. The first 32-bits of info contain
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@ -110,6 +87,86 @@ void _rtld_relocate_nonplt_self(Elf_Dyn *, Elf_Addr);
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#define Elf_Sxword Elf32_Sword
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#endif
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void _rtld_pltbind_start(void);
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void
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init_pltgot(Obj_Entry *obj)
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{
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if (obj->pltgot != NULL) {
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obj->pltgot[0] = (Elf_Addr) &_rtld_bind_start;
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if (GOT1_RESERVED_FOR_RTLD(obj->pltgot))
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obj->pltgot[1] = (Elf_Addr) obj | GOT1_MASK;
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}
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if (obj->mips_pltgot != NULL) {
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obj->mips_pltgot[0] = (Elf_Addr) &_rtld_pltbind_start;
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obj->mips_pltgot[1] = (Elf_Addr) obj;
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}
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}
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int
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do_copy_relocations(Obj_Entry *dstobj)
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{
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const Obj_Entry *srcobj, *defobj;
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const Elf_Rel *rellim;
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const Elf_Rel *rel;
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const Elf_Sym *srcsym;
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const Elf_Sym *dstsym;
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const void *srcaddr;
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const char *name;
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void *dstaddr;
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SymLook req;
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size_t size;
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int res;
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/*
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* COPY relocs are invalid outside of the main program
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*/
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assert(dstobj->mainprog);
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rellim = (const Elf_Rel *)((caddr_t)dstobj->rel + dstobj->relsize);
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for (rel = dstobj->rel; rel < rellim; rel++) {
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if (ELF_R_TYPE(rel->r_info) != R_MIPS_COPY)
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continue;
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dstaddr = (void *)(dstobj->relocbase + rel->r_offset);
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dstsym = dstobj->symtab + ELF_R_SYM(rel->r_info);
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name = dstobj->strtab + dstsym->st_name;
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size = dstsym->st_size;
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symlook_init(&req, name);
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req.ventry = fetch_ventry(dstobj, ELF_R_SYM(rel->r_info));
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req.flags = SYMLOOK_EARLY;
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for (srcobj = globallist_next(dstobj); srcobj != NULL;
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srcobj = globallist_next(srcobj)) {
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res = symlook_obj(&req, srcobj);
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if (res == 0) {
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srcsym = req.sym_out;
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defobj = req.defobj_out;
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break;
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}
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}
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if (srcobj == NULL) {
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_rtld_error(
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"Undefined symbol \"%s\" referenced from COPY relocation in %s",
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name, dstobj->path);
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return (-1);
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}
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srcaddr = (const void *)(defobj->relocbase + srcsym->st_value);
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memcpy(dstaddr, srcaddr, size);
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}
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return (0);
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}
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void _rtld_relocate_nonplt_self(Elf_Dyn *, Elf_Addr);
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/*
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* It is possible for the compiler to emit relocations for unaligned data.
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* We handle this situation with these inlines.
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*/
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static __inline Elf_Sxword
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load_ptr(void *where, size_t len)
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{
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@ -475,6 +532,20 @@ reloc_non_plt(Obj_Entry *obj, Obj_Entry *obj_rtld, int flags,
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break;
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}
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case R_TYPE(COPY):
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/*
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* These are deferred until all other relocations have
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* been done. All we do here is make sure that the
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* COPY relocation is not in a shared library. They
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* are allowed only in executable files.
