glibc/sysdeps/powerpc/dl-machine.h

/* Machine-dependent ELF dynamic relocation inline functions.  PowerPC version.
   Copyright (C) 1995, 1996, 1997 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.  */

#define ELF_MACHINE_NAME "powerpc"

#include <assert.h>
#include <string.h>
#include <link.h>

/* stuff for the PLT */
#define PLT_INITIAL_ENTRY_WORDS 18
#define PLT_LONGBRANCH_ENTRY_WORDS 10
#define PLT_DOUBLE_SIZE (1<<13)
#define PLT_ENTRY_START_WORDS(entry_number) \
  (PLT_INITIAL_ENTRY_WORDS + (entry_number)*2 + \
   ((entry_number) > PLT_DOUBLE_SIZE ? \
    ((entry_number) - PLT_DOUBLE_SIZE)*2 : \
    0))
#define PLT_DATA_START_WORDS(num_entries) PLT_ENTRY_START_WORDS(num_entries)

#define OPCODE_ADDI(rd,ra,simm) \
  (0x38000000 | (rd) << 21 | (ra) << 16 | (simm) & 0xffff)
#define OPCODE_ADDIS(rd,ra,simm) \
  (0x3c000000 | (rd) << 21 | (ra) << 16 | (simm) & 0xffff)
#define OPCODE_ADD(rd,ra,rb) \
  (0x7c000214 | (rd) << 21 | (ra) << 16 | (rb) << 11)
#define OPCODE_B(target) (0x48000000 | (target) & 0x03fffffc)
#define OPCODE_BA(target) (0x48000002 | (target) & 0x03fffffc)
#define OPCODE_BCTR() 0x4e800420
#define OPCODE_LWZ(rd,d,ra) \
  (0x80000000 | (rd) << 21 | (ra) << 16 | (d) & 0xffff)
#define OPCODE_MTCTR(rd) (0x7C0903A6 | (rd) << 21)
#define OPCODE_RLWINM(ra,rs,sh,mb,me) \
  (0x54000000 | (rs) << 21 | (ra) << 16 | (sh) << 11 | (mb) << 6 | (me) << 1)

#define OPCODE_LI(rd,simm)    OPCODE_ADDI(rd,0,simm)
#define OPCODE_SLWI(ra,rs,sh) OPCODE_RLWINM(ra,rs,sh,0,31-sh)

#define PPC_DCBST(where) asm __volatile__ ("dcbst 0,%0" : : "r"(where))
+#define PPC_SYNC asm __volatile__ ("sync")
+#define PPC_ISYNC asm __volatile__ ("sync; isync")
+#define PPC_ICBI(where) asm __volatile__ ("icbi 0,%0" : : "r"(where))

/* Use this when you've modified some code, but it won't be in the
   instruction fetch queue (or when it doesn't matter if it is). */
#define MODIFIED_CODE_NOQUEUE(where) \
     do { PPC_DCBST(where); PPC_SYNC; PPC_ICBI(where); } while (0)
/* Use this when it might be in the instruction queue. */
#define MODIFIED_CODE(where) \
     do { PPC_DCBST(where); PPC_SYNC; PPC_ICBI(where); PPC_ISYNC; } while (0)


/* Return nonzero iff E_MACHINE is compatible with the running host.  */
static inline int
elf_machine_matches_host (Elf32_Half e_machine)
{
  return 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 *got;
  unsigned *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 +
    (*branchaddr & 0x3fffffc |
     (int)(*branchaddr << 6 & 0x80000000) >> 6);
}

#define ELF_MACHINE_BEFORE_RTLD_RELOC(dynamic_info) /* nothing */

/* 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.  */

#ifdef RESOLVE

static 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 = (Elf32_Addr *)(map->l_addr + reloc->r_offset);
  Elf32_Word loadbase, finaladdr;
  const int rinfo = ELF32_R_TYPE (reloc->r_info);

  if (rinfo == R_PPC_NONE)
    return;

  assert (sym != NULL);
  if (ELF32_ST_TYPE (sym->st_info) == STT_SECTION ||
      rinfo == R_PPC_RELATIVE)
    {
      /* Has already been relocated.  */
      loadbase = map->l_addr;
      finaladdr = loadbase + reloc->r_addend;
    }
  else
    {
      int flags;

