351 lines
11 KiB
C
351 lines
11 KiB
C
/* Machine-dependent ELF dynamic relocation inline functions. PowerPC version.
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Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000
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Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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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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#ifndef dl_machine_h
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#define dl_machine_h
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#define ELF_MACHINE_NAME "powerpc"
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#include <assert.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 (Elf32_Half e_machine)
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{
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return e_machine == EM_PPC;
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}
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/* Return the link-time address of _DYNAMIC, stored as
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the first value in the GOT. */
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static inline Elf32_Addr
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elf_machine_dynamic (void)
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{
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Elf32_Addr *got;
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asm (" bl _GLOBAL_OFFSET_TABLE_-4@local"
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: "=l"(got));
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return *got;
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}
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/* Return the run-time load address of the shared object. */
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static inline Elf32_Addr
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elf_machine_load_address (void)
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{
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unsigned int *got;
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unsigned int *branchaddr;
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/* This is much harder than you'd expect. Possibly I'm missing something.
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The 'obvious' way:
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Apparently, "bcl 20,31,$+4" is what should be used to load LR
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with the address of the next instruction.
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I think this is so that machines that do bl/blr pairing don't
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get confused.
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asm ("bcl 20,31,0f ;"
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"0: mflr 0 ;"
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"lis %0,0b@ha;"
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"addi %0,%0,0b@l;"
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"subf %0,%0,0"
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: "=b" (addr) : : "r0", "lr");
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doesn't work, because the linker doesn't have to (and in fact doesn't)
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update the @ha and @l references; the loader (which runs after this
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code) will do that.
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Instead, we use the following trick:
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The linker puts the _link-time_ address of _DYNAMIC at the first
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word in the GOT. We could branch to that address, if we wanted,
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by using an @local reloc; the linker works this out, so it's safe
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to use now. We can't, of course, actually branch there, because
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we'd cause an illegal instruction exception; so we need to compute
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the address ourselves. That gives us the following code: */
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/* Get address of the 'b _DYNAMIC@local'... */
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asm ("bl 0f ;"
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"b _DYNAMIC@local;"
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"0:"
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: "=l"(branchaddr));
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/* ... and the address of the GOT. */
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asm (" bl _GLOBAL_OFFSET_TABLE_-4@local"
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: "=l"(got));
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/* So now work out the difference between where the branch actually points,
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and the offset of that location in memory from the start of the file. */
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return ((Elf32_Addr)branchaddr - *got
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+ ((int)(*branchaddr << 6 & 0xffffff00) >> 6));
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}
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#define ELF_MACHINE_BEFORE_RTLD_RELOC(dynamic_info) /* nothing */
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/* The PLT uses Elf32_Rela relocs. */
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#define elf_machine_relplt elf_machine_rela
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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. It is called
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from code built in the PLT by elf_machine_runtime_setup. */
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#define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ("\
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.section \".text\"
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.align 2
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.globl _dl_runtime_resolve
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.type _dl_runtime_resolve,@function
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_dl_runtime_resolve:
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# We need to save the registers used to pass parameters, and register 0,
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# which is used by _mcount; the registers are saved in a stack frame.
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stwu 1,-64(1)
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stw 0,12(1)
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stw 3,16(1)
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stw 4,20(1)
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# The code that calls this has put parameters for `fixup' in r12 and r11.
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mr 3,12
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stw 5,24(1)
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mr 4,11
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stw 6,28(1)
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mflr 0
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# We also need to save some of the condition register fields.
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stw 7,32(1)
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stw 0,48(1)
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stw 8,36(1)
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mfcr 0
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stw 9,40(1)
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stw 10,44(1)
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stw 0,8(1)
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bl fixup@local
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# 'fixup' returns the address we want to branch to.
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mtctr 3
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# Put the registers back...
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lwz 0,48(1)
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lwz 10,44(1)
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lwz 9,40(1)
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mtlr 0
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lwz 8,36(1)
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lwz 0,8(1)
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lwz 7,32(1)
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lwz 6,28(1)
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mtcrf 0xFF,0
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lwz 5,24(1)
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lwz 4,20(1)
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lwz 3,16(1)
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lwz 0,12(1)
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# ...unwind the stack frame, and jump to the PLT entry we updated.
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addi 1,1,64
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bctr
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.size _dl_runtime_resolve,.-_dl_runtime_resolve
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.align 2
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.globl _dl_prof_resolve
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.type _dl_prof_resolve,@function
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_dl_prof_resolve:
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# We need to save the registers used to pass parameters, and register 0,
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# which is used by _mcount; the registers are saved in a stack frame.
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stwu 1,-64(1)
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stw 0,12(1)
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stw 3,16(1)
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stw 4,20(1)
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# The code that calls this has put parameters for `fixup' in r12 and r11.
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mr 3,12
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stw 5,24(1)
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mr 4,11
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stw 6,28(1)
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mflr 5
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# We also need to save some of the condition register fields.
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stw 7,32(1)
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stw 5,48(1)
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stw 8,36(1)
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mfcr 0
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stw 9,40(1)
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stw 10,44(1)
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stw 0,8(1)
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bl profile_fixup@local
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# 'fixup' returns the address we want to branch to.
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mtctr 3
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# Put the registers back...
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lwz 0,48(1)
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lwz 10,44(1)
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lwz 9,40(1)
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mtlr 0
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lwz 8,36(1)
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lwz 0,8(1)
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lwz 7,32(1)
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lwz 6,28(1)
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mtcrf 0xFF,0
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lwz 5,24(1)
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lwz 4,20(1)
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lwz 3,16(1)
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lwz 0,12(1)
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# ...unwind the stack frame, and jump to the PLT entry we updated.