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*/
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if (!obj->mainprog) {
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_rtld_error("%s: Unexpected R_MIPS_COPY "
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"relocation in shared library", obj->path);
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return (-1);
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}
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break;
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#ifdef __mips_n64
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case R_TYPE(TLS_DTPMOD64):
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#else
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@ -581,23 +652,25 @@ reloc_non_plt(Obj_Entry *obj, Obj_Entry *obj_rtld, int flags,
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int
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reloc_plt(Obj_Entry *obj)
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{
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#if 0
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const Elf_Rel *rellim;
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const Elf_Rel *rel;
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dbg("reloc_plt obj:%p pltrel:%p sz:%s", obj, obj->pltrel, (int)obj->pltrelsize);
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dbg("gottable %p num syms:%s", obj->pltgot, obj->symtabno );
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dbg("*****************************************************");
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rellim = (const Elf_Rel *)((char *)obj->pltrel +
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obj->pltrelsize);
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for (rel = obj->pltrel; rel < rellim; rel++) {
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rellim = (const Elf_Rel *)((char *)obj->pltrel + obj->pltrelsize);
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for (rel = obj->pltrel; rel < rellim; rel++) {
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Elf_Addr *where;
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where = (Elf_Addr *)(obj->relocbase + rel->r_offset);
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*where += (Elf_Addr )obj->relocbase;
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switch (ELF_R_TYPE(rel->r_info)) {
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case R_MIPS_JUMP_SLOT:
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where = (Elf_Addr *)(obj->relocbase + rel->r_offset);
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*where += (Elf_Addr )obj->relocbase;
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break;
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default:
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_rtld_error("Unknown relocation type %u in PLT",
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(unsigned int)ELF_R_TYPE(rel->r_info));
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return (-1);
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}
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}
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#endif
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/* PLT fixups were done above in the GOT relocation. */
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return (0);
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}
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@ -607,9 +680,34 @@ reloc_plt(Obj_Entry *obj)
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int
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reloc_jmpslots(Obj_Entry *obj, int flags, RtldLockState *lockstate)
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{
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/* Do nothing */
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obj->jmpslots_done = true;
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const Obj_Entry *defobj;
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const Elf_Rel *rellim;
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const Elf_Rel *rel;
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const Elf_Sym *def;
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rellim = (const Elf_Rel *)((char *)obj->pltrel + obj->pltrelsize);
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for (rel = obj->pltrel; rel < rellim; rel++) {
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Elf_Addr *where;
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switch (ELF_R_TYPE(rel->r_info)) {
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case R_MIPS_JUMP_SLOT:
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def = find_symdef(ELF_R_SYM(rel->r_info), obj,
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&defobj, SYMLOOK_IN_PLT | flags, NULL, lockstate);
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if (def == NULL) {
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dbg("reloc_jmpslots: sym not found");
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return (-1);
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}
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where = (Elf_Addr *)(obj->relocbase + rel->r_offset);
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*where = (Elf_Addr)(defobj->relocbase + def->st_value);
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break;
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default:
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_rtld_error("Unknown relocation type %u in PLT",
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(unsigned int)ELF_R_TYPE(rel->r_info));
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return (-1);
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}
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}
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return (0);
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}
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@ -635,9 +733,11 @@ reloc_jmpslot(Elf_Addr *where, Elf_Addr target, const Obj_Entry *defobj,
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const Obj_Entry *obj, const Elf_Rel *rel)
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{
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/* Do nothing */
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assert(ELF_R_TYPE(rel->r_info) == R_MIPS_JUMP_SLOT);
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return target;
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if (*where != target && !ld_bind_not)
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*where = target;
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return (target);
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}
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void
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@ -100,6 +100,9 @@ END(rtld_start)
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#define XCALLFRAME_A4 (0*SZREG)
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#endif
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/*
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* Trampoline for "old" PLT stubs which use .got entries.
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*/
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.globl _rtld_bind_start
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.ent _rtld_bind_start
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_rtld_bind_start:
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@ -188,3 +191,94 @@ _rtld_bind_start:
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nop
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.cfi_endproc
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END(_rtld_bind_start)
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/*
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* Trampoline for PLT stubs using .pltrel entries and .got.plt.