      /* 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.  */
      if (rinfo == R_PPC_REL24 ||
	  rinfo == R_PPC_ADDR24 ||
	  rinfo == R_PPC_JMP_SLOT)
	flags = DL_LOOKUP_NOPLT;
      else if (rinfo == R_PPC_COPY)
	flags = DL_LOOKUP_NOEXEC;
      else
	flags = 0;

      loadbase = (Elf32_Word) (char *) (RESOLVE (&sym, version, flags));
      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);
    }

  /* This is an if/else if chain because GCC 2.7.2.[012] turns case
     statements into non-PIC table lookups.  When a later version
     comes out that fixes this, this should be changed.  */
  if (rinfo == R_PPC_ADDR16_LO)
    {
      *(Elf32_Half*) reloc_addr = finaladdr;
    }
  else if (rinfo == R_PPC_ADDR16_HI)
    {
      *(Elf32_Half*) reloc_addr = finaladdr >> 16;
    }
  else if (rinfo == R_PPC_ADDR16_HA)
    {
      *(Elf32_Half*) reloc_addr = finaladdr + 0x8000 >> 16;
    }
  else if (rinfo == R_PPC_REL24)
    {
      Elf32_Sword delta = finaladdr - (Elf32_Word) (char *) reloc_addr;
      assert (delta << 6 >> 6 == delta);
      *reloc_addr = *reloc_addr & 0xfc000003 | delta & 0x3fffffc;
    }
  else if (rinfo == R_PPC_UADDR32 ||
      rinfo == R_PPC_GLOB_DAT ||
      rinfo == R_PPC_ADDR32 ||
      rinfo == R_PPC_RELATIVE)
    {
      *reloc_addr = finaladdr;
    }
  else if (rinfo == R_PPC_ADDR24)
    {
      assert (finaladdr << 6 >> 6 == finaladdr);
      *reloc_addr = *reloc_addr & 0xfc000003 | finaladdr & 0x3fffffc;
    }
  else if (rinfo == R_PPC_COPY)
    {
      /* Memcpy is safe to use here, because ld.so doesn't have any
	 COPY relocs (it's self-contained).  */
      memcpy (reloc_addr, (char *) finaladdr, sym->st_size);
    }
  else if (rinfo == R_PPC_REL32)
    {
      *reloc_addr = finaladdr - (Elf32_Word) (char *) reloc_addr;
    }
  else if (rinfo == R_PPC_JMP_SLOT)
    {
      Elf32_Sword delta = finaladdr - (Elf32_Word) (char *) reloc_addr;
      if (delta << 6 >> 6 == delta)
	*reloc_addr = OPCODE_B(delta);
      else if (finaladdr <= 0x01fffffc || finaladdr >= 0xfe000000)
	*reloc_addr = OPCODE_BA(finaladdr);
      else
	{
	  Elf32_Word *plt = (Elf32_Word *)((char *)map->l_addr +
					   map->l_info[DT_PLTGOT]->d_un.d_val);
	  Elf32_Word index = (reloc_addr - plt - PLT_INITIAL_ENTRY_WORDS)/2;
	  Elf32_Word offset = index * 2 + PLT_INITIAL_ENTRY_WORDS;

	  if (index >= PLT_DOUBLE_SIZE)
	    {
	     /* Slots greater than or equal to 2^13 have 4 words
		available instead of two.  */
	      plt[offset  ] = OPCODE_LI (11,finaladdr);
	      plt[offset+1] = OPCODE_ADDIS (11,11,finaladdr + 0x8000 >> 16);
	      plt[offset+2] = OPCODE_MTCTR (11);
	      plt[offset+3] = OPCODE_BCTR ();
	    }
	  else
	    {
	      Elf32_Word num_plt_entries;
	      Elf32_Word rel_offset_words;

