glibc/sysdeps/mips/dl-machine.h

/* Machine-dependent ELF dynamic relocation inline functions.  MIPS version.
   Copyright (C) 1996-2001, 2002, 2003, 2004 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Kazumoto Kojima <kkojima@info.kanagawa-u.ac.jp>.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 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
   Lesser General Public License for more details.

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

/*  FIXME: Profiling of shared libraries is not implemented yet.  */
#ifndef dl_machine_h
#define dl_machine_h

#define ELF_MACHINE_NAME "MIPS"

#define ELF_MACHINE_NO_PLT

#include <entry.h>

#ifndef ENTRY_POINT
#error ENTRY_POINT needs to be defined for MIPS.
#endif

#include <sgidefs.h>
#include <sys/asm.h>

/* The offset of gp from GOT might be system-dependent.  It's set by
   ld.  The same value is also */
#define OFFSET_GP_GOT 0x7ff0

#ifndef _RTLD_PROLOGUE
# define _RTLD_PROLOGUE(entry)						\
	".globl\t" __STRING(entry) "\n\t"				\
	".ent\t" __STRING(entry) "\n\t"					\
	".type\t" __STRING(entry) ", @function\n"			\
	__STRING(entry) ":\n\t"
#endif

#ifndef _RTLD_EPILOGUE
# define _RTLD_EPILOGUE(entry)						\
	".end\t" __STRING(entry) "\n\t"					\
	".size\t" __STRING(entry) ", . - " __STRING(entry) "\n\t"
#endif

/* A reloc type used for ld.so cmdline arg lookups to reject PLT entries.
   This makes no sense on MIPS but we have to define this to R_MIPS_REL32
   to avoid the asserts in dl-lookup.c from blowing.  */
#define ELF_MACHINE_JMP_SLOT			R_MIPS_REL32
#define elf_machine_type_class(type)		ELF_RTYPE_CLASS_PLT

/* Translate a processor specific dynamic tag to the index
   in l_info array.  */
#define DT_MIPS(x) (DT_MIPS_##x - DT_LOPROC + DT_NUM)

/* If there is a DT_MIPS_RLD_MAP entry in the dynamic section, fill it in
   with the run-time address of the r_debug structure  */
#define ELF_MACHINE_DEBUG_SETUP(l,r) \
do { if ((l)->l_info[DT_MIPS (RLD_MAP)]) \
       *(ElfW(Addr) *)((l)->l_info[DT_MIPS (RLD_MAP)]->d_un.d_ptr) = \
       (ElfW(Addr)) (r); \
   } while (0)

/* Return nonzero iff ELF header is compatible with the running host.  */
static inline int __attribute_used__
elf_machine_matches_host (const ElfW(Ehdr) *ehdr)
{
#if _MIPS_SIM == _ABIO32 || _MIPS_SIM == _ABIN32
  /* Don't link o32 and n32 together.  */
  if (((ehdr->e_flags & EF_MIPS_ABI2) != 0) != (_MIPS_SIM == _ABIN32))
    return 0;
#endif

  switch (ehdr->e_machine)
    {
    case EM_MIPS:
    case EM_MIPS_RS3_LE:
      return 1;
    default:
      return 0;
    }
}

static inline ElfW(Addr) *
elf_mips_got_from_gpreg (ElfW(Addr) gpreg)
{
  /* FIXME: the offset of gp from GOT may be system-dependent. */
  return (ElfW(Addr) *) (gpreg - OFFSET_GP_GOT);
}

/* Return the link-time address of _DYNAMIC.  Conveniently, this is the
   first element of the GOT.  This must be inlined in a function which
   uses global data.  We assume its $gp points to the primary GOT.  */
static inline ElfW(Addr)
elf_machine_dynamic (void)
{
  register ElfW(Addr) gp __asm__ ("$28");
  return *elf_mips_got_from_gpreg (gp);
}

#define STRINGXP(X) __STRING(X)
#define STRINGXV(X) STRINGV_(X)
#define STRINGV_(...) # __VA_ARGS__

/* Return the run-time load address of the shared object.  */
static inline ElfW(Addr)
elf_machine_load_address (void)
{
  ElfW(Addr) addr;
  asm ("	.set noreorder\n"
       "	" STRINGXP (PTR_LA) " %0, 0f\n"
       "	bltzal $0, 0f\n"
       "	nop\n"
       "0:	" STRINGXP (PTR_SUBU) " %0, $31, %0\n"
       "	.set reorder\n"
       :	"=r" (addr)
       :	/* No inputs */
       :	"$31");
  return addr;
}

