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[/] [or1k/] [trunk/] [gdb-5.0/] [gdb/] [ppc-linux-tdep.c] - Diff between revs 105 and 1765

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Rev 105 Rev 1765
/* Target-dependent code for GDB, the GNU debugger.
/* Target-dependent code for GDB, the GNU debugger.
   Copyright 1986, 1987, 1989, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 2000
   Copyright 1986, 1987, 1989, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 2000
   Free Software Foundation, Inc.
   Free Software Foundation, Inc.
 
 
   This file is part of GDB.
   This file is part of GDB.
 
 
   This program is free software; you can redistribute it and/or modify
   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
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.
   (at your option) any later version.
 
 
   This program is distributed in the hope that it will be useful,
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   GNU General Public License for more details.
 
 
   You should have received a copy of the GNU General Public License
   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place - Suite 330,
   Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */
   Boston, MA 02111-1307, USA.  */
 
 
#include "defs.h"
#include "defs.h"
#include "frame.h"
#include "frame.h"
#include "inferior.h"
#include "inferior.h"
#include "symtab.h"
#include "symtab.h"
#include "target.h"
#include "target.h"
#include "gdbcore.h"
#include "gdbcore.h"
#include "gdbcmd.h"
#include "gdbcmd.h"
#include "symfile.h"
#include "symfile.h"
#include "objfiles.h"
#include "objfiles.h"
 
 
/* The following two instructions are used in the signal trampoline
/* The following two instructions are used in the signal trampoline
   code on linux/ppc */
   code on linux/ppc */
#define INSTR_LI_R0_0x7777      0x38007777
#define INSTR_LI_R0_0x7777      0x38007777
#define INSTR_SC                0x44000002
#define INSTR_SC                0x44000002
 
 
/* Since the *-tdep.c files are platform independent (i.e, they may be
/* Since the *-tdep.c files are platform independent (i.e, they may be
   used to build cross platform debuggers), we can't include system
   used to build cross platform debuggers), we can't include system
   headers.  Therefore, details concerning the sigcontext structure
   headers.  Therefore, details concerning the sigcontext structure
   must be painstakingly rerecorded.  What's worse, if these details
   must be painstakingly rerecorded.  What's worse, if these details
   ever change in the header files, they'll have to be changed here
   ever change in the header files, they'll have to be changed here
   as well. */
   as well. */
 
 
/* __SIGNAL_FRAMESIZE from <asm/ptrace.h> */
/* __SIGNAL_FRAMESIZE from <asm/ptrace.h> */
#define PPC_LINUX_SIGNAL_FRAMESIZE 64
#define PPC_LINUX_SIGNAL_FRAMESIZE 64
 
 
/* From <asm/sigcontext.h>, offsetof(struct sigcontext_struct, regs) == 0x1c */
/* From <asm/sigcontext.h>, offsetof(struct sigcontext_struct, regs) == 0x1c */
#define PPC_LINUX_REGS_PTR_OFFSET (PPC_LINUX_SIGNAL_FRAMESIZE + 0x1c)
#define PPC_LINUX_REGS_PTR_OFFSET (PPC_LINUX_SIGNAL_FRAMESIZE + 0x1c)
 
 
/* From <asm/sigcontext.h>,
/* From <asm/sigcontext.h>,
   offsetof(struct sigcontext_struct, handler) == 0x14 */
   offsetof(struct sigcontext_struct, handler) == 0x14 */
#define PPC_LINUX_HANDLER_PTR_OFFSET (PPC_LINUX_SIGNAL_FRAMESIZE + 0x14)
#define PPC_LINUX_HANDLER_PTR_OFFSET (PPC_LINUX_SIGNAL_FRAMESIZE + 0x14)
 