	      num_plt_entries = (map->l_info[DT_PLTRELSZ]->d_un.d_val
				 / sizeof(Elf32_Rela));
	      rel_offset_words = PLT_DATA_START_WORDS (num_plt_entries);

	      plt[offset  ] = OPCODE_LI (11,index * 4);
	      plt[offset+1] = OPCODE_B (-(4 * (offset + 1
					       - PLT_LONGBRANCH_ENTRY_WORDS)));
	      plt[index + rel_offset_words] = finaladdr;
	    }
	}
      MODIFIED_CODE(reloc_addr);
    }
  else
    assert (! "unexpected dynamic reloc type");

  if (rinfo == R_PPC_ADDR16_LO ||
      rinfo == R_PPC_ADDR16_HI ||
      rinfo == R_PPC_ADDR16_HA ||
      rinfo == R_PPC_REL24 ||
      rinfo == R_PPC_ADDR24)
    MODIFIED_CODE_NOQUEUE (reloc_addr);
}

#define ELF_MACHINE_NO_REL 1

#endif

/* Nonzero iff TYPE describes relocation of a PLT entry, so
   PLT entries should not be allowed to define the value.  */
#define elf_machine_pltrel_p(type) ((type) == R_PPC_JMP_SLOT)

/* 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.  */
static inline void
elf_machine_runtime_setup (struct link_map *map, int lazy)
{
  if (map->l_info[DT_JMPREL])
    {
      int i;
      /* Fill in the PLT. Its initial contents are directed to a
	 function earlier in the PLT which arranges for the dynamic
	 linker to be called back.  */
      Elf32_Word *plt = (Elf32_Word *) ((char *) map->l_addr
					+ map->l_info[DT_PLTGOT]->d_un.d_val);
      Elf32_Word num_plt_entries = (map->l_info[DT_PLTRELSZ]->d_un.d_val
				    / sizeof (Elf32_Rela));
      Elf32_Word rel_offset_words = PLT_DATA_START_WORDS (num_plt_entries);
      extern void _dl_runtime_resolve (void);
      Elf32_Word size_modified;

      if (lazy)
	for (i = 0; i < num_plt_entries; i++)
	{
	  Elf32_Word offset = PLT_ENTRY_START_WORDS(i);

	  if (i >= PLT_DOUBLE_SIZE)
	    {
	      plt[offset	] = OPCODE_LI (11, i * 4);
	      plt[offset+1] = OPCODE_ADDIS (11, 11, i * 4 + 0x8000 >> 16);
	      plt[offset+2] = OPCODE_B (-(4 * (offset + 2)));
	    }
	  else
	    {
	      plt[offset	] = OPCODE_LI (11, i * 4);
	      plt[offset+1] = OPCODE_B(-(4 * (offset + 1)));
	    }

