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[glibc.git] / sysdeps / arm / dl-machine.h

/* Machine-dependent ELF dynamic relocation inline functions.  ARM version.
   Copyright (C) 1995,96,97,98,99,2000 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 "ARM"

#include <sys/param.h>

#define VALID_ELF_ABIVERSION(ver)       (ver == 0)
#define VALID_ELF_OSABI(osabi) \
  (osabi == ELFOSABI_SYSV || osabi == ELFOSABI_ARM)
#define VALID_ELF_HEADER(hdr,exp,size) \
  memcmp (hdr,exp,size-2) == 0 \
  && VALID_ELF_OSABI (hdr[EI_OSABI]) \
  && VALID_ELF_ABIVERSION (hdr[EI_ABIVERSION])

#define CLEAR_CACHE(BEG,END)                                            \
{                                                                       \
  register unsigned long _beg __asm ("a1") = (unsigned long)(BEG);      \
  register unsigned long _end __asm ("a2") = (unsigned long)(END);      \
  register unsigned long _flg __asm ("a3") = 0;                         \
  __asm __volatile ("swi 0x9f0002               @ sys_cacheflush"       \
                    : /* no outputs */                                  \
                    : /* no inputs */                                   \
                    : "a1");                                            \
}

/* Return nonzero iff E_MACHINE is compatible with the running host.  */
static inline int __attribute__ ((unused))
elf_machine_matches_host (Elf32_Half e_machine)
{
  switch (e_machine)
    {
    case EM_ARM:
      return 1;
    default:
      return 0;
    }
}


/* 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.  */
static inline Elf32_Addr __attribute__ ((unused))
elf_machine_dynamic (void)
{
  register Elf32_Addr *got asm ("r10");
  return *got;
}


/* Return the run-time load address of the shared object.  */
static inline Elf32_Addr __attribute__ ((unused))
elf_machine_load_address (void)
{
  extern void __dl_start asm ("_dl_start");
  Elf32_Addr got_addr = (Elf32_Addr) &__dl_start;
  Elf32_Addr pcrel_addr;
  asm ("adr %0, _dl_start" : "=r" (pcrel_addr));
  return pcrel_addr - got_addr;
}


/* 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 int __attribute__ ((unused))
elf_machine_runtime_setup (struct link_map *l, int lazy, int profile)
{
  Elf32_Addr *got;
  extern void _dl_runtime_resolve (Elf32_Word);
  extern void _dl_runtime_profile (Elf32_Word);

  if (l->l_info[DT_JMPREL] && lazy)
    {
      /* patb: this is different than i386 */
      /* The GOT entries for functions in the PLT have not yet been filled
         in.  Their initial contents will arrange when called to push an
         index into the .got section, load ip with &_GLOBAL_OFFSET_TABLE_[3],
         and then jump to _GLOBAL_OFFSET_TABLE[2].  */
      got = (Elf32_Addr *) D_PTR (l, l_info[DT_PLTGOT]);
      got[1] = (Elf32_Addr) l;  /* Identify this shared object.  */

      /* The got[2] entry contains the address of a function which gets
         called to get the address of a so far unresolved function and
         jump to it.  The profiling extension of the dynamic linker allows
         to intercept the calls to collect information.  In this case we
         don't store the address in the GOT so that all future calls also
         end in this function.  */
      if (profile)
        {
          got[2] = (Elf32_Addr) &_dl_runtime_profile;
          /* Say that we really want profiling and the timers are started.  */
          _dl_profile_map = l;
        }
      else
        /* This function will get called to fix up the GOT entry indicated by
           the offset on the stack, and then jump to the resolved address.  */
        got[2] = (Elf32_Addr) &_dl_runtime_resolve;
    }
  return lazy;
}