/* The MSB of got[1] of a gnu object is set to identify gnu objects.  */
#if _MIPS_SIM == _ABI64
# define ELF_MIPS_GNU_GOT1_MASK	0x8000000000000000L
#else
# define ELF_MIPS_GNU_GOT1_MASK	0x80000000L
#endif

/* We can't rely on elf_machine_got_rel because _dl_object_relocation_scope
   fiddles with global data.  */
#define ELF_MACHINE_BEFORE_RTLD_RELOC(dynamic_info)			\
do {									\
  struct link_map *map = &bootstrap_map;				\
  ElfW(Sym) *sym;							\
  ElfW(Addr) *got;							\
  int i, n;								\
									\
  got = (ElfW(Addr) *) D_PTR (map, l_info[DT_PLTGOT]);			\
									\
  if (__builtin_expect (map->l_addr == 0, 1))				\
    break;								\
									\
  /* got[0] is reserved. got[1] is also reserved for the dynamic object	\
     generated by gnu ld. Skip these reserved entries from		\
     relocation.  */							\
  i = (got[1] & ELF_MIPS_GNU_GOT1_MASK)? 2 : 1;				\
  n = map->l_info[DT_MIPS (LOCAL_GOTNO)]->d_un.d_val;			\
									\
  /* Add the run-time displacement to all local got entries. */		\
  while (i < n)								\
    got[i++] += map->l_addr;						\
									\
  /* Handle global got entries. */					\
  got += n;								\
  sym = (ElfW(Sym) *) D_PTR(map, l_info[DT_SYMTAB])			\
       + map->l_info[DT_MIPS (GOTSYM)]->d_un.d_val;			\
  i = (map->l_info[DT_MIPS (SYMTABNO)]->d_un.d_val			\
       - map->l_info[DT_MIPS (GOTSYM)]->d_un.d_val);			\
									\
  while (i--)								\
    {									\
      if (sym->st_shndx == SHN_UNDEF || sym->st_shndx == SHN_COMMON)	\
	*got = map->l_addr + sym->st_value;				\
      else if (ELFW(ST_TYPE) (sym->st_info) == STT_FUNC			\
	       && *got != sym->st_value)				\
	*got += map->l_addr;						\
      else if (ELFW(ST_TYPE) (sym->st_info) == STT_SECTION)		\
	{								\
	  if (sym->st_other == 0)					\
	    *got += map->l_addr;					\
	}								\
      else								\
	*got = map->l_addr + sym->st_value;				\
									\
      got++;								\
      sym++;								\
    }									\
} while(0)


/* Mask identifying addresses reserved for the user program,
   where the dynamic linker should not map anything.  */
#define ELF_MACHINE_USER_ADDRESS_MASK	0x80000000UL


/* 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.
   Note how we have to be careful about two things:

   1) That we allocate a minimal stack of 24 bytes for
      every function call, the MIPS ABI states that even
      if all arguments are passed in registers the procedure
      called can use the 16 byte area pointed to by $sp
      when it is called to store away the arguments passed
      to it.

   2) That under Linux the entry is named __start
      and not just plain _start.  */