	  /* Multiply index of entry, by 0xC.  */
	  plt[0] = OPCODE_SLWI (12, 11, 1);
	  plt[1] = OPCODE_ADD (11, 12, 11);
	  if ((Elf32_Word) (char *) _dl_runtime_resolve <= 0x01fffffc
	      || (Elf32_Word) (char *) _dl_runtime_resolve >= 0xfe000000)
	    {
	      plt[2] = OPCODE_LI (12, (Elf32_Word) (char *) map);
	      plt[3] = OPCODE_ADDIS (12, 12,
				     (Elf32_Word) (char *) map + 0x8000 >> 16);
	      plt[4] = OPCODE_BA ((Elf32_Word) (char *) _dl_runtime_resolve);
	    }
	}
      else
	{
	  plt[2] = OPCODE_LI (12, (Elf32_Word) (char *) _dl_runtime_resolve);
	  plt[3] = OPCODE_ADDIS(12, 12, 0x8000 +
				((Elf32_Word) (char *) _dl_runtime_resolve
				 >> 16));
	  plt[4] = OPCODE_MTCTR (12);
	  plt[5] = OPCODE_LI (12, (Elf32_Word) (char *) map);
	  plt[6] = OPCODE_ADDIS (12, 12, ((Elf32_Word) (char *) map
					  + 0x8000 >> 16));
	  plt[7] = OPCODE_BCTR ();
	}
      plt[PLT_LONGBRANCH_ENTRY_WORDS] =
	OPCODE_ADDIS (11, 11, (Elf32_Word) (char*) (plt + rel_offset_words)
		      + 0x8000 >> 16);
      plt[PLT_LONGBRANCH_ENTRY_WORDS+1] =
	OPCODE_LWZ(11,(Elf32_Word)(char*)(plt+rel_offset_words),11);
      plt[PLT_LONGBRANCH_ENTRY_WORDS+2] = OPCODE_MTCTR (11);
      plt[PLT_LONGBRANCH_ENTRY_WORDS+3] = OPCODE_BCTR ();

      size_modified = lazy ? rel_offset_words : PLT_INITIAL_ENTRY_WORDS;
      /* Now we need to keep the caches in sync.  */
      for (i = 0; i < size_modified; i+=8)
	PPC_DCBST (plt + i);
      PPC_SYNC;
      for (i = 0; i < size_modified; i+=8)
	PPC_ICBI (plt + i);
      PPC_ISYNC;
    }
}

static inline void
elf_machine_lazy_rel (struct link_map *map, const Elf32_Rela *reloc)
{
  assert (ELF32_R_TYPE (reloc->r_info) == R_PPC_JMP_SLOT);
  /* elf_machine_runtime_setup handles this. */
}

/* 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 ("\
	.section \".text\"
	.align 2
	.globl _dl_runtime_resolve
	.type _dl_runtime_resolve,@function
_dl_runtime_resolve:
 # We need to save the registers used to pass parameters.
 # We build a stack frame to put them in.
	stwu 1,-48(1)
	mflr 0
	stw 3,16(1)
	stw 4,20(1)
	stw 0,52(1)
	stw 5,24(1)
 # We also need to save some of the condition register fields.
	mfcr 0
	stw 6,28(1)
	stw 7,32(1)
	stw 8,36(1)
	stw 9,40(1)
	stw 10,44(1)
	stw 0,12(1)
 # The code that calls this has put parameters for `fixup' in r12 and r11.
	mr 3,12
	mr 4,11
	bl fixup
 # 'fixup' returns the address we want to branch to.
	mtctr 3
 # Put the registers back...
	lwz 0,52(1)
	lwz 10,44(1)
	lwz 9,40(1)
	mtlr 0
	lwz 0,12(1)
	lwz 8,36(1)
	lwz 7,32(1)
	lwz 6,28(1)
	mtcrf 0xFF,0
	lwz 5,24(1)
	lwz 4,20(1)
	lwz 3,16(1)
 # ...unwind the stack frame, and jump to the PLT entry we updated.
	addi 1,1,48
	bctr
0:
	.size	 _dl_runtime_resolve,0b-_dl_runtime_resolve
 # undo '.section text'.
	.previous
");

/* Initial entry point code for the dynamic linker.
   The C function `_dl_start' is the real entry point;
   its return value is the user program's entry point.	*/
#define RTLD_START \
asm ("\
	.text
	.align 2
	.globl _start
	.type _start,@function
_start:
 # We start with the following on the stack, from top:
 # argc (4 bytes)
 # arguments for program (terminated by NULL)
 # environment variables (terminated by NULL)
 # arguments for the program loader
 # FIXME: perhaps this should do the same trick as elf/start.c?

