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/* Target-dependent code for GDB, the GNU debugger.

   Copyright (C) 1986, 1987, 1989, 1991, 1992, 1993, 1994, 1995, 1996, 1997,

   2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010

   Free Software Foundation, Inc.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify

   it under the terms of the GNU General Public License as published by

   the Free Software Foundation; either version 3 of the License, or

   (at your option) any later version.

   This program 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 General Public License for more details.

   You should have received a copy of the GNU General Public License

   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#include "defs.h"

#include "frame.h"

#include "inferior.h"

#include "symtab.h"

#include "target.h"

#include "gdbcore.h"

#include "gdbcmd.h"

#include "symfile.h"

#include "objfiles.h"

#include "regcache.h"

#include "value.h"

#include "osabi.h"

#include "regset.h"

#include "solib-svr4.h"

#include "solib-spu.h"

#include "solib.h"

#include "solist.h"

#include "ppc-tdep.h"

#include "ppc-linux-tdep.h"

#include "trad-frame.h"

#include "frame-unwind.h"

#include "tramp-frame.h"

#include "observer.h"

#include "auxv.h"

#include "elf/common.h"

#include "exceptions.h"

#include "arch-utils.h"

#include "spu-tdep.h"

#include "xml-syscall.h"

#include "features/rs6000/powerpc-32l.c"

#include "features/rs6000/powerpc-altivec32l.c"

#include "features/rs6000/powerpc-cell32l.c"

#include "features/rs6000/powerpc-vsx32l.c"

#include "features/rs6000/powerpc-isa205-32l.c"

#include "features/rs6000/powerpc-isa205-altivec32l.c"

#include "features/rs6000/powerpc-isa205-vsx32l.c"

#include "features/rs6000/powerpc-64l.c"

#include "features/rs6000/powerpc-altivec64l.c"

#include "features/rs6000/powerpc-cell64l.c"

#include "features/rs6000/powerpc-vsx64l.c"

#include "features/rs6000/powerpc-isa205-64l.c"

#include "features/rs6000/powerpc-isa205-altivec64l.c"

#include "features/rs6000/powerpc-isa205-vsx64l.c"

#include "features/rs6000/powerpc-e500l.c"

/* The syscall's XML filename for PPC and PPC64.  */

#define XML_SYSCALL_FILENAME_PPC "syscalls/ppc-linux.xml"

#define XML_SYSCALL_FILENAME_PPC64 "syscalls/ppc64-linux.xml"

/* ppc_linux_memory_remove_breakpoints attempts to remove a breakpoint

   in much the same fashion as memory_remove_breakpoint in mem-break.c,

   but is careful not to write back the previous contents if the code

   in question has changed in between inserting the breakpoint and

   removing it.

   Here is the problem that we're trying to solve...

   Once upon a time, before introducing this function to remove

   breakpoints from the inferior, setting a breakpoint on a shared

   library function prior to running the program would not work

   properly.  In order to understand the problem, it is first

   necessary to understand a little bit about dynamic linking on

   this platform.

   A call to a shared library function is accomplished via a bl

   (branch-and-link) instruction whose branch target is an entry

   in the procedure linkage table (PLT).  The PLT in the object

   file is uninitialized.  To gdb, prior to running the program, the

   entries in the PLT are all zeros.

   Once the program starts running, the shared libraries are loaded

   and the procedure linkage table is initialized, but the entries in

   the table are not (necessarily) resolved.  Once a function is

   actually called, the code in the PLT is hit and the function is

   resolved.  In order to better illustrate this, an example is in

   order; the following example is from the gdb testsuite.

        We start the program shmain.

            [kev@arroyo testsuite]$ ../gdb gdb.base/shmain

            [...]

        We place two breakpoints, one on shr1 and the other on main.

            (gdb) b shr1

            Breakpoint 1 at 0x100409d4

            (gdb) b main

            Breakpoint 2 at 0x100006a0: file gdb.base/shmain.c, line 44.

        Examine the instruction (and the immediatly following instruction)

        upon which the breakpoint was placed.  Note that the PLT entry

        for shr1 contains zeros.

            (gdb) x/2i 0x100409d4

            0x100409d4 <shr1>:      .long 0x0

            0x100409d8 <shr1+4>:    .long 0x0

        Now run 'til main.

            (gdb) r

            Starting program: gdb.base/shmain

            Breakpoint 1 at 0xffaf790: file gdb.base/shr1.c, line 19.

