glibc/sysdeps/powerpc/dl-machine.h

/* Machine-dependent ELF dynamic relocation inline functions.  PowerPC version.
   Copyright (C) 1995-2000, 2001 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#ifndef dl_machine_h
#define dl_machine_h

#define ELF_MACHINE_NAME "powerpc"

#include <assert.h>

/* Return nonzero iff ELF header is compatible with the running host.  */
static inline int
elf_machine_matches_host (const Elf32_Ehdr *ehdr)
{
  return ehdr->e_machine == EM_PPC;
}


/* Return the link-time address of _DYNAMIC, stored as
   the first value in the GOT. */
static inline Elf32_Addr
elf_machine_dynamic (void)
{
  Elf32_Addr *got;
  asm (" bl _GLOBAL_OFFSET_TABLE_-4@local"
       : "=l"(got));
  return *got;
}

/* Return the run-time load address of the shared object.  */
static inline Elf32_Addr
elf_machine_load_address (void)
{
  unsigned int *got;
  unsigned int *branchaddr;

  /* This is much harder than you'd expect.  Possibly I'm missing something.
     The 'obvious' way:

       Apparently, "bcl 20,31,$+4" is what should be used to load LR
       with the address of the next instruction.
       I think this is so that machines that do bl/blr pairing don't
       get confused.

     asm ("bcl 20,31,0f ;"
	  "0: mflr 0 ;"
	  "lis %0,0b@ha;"
	  "addi %0,%0,0b@l;"
	  "subf %0,%0,0"
	  : "=b" (addr) : : "r0", "lr");

     doesn't work, because the linker doesn't have to (and in fact doesn't)
     update the @ha and @l references; the loader (which runs after this
     code) will do that.

     Instead, we use the following trick:

     The linker puts the _link-time_ address of _DYNAMIC at the first
     word in the GOT. We could branch to that address, if we wanted,
     by using an @local reloc; the linker works this out, so it's safe
     to use now. We can't, of course, actually branch there, because
     we'd cause an illegal instruction exception; so we need to compute
     the address ourselves. That gives us the following code: */

  /* Get address of the 'b _DYNAMIC@local'...  */
  asm ("bl 0f ;"
       "b _DYNAMIC@local;"
       "0:"
       : "=l"(branchaddr));

  /* ... and the address of the GOT.  */
  asm (" bl _GLOBAL_OFFSET_TABLE_-4@local"
       : "=l"(got));

  /* So now work out the difference between where the branch actually points,
     and the offset of that location in memory from the start of the file.  */
  return ((Elf32_Addr)branchaddr - *got
	  + ((int)(*branchaddr << 6 & 0xffffff00) >> 6));
}

#define ELF_MACHINE_BEFORE_RTLD_RELOC(dynamic_info) /* nothing */

/* The PLT uses Elf32_Rela relocs.  */
#define elf_machine_relplt elf_machine_rela