#define RTLD_START asm (\
	".text\n\
	" _RTLD_PROLOGUE(ENTRY_POINT) "\
	" STRINGXV(SETUP_GPX($25)) "\n\
	" STRINGXV(SETUP_GPX64($18,$25)) "\n\
	# i386 ABI book says that the first entry of GOT holds\n\
	# the address of the dynamic structure. Though MIPS ABI\n\
	# doesn't say nothing about this, I emulate this here.\n\
	" STRINGXP(PTR_LA) " $4, _DYNAMIC\n\
	# Subtract OFFSET_GP_GOT\n\
	" STRINGXP(PTR_S) " $4, -0x7ff0($28)\n\
	move $4, $29\n\
	" STRINGXP(PTR_SUBIU) " $29, 16\n\
	\n\
	" STRINGXP(PTR_LA) " $8, .Lcoff\n\
	bltzal $8, .Lcoff\n\
.Lcoff:	" STRINGXP(PTR_SUBU) " $8, $31, $8\n\
	\n\
	" STRINGXP(PTR_LA) " $25, _dl_start\n\
	" STRINGXP(PTR_ADDU) " $25, $8\n\
	jalr $25\n\
	\n\
	" STRINGXP(PTR_ADDIU) " $29, 16\n\
	# Get the value of label '_dl_start_user' in t9 ($25).\n\
	" STRINGXP(PTR_LA) " $25, _dl_start_user\n\
	" _RTLD_EPILOGUE(ENTRY_POINT) "\
	\n\
	\n\
	" _RTLD_PROLOGUE(_dl_start_user) "\
	" STRINGXP(SETUP_GP) "\n\
	" STRINGXV(SETUP_GP64($18,_dl_start_user)) "\n\
	move $16, $28\n\
	# Save the user entry point address in a saved register.\n\
	move $17, $2\n\
	# See if we were run as a command with the executable file\n\
	# name as an extra leading argument.\n\
	lw $2, _dl_skip_args\n\
	beq $2, $0, 1f\n\
	# Load the original argument count.\n\
	" STRINGXP(PTR_L) " $4, 0($29)\n\
	# Subtract _dl_skip_args from it.\n\
	subu $4, $2\n\
	# Adjust the stack pointer to skip _dl_skip_args words.\n\
	sll $2, " STRINGXP (PTRLOG) "\n\
	" STRINGXP(PTR_ADDU) " $29, $2\n\
	# Save back the modified argument count.\n\
	" STRINGXP(PTR_S) " $4, 0($29)\n\
1:	# Call _dl_init (struct link_map *main_map, int argc, char **argv, char **env) \n\
	" STRINGXP(PTR_L) " $4, _rtld_local\n\
	" STRINGXP(PTR_L) /* or lw???  fixme */ " $5, 0($29)\n\
	" STRINGXP(PTR_LA) " $6, " STRINGXP (PTRSIZE) "($29)\n\
	sll $7, $5, " STRINGXP (PTRLOG) "\n\
	" STRINGXP(PTR_ADDU) " $7, $7, $6\n\
	" STRINGXP(PTR_ADDU) " $7, $7, " STRINGXP (PTRSIZE) " \n\
	# Make sure the stack pointer is aligned for _dl_init_internal.\n\
	and $2, $29, -2 * " STRINGXP(SZREG) "\n\
	" STRINGXP(PTR_S) " $29, -4($2)\n\
	" STRINGXP(PTR_SUBIU) " $29, $2, 32\n\
	" STRINGXP(SAVE_GP(16)) "\n\
	# Call the function to run the initializers.\n\
	jal _dl_init_internal\n\
	# Restore the stack pointer for _start.\n\
	" STRINGXP(PTR_L)  " $29, 28($29)\n\
	# Pass our finalizer function to the user in $2 as per ELF ABI.\n\
	" STRINGXP(PTR_LA) " $2, _dl_fini\n\
	# Jump to the user entry point.\n\
	move $25, $17\n\
	jr $25\n\t"\
	_RTLD_EPILOGUE(_dl_start_user)\
	".previous"\
);

/* The MIPS never uses Elfxx_Rela relocations.  */
#define ELF_MACHINE_NO_RELA 1

/* Names of the architecture-specific auditing callback functions.  */
# if _MIPS_SIM == _ABIO32
#  define ARCH_LA_PLTENTER mips_o32_gnu_pltenter
#  define ARCH_LA_PLTEXIT mips_o32_gnu_pltexit
# elif _MIPS_SIM == _ABIN32
#  define ARCH_LA_PLTENTER mips_n32_gnu_pltenter
#  define ARCH_LA_PLTEXIT mips_n32_gnu_pltexit
# else
#  define ARCH_LA_PLTENTER mips_n64_gnu_pltenter
#  define ARCH_LA_PLTEXIT mips_n64_gnu_pltexit
# endif

#endif /* !dl_machine_h */

#ifdef RESOLVE_MAP

/* Perform the relocation specified by RELOC and SYM (which is fully resolved).
   MAP is the object containing the reloc.  */

auto inline void
__attribute__ ((always_inline))
elf_machine_rel (struct link_map *map, const ElfW(Rel) *reloc,
		 const ElfW(Sym) *sym, const struct r_found_version *version,
		 void *const reloc_addr)
{
  const unsigned long int r_type = ELFW(R_TYPE) (reloc->r_info);

#if !defined RTLD_BOOTSTRAP && !defined SHARED
  /* This is defined in rtld.c, but nowhere in the static libc.a;
     make the reference weak so static programs can still link.  This
     declaration cannot be done when compiling rtld.c (i.e.  #ifdef
     RTLD_BOOTSTRAP) because rtld.c contains the common defn for
     _dl_rtld_map, which is incompatible with a weak decl in the same
     file.  */
  weak_extern (GL(dl_rtld_map));
#endif

  switch (r_type)
    {
#if _MIPS_SIM == _ABI64
    case (R_MIPS_64 << 8) | R_MIPS_REL32:
#else
    case R_MIPS_REL32:
#endif
      {
	int symidx = ELFW(R_SYM) (reloc->r_info);
	ElfW(Addr) reloc_value;