            Breakpoint 2, main ()

                at gdb.base/shmain.c:44

            44        g = 1;

        Examine the PLT again.  Note that the loading of the shared

        library has initialized the PLT to code which loads a constant

        (which I think is an index into the GOT) into r11 and then

        branchs a short distance to the code which actually does the

        resolving.

            (gdb) x/2i 0x100409d4

            0x100409d4 <shr1>:      li      r11,4

            0x100409d8 <shr1+4>:    b       0x10040984 <sg+4>

            (gdb) c

            Continuing.

            Breakpoint 1, shr1 (x=1)

                at gdb.base/shr1.c:19

            19        l = 1;

        Now we've hit the breakpoint at shr1.  (The breakpoint was

        reset from the PLT entry to the actual shr1 function after the

        shared library was loaded.) Note that the PLT entry has been

        resolved to contain a branch that takes us directly to shr1.

        (The real one, not the PLT entry.)

            (gdb) x/2i 0x100409d4

            0x100409d4 <shr1>:      b       0xffaf76c <shr1>

            0x100409d8 <shr1+4>:    b       0x10040984 <sg+4>

   The thing to note here is that the PLT entry for shr1 has been

   changed twice.

   Now the problem should be obvious.  GDB places a breakpoint (a

   trap instruction) on the zero value of the PLT entry for shr1.

   Later on, after the shared library had been loaded and the PLT

   initialized, GDB gets a signal indicating this fact and attempts

   (as it always does when it stops) to remove all the breakpoints.

   The breakpoint removal was causing the former contents (a zero

   word) to be written back to the now initialized PLT entry thus

   destroying a portion of the initialization that had occurred only a

   short time ago.  When execution continued, the zero word would be

   executed as an instruction an an illegal instruction trap was

   generated instead.  (0 is not a legal instruction.)

   The fix for this problem was fairly straightforward.  The function

   memory_remove_breakpoint from mem-break.c was copied to this file,

   modified slightly, and renamed to ppc_linux_memory_remove_breakpoint.

   In tm-linux.h, MEMORY_REMOVE_BREAKPOINT is defined to call this new

   function.

   The differences between ppc_linux_memory_remove_breakpoint () and

   memory_remove_breakpoint () are minor.  All that the former does

   that the latter does not is check to make sure that the breakpoint

   location actually contains a breakpoint (trap instruction) prior

   to attempting to write back the old contents.  If it does contain

   a trap instruction, we allow the old contents to be written back.

   Otherwise, we silently do nothing.

   The big question is whether memory_remove_breakpoint () should be

   changed to have the same functionality.  The downside is that more

   traffic is generated for remote targets since we'll have an extra

   fetch of a memory word each time a breakpoint is removed.

   For the time being, we'll leave this self-modifying-code-friendly

   version in ppc-linux-tdep.c, but it ought to be migrated somewhere

   else in the event that some other platform has similar needs with

   regard to removing breakpoints in some potentially self modifying

   code.  */

static int

ppc_linux_memory_remove_breakpoint (struct gdbarch *gdbarch,

                                    struct bp_target_info *bp_tgt)

{

  CORE_ADDR addr = bp_tgt->placed_address;

  const unsigned char *bp;

  int val;

  int bplen;

  gdb_byte old_contents[BREAKPOINT_MAX];

  struct cleanup *cleanup;

  /* Determine appropriate breakpoint contents and size for this address.  */

  bp = gdbarch_breakpoint_from_pc (gdbarch, &addr, &bplen);

  if (bp == NULL)

    error (_("Software breakpoints not implemented for this target."));

  /* Make sure we see the memory breakpoints.  */

  cleanup = make_show_memory_breakpoints_cleanup (1);

  val = target_read_memory (addr, old_contents, bplen);

  /* If our breakpoint is no longer at the address, this means that the

     program modified the code on us, so it is wrong to put back the

     old value */

  if (val == 0 && memcmp (bp, old_contents, bplen) == 0)

    val = target_write_memory (addr, bp_tgt->shadow_contents, bplen);

  do_cleanups (cleanup);

  return val;

}

/* For historic reasons, PPC 32 GNU/Linux follows PowerOpen rather

   than the 32 bit SYSV R4 ABI structure return convention - all

   structures, no matter their size, are put in memory.  Vectors,

   which were added later, do get returned in a register though.  */

static enum return_value_convention

ppc_linux_return_value (struct gdbarch *gdbarch, struct type *func_type,

                        struct type *valtype, struct regcache *regcache,

                        gdb_byte *readbuf, const gdb_byte *writebuf)