/* This code is used in dl-runtime.c to call the `fixup' function
   and then redirect to the address it returns.  It is called
   from code built in the PLT by elf_machine_runtime_setup.  */
#define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ("\n\
	.section \".text\"	\n\
	.align 2	\n\
	.globl _dl_runtime_resolve	\n\
	.type _dl_runtime_resolve,@function	\n\
_dl_runtime_resolve:	\n\
 # We need to save the registers used to pass parameters, and register 0,\n\
 # which is used by _mcount; the registers are saved in a stack frame.\n\
	stwu 1,-64(1)	\n\
	stw 0,12(1)	\n\
	stw 3,16(1)	\n\
	stw 4,20(1)	\n\
 # The code that calls this has put parameters for `fixup' in r12 and r11.\n\
	mr 3,12	\n\
	stw 5,24(1)	\n\
	mr 4,11	\n\
	stw 6,28(1)	\n\
	mflr 0	\n\
 # We also need to save some of the condition register fields.\n\
	stw 7,32(1)	\n\
	stw 0,48(1)	\n\
	stw 8,36(1)	\n\
	mfcr 0	\n\
	stw 9,40(1)	\n\
	stw 10,44(1)	\n\
	stw 0,8(1)	\n\
	bl fixup@local	\n\
 # 'fixup' returns the address we want to branch to.\n\
	mtctr 3	\n\
 # Put the registers back...\n\
	lwz 0,48(1)	\n\
	lwz 10,44(1)	\n\
	lwz 9,40(1)	\n\
	mtlr 0	\n\
	lwz 8,36(1)	\n\
	lwz 0,8(1)	\n\
	lwz 7,32(1)	\n\
	lwz 6,28(1)	\n\
	mtcrf 0xFF,0	\n\
	lwz 5,24(1)	\n\
	lwz 4,20(1)	\n\
	lwz 3,16(1)	\n\
	lwz 0,12(1)	\n\
 # ...unwind the stack frame, and jump to the PLT entry we updated.\n\
	addi 1,1,64	\n\
	bctr	\n\
	.size	 _dl_runtime_resolve,.-_dl_runtime_resolve	\n\
	\n\
	.align 2	\n\
	.globl _dl_prof_resolve	\n\
	.type _dl_prof_resolve,@function	\n\
_dl_prof_resolve:	\n\
 # We need to save the registers used to pass parameters, and register 0,\n\
 # which is used by _mcount; the registers are saved in a stack frame.\n\
	stwu 1,-64(1)	\n\
        stw 0,12(1)	\n\
	stw 3,16(1)	\n\
	stw 4,20(1)	\n\
 # The code that calls this has put parameters for `fixup' in r12 and r11.\n\
	mr 3,12	\n\
	stw 5,24(1)	\n\
	mr 4,11	\n\
	stw 6,28(1)	\n\
	mflr 5	\n\
 # We also need to save some of the condition register fields.\n\
	stw 7,32(1)	\n\
	stw 5,48(1)	\n\
	stw 8,36(1)	\n\
	mfcr 0	\n\
	stw 9,40(1)	\n\
	stw 10,44(1)	\n\
	stw 0,8(1)	\n\
	bl profile_fixup@local	\n\
 # 'fixup' returns the address we want to branch to.\n\
	mtctr 3	\n\
 # Put the registers back...\n\
	lwz 0,48(1)	\n\
	lwz 10,44(1)	\n\
	lwz 9,40(1)	\n\
	mtlr 0	\n\
	lwz 8,36(1)	\n\
	lwz 0,8(1)	\n\
	lwz 7,32(1)	\n\
	lwz 6,28(1)	\n\
	mtcrf 0xFF,0	\n\
	lwz 5,24(1)	\n\
	lwz 4,20(1)	\n\
	lwz 3,16(1)	\n\
        lwz 0,12(1)	\n\
 # ...unwind the stack frame, and jump to the PLT entry we updated.\n\
	addi 1,1,64	\n\
	bctr	\n\
	.size	 _dl_prof_resolve,.-_dl_prof_resolve	\n\
 # Undo '.section text'.\n\
	.previous	\n\
");

/* The actual _start code is in dl-start.S.  Use a really
   ugly bit of assembler to let dl-start.o see _dl_start.  */
#define RTLD_START asm (".globl _dl_start");

/* Decide where a relocatable object should be loaded.  */
extern ElfW(Addr)
__elf_preferred_address(struct link_map *loader, size_t maplength,
			ElfW(Addr) mapstartpref);
#define ELF_PREFERRED_ADDRESS(loader, maplength, mapstartpref) \
  __elf_preferred_address (loader, maplength, mapstartpref)

/* Nonzero iff TYPE should not be allowed to resolve to one of
   the main executable's symbols, as for a COPY reloc.  */
#define elf_machine_lookup_noexec_p(type) ((type) == R_PPC_COPY)

/* Nonzero iff TYPE describes relocation of a PLT entry, so
   PLT entries should not be allowed to define the value.  */
/* We never want to use a PLT entry as the destination of a
   reloc, when what is being relocated is a branch. This is
   partly for efficiency, but mostly so we avoid loops.  */
#define elf_machine_lookup_noplt_p(type) ((type) == R_PPC_REL24 ||            \
					  (type) == R_PPC_ADDR24 ||           \
					  (type) == R_PPC_JMP_SLOT)

/* A reloc type used for ld.so cmdline arg lookups to reject PLT entries.  */
#define ELF_MACHINE_JMP_SLOT	R_PPC_JMP_SLOT

