sysdeps/sparc/sparc64/dl-plt.h

   1 /* PLT fixups.  Sparc 64-bit version.
   2    Copyright (C) 1997-2014 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #ifndef _DL_PLT_H
  20 #define _DL_PLT_H
  21
  22 /* We have 4 cases to handle.  And we code different code sequences
  23    for each one.  I love V9 code models...  */
  24 static inline void __attribute__ ((always_inline))
  25 sparc64_fixup_plt (struct link_map *map, const Elf64_Rela *reloc,
  26                    Elf64_Addr *reloc_addr, Elf64_Addr value,
  27                    Elf64_Addr high, int t)
  28 {
  29   unsigned int *insns = (unsigned int *) reloc_addr;
  30   Elf64_Addr plt_vaddr = (Elf64_Addr) reloc_addr;
  31   Elf64_Sxword disp = value - plt_vaddr;
  32
  33   /* 't' is '0' if we are resolving this PLT entry for RTLD bootstrap,
  34      in which case we'll be resolving all PLT entries and thus can
  35      optimize by overwriting instructions starting at the first PLT entry
  36      instruction and we need not be mindful of thread safety.
  37
  38      Otherwise, 't' is '1'.
  39
  40      Now move plt_vaddr up to the call instruction.  */
  41   plt_vaddr += ((t + 1) * 4);
  42
  43   /* PLT entries .PLT32768 and above look always the same.  */
  44   if (__builtin_expect (high, 0) != 0)
  45     {
  46       *reloc_addr = value - map->l_addr;
  47     }
  48   /* Near destination.  */
  49   else if (disp >= -0x800000 && disp < 0x800000)
  50     {
  51       unsigned int insn;
  52
  53       /* ba,a */
  54       insn = 0x30800000 | ((disp >> 2) & 0x3fffff);
  55
  56       if (disp >= -0x100000 && disp < 0x100000)
  57         {
  58           /* ba,a,pt %icc */
  59           insn = 0x30480000  | ((disp >> 2) & 0x07ffff);
  60         }
  61
  62       /* As this is just one instruction, it is thread safe and so we
  63          can avoid the unnecessary sethi FOO, %g1.  Each 64-bit PLT
  64          entry is 8 instructions long, so we can't run into the 'jmp'
  65          delay slot problems 32-bit PLTs can.  */
  66       insns[0] = insn;
  67       __asm __volatile ("flush %0" : : "r" (insns));
  68     }
  69   /* 32-bit Sparc style, the target is in the lower 32-bits of
  70      address space.  */
  71   else if (insns += t, (value >> 32) == 0)
  72     {
  73       /* sethi  %hi(target), %g1
  74          jmpl   %g1 + %lo(target), %g0  */
  75
  76       insns[1] = 0x81c06000 | (value & 0x3ff);
  77       __asm __volatile ("flush %0 + 4" : : "r" (insns));
  78
  79       insns[0] = 0x03000000 | ((unsigned int)(value >> 10));
  80       __asm __volatile ("flush %0" : : "r" (insns));
  81     }
  82   /* We can also get somewhat simple sequences if the distance between
  83      the target and the PLT entry is within +/- 2GB.  */
  84   else if ((plt_vaddr > value
  85             && ((plt_vaddr - value) >> 31) == 0)
  86            || (value > plt_vaddr
  87                && ((value - plt_vaddr) >> 31) == 0))
  88     {
  89       unsigned int displacement;
  90
  91       if (plt_vaddr > value)
  92         displacement = (0 - (plt_vaddr - value));
  93       else
  94         displacement = value - plt_vaddr;
  95
  96       /* mov    %o7, %g1
  97          call   displacement
  98           mov   %g1, %o7  */
  99
 100       insns[2] = 0x9e100001;
 101       __asm __volatile ("flush %0 + 8" : : "r" (insns));
 102
 103       insns[1] = 0x40000000 | (displacement >> 2);
 104       __asm __volatile ("flush %0 + 4" : : "r" (insns));
 105
 106       insns[0] = 0x8210000f;
 107       __asm __volatile ("flush %0" : : "r" (insns));
 108     }
 109   /* Worst case, ho hum...  */
 110   else
 111     {
 112       unsigned int high32 = (value >> 32);
 113       unsigned int low32 = (unsigned int) value;
 114
 115       /* ??? Some tricks can be stolen from the sparc64 egcs backend
 116              constant formation code I wrote.  -DaveM  */
 117
 118       if (__builtin_expect (high32 & 0x3ff, 0))
 119         {
 120           /* sethi      %hh(value), %g1
 121              sethi      %lm(value), %g5
 122              or         %g1, %hm(value), %g1
 123              or         %g5, %lo(value), %g5
 124              sllx       %g1, 32, %g1
 125              jmpl       %g1 + %g5, %g0
 126               nop  */
 127
 128           insns[5] = 0x81c04005;
 129           __asm __volatile ("flush %0 + 20" : : "r" (insns));
 130
 131           insns[4] = 0x83287020;
 132           __asm __volatile ("flush %0 + 16" : : "r" (insns));
 133
 134           insns[3] = 0x8a116000 | (low32 & 0x3ff);
 135           __asm __volatile ("flush %0 + 12" : : "r" (insns));
 136
 137           insns[2] = 0x82106000 | (high32 & 0x3ff);
 138         }
 139       else
 140         {
 141           /* sethi      %hh(value), %g1
 142              sethi      %lm(value), %g5
 143              sllx       %g1, 32, %g1
 144              or         %g5, %lo(value), %g5
 145              jmpl       %g1 + %g5, %g0
 146               nop  */
 147
 148           insns[4] = 0x81c04005;
 149           __asm __volatile ("flush %0 + 16" : : "r" (insns));
 150
 151           insns[3] = 0x8a116000 | (low32 & 0x3ff);
 152           __asm __volatile ("flush %0 + 12" : : "r" (insns));
 153
 154           insns[2] = 0x83287020;
 155         }
 156
 157       __asm __volatile ("flush %0 + 8" : : "r" (insns));
 158
 159       insns[1] = 0x0b000000 | (low32 >> 10);
 160       __asm __volatile ("flush %0 + 4" : : "r" (insns));
 161
 162       insns[0] = 0x03000000 | (high32 >> 10);
 163       __asm __volatile ("flush %0" : : "r" (insns));
 164     }
 165 }
 166
 167 #endif /* dl-plt.h */