{

  if ((TYPE_CODE (valtype) == TYPE_CODE_STRUCT

       || TYPE_CODE (valtype) == TYPE_CODE_UNION)

      && !((TYPE_LENGTH (valtype) == 16 || TYPE_LENGTH (valtype) == 8)

           && TYPE_VECTOR (valtype)))

    return RETURN_VALUE_STRUCT_CONVENTION;

  else

    return ppc_sysv_abi_return_value (gdbarch, func_type, valtype, regcache,

                                      readbuf, writebuf);

}

/* Macros for matching instructions.  Note that, since all the

   operands are masked off before they're or-ed into the instruction,

   you can use -1 to make masks.  */

#define insn_d(opcd, rts, ra, d)                \

  ((((opcd) & 0x3f) << 26)                      \

   | (((rts) & 0x1f) << 21)                     \

   | (((ra) & 0x1f) << 16)                      \

   | ((d) & 0xffff))

#define insn_ds(opcd, rts, ra, d, xo)           \

  ((((opcd) & 0x3f) << 26)                      \

   | (((rts) & 0x1f) << 21)                     \

   | (((ra) & 0x1f) << 16)                      \

   | ((d) & 0xfffc)                             \

   | ((xo) & 0x3))

#define insn_xfx(opcd, rts, spr, xo)            \

  ((((opcd) & 0x3f) << 26)                      \

   | (((rts) & 0x1f) << 21)                     \

   | (((spr) & 0x1f) << 16)                     \

   | (((spr) & 0x3e0) << 6)                     \

   | (((xo) & 0x3ff) << 1))

/* Read a PPC instruction from memory.  PPC instructions are always

   big-endian, no matter what endianness the program is running in, so

   we can't use read_memory_integer or one of its friends here.  */

static unsigned int

read_insn (CORE_ADDR pc)

{

  unsigned char buf[4];

  read_memory (pc, buf, 4);

  return (buf[0] << 24) | (buf[1] << 16) | (buf[2] << 8) | buf[3];

}

/* An instruction to match.  */

struct insn_pattern

{

  unsigned int mask;            /* mask the insn with this... */

  unsigned int data;            /* ...and see if it matches this. */

  int optional;                 /* If non-zero, this insn may be absent.  */

};

/* Return non-zero if the instructions at PC match the series

   described in PATTERN, or zero otherwise.  PATTERN is an array of

   'struct insn_pattern' objects, terminated by an entry whose mask is

   zero.

   When the match is successful, fill INSN[i] with what PATTERN[i]

   matched.  If PATTERN[i] is optional, and the instruction wasn't

   present, set INSN[i] to 0 (which is not a valid PPC instruction).

   INSN should have as many elements as PATTERN.  Note that, if

   PATTERN contains optional instructions which aren't present in

   memory, then INSN will have holes, so INSN[i] isn't necessarily the

   i'th instruction in memory.  */

static int

insns_match_pattern (CORE_ADDR pc,

                     struct insn_pattern *pattern,

                     unsigned int *insn)

{

  int i;

  for (i = 0; pattern[i].mask; i++)

    {

      insn[i] = read_insn (pc);

      if ((insn[i] & pattern[i].mask) == pattern[i].data)

        pc += 4;

      else if (pattern[i].optional)

        insn[i] = 0;

      else

        return 0;

    }

  return 1;

}

/* Return the 'd' field of the d-form instruction INSN, properly

   sign-extended.  */

static CORE_ADDR

insn_d_field (unsigned int insn)

{

  return ((((CORE_ADDR) insn & 0xffff) ^ 0x8000) - 0x8000);

}

/* Return the 'ds' field of the ds-form instruction INSN, with the two

   zero bits concatenated at the right, and properly

   sign-extended.  */

static CORE_ADDR

insn_ds_field (unsigned int insn)

{

  return ((((CORE_ADDR) insn & 0xfffc) ^ 0x8000) - 0x8000);

}

/* If DESC is the address of a 64-bit PowerPC GNU/Linux function

   descriptor, return the descriptor's entry point.  */

static CORE_ADDR

ppc64_desc_entry_point (struct gdbarch *gdbarch, CORE_ADDR desc)

{

  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);

  /* The first word of the descriptor is the entry point.  */

  return (CORE_ADDR) read_memory_unsigned_integer (desc, 8, byte_order);