/* The PowerPC never uses REL relocations.  */
#define ELF_MACHINE_NO_REL 1

/* Set up the loaded object described by L so its unrelocated PLT
   entries will jump to the on-demand fixup code in dl-runtime.c.
   Also install a small trampoline to be used by entries that have
   been relocated to an address too far away for a single branch.  */
extern int __elf_machine_runtime_setup (struct link_map *map,
					int lazy, int profile);
#define elf_machine_runtime_setup __elf_machine_runtime_setup

static inline void
elf_machine_lazy_rel (struct link_map *map,
		      Elf32_Addr l_addr, const Elf32_Rela *reloc)
{
  /* elf_machine_runtime_setup handles this. */
}

/* Change the PLT entry whose reloc is 'reloc' to call the actual routine.  */
extern Elf32_Addr __elf_machine_fixup_plt (struct link_map *map,
					   const Elf32_Rela *reloc,
					   Elf32_Addr *reloc_addr,
					   Elf32_Addr finaladdr);

static inline Elf32_Addr
elf_machine_fixup_plt (struct link_map *map, lookup_t t,
		       const Elf32_Rela *reloc,
		       Elf32_Addr *reloc_addr, Elf64_Addr finaladdr)
{
  return __elf_machine_fixup_plt (map, reloc, reloc_addr, finaladdr);
}

/* Return the final value of a plt relocation.  */
static inline Elf32_Addr
elf_machine_plt_value (struct link_map *map, const Elf32_Rela *reloc,
		       Elf32_Addr value)
{
  return value + reloc->r_addend;
}

#endif /* dl_machine_h */

#ifdef RESOLVE

/* Do the actual processing of a reloc, once its target address
   has been determined.  */
extern void __process_machine_rela (struct link_map *map,
				    const Elf32_Rela *reloc,
				    const Elf32_Sym *sym,
				    const Elf32_Sym *refsym,
				    Elf32_Addr *const reloc_addr,
				    Elf32_Addr finaladdr,
				    int rinfo);

/* Perform the relocation specified by RELOC and SYM (which is fully resolved).
   LOADADDR is the load address of the object; INFO is an array indexed
   by DT_* of the .dynamic section info.  */

inline void
elf_machine_rela (struct link_map *map, const Elf32_Rela *reloc,
		  const Elf32_Sym *sym, const struct r_found_version *version,
		  Elf32_Addr *const reloc_addr)
{
  const Elf32_Sym *const refsym = sym;
  Elf32_Word loadbase, finaladdr;
  const int rinfo = ELF32_R_TYPE (reloc->r_info);

  if (rinfo == R_PPC_NONE)
    return;

  /* The condition on the next two lines is a hack around a bug in Solaris
     tools on Sparc.  It's not clear whether it should really be here at all,
     but if not the binutils need to be changed.  */
  if (rinfo == R_PPC_RELATIVE
      || (sym->st_shndx != SHN_UNDEF
	  && ELF32_ST_BIND (sym->st_info) == STB_LOCAL))
    {
      /* Has already been relocated.  */
      loadbase = map->l_addr;
      finaladdr = loadbase + reloc->r_addend;
    }
  else
    {
      loadbase = (Elf32_Word) (char *) (RESOLVE (&sym, version,
						 ELF32_R_TYPE(reloc->r_info)));
      if (sym == NULL)
	{
	  /* Weak symbol that wasn't actually defined anywhere.  */
	  assert(loadbase == 0);
	  finaladdr = reloc->r_addend;
	}
      else
	finaladdr = (loadbase + (Elf32_Word) (char *) sym->st_value
		     + reloc->r_addend);
    }

  /* A small amount of code is duplicated here for speed.  In libc,
     more than 90% of the relocs are R_PPC_RELATIVE; in the X11 shared
     libraries, 60% are R_PPC_RELATIVE, 24% are R_PPC_GLOB_DAT or
     R_PPC_ADDR32, and 16% are R_PPC_JMP_SLOT (which this routine
     wouldn't usually handle).  As an bonus, doing this here allows
     the switch statement in __process_machine_rela to work.  */
  if (rinfo == R_PPC_RELATIVE
      || rinfo == R_PPC_GLOB_DAT
      || rinfo == R_PPC_ADDR32)
    {
      *reloc_addr = finaladdr;
    }
  else
    __process_machine_rela (map, reloc, sym, refsym,
			    reloc_addr, finaladdr, rinfo);
}


/* The SVR4 ABI specifies that the JMPREL relocs must be inside the
   DT_RELA table.  */
#define ELF_MACHINE_PLTREL_OVERLAP 1

#endif /* RESOLVE */