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76a2c2cb6a
not looking at the new thread-safe .plt, don't be lazy about relocs. (_dl_runtime_resolve): Fix up arithmetic for new .plt layout. (elf_alpha_fix_plt): Insert wmb as appropriate to ensure safety.
437 lines
13 KiB
C
437 lines
13 KiB
C
/* Machine-dependent ELF dynamic relocation inline functions. Alpha version.
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Copyright (C) 1996, 1997 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Richard Henderson <rth@tamu.edu>.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If not,
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write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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/* This was written in the absence of an ABI -- don't expect
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it to remain unchanged. */
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#ifndef dl_machine_h
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#define dl_machine_h 1
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#define ELF_MACHINE_NAME "alpha"
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#include <assert.h>
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#include <string.h>
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/* Return nonzero iff E_MACHINE is compatible with the running host. */
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static inline int
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elf_machine_matches_host (Elf64_Word e_machine)
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{
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return e_machine == EM_ALPHA;
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}
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/* Return the link-time address of _DYNAMIC. The multiple-got-capable
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linker no longer allocates the first .got entry for this. But not to
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worry, no special tricks are needed. */
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static inline Elf64_Addr
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elf_machine_dynamic (void)
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{
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#ifndef NO_AXP_MULTI_GOT_LD
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return (Elf64_Addr) &_DYNAMIC;
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#else
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register Elf64_Addr *gp __asm__ ("$29");
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return gp[-4096];
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#endif
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}
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/* Return the run-time load address of the shared object. */
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static inline Elf64_Addr
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elf_machine_load_address (void)
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{
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/* NOTE: While it is generally unfriendly to put data in the text
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segment, it is only slightly less so when the "data" is an
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instruction. While we don't have to worry about GLD just yet, an
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optimizing linker might decide that our "data" is an unreachable
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instruction and throw it away -- with the right switches, DEC's
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linker will do this. What ought to happen is we should add
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something to GAS to allow us access to the new GPREL_HI32/LO32
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relocation types stolen from OSF/1 3.0. */
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/* This code relies on the fact that BRADDR relocations do not
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appear in dynamic relocation tables. Not that that would be very
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useful anyway -- br/bsr has a 4MB range and the shared libraries
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are usually many many terabytes away. */
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Elf64_Addr dot;
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long zero_disp;
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asm("br %0, 1f\n\t"
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".weak __load_address_undefined\n\t"
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"br $0, __load_address_undefined\n"
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"1:"
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: "=r"(dot));
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zero_disp = *(int *)dot;
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zero_disp = (zero_disp << 43) >> 41;
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return dot + 4 + zero_disp;
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}
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/* Set up the loaded object described by L so its unrelocated PLT
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entries will jump to the on-demand fixup code in dl-runtime.c. */
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static inline int
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elf_machine_runtime_setup (struct link_map *l, int lazy)
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{
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Elf64_Addr plt;
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extern void _dl_runtime_resolve (void);
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if (l->l_info[DT_JMPREL] && lazy)
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{
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/* The GOT entries for the functions in the PLT have not been
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filled in yet. Their initial contents are directed to the
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PLT which arranges for the dynamic linker to be called. */
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plt = l->l_addr + l->l_info[DT_PLTGOT]->d_un.d_ptr;
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/* This function will be called to perform the relocation. */
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*(Elf64_Addr *)(plt + 16) = (Elf64_Addr) &_dl_runtime_resolve;
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/* Identify this shared object */
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*(Elf64_Addr *)(plt + 24) = (Elf64_Addr) l;
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/* If the first instruction of the plt entry is not
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"br $28, plt0", we cannot do lazy relocation. */
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lazy = (*(unsigned *)(plt + 32) == 0xc39ffff7);
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}
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return lazy;
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}
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/* This code is used in dl-runtime.c to call the `fixup' function
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and then redirect to the address it returns. */
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#define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ( \
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"/* Trampoline for _dl_runtime_resolver */
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.globl _dl_runtime_resolve
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.ent _dl_runtime_resolve
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_dl_runtime_resolve:
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lda $sp, -168($sp)
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.frame $sp, 168, $26
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/* Preserve all registers that C normally doesn't. */
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stq $26, 0($sp)
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stq $0, 8($sp)
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stq $1, 16($sp)
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stq $2, 24($sp)
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stq $3, 32($sp)
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stq $4, 40($sp)
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stq $5, 48($sp)
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stq $6, 56($sp)
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stq $7, 64($sp)
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stq $8, 72($sp)
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stq $16, 80($sp)
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stq $17, 88($sp)
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stq $18, 96($sp)
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stq $19, 104($sp)
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stq $20, 112($sp)
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stq $21, 120($sp)
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stq $22, 128($sp)
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stq $23, 136($sp)
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stq $24, 144($sp)
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stq $25, 152($sp)
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stq $29, 160($sp)
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.mask 0x27ff01ff, -168
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/* Set up our $gp */
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br $gp, 0f
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0: ldgp $gp, 0($gp)
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.prologue 1
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/* Set up the arguments for _dl_runtime_resolve. */
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/* $16 = link_map out of plt0 */
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/* $17 = offset of reloc entry = ($28 - $27 - 20) /12 * 24 */
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subq $28, $27, $17
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ldq $16, 8($27)
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subq $17, 20, $17
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addq $17, $17, $17
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/* Do the fixup */
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bsr $26, fixup..ng
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/* Move the destination address into position. */
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mov $0, $27
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/* Restore program registers. */
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ldq $26, 0($sp)
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ldq $0, 8($sp)
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ldq $1, 16($sp)
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ldq $2, 24($sp)
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ldq $3, 32($sp)
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ldq $4, 40($sp)
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ldq $5, 48($sp)
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ldq $6, 56($sp)
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ldq $7, 64($sp)
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ldq $8, 72($sp)
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ldq $16, 80($sp)
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ldq $17, 88($sp)
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ldq $18, 96($sp)
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ldq $19, 104($sp)
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ldq $20, 112($sp)
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ldq $21, 120($sp)
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ldq $22, 128($sp)
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ldq $23, 136($sp)
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ldq $24, 144($sp)
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ldq $25, 152($sp)
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ldq $29, 160($sp)
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/* Flush the Icache after having modified the .plt code. */
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imb
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/* Clean up and turn control to the destination */
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lda $sp, 168($sp)
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jmp $31, ($27)
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.end _dl_runtime_resolve");
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/* The PLT uses Elf64_Rela relocs. */
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#define elf_machine_relplt elf_machine_rela
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/* Initial entry point code for the dynamic linker.