}

/* Pattern for the standard linkage function.  These are built by

   build_plt_stub in elf64-ppc.c, whose GLINK argument is always

   zero.  */

static struct insn_pattern ppc64_standard_linkage1[] =

  {

    /* addis r12, r2, <any> */

    { insn_d (-1, -1, -1, 0), insn_d (15, 12, 2, 0), 0 },

    /* std r2, 40(r1) */

    { -1, insn_ds (62, 2, 1, 40, 0), 0 },

    /* ld r11, <any>(r12) */

    { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 11, 12, 0, 0), 0 },

    /* addis r12, r12, 1 <optional> */

    { insn_d (-1, -1, -1, -1), insn_d (15, 12, 12, 1), 1 },

    /* ld r2, <any>(r12) */

    { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 2, 12, 0, 0), 0 },

    /* addis r12, r12, 1 <optional> */

    { insn_d (-1, -1, -1, -1), insn_d (15, 12, 12, 1), 1 },

    /* mtctr r11 */

    { insn_xfx (-1, -1, -1, -1), insn_xfx (31, 11, 9, 467), 0 },

    /* ld r11, <any>(r12) */

    { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 11, 12, 0, 0), 0 },

    /* bctr */

    { -1, 0x4e800420, 0 },

    { 0, 0, 0 }

  };

#define PPC64_STANDARD_LINKAGE1_LEN \

  (sizeof (ppc64_standard_linkage1) / sizeof (ppc64_standard_linkage1[0]))

static struct insn_pattern ppc64_standard_linkage2[] =

  {

    /* addis r12, r2, <any> */

    { insn_d (-1, -1, -1, 0), insn_d (15, 12, 2, 0), 0 },

    /* std r2, 40(r1) */

    { -1, insn_ds (62, 2, 1, 40, 0), 0 },

    /* ld r11, <any>(r12) */

    { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 11, 12, 0, 0), 0 },

    /* addi r12, r12, <any> <optional> */

    { insn_d (-1, -1, -1, 0), insn_d (14, 12, 12, 0), 1 },

    /* mtctr r11 */

    { insn_xfx (-1, -1, -1, -1), insn_xfx (31, 11, 9, 467), 0 },

    /* ld r2, <any>(r12) */

    { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 2, 12, 0, 0), 0 },

    /* ld r11, <any>(r12) */

    { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 11, 12, 0, 0), 0 },

    /* bctr */

    { -1, 0x4e800420, 0 },

    { 0, 0, 0 }

  };

#define PPC64_STANDARD_LINKAGE2_LEN \

  (sizeof (ppc64_standard_linkage2) / sizeof (ppc64_standard_linkage2[0]))

static struct insn_pattern ppc64_standard_linkage3[] =

  {

    /* std r2, 40(r1) */

    { -1, insn_ds (62, 2, 1, 40, 0), 0 },

    /* ld r11, <any>(r2) */

    { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 11, 2, 0, 0), 0 },

    /* addi r2, r2, <any> <optional> */

    { insn_d (-1, -1, -1, 0), insn_d (14, 2, 2, 0), 1 },

    /* mtctr r11 */

    { insn_xfx (-1, -1, -1, -1), insn_xfx (31, 11, 9, 467), 0 },

    /* ld r11, <any>(r2) */

    { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 11, 2, 0, 0), 0 },

    /* ld r2, <any>(r2) */

    { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 2, 2, 0, 0), 0 },

    /* bctr */

    { -1, 0x4e800420, 0 },

    { 0, 0, 0 }

  };

#define PPC64_STANDARD_LINKAGE3_LEN \

  (sizeof (ppc64_standard_linkage3) / sizeof (ppc64_standard_linkage3[0]))

/* When the dynamic linker is doing lazy symbol resolution, the first

   call to a function in another object will go like this:

   - The user's function calls the linkage function:

     100007c4:  4b ff fc d5     bl      10000498

     100007c8:  e8 41 00 28     ld      r2,40(r1)

   - The linkage function loads the entry point (and other stuff) from

     the function descriptor in the PLT, and jumps to it:

     10000498:  3d 82 00 00     addis   r12,r2,0

     1000049c:  f8 41 00 28     std     r2,40(r1)

     100004a0:  e9 6c 80 98     ld      r11,-32616(r12)

     100004a4:  e8 4c 80 a0     ld      r2,-32608(r12)