/* This code is used in dl-runtime.c to call the `fixup' function
   and then redirect to the address it returns.  */
   // macro for handling PIC situation....
#ifdef PIC
#define CALL_ROUTINE(x) " ldr sl,0f
        add     sl, pc, sl
1:      ldr     r2, 2f
        mov     lr, pc
        add     pc, sl, r2
        b       3f
0:      .word   _GLOBAL_OFFSET_TABLE_ - 1b - 4
2:      .word " #x "(GOTOFF)
3:      "
#else
#define CALL_ROUTINE(x) " bl " #x
#endif

#ifndef PROF
# define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ("\
        .text
        .globl _dl_runtime_resolve
        .type _dl_runtime_resolve, #function
        .align 2
_dl_runtime_resolve:
        @ we get called with
        @       stack[0] contains the return address from this call
        @       ip contains &GOT[n+3] (pointer to function)
        @       lr points to &GOT[2]

        @ save almost everything; lr is already on the stack
        stmdb   sp!,{r0-r3,sl,fp}

        @ prepare to call fixup()
        @ change &GOT[n+3] into 8*n        NOTE: reloc are 8 bytes each
        sub     r1, ip, lr
        sub     r1, r1, #4
        add     r1, r1, r1

        @ get pointer to linker struct
        ldr     r0, [lr, #-4]

        @ call fixup routine
        " CALL_ROUTINE(fixup) "

        @ save the return
        mov     ip, r0

        @ restore the stack
        ldmia   sp!,{r0-r3,sl,fp,lr}

        @ jump to the newly found address
        mov     pc, ip

        .size _dl_runtime_resolve, .-_dl_runtime_resolve

        .globl _dl_runtime_profile
        .type _dl_runtime_profile, #function
        .align 2
_dl_runtime_profile:
        @ save almost everything; lr is already on the stack
        stmdb   sp!,{r0-r3,sl,fp}

        @ prepare to call fixup()
        @ change &GOT[n+3] into 8*n        NOTE: reloc are 8 bytes each
        sub     r1, ip, lr
        sub     r1, r1, #4
        add     r1, r1, r1

        @ get pointer to linker struct
        ldr     r0, [lr, #-4]

        @ call profiling fixup routine
        " CALL_ROUTINE(profile_fixup) "

        @ save the return
        mov     ip, r0

        @ restore the stack
        ldmia   sp!,{r0-r3,sl,fp,lr}

        @ jump to the newly found address
        mov     pc, ip

        .size _dl_runtime_resolve, .-_dl_runtime_resolve
        .previous
");
#else // PROF
# define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ("\
        .text
        .globl _dl_runtime_resolve
        .globl _dl_runtime_profile
        .type _dl_runtime_resolve, #function
        .type _dl_runtime_profile, #function
        .align 2
_dl_runtime_resolve:
_dl_runtime_profile:
        @ we get called with
        @       stack[0] contains the return address from this call
        @       ip contains &GOT[n+3] (pointer to function)
        @       lr points to &GOT[2]

        @ save almost everything; return add is already on the stack
        stmdb   sp!,{r0-r3,sl,fp}

        @ prepare to call fixup()
        @ change &GOT[n+3] into 8*n        NOTE: reloc are 8 bytes each
        sub     r1, ip, lr
        sub     r1, r1, #4
        add     r1, r1, r1

        @ get pointer to linker struct
        ldr     r0, [lr, #-4]

        @ call profiling fixup routine
        " CALL_ROUTINE(fixup) "

        @ save the return
        mov     ip, r0

        @ restore the stack
        ldmia   sp!,{r0-r3,sl,fp,lr}

        @ jump to the newly found address
        mov     pc, ip

        .size _dl_runtime_profile, .-_dl_runtime_profile
        .previous
");
#endif //PROF

/* Mask identifying addresses reserved for the user program,
   where the dynamic linker should not map anything.  */
#define ELF_MACHINE_USER_ADDRESS_MASK   0xf8000000UL