	/* Support relocations on mis-aligned offsets.  Should we ever
	   implement RELA, this should be replaced with an assignment
	   from reloc->r_addend.  */
	__builtin_memcpy (&reloc_value, reloc_addr, sizeof (reloc_value));

	if (symidx)
	  {
	    const ElfW(Word) gotsym
	      = (const ElfW(Word)) map->l_info[DT_MIPS (GOTSYM)]->d_un.d_val;

	    if ((ElfW(Word))symidx < gotsym)
	      {
		/* This wouldn't work for a symbol imported from other
		   libraries for which there's no GOT entry, but MIPS
		   requires every symbol referenced in a dynamic
		   relocation to have a GOT entry in the primary GOT,
		   so we only get here for locally-defined symbols.
		   For section symbols, we should *NOT* be adding
		   sym->st_value (per the definition of the meaning of
		   S in reloc expressions in the ELF64 MIPS ABI),
		   since it should have already been added to
		   reloc_value by the linker, but older versions of
		   GNU ld didn't add it, and newer versions don't emit
		   useless relocations to section symbols any more, so
		   it is safe to keep on adding sym->st_value, even
		   though it's not ABI compliant.  Some day we should
		   bite the bullet and stop doing this.  */
#ifndef RTLD_BOOTSTRAP
		if (map != &GL(dl_rtld_map))
#endif
		  reloc_value += sym->st_value + map->l_addr;
	      }
	    else
	      {
#ifndef RTLD_BOOTSTRAP
		const ElfW(Addr) *got
		  = (const ElfW(Addr) *) D_PTR (map, l_info[DT_PLTGOT]);
		const ElfW(Word) local_gotno
		  = (const ElfW(Word))
		    map->l_info[DT_MIPS (LOCAL_GOTNO)]->d_un.d_val;

		reloc_value += got[symidx + local_gotno - gotsym];
#endif
	      }
	  }
	else
#ifndef RTLD_BOOTSTRAP
	  if (map != &GL(dl_rtld_map))
#endif
	    reloc_value += map->l_addr;

	__builtin_memcpy (reloc_addr, &reloc_value, sizeof (reloc_value));
      }
      break;
    case R_MIPS_NONE:		/* Alright, Wilbur.  */
      break;
#if _MIPS_SIM == _ABI64
    case R_MIPS_64:
      /* For full compliance with the ELF64 ABI, one must precede the
	 _REL32/_64 pair of relocations with a _64 relocation, such
	 that the in-place addend is read as a 64-bit value.  IRIX
	 didn't pick up on this requirement, so we treat the
	 _REL32/_64 relocation as a 64-bit relocation even if it's by
	 itself.  For ABI compliance, we ignore such _64 dummy
	 relocations.  For RELA, this may be simply removed, since
	 it's totally unnecessary.  */
      if (ELFW(R_SYM) (reloc->r_info) == 0)
	break;
      /* Fall through.  */
#endif
    default:
      _dl_reloc_bad_type (map, r_type, 0);
      break;
    }
}

auto inline void
__attribute__((always_inline))
elf_machine_rel_relative (ElfW(Addr) l_addr, const ElfW(Rel) *reloc,
			  void *const reloc_addr)
{
  /* XXX Nothing to do.  There is no relative relocation, right?  */
}

auto inline void
__attribute__((always_inline))
elf_machine_lazy_rel (struct link_map *map,
		      ElfW(Addr) l_addr, const ElfW(Rel) *reloc)
{
  /* Do nothing.  */
}

auto inline void
__attribute__ ((always_inline))
elf_machine_rela (struct link_map *map, const ElfW(Rela) *reloc,
		  const ElfW(Sym) *sym, const struct r_found_version *version,
		 void *const reloc_addr)
{
}

auto inline void
__attribute__((always_inline))
elf_machine_rela_relative (ElfW(Addr) l_addr, const ElfW(Rela) *reloc,
			   void *const reloc_addr)
{
}

#ifndef RTLD_BOOTSTRAP
/* Relocate GOT. */
auto inline void
__attribute__((always_inline))
elf_machine_got_rel (struct link_map *map, int lazy)
{
  ElfW(Addr) *got;
  ElfW(Sym) *sym;
  const ElfW(Half) *vernum;
  int i, n, symidx;