     100004a8:  7d 69 03 a6     mtctr   r11

     100004ac:  e9 6c 80 a8     ld      r11,-32600(r12)

     100004b0:  4e 80 04 20     bctr

   - But since this is the first time that PLT entry has been used, it

     sends control to its glink entry.  That loads the number of the

     PLT entry and jumps to the common glink0 code:

     10000c98:  38 00 00 00     li      r0,0

     10000c9c:  4b ff ff dc     b       10000c78

   - The common glink0 code then transfers control to the dynamic

     linker's fixup code:

     10000c78:  e8 41 00 28     ld      r2,40(r1)

     10000c7c:  3d 82 00 00     addis   r12,r2,0

     10000c80:  e9 6c 80 80     ld      r11,-32640(r12)

     10000c84:  e8 4c 80 88     ld      r2,-32632(r12)

     10000c88:  7d 69 03 a6     mtctr   r11

     10000c8c:  e9 6c 80 90     ld      r11,-32624(r12)

     10000c90:  4e 80 04 20     bctr

   Eventually, this code will figure out how to skip all of this,

   including the dynamic linker.  At the moment, we just get through

   the linkage function.  */

/* If the current thread is about to execute a series of instructions

   at PC matching the ppc64_standard_linkage pattern, and INSN is the result

   from that pattern match, return the code address to which the

   standard linkage function will send them.  (This doesn't deal with

   dynamic linker lazy symbol resolution stubs.)  */

static CORE_ADDR

ppc64_standard_linkage1_target (struct frame_info *frame,

                                CORE_ADDR pc, unsigned int *insn)

{

  struct gdbarch *gdbarch = get_frame_arch (frame);

  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);

  /* The address of the function descriptor this linkage function

     references.  */

  CORE_ADDR desc

    = ((CORE_ADDR) get_frame_register_unsigned (frame,

                                                tdep->ppc_gp0_regnum + 2)

       + (insn_d_field (insn[0]) << 16)

       + insn_ds_field (insn[2]));

  /* The first word of the descriptor is the entry point.  Return that.  */

  return ppc64_desc_entry_point (gdbarch, desc);

}

static struct core_regset_section ppc_linux_vsx_regset_sections[] =

{

  { ".reg", 268, "general-purpose" },

  { ".reg2", 264, "floating-point" },

  { ".reg-ppc-vmx", 544, "ppc Altivec" },

  { ".reg-ppc-vsx", 256, "POWER7 VSX" },

  { NULL, 0}

};

static struct core_regset_section ppc_linux_vmx_regset_sections[] =

{

  { ".reg", 268, "general-purpose" },

  { ".reg2", 264, "floating-point" },

  { ".reg-ppc-vmx", 544, "ppc Altivec" },

  { NULL, 0}

};

static struct core_regset_section ppc_linux_fp_regset_sections[] =

{

  { ".reg", 268, "general-purpose" },

  { ".reg2", 264, "floating-point" },

  { NULL, 0}

};

static CORE_ADDR

ppc64_standard_linkage2_target (struct frame_info *frame,

                                CORE_ADDR pc, unsigned int *insn)

{

  struct gdbarch *gdbarch = get_frame_arch (frame);

  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);

  /* The address of the function descriptor this linkage function

     references.  */

  CORE_ADDR desc

    = ((CORE_ADDR) get_frame_register_unsigned (frame,

                                                tdep->ppc_gp0_regnum + 2)

       + (insn_d_field (insn[0]) << 16)

       + insn_ds_field (insn[2]));

  /* The first word of the descriptor is the entry point.  Return that.  */

  return ppc64_desc_entry_point (gdbarch, desc);

}

static CORE_ADDR

ppc64_standard_linkage3_target (struct frame_info *frame,

                                CORE_ADDR pc, unsigned int *insn)

{

  struct gdbarch *gdbarch = get_frame_arch (frame);

  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);

  /* The address of the function descriptor this linkage function

     references.  */

  CORE_ADDR desc

    = ((CORE_ADDR) get_frame_register_unsigned (frame,

                                                tdep->ppc_gp0_regnum + 2)

       + insn_ds_field (insn[1]));

  /* The first word of the descriptor is the entry point.  Return that.  */

  return ppc64_desc_entry_point (gdbarch, desc);

}

/* Given that we've begun executing a call trampoline at PC, return

   the entry point of the function the trampoline will go to.  */

static CORE_ADDR

ppc64_skip_trampoline_code (struct frame_info *frame, CORE_ADDR pc)