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addi 1,1,64
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bctr
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.size _dl_prof_resolve,.-_dl_prof_resolve
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# Undo '.section text'.
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.previous
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");
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/* The actual _start code is in dl-start.S. Use a really
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ugly bit of assembler to let dl-start.o see _dl_start. */
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#define RTLD_START asm (".globl _dl_start");
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/* Decide where a relocatable object should be loaded. */
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extern ElfW(Addr)
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__elf_preferred_address(struct link_map *loader, size_t maplength,
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ElfW(Addr) mapstartpref);
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#define ELF_PREFERRED_ADDRESS(loader, maplength, mapstartpref) \
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__elf_preferred_address (loader, maplength, mapstartpref)
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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. */
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#define elf_machine_lookup_noexec_p(type) ((type) == R_PPC_COPY)
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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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/* We never want to use a PLT entry as the destination of a
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reloc, when what is being relocated is a branch. This is
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partly for efficiency, but mostly so we avoid loops. */
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#define elf_machine_lookup_noplt_p(type) ((type) == R_PPC_REL24 || \
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(type) == R_PPC_ADDR24 || \
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(type) == R_PPC_JMP_SLOT)
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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_JMP_SLOT R_PPC_JMP_SLOT
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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_pltrel_p(type) ((type) == R_PPC_JMP_SLOT)
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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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Also install a small trampoline to be used by entries that have
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been relocated to an address too far away for a single branch. */
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extern int __elf_machine_runtime_setup (struct link_map *map,
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int lazy, int profile);
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#define elf_machine_runtime_setup __elf_machine_runtime_setup
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static inline void
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elf_machine_lazy_rel (struct link_map *map,
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Elf32_Addr l_addr, const Elf32_Rela *reloc)
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{
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/* elf_machine_runtime_setup handles this. */
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}
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/* Change the PLT entry whose reloc is 'reloc' to call the actual routine. */
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extern Elf32_Addr __elf_machine_fixup_plt (struct link_map *map,
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const Elf32_Rela *reloc,
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Elf32_Addr *reloc_addr,
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Elf32_Addr finaladdr);
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static inline Elf32_Addr
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elf_machine_fixup_plt (struct link_map *map, lookup_t t,
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const Elf32_Rela *reloc,
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Elf32_Addr *reloc_addr, Elf64_Addr finaladdr)
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{
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return __elf_machine_fixup_plt (map, reloc, reloc_addr, finaladdr);
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}
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/* Return the final value of a plt relocation. */
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static inline Elf32_Addr
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elf_machine_plt_value (struct link_map *map, const Elf32_Rela *reloc,
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Elf32_Addr value)
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{
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return value + reloc->r_addend;
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}
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#endif /* dl_machine_h */
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#ifdef RESOLVE
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/* Do the actual processing of a reloc, once its target address
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has been determined. */
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extern void __process_machine_rela (struct link_map *map,
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const Elf32_Rela *reloc,
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const Elf32_Sym *sym,
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const Elf32_Sym *refsym,
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Elf32_Addr *const reloc_addr,
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Elf32_Addr finaladdr,
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int rinfo);
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/* Perform the relocation specified by RELOC and SYM (which is fully resolved).
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LOADADDR is the load address of the object; INFO is an array indexed
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by DT_* of the .dynamic section info. */
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inline void
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elf_machine_rela (struct link_map *map, const Elf32_Rela *reloc,
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const Elf32_Sym *sym, const struct r_found_version *version,
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Elf32_Addr *const reloc_addr)
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{
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const Elf32_Sym *const refsym = sym;
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Elf32_Word loadbase, finaladdr;
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const int rinfo = ELF32_R_TYPE (reloc->r_info);
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if (rinfo == R_PPC_NONE)
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return;
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/* The condition on the next two lines is a hack around a bug in Solaris
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tools on Sparc. It's not clear whether it should really be here at all,
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but if not the binutils need to be changed. */
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if (rinfo == R_PPC_RELATIVE
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|| (sym->st_shndx != SHN_UNDEF
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&& ELF32_ST_BIND (sym->st_info) == STB_LOCAL))
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{
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/* Has already been relocated. */
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loadbase = map->l_addr;
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finaladdr = loadbase + reloc->r_addend;
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}
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else
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{
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loadbase = (Elf32_Word) (char *) (RESOLVE (&sym, version,
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ELF32_R_TYPE(reloc->r_info)));
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if (sym == NULL)
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{
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/* Weak symbol that wasn't actually defined anywhere. */
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assert(loadbase == 0);
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finaladdr = reloc->r_addend;
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}
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else
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finaladdr = (loadbase + (Elf32_Word) (char *) sym->st_value
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+ reloc->r_addend);
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}
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/* A small amount of code is duplicated here for speed. In libc,
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more than 90% of the relocs are R_PPC_RELATIVE; in the X11 shared
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libraries, 60% are R_PPC_RELATIVE, 24% are R_PPC_GLOB_DAT or
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R_PPC_ADDR32, and 16% are R_PPC_JMP_SLOT (which this routine
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wouldn't usually handle). As an bonus, doing this here allows
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the switch statement in __process_machine_rela to work. */
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if (rinfo == R_PPC_RELATIVE
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|| rinfo == R_PPC_GLOB_DAT
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|| rinfo == R_PPC_ADDR32)
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{
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*reloc_addr = finaladdr;
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}
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else
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__process_machine_rela (map, reloc, sym, refsym,
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reloc_addr, finaladdr, rinfo);
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}
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#define ELF_MACHINE_NO_REL 1
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/* The SVR4 ABI specifies that the JMPREL relocs must be inside the
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DT_RELA table. */
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#define ELF_MACHINE_PLTREL_OVERLAP 1
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#endif /* RESOLVE */
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