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The C function `_dl_start' is the real entry point;
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its return value is the user program's entry point. */
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#define RTLD_START asm ("\
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.text
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.globl _start
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.ent _start
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_start:
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br $gp, 0f
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0: ldgp $gp, 0($gp)
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/* Pass pointer to argument block to _dl_start. */
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mov $sp, $16
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bsr $26, _dl_start..ng
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.end _start
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/* FALLTHRU */
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.globl _dl_start_user
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.ent _dl_start_user
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_dl_start_user:
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/* Save the user entry point address in s0. */
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mov $0, $9
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/* See if we were run as a command with the executable file
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name as an extra leading argument. If so, adjust the stack
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pointer to skip _dl_skip_args words. */
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ldl $1, _dl_skip_args
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beq $1, 0f
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ldq $2, 0($sp)
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subq $2, $1, $2
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s8addq $1, $sp, $sp
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stq $2, 0($sp)
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/* Load _dl_default_scope[2] into s1 to pass to _dl_init_next. */
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0: ldq $10, _dl_default_scope+16
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/* Call _dl_init_next to return the address of an initializer
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function to run. */
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1: mov $10, $16
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jsr $26, _dl_init_next
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ldgp $gp, 0($26)
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beq $0, 2f
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mov $0, $27
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jsr $26, ($0)
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ldgp $gp, 0($26)
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br 1b
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2: /* Clear the startup flag. */
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.set at
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stl $31, _dl_starting_up
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.set noat
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/* Pass our finalizer function to the user in $0. */
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lda $0, _dl_fini
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/* Jump to the user's entry point. */
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mov $9, $27
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jmp ($9)
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.end _dl_start_user");
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/* Nonzero iff TYPE describes relocation of a PLT entry, so
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PLT entries should not be allowed to define the value. */
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#define elf_machine_lookup_noplt_p(type) ((type) == R_ALPHA_JMP_SLOT)
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/* Nonzero iff TYPE should not be allowed to resolve to one of
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the main executable's symbols, as for a COPY reloc, which we don't use. */
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#define elf_machine_lookup_noexec_p(type) (0)
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/* A reloc type used for ld.so cmdline arg lookups to reject PLT entries. */
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#define ELF_MACHINE_RELOC_NOPLT R_ALPHA_JMP_SLOT
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/* The alpha never uses Elf64_Rel relocations. */
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#define ELF_MACHINE_NO_REL 1
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#endif /* !dl_machine_h */
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#ifdef RESOLVE
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/* Fix up the instructions of a PLT entry to invoke the function
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rather than the dynamic linker. */
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static inline void
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elf_alpha_fix_plt(struct link_map *l,
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const Elf64_Rela *reloc,
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Elf64_Addr got_addr,
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Elf64_Addr value)
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{
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const Elf64_Rela *rela_plt;
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Elf64_Word *plte;
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long edisp;
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/* Recover the PLT entry address by calculating reloc's index into the
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.rela.plt, and finding that entry in the .plt. */
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rela_plt = (void *)(l->l_addr + l->l_info[DT_JMPREL]->d_un.d_ptr);
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plte = (void *)(l->l_addr + l->l_info[DT_PLTGOT]->d_un.d_ptr + 32);
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plte += 3 * (reloc - rela_plt);
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/* Find the displacement from the plt entry to the function. */
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edisp = (long)(value - (Elf64_Addr)&plte[3]) / 4;
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if (edisp >= -0x100000 && edisp < 0x100000)
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{
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/* If we are in range, use br to perfect branch prediction and
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elide the dependency on the address load. This case happens,
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e.g., when a shared library call is resolved to the same library. */
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int hi, lo;
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hi = value - (Elf64_Addr)&plte[0];
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lo = (short)hi;
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hi = (hi - lo) >> 16;
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/* Emit "lda $27,L($27)" */
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plte[1] = 0x237b0000 | (lo & 0xffff);
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/* Emit "br $31,function" */
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plte[2] = 0xc3e00000 | (edisp & 0x1fffff);
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/* Think about thread-safety -- the previous instructions must be
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committed to memory before the first is overwritten. */
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__asm__ __volatile__("wmb" : : : "memory");
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/* Emit "ldah $27,H($27)" */
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plte[0] = 0x277b0000 | (hi & 0xffff);
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}
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else
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{
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/* Don't bother with the hint since we already know the hint is
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wrong. Eliding it prevents the wrong page from getting pulled
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into the cache. */
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int hi, lo;
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hi = got_addr - (Elf64_Addr)&plte[0];
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lo = (short)hi;
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hi = (hi - lo) >> 16;
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/* Emit "ldq $27,L($27)" */
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plte[1] = 0xa77b0000 | (lo & 0xffff);
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/* Emit "jmp $31,($27)" */
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plte[2] = 0x6bfb0000;
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/* Think about thread-safety -- the previous instructions must be
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committed to memory before the first is overwritten. */
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__asm__ __volatile__("wmb" : : : "memory");
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/* Emit "ldah $27,H($27)" */
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plte[0] = 0x277b0000 | (hi & 0xffff);
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}
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/* At this point, if we've been doing runtime resolution, Icache is dirty.