/* 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
.globl _start
.globl _dl_start_user
_start:
        @ at start time, all the args are on the stack
        mov     r0, sp
        bl      _dl_start
        @ returns user entry point in r0
_dl_start_user:
        mov     r6, r0
        @ we are PIC code, so get global offset table
        ldr     sl, .L_GET_GOT
        add     sl, pc, sl
.L_GOT_GOT:
        @ Store the highest stack address
        ldr     r1, .L_STACK_END
        ldr     r1, [sl, r1]
        str     sp, [r1]
        @ See if we were run as a command with the executable file
        @ name as an extra leading argument.
        ldr     r4, .L_SKIP_ARGS
        ldr     r4, [sl, r4]
        @ get the original arg count
        ldr     r1, [sp]
        @ subtract _dl_skip_args from it
        sub     r1, r1, r4
        @ adjust the stack pointer to skip them
        add     sp, sp, r4, lsl #2
        @ get the argv address
        add     r2, sp, #4
        @ store the new argc in the new stack location
        str     r1, [sp]
        @ compute envp
        add     r3, r2, r1, lsl #2
        add     r3, r3, #4

        @ now we call _dl_init
        ldr     r0, .L_LOADED
        ldr     r0, [sl, r0]
        ldr     r0, [r0]
        @ call _dl_init
        bl      _dl_init(PLT)
        @ clear the startup flag
        ldr     r2, .L_STARTUP_FLAG
        ldr     r1, [sl, r2]
        mov     r0, #0
        str     r0, [r1]
        @ load the finalizer function
        ldr     r0, .L_FINI_PROC
        ldr     r0, [sl, r0]
        @ jump to the user_s entry point
        mov     pc, r6
.L_GET_GOT:
        .word   _GLOBAL_OFFSET_TABLE_ - .L_GOT_GOT - 4  \n\
.L_SKIP_ARGS:                                   \n\
        .word   _dl_skip_args(GOTOFF)           \n\
.L_STARTUP_FLAG:
        .word   _dl_starting_up(GOT)
.L_FINI_PROC:
        .word   _dl_fini(GOT)
.L_STACK_END:
        .word   __libc_stack_end(GOT)
.L_LOADED:
        .word   _dl_loaded(GOT)
.previous\n\
");

/* 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_ARM_COPY)

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

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

/* The ARM never uses Elf32_Rela relocations.  */
#define ELF_MACHINE_NO_RELA 1

/* We define an initialization functions.  This is called very early in
   _dl_sysdep_start.  */
#define DL_PLATFORM_INIT dl_platform_init ()

extern const char *_dl_platform;

static inline void __attribute__ ((unused))
dl_platform_init (void)
{
  if (_dl_platform != NULL && *_dl_platform == '\0')
    /* Avoid an empty string which would disturb us.  */
    _dl_platform = NULL;
}

static inline Elf32_Addr
elf_machine_fixup_plt (struct link_map *map, lookup_t t,
                       const Elf32_Rel *reloc,
                       Elf32_Addr *reloc_addr, Elf32_Addr value)
{
  return *reloc_addr = value;
}

/* Return the final value of a plt relocation.  */
static inline Elf32_Addr
elf_machine_plt_value (struct link_map *map, const Elf32_Rel *reloc,
                       Elf32_Addr value)
{
  return value;
}

#endif /* !dl_machine_h */

#ifdef RESOLVE

extern char **_dl_argv;

/* Deal with an out-of-range PC24 reloc.  */
static Elf32_Addr
fix_bad_pc24 (Elf32_Addr *const reloc_addr, Elf32_Addr value)
{
  static void *fix_page;
  static unsigned int fix_offset;
  static size_t pagesize;
  Elf32_Word *fix_address;

  if (! fix_page)
    {
      if (! pagesize)
        pagesize = getpagesize ();
      fix_page = mmap (NULL, pagesize, PROT_READ | PROT_WRITE | PROT_EXEC,
                       MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
      if (! fix_page)
        assert (! "could not map page for fixup");
      fix_offset = 0;
    }