{

  unsigned int ppc64_standard_linkage1_insn[PPC64_STANDARD_LINKAGE1_LEN];

  unsigned int ppc64_standard_linkage2_insn[PPC64_STANDARD_LINKAGE2_LEN];

  unsigned int ppc64_standard_linkage3_insn[PPC64_STANDARD_LINKAGE3_LEN];

  CORE_ADDR target;

  if (insns_match_pattern (pc, ppc64_standard_linkage1,

                           ppc64_standard_linkage1_insn))

    pc = ppc64_standard_linkage1_target (frame, pc,

                                         ppc64_standard_linkage1_insn);

  else if (insns_match_pattern (pc, ppc64_standard_linkage2,

                                ppc64_standard_linkage2_insn))

    pc = ppc64_standard_linkage2_target (frame, pc,

                                         ppc64_standard_linkage2_insn);

  else if (insns_match_pattern (pc, ppc64_standard_linkage3,

                                ppc64_standard_linkage3_insn))

    pc = ppc64_standard_linkage3_target (frame, pc,

                                         ppc64_standard_linkage3_insn);

  else

    return 0;

  /* The PLT descriptor will either point to the already resolved target

     address, or else to a glink stub.  As the latter carry synthetic @plt

     symbols, find_solib_trampoline_target should be able to resolve them.  */

  target = find_solib_trampoline_target (frame, pc);

  return target? target : pc;

}

/* Support for convert_from_func_ptr_addr (ARCH, ADDR, TARG) on PPC64

   GNU/Linux.

   Usually a function pointer's representation is simply the address

   of the function.  On GNU/Linux on the PowerPC however, a function

   pointer may be a pointer to a function descriptor.

   For PPC64, a function descriptor is a TOC entry, in a data section,

   which contains three words: the first word is the address of the

   function, the second word is the TOC pointer (r2), and the third word

   is the static chain value.

   Throughout GDB it is currently assumed that a function pointer contains

   the address of the function, which is not easy to fix.  In addition, the

   conversion of a function address to a function pointer would

   require allocation of a TOC entry in the inferior's memory space,

   with all its drawbacks.  To be able to call C++ virtual methods in

   the inferior (which are called via function pointers),

   find_function_addr uses this function to get the function address

   from a function pointer.

   If ADDR points at what is clearly a function descriptor, transform

   it into the address of the corresponding function, if needed.  Be

   conservative, otherwise GDB will do the transformation on any

   random addresses such as occur when there is no symbol table.  */

static CORE_ADDR

ppc64_linux_convert_from_func_ptr_addr (struct gdbarch *gdbarch,

                                        CORE_ADDR addr,

                                        struct target_ops *targ)

{

  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);

  struct target_section *s = target_section_by_addr (targ, addr);

  /* Check if ADDR points to a function descriptor.  */

  if (s && strcmp (s->the_bfd_section->name, ".opd") == 0)

    {

      /* There may be relocations that need to be applied to the .opd

         section.  Unfortunately, this function may be called at a time

         where these relocations have not yet been performed -- this can

         happen for example shortly after a library has been loaded with

         dlopen, but ld.so has not yet applied the relocations.

         To cope with both the case where the relocation has been applied,

         and the case where it has not yet been applied, we do *not* read

         the (maybe) relocated value from target memory, but we instead

         read the non-relocated value from the BFD, and apply the relocation

         offset manually.

         This makes the assumption that all .opd entries are always relocated

         by the same offset the section itself was relocated.  This should

         always be the case for GNU/Linux executables and shared libraries.

         Note that other kind of object files (e.g. those added via

         add-symbol-files) will currently never end up here anyway, as this

         function accesses *target* sections only; only the main exec and

         shared libraries are ever added to the target.  */

      gdb_byte buf[8];

      int res;

      res = bfd_get_section_contents (s->bfd, s->the_bfd_section,

                                      &buf, addr - s->addr, 8);

      if (res != 0)

        return extract_unsigned_integer (buf, 8, byte_order)

                - bfd_section_vma (s->bfd, s->the_bfd_section) + s->addr;

   }

  return addr;

}

/* Wrappers to handle Linux-only registers.  */

static void

ppc_linux_supply_gregset (const struct regset *regset,

                          struct regcache *regcache,

                          int regnum, const void *gregs, size_t len)

{

  const struct ppc_reg_offsets *offsets = regset->descr;