 # Call _dl_start with one parameter pointing at argc
	mr 3,1
 #  (we have to frob the stack pointer a bit to allow room for
 #   _dl_start to save the link register)
	li 4,0
	addi 1,1,-16
	stw 4,0(1)
	bl _dl_start@local

 # Now, we do our main work of calling initialisation procedures.
 # The ELF ABI doesn't say anything about parameters for these,
 # so we just pass argc, argv, and the environment.
 # Changing these is strongly discouraged (not least because argc is
 # passed by value!).

 #  put our GOT pointer in r31
	bl _GLOBAL_OFFSET_TABLE_-4@local
	mflr 31
 #  the address of _start in r30
	mr 30,3
 #  &_dl_argc in 29, &_dl_argv in 27, and _dl_default_scope in 28
	lwz 28,_dl_default_scope@got(31)
	lwz 29,_dl_argc@got(31)
	lwz 27,_dl_argv@got(31)
0:
 #  call initfunc = _dl_init_next(_dl_default_scope[2])
	lwz 3,8(28)
	bl _dl_init_next@plt
 # if initfunc is NULL, we exit the loop
	mr. 0,3
	beq 1f
 # call initfunc(_dl_argc, _dl_argv, _dl_argv+_dl_argc+1)
	mtlr 0
	lwz 3,0(29)
	lwz 4,0(27)
	slwi 5,3,2
	add 5,4,5
	addi 5,5,4
	blrl
 # and loop.
	b 0b
1:
 # Now, to conform to the ELF ABI, we have to:
 # pass argv (actually _dl_argv) in r4
	lwz 4,0(27)
 # pass argc (actually _dl_argc) in r3
	lwz 3,0(29)
 # pass envp (actually _dl_argv+_dl_argc+1) in r5
	slwi 5,3,2
	add 5,4,5
	addi 5,5,4
 # pass the auxilary vector in r6. This is passed just after _envp.
	addi 6,5,-4
2:	lwzu 0,4(6)
	cmpwi 1,0,0
	bne 2b
	addi 6,6,4
 # pass a termination function pointer (in this case _dl_fini) in r7
	lwz 7,_dl_fini@got(31)
 # now, call the start function in r30...
	mtctr 30
 # pass the stack pointer in r1 (so far so good), pointing to a NULL value
 # (this lets our startup code distinguish between a program linked statically,
 # which linux will call with argc on top of the stack which will hopefully
 # never be zero, and a dynamically linked program which will always have
 # a NULL on the top of the stack).
 # Take the opportunity to clear LR, so anyone who accidentally returns
 # from _start gets SEGV.
	li 0,0
	stw 0,0(1)
	mtlr 0
 # and also clear _dl_starting_up
	lwz 26,_dl_starting_up@got(31)
	stw 0,0(26)
 # go do it!
	bctr
0:
	.size	 _start,0b-_start
 # undo '.section text'.
	.previous
");

#define ELF_PREFERRED_ADDRESS_DATA					      \
static ElfW(Addr) _dl_preferred_address = 0;

#define ELF_PREFERRED_ADDRESS(loader, maplength, mapstartpref)		      \
( {									      \
   ElfW(Addr) prefd;							      \
   if (mapstartpref != 0 && _dl_preferred_address == 0)			      \
     _dl_preferred_address = mapstartpref;				      \
   if (mapstartpref != 0)						      \
     prefd = mapstartpref;						      \
   else if (_dl_preferred_address < maplength + 0x50000)		      \
     prefd = 0;								      \
   else									      \
     prefd = _dl_preferred_address =					      \
       ((_dl_preferred_address - maplength - 0x10000)			      \
	& ~(_dl_pagesize - 1));						      \
   prefd;								      \
} )

#define ELF_FIXED_ADDRESS(loader, mapstart)				      \
( {									      \
   if (mapstart != 0 && _dl_preferred_address < mapstart)		      \
     _dl_preferred_address = mapstart;					      \
} )

#define ELF_FIXUP_RETURNS_ADDRESS 1