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*/
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.globl _rtld_pltbind_start
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.ent _rtld_pltbind_start
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_rtld_pltbind_start:
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.frame sp, XCALLFRAME_SIZ, $15
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.cfi_startproc simple
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.cfi_register ra, $15
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#if defined(__mips_o32)
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move v1, gp /* save pointer to .got.plt */
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#else
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move v1, t2 /* save pointer to .got.plt */
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#endif
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#if defined(__mips_o32) || defined(__mips_o64)
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PTR_ADDU t9, 8 /* modify T9 to point at .cpload */
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#endif
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SETUP_GP
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PTR_SUBU sp, XCALLFRAME_SIZ /* save arguments and sp value in stack */
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.cfi_def_cfa sp, XCALLFRAME_SIZ
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SETUP_GP64(XCALLFRAME_GP, _rtld_pltbind_start)
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SAVE_GP(XCALLFRAME_GP)
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#if defined(__mips_n32) || defined(__mips_n64)
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REG_S a4, XCALLFRAME_A4(sp)
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.cfi_rel_offset a4, XCALLFRAME_A4
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REG_S a5, XCALLFRAME_A5(sp)
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.cfi_rel_offset a5, XCALLFRAME_A5
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REG_S a6, XCALLFRAME_A6(sp)
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.cfi_rel_offset a6, XCALLFRAME_A6
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REG_S a7, XCALLFRAME_A7(sp)
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.cfi_rel_offset a7, XCALLFRAME_A7
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#endif
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REG_S a0, XCALLFRAME_A0(sp)
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.cfi_rel_offset a0, XCALLFRAME_A0
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REG_S a1, XCALLFRAME_A1(sp)
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.cfi_rel_offset a1, XCALLFRAME_A1
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REG_S a2, XCALLFRAME_A2(sp)
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.cfi_rel_offset a2, XCALLFRAME_A2
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REG_S a3, XCALLFRAME_A3(sp)
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.cfi_rel_offset a3, XCALLFRAME_A3
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REG_S $15, XCALLFRAME_RA(sp) /* ra is in t7/t3 */
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.cfi_rel_offset ra, XCALLFRAME_RA
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REG_S s0, XCALLFRAME_S0(sp)
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.cfi_rel_offset s0, XCALLFRAME_S0
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move s0, sp
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move a0, v1 /* .got.plt */
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#if defined(__mips_n64)
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ld a0, 8(a0) /* object = .got.plt[1] */
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sll a1, t8, 4 /* PLT entry index to .rel.plt offset */
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#else
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lw a0, 4(a0) /* object = .got.plt[1] */
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sll a1, t8, 3 /* PLT entry index to .rel.plt offset */
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#endif
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PTR_LA t9, _C_LABEL(_rtld_bind)
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jalr t9
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nop
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move sp, s0
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REG_L ra, XCALLFRAME_RA(sp)
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.cfi_restore ra
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REG_L s0, XCALLFRAME_S0(sp)
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.cfi_restore s0
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REG_L a0, XCALLFRAME_A0(sp)
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.cfi_restore a0
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REG_L a1, XCALLFRAME_A1(sp)
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.cfi_restore a1
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REG_L a2, XCALLFRAME_A2(sp)
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.cfi_restore a2
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REG_L a3, XCALLFRAME_A3(sp)
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.cfi_restore a3
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#if defined(__mips_n32) || defined(__mips_n64)
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REG_L a4, XCALLFRAME_A4(sp)
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.cfi_restore a4
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REG_L a5, XCALLFRAME_A5(sp)
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.cfi_restore a5
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REG_L a6, XCALLFRAME_A6(sp)
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.cfi_restore a6
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REG_L a7, XCALLFRAME_A7(sp)
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.cfi_restore a7
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#endif
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RESTORE_GP64
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PTR_ADDU sp, XCALLFRAME_SIZ
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move t9, v0
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jr t9
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nop
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.cfi_endproc
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END(_rtld_pltbind_start)
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@ -1257,6 +1257,12 @@ digest_dynamic1(Obj_Entry *obj, int early, const Elf_Dyn **dyn_rpath,
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case DT_MIPS_RLD_MAP:
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*((Elf_Addr *)(dynp->d_un.d_ptr)) = (Elf_Addr) &r_debug;
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break;
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case DT_MIPS_PLTGOT:
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obj->mips_pltgot = (Elf_Addr *) (obj->relocbase +
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dynp->d_un.d_ptr);
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break;
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#endif
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#ifdef __powerpc64__
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@ -187,6 +187,7 @@ typedef struct Struct_Obj_Entry {
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Elf_Word local_gotno; /* Number of local GOT entries */
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Elf_Word symtabno; /* Number of dynamic symbols */
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Elf_Word gotsym; /* First dynamic symbol in GOT */
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Elf_Addr *mips_pltgot; /* Second PLT GOT */
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#endif
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#ifdef __powerpc64__
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Elf_Addr glink; /* GLINK PLT call stub section */
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@ -1059,6 +1059,8 @@ typedef struct {
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#define R_MIPS_CALLLO16 31 /* lower 16 bit GOT entry for function */
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#define R_MIPS_JALR 37
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#define R_MIPS_TLS_GD 42
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#define R_MIPS_COPY 126
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#define R_MIPS_JUMP_SLOT 127
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#define R_PPC_NONE 0 /* No relocation. */
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#define R_PPC_ADDR32 1
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