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This will be taken care of in _dl_runtime_resolve. If instead we are
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doing this as part of non-lazy startup relocation, that bit of code
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hasn't made it into Icache yet, so there's nothing to clean up. */
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}
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/* Perform the relocation specified by RELOC and SYM (which is fully resolved).
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MAP is the object containing the reloc. */
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static inline void
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elf_machine_rela (struct link_map *map,
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const Elf64_Rela *reloc,
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const Elf64_Sym *sym,
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const struct r_found_version *version)
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{
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Elf64_Addr * const reloc_addr = (void *)(map->l_addr + reloc->r_offset);
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unsigned long const r_type = ELF64_R_TYPE (reloc->r_info);
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#ifndef RTLD_BOOTSTRAP
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/* This is defined in rtld.c, but nowhere in the static libc.a; make the
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reference weak so static programs can still link. This declaration
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cannot be done when compiling rtld.c (i.e. #ifdef RTLD_BOOTSTRAP)
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because rtld.c contains the common defn for _dl_rtld_map, which is
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incompatible with a weak decl in the same file. */
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weak_extern (_dl_rtld_map);
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#endif
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/* We cannot use a switch here because we cannot locate the switch
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jump table until we've self-relocated. */
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if (r_type == R_ALPHA_RELATIVE)
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{
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#ifndef RTLD_BOOTSTRAP
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/* Already done in dynamic linker. */
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if (map != &_dl_rtld_map)
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#endif
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*reloc_addr += map->l_addr;
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}
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else if (r_type == R_ALPHA_NONE)
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return;
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else
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{
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Elf64_Addr loadbase, sym_value;
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loadbase = RESOLVE (&sym, version, r_type);
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sym_value = sym ? loadbase + sym->st_value : 0;
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if (r_type == R_ALPHA_GLOB_DAT)
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*reloc_addr = sym_value;
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else if (r_type == R_ALPHA_JMP_SLOT)
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{
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*reloc_addr = sym_value;
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elf_alpha_fix_plt (map, reloc, (Elf64_Addr) reloc_addr, sym_value);
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}
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else if (r_type == R_ALPHA_REFQUAD)
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{
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sym_value += *reloc_addr;
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#ifndef RTLD_BOOTSTRAP
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if (map == &_dl_rtld_map)
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{
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/* Undo the relocation done here during bootstrapping.
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Now we will relocate anew, possibly using a binding
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found in the user program or a loaded library rather
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than the dynamic linker's built-in definitions used
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while loading those libraries. */
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const Elf64_Sym *const dlsymtab
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= (void *)(map->l_addr + map->l_info[DT_SYMTAB]->d_un.d_ptr);
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sym_value -= map->l_addr;
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sym_value -= dlsymtab[ELF64_R_SYM(reloc->r_info)].st_value;
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}
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else
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#endif
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sym_value += reloc->r_addend;
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*reloc_addr = sym_value;
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}
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else
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assert (! "unexpected dynamic reloc type");
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}
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}
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static inline void
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elf_machine_lazy_rel (struct link_map *map, const Elf64_Rela *reloc)
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{
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Elf64_Addr * const reloc_addr = (void *)(map->l_addr + reloc->r_offset);
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unsigned long const r_type = ELF64_R_TYPE (reloc->r_info);
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if (r_type == R_ALPHA_JMP_SLOT)
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{
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/* Perform a RELATIVE reloc on the .got entry that transfers
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to the .plt. */
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*reloc_addr += map->l_addr;
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}
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else if (r_type == R_ALPHA_NONE)
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return;
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else
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assert (! "unexpected PLT reloc type");
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}
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#endif /* RESOLVE */
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