dl-machine.h

Glibc 2.3.2源代码(解压后有100多M)

	  for (this = 0; this < nent; this++)
	    {
	      if (p[this].p_type == PT_LOAD)
		{
		  base = p[this].p_vaddr + l->l_addr;
		  limit = base + p[this].p_memsz;
		  if (stub_pc >= base && stub_pc < limit)
		    return l;
		}
	    }
	  l = l->l_next;
	}
    }

  _dl_signal_error (0, NULL, NULL, "cannot find runtime link map");
  return NULL;
}

/* Mips has no PLT but define elf_machine_relplt to be elf_machine_rel. */
#define elf_machine_relplt elf_machine_rel

/* Define mips specific runtime resolver. The function __dl_runtime_resolve
   is called from assembler function _dl_runtime_resolve which converts
   special argument registers t7 ($15) and t8 ($24):
     t7  address to return to the caller of the function
     t8  index for this function symbol in .dynsym
   to usual c arguments.  */

#define ELF_MACHINE_RUNTIME_TRAMPOLINE					      \
/* The flag _dl_mips_gnu_objects is set if all dynamic objects are	      \
   generated by the gnu linker. */					      \
int _dl_mips_gnu_objects = 1;						      \
									      \
/* This is called from assembly stubs below which the compiler can't see.  */ \
static ElfW(Addr)							      \
__dl_runtime_resolve (ElfW(Word), ElfW(Word), ElfW(Addr), ElfW(Addr))	      \
                  __attribute__ ((unused));				      \
									      \
static ElfW(Addr)							      \
__dl_runtime_resolve (ElfW(Word) sym_index,				      \
		      ElfW(Word) return_address,			      \
		      ElfW(Addr) old_gpreg,				      \
		      ElfW(Addr) stub_pc)				      \
{									      \
  struct link_map *l = elf_machine_runtime_link_map (old_gpreg, stub_pc);     \
  const ElfW(Sym) *const symtab						      \
    = (const ElfW(Sym) *) D_PTR (l, l_info[DT_SYMTAB]);			      \
  const char *strtab = (const void *) D_PTR (l, l_info[DT_STRTAB]);	      \
  const ElfW(Addr) *got							      \
    = (const ElfW(Addr) *) D_PTR (l, l_info[DT_PLTGOT]);		      \
  const ElfW(Word) local_gotno						      \
    = (const ElfW(Word)) l->l_info[DT_MIPS (LOCAL_GOTNO)]->d_un.d_val;	      \
  const ElfW(Word) gotsym						      \
    = (const ElfW(Word)) l->l_info[DT_MIPS (GOTSYM)]->d_un.d_val;	      \
  const ElfW(Sym) *definer;						      \
  ElfW(Addr) loadbase;							      \
  ElfW(Addr) funcaddr;							      \
									      \
  /* Look up the symbol's run-time value.  */				      \
  definer = &symtab[sym_index];						      \
									      \
  loadbase = _dl_lookup_symbol (strtab + definer->st_name, &definer,	      \
				l->l_scope, l->l_name,			      \
				R_MIPS_REL32);				      \
									      \
  /* Apply the relocation with that value.  */				      \
  funcaddr = loadbase + definer->st_value;				      \
  *(got + local_gotno + sym_index - gotsym) = funcaddr;			      \
									      \
  return funcaddr;							      \
}									      \
									      \
asm ("\n								      \
	.text\n								      \
	.align	3\n							      \
	.globl	_dl_runtime_resolve\n					      \
	.type	_dl_runtime_resolve,@function\n				      \
	.ent	_dl_runtime_resolve\n					      \
_dl_runtime_resolve:\n							      \
	.set noreorder\n						      \
	# Save old GP to $3.\n						      \
	move	$3,$28\n						      \
	# Modify t9 ($25) so as to point .cpload instruction.\n		      \
	daddu	$25,2*8\n						      \
	# Compute GP.\n							      \
	.cpload $25\n							      \
	.set reorder\n							      \
	# Save slot call pc.\n						      \
        move	$2, $31\n						      \
	# Save arguments and sp value in stack.\n			      \
	dsubu	$29, 10*8\n						      \
	.cprestore 8*8\n						      \
	sd	$15, 9*8($29)\n						      \
	sd	$4, 3*8($29)\n						      \
	sd	$5, 4*8($29)\n						      \
	sd	$6, 5*8($29)\n						      \
	sd	$7, 6*8($29)\n						      \
	sd	$16, 7*8($29)\n						      \
	move	$16, $29\n						      \
	move	$4, $24\n						      \
	move	$5, $15\n						      \
	move	$6, $3\n						      \
	move	$7, $2\n						      \
	jal	__dl_runtime_resolve\n					      \
	move	$29, $16\n						      \
	ld	$31, 9*8($29)\n						      \
	ld	$4, 3*8($29)\n						      \
	ld	$5, 4*8($29)\n						      \
	ld	$6, 5*8($29)\n						      \
	ld	$7, 6*8($29)\n						      \
	ld	$16, 7*8($29)\n						      \
	daddu	$29, 10*8\n						      \
	move	$25, $2\n						      \
	jr	$25\n							      \
	.end	_dl_runtime_resolve\n					      \
	.previous\n							      \
");