#define RESOLVE_GOTSYM(sym,vernum,sym_index)				  \
    ({									  \
      const ElfW(Sym) *ref = sym;					  \
      const struct r_found_version *version				  \
        = vernum ? &map->l_versions[vernum[sym_index] & 0x7fff] : NULL;	  \
      struct link_map *sym_map;						  \
      sym_map = RESOLVE_MAP (&ref, version, R_MIPS_REL32);		  \
      ref ? sym_map->l_addr + ref->st_value : 0;			  \
    })

  if (map->l_info[VERSYMIDX (DT_VERSYM)] != NULL)
    vernum = (const void *) D_PTR (map, l_info[VERSYMIDX (DT_VERSYM)]);
  else
    vernum = NULL;

  got = (ElfW(Addr) *) D_PTR (map, l_info[DT_PLTGOT]);

  n = map->l_info[DT_MIPS (LOCAL_GOTNO)]->d_un.d_val;
  /* The dynamic linker's local got entries have already been relocated.  */
  if (map != &GL(dl_rtld_map))
    {
      /* got[0] is reserved. got[1] is also reserved for the dynamic object
	 generated by gnu ld. Skip these reserved entries from relocation.  */
      i = (got[1] & ELF_MIPS_GNU_GOT1_MASK)? 2 : 1;

      /* Add the run-time displacement to all local got entries if
         needed.  */
      if (__builtin_expect (map->l_addr != 0, 0))
	{
	  while (i < n)
	    got[i++] += map->l_addr;
	}
    }

  /* Handle global got entries. */
  got += n;
  /* Keep track of the symbol index.  */
  symidx = map->l_info[DT_MIPS (GOTSYM)]->d_un.d_val;
  sym = (ElfW(Sym) *) D_PTR (map, l_info[DT_SYMTAB]) + symidx;
  i = (map->l_info[DT_MIPS (SYMTABNO)]->d_un.d_val
       - map->l_info[DT_MIPS (GOTSYM)]->d_un.d_val);

  /* This loop doesn't handle Quickstart.  */
  while (i--)
    {
      if (sym->st_shndx == SHN_UNDEF)
	{
	  if (ELFW(ST_TYPE) (sym->st_info) == STT_FUNC
	      && sym->st_value && lazy)
	    *got = sym->st_value + map->l_addr;
	  else
	    *got = RESOLVE_GOTSYM (sym, vernum, symidx);
	}
      else if (sym->st_shndx == SHN_COMMON)
	*got = RESOLVE_GOTSYM (sym, vernum, symidx);
      else if (ELFW(ST_TYPE) (sym->st_info) == STT_FUNC
	       && *got != sym->st_value
	       && lazy)
	*got += map->l_addr;
      else if (ELFW(ST_TYPE) (sym->st_info) == STT_SECTION)
	{
	  if (sym->st_other == 0)
	    *got += map->l_addr;
	}
      else
	*got = RESOLVE_GOTSYM (sym, vernum, symidx);

      ++got;
      ++sym;
      ++symidx;
    }

#undef RESOLVE_GOTSYM
}
#endif

/* Set up the loaded object described by L so its stub function
   will jump to the on-demand fixup code __dl_runtime_resolve.  */

auto inline int
__attribute__((always_inline))
elf_machine_runtime_setup (struct link_map *l, int lazy, int profile)
{
# ifndef RTLD_BOOTSTRAP
  ElfW(Addr) *got;
  extern void _dl_runtime_resolve (ElfW(Word));
  extern int _dl_mips_gnu_objects;

  if (lazy)
    {
      /* The GOT entries for functions have not yet been filled in.
	 Their initial contents will arrange when called to put an
	 offset into the .dynsym section in t8, the return address
	 in t7 and then jump to _GLOBAL_OFFSET_TABLE[0].  */
      got = (ElfW(Addr) *) D_PTR (l, l_info[DT_PLTGOT]);

      /* This function will get called to fix up the GOT entry indicated by
	 the register t8, and then jump to the resolved address.  */
      got[0] = (ElfW(Addr)) &_dl_runtime_resolve;

      /* Store l to _GLOBAL_OFFSET_TABLE[1] for gnu object. The MSB
	 of got[1] of a gnu object is set to identify gnu objects.
	 Where we can store l for non gnu objects? XXX  */
      if ((got[1] & ELF_MIPS_GNU_GOT1_MASK) != 0)
	got[1] = ((ElfW(Addr)) l | ELF_MIPS_GNU_GOT1_MASK);
      else
	_dl_mips_gnu_objects = 0;
    }

  /* Relocate global offset table.  */
  elf_machine_got_rel (l, lazy);

# endif
  return lazy;
}

#endif /* RESOLVE_MAP */