ldso/ldso/arc/dl-startup.h

   1 /*
   2  * Copyright (C) 2013 Synopsys, Inc. (www.synopsys.com)
   3  *
   4  * Licensed under the LGPL v2.1 or later, see the file COPYING.LIB in this tarball.
   5  */
   6
   7 /*
   8  * vineetg: Refactoring/cleanup of loader entry point
   9  *  Removed 6 useless insns
  10  * Joern Improved it even further:
  11  *  -better insn scheduling
  12  *  -no need for conditional code for _dl_skip_args
  13  *  -use of assembler .&2 expressions vs. @gotpc refs (avoids need for GP)
  14  *
  15  * What this code does:
  16  *  -ldso starts execution here when kernel returns from execve()
  17  *  -calls into generic ldso entry point _dl_start( )
  18  *  -optionally adjusts argc for executable if exec passed as cmd
  19  *  -calls into app main with address of finaliser
  20  */
  21 __asm__(
  22     ".section .text                                             \n"
  23     ".align 4                                                   \n"
  24     ".global _start                                             \n"
  25     ".hidden _start                                             \n"
  26     ".type  _start,@function                                    \n"
  27
  28     "_start:                                                    \n"
  29     "   ; ldso entry point, returns app entry point             \n"
  30     "   bl.d    _dl_start                                       \n"
  31     "   mov_s   r0, sp          ; pass ptr to aux vector tbl    \n"
  32
  33     "   ; If ldso ran as cmd with executable file nm as arg     \n"
  34     "   ; skip the extra args calc by dl_start()                \n"
  35     "   ld_s    r1, [sp]       ; orig argc from aux-vec Tbl     \n"
  36
  37     "   ld      r12, [pcl, _dl_skip_args@pcl]                   \n"
  38     "   add     r2, pcl, _dl_fini@pcl       ; finalizer         \n"
  39
  40     "   add2    sp, sp, r12    ; discard argv entries from stack\n"
  41     "   sub_s   r1, r1, r12    ; adjusted argc, on stack        \n"
  42     "   st_s    r1, [sp]                                        \n"
  43
  44     "   j_s.d   [r0]           ; app entry point                \n"
  45     "   mov_s   r0, r2         ; ptr to finalizer _dl_fini      \n"
  46
  47     ".size  _start,.-_start                                     \n"
  48     ".previous                                                  \n"
  49 );
  50
  51 /*
  52  * Get a pointer to the argv array.  On many platforms this can be just
  53  * the address if the first argument, on other platforms we need to
  54  * do something a little more subtle here.
  55  */
  56 #define GET_ARGV(ARGVP, ARGS) ARGVP = ((unsigned long*) ARGS + 1)
  57
  58 /*
  59  * Dynamic loader bootstrapping:
  60  * The only relocations that should be found are either R_ARC_RELATIVE for
  61  * data relocations (.got, etc) or R_ARC_JMP_SLOT for code relocations
  62  * (.plt).  It is safe to assume that all of these relocations are word
  63  * aligned.
  64  * @RELP is the reloc entry being processed
  65  * @REL is the pointer to the address we are relocating.
  66  * @SYMBOL is the symbol involved in the relocation
  67  * @LOAD is the load address.
  68  */
  69
  70 #define PERFORM_BOOTSTRAP_RELOC(RELP,REL,SYMBOL,LOAD,SYMTAB)            \
  71 do {                                                                    \
  72         int type = ELF32_R_TYPE((RELP)->r_info);                        \
  73         if (likely(type == R_ARC_RELATIVE))                             \
  74                 *REL += (unsigned long) LOAD;                           \
  75         else if (type == R_ARC_JMP_SLOT)                                \
  76                 *REL = SYMBOL;                                          \
  77         else if (type != R_ARC_NONE)                                    \
  78                 _dl_exit(1);                                            \
  79 }while(0)
  80
  81 /*
  82  * This will go away once we have DT_RELACOUNT
  83  */
  84 #define ARCH_NEEDS_BOOTSTRAP_RELOCS
  85
  86 /* we dont need to spit out argc, argv etc for debugging */
  87 #define NO_EARLY_SEND_STDERR    1