  fix_address = (Elf32_Word *)(fix_page + fix_offset);
  fix_address[0] = 0xe51ff004;  /* ldr pc, [pc, #-4] */
  fix_address[1] = value;

  fix_offset += 8;
  if (fix_offset >= pagesize)
    fix_page = NULL;

  return (Elf32_Addr)fix_address;
}

/* 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 Elf32_Rel *reloc,
                 const Elf32_Sym *sym, const struct r_found_version *version,
                 Elf32_Addr *const reloc_addr)
{
  if (ELF32_R_TYPE (reloc->r_info) == R_ARM_RELATIVE)
    {
#ifndef RTLD_BOOTSTRAP
      if (map != &_dl_rtld_map) /* Already done in rtld itself.  */
#endif
        *reloc_addr += map->l_addr;
    }
  else if (ELF32_R_TYPE (reloc->r_info) != R_ARM_NONE)
    {
      const Elf32_Sym *const refsym = sym;
      Elf32_Addr value = RESOLVE (&sym, version, ELF32_R_TYPE (reloc->r_info));
      if (sym)
        value += sym->st_value;

      switch (ELF32_R_TYPE (reloc->r_info))
        {
        case R_ARM_COPY:
          if (sym == NULL)
            /* This can happen in trace mode if an object could not be
               found.  */
            break;
          if (sym->st_size > refsym->st_size
              || (_dl_verbose && sym->st_size < refsym->st_size))
            {
              const char *strtab;

              strtab = (const void *) D_PTR (map, l_info[DT_STRTAB]);
              _dl_sysdep_error (_dl_argv[0] ?: "<program name unknown>",
                                ": Symbol `", strtab + refsym->st_name,
                                "' has different size in shared object, "
                                "consider re-linking\n", NULL);
            }
          memcpy (reloc_addr, (void *) value, MIN (sym->st_size,
                                                   refsym->st_size));
          break;
        case R_ARM_GLOB_DAT:
        case R_ARM_JUMP_SLOT:
#ifdef RTLD_BOOTSTRAP
          /* Fix weak undefined references.  */
          if (sym != NULL && sym->st_value == 0)
            *reloc_addr = 0;
          else
#endif
            *reloc_addr = value;
          break;
        case R_ARM_ABS32:
          {
#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.  */
            weak_extern (_dl_rtld_map);
            if (map == &_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.  */
              value -= map->l_addr + refsym->st_value;
#endif
            *reloc_addr += value;
            break;
          }
        case R_ARM_PC24:
          {
             Elf32_Sword addend;
             Elf32_Addr newvalue;

             addend = *reloc_addr & 0x00ffffff;
             if (addend & 0x00800000) addend |= 0xff000000;

             newvalue = value - (Elf32_Addr)reloc_addr + (addend << 2);
             if (newvalue & 0xfc000003)
               newvalue = fix_bad_pc24(reloc_addr, value) 
                 - (Elf32_Addr)reloc_addr + (addend << 2);

             newvalue = newvalue >> 2;
             value = (*reloc_addr & 0xff000000) | (newvalue & 0x00ffffff);
             *reloc_addr = value;
          }
        break;
        default:
          _dl_reloc_bad_type (map, ELF32_R_TYPE (reloc->r_info), 0);
          break;
        }
    }
}

static inline void
elf_machine_lazy_rel (struct link_map *map,
                      Elf32_Addr l_addr, const Elf32_Rel *reloc)
{
  Elf32_Addr *const reloc_addr = (void *) (l_addr + reloc->r_offset);
  /* Check for unexpected PLT reloc type.  */
  if (ELF32_R_TYPE (reloc->r_info) == R_ARM_JUMP_SLOT)
    *reloc_addr += l_addr;
  else
    _dl_reloc_bad_type (map, ELF32_R_TYPE (reloc->r_info), 1);
}

#endif /* RESOLVE */