/* 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\
	.align	3\n"\
_RTLD_PROLOGUE (ENTRY_POINT)\
"	.globl _dl_start_user\n\
	.set noreorder\n\
	bltzal $0, 0f\n\
	nop\n\
0:	.cpload $31\n\
	.set reorder\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\
	dla $4, _DYNAMIC\n\
	sd $4, -0x7ff0($28)\n\
	dsubu $29, 16\n\
	move $4, $29\n\
	jal _dl_start\n\
	daddiu $29, 16\n\
	# Get the value of label '_dl_start_user' in t9 ($25).\n\
	dla $25, _dl_start_user\n\
_dl_start_user:\n\
	.set noreorder\n\
	.cpload $25\n\
	.set reorder\n\
	move $16, $28\n\
	# Save the user entry point address in saved register.\n\
	move $17, $2\n\
	# Store the highest stack address\n\
	sd $29, __libc_stack_end\n\
	# See if we were run as a command with the executable file\n\
	# name as an extra leading argument.\n\
	ld $2, _dl_skip_args\n\
	beq $2, $0, 1f\n\
	# Load the original argument count.\n\
	ld $4, 0($29)\n\
	# Subtract _dl_skip_args from it.\n\
	dsubu $4, $2\n\
	# Adjust the stack pointer to skip _dl_skip_args words.\n\
	dsll $2,2\n\
	daddu $29, $2\n\
	# Save back the modified argument count.\n\
	sd $4, 0($29)\n\
1:	# Call _dl_init (struct link_map *main_map, int argc, char **argv, char **env) \n\
	ld $4, _rtld_local\n\
	ld $5, 0($29)\n\
	dla $6, 4($29)\n\
	dla $7, 8($29)\n\
	dsubu $29, 16\n\
	# Call the function to run the initializers.\n\
	jal _dl_init_internal\n\
	daddiu $29, 16\n\
	# Pass our finalizer function to the user in ra.\n\
	dla $31, _dl_fini\n\
	# Jump to the user entry point.\n\
1:	# Call _dl_init (struct link_map *main_map, int argc, char **argv, char **env) \n\
	lw $4, _rtld_local\n\
	lw $5, 0($29)\n\
	la $6, 4($29)\n\
	la $7, 8($29)\n\
	subu $29, 16\n\
	# Call the function to run the initializers.\n\
	jal _dl_init_internal\n\
	addiu $29, 16\n\
	# Pass our finalizer function to the user in ra.\n\
	dla $31, _dl_fini\n\
	# Jump to the user entry point.\n\
	move $25, $17\n\
	ld $4, 0($29)\n\
	ld $5, 1*8($29)\n\
	ld $6, 2*8$29)\n\
	ld $7, 3*8($29)\n\
	jr $25\n"\
_RTLD_EPILOGUE(ENTRY_POINT) \
	"\n.previous"\
);


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

#endif /* !dl_machine_h */

#ifdef RESOLVE

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

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

  switch (r_type)
    {
    case R_MIPS_REL32:
      {
	ElfW(Addr) undo = 0;

	if (ELFW(ST_BIND) (sym->st_info) == STB_LOCAL
	    && (ELFW(ST_TYPE) (sym->st_info) == STT_SECTION
		|| ELFW(ST_TYPE) (sym->st_info) == STT_NOTYPE))
	  {
	    *reloc_addr += map->l_addr;
	    break;
	  }
#ifndef RTLD_BOOTSTRAP
	/* 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.  */
# ifndef SHARED
	weak_extern (GL(dl_rtld_map));
# endif
	if (map == &GL(dl_rtld_map))
	  /* Undo the relocation done here during bootstrapping.  Now we will
	     relocate it anew, possibly using a binding found in the user
	     program or a loaded library rather than the dynamic linker's
	     built-in definitions used while loading those libraries.  */
	  undo = map->l_addr + sym->st_value;
#endif
	  loadbase = RESOLVE (&sym, version, 0);
	  *reloc_addr += (sym ? (loadbase + sym->st_value) : 0) - undo;
	}
      break;
#ifndef RTLD_BOOTSTRAP
    case R_MIPS_NONE:		/* Alright, Wilbur.  */
      break;
#endif
    default:
      _dl_reloc_bad_type (map, r_type, 0);
      break;
    }
}

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

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

#endif /* RESOLVE */