 
/* From <asm/ptrace.h>, values for PT_NIP, PT_R1, and PT_LNK */
/* From <asm/ptrace.h>, values for PT_NIP, PT_R1, and PT_LNK */
#define PPC_LINUX_PT_R0         0
#define PPC_LINUX_PT_R0         0
#define PPC_LINUX_PT_R1         1
#define PPC_LINUX_PT_R1         1
#define PPC_LINUX_PT_R2         2
#define PPC_LINUX_PT_R2         2
#define PPC_LINUX_PT_R3         3
#define PPC_LINUX_PT_R3         3
#define PPC_LINUX_PT_R4         4
#define PPC_LINUX_PT_R4         4
#define PPC_LINUX_PT_R5         5
#define PPC_LINUX_PT_R5         5
#define PPC_LINUX_PT_R6         6
#define PPC_LINUX_PT_R6         6
#define PPC_LINUX_PT_R7         7
#define PPC_LINUX_PT_R7         7
#define PPC_LINUX_PT_R8         8
#define PPC_LINUX_PT_R8         8
#define PPC_LINUX_PT_R9         9
#define PPC_LINUX_PT_R9         9
#define PPC_LINUX_PT_R10        10
#define PPC_LINUX_PT_R10        10
#define PPC_LINUX_PT_R11        11
#define PPC_LINUX_PT_R11        11
#define PPC_LINUX_PT_R12        12
#define PPC_LINUX_PT_R12        12
#define PPC_LINUX_PT_R13        13
#define PPC_LINUX_PT_R13        13
#define PPC_LINUX_PT_R14        14
#define PPC_LINUX_PT_R14        14
#define PPC_LINUX_PT_R15        15
#define PPC_LINUX_PT_R15        15
#define PPC_LINUX_PT_R16        16
#define PPC_LINUX_PT_R16        16
#define PPC_LINUX_PT_R17        17
#define PPC_LINUX_PT_R17        17
#define PPC_LINUX_PT_R18        18
#define PPC_LINUX_PT_R18        18
#define PPC_LINUX_PT_R19        19
#define PPC_LINUX_PT_R19        19
#define PPC_LINUX_PT_R20        20
#define PPC_LINUX_PT_R20        20
#define PPC_LINUX_PT_R21        21
#define PPC_LINUX_PT_R21        21
#define PPC_LINUX_PT_R22        22
#define PPC_LINUX_PT_R22        22
#define PPC_LINUX_PT_R23        23
#define PPC_LINUX_PT_R23        23
#define PPC_LINUX_PT_R24        24
#define PPC_LINUX_PT_R24        24
#define PPC_LINUX_PT_R25        25
#define PPC_LINUX_PT_R25        25
#define PPC_LINUX_PT_R26        26
#define PPC_LINUX_PT_R26        26
#define PPC_LINUX_PT_R27        27
#define PPC_LINUX_PT_R27        27
#define PPC_LINUX_PT_R28        28
#define PPC_LINUX_PT_R28        28
#define PPC_LINUX_PT_R29        29
#define PPC_LINUX_PT_R29        29
#define PPC_LINUX_PT_R30        30
#define PPC_LINUX_PT_R30        30
#define PPC_LINUX_PT_R31        31
#define PPC_LINUX_PT_R31        31
#define PPC_LINUX_PT_NIP        32
#define PPC_LINUX_PT_NIP        32
#define PPC_LINUX_PT_MSR        33
#define PPC_LINUX_PT_MSR        33
#define PPC_LINUX_PT_CTR        35
#define PPC_LINUX_PT_CTR        35
#define PPC_LINUX_PT_LNK        36
#define PPC_LINUX_PT_LNK        36
#define PPC_LINUX_PT_XER        37
#define PPC_LINUX_PT_XER        37
#define PPC_LINUX_PT_CCR        38
#define PPC_LINUX_PT_CCR        38
#define PPC_LINUX_PT_MQ         39
#define PPC_LINUX_PT_MQ         39
#define PPC_LINUX_PT_FPR0       48      /* each FP reg occupies 2 slots in this space */
#define PPC_LINUX_PT_FPR0       48      /* each FP reg occupies 2 slots in this space */
#define PPC_LINUX_PT_FPR31 (PPC_LINUX_PT_FPR0 + 2*31)
#define PPC_LINUX_PT_FPR31 (PPC_LINUX_PT_FPR0 + 2*31)
#define PPC_LINUX_PT_FPSCR (PPC_LINUX_PT_FPR0 + 2*32 + 1)
#define PPC_LINUX_PT_FPSCR (PPC_LINUX_PT_FPR0 + 2*32 + 1)
 
 
int ppc_linux_at_sigtramp_return_path (CORE_ADDR pc);
int ppc_linux_at_sigtramp_return_path (CORE_ADDR pc);
 
 
/* Determine if pc is in a signal trampoline...
/* Determine if pc is in a signal trampoline...
 
 
   Ha!  That's not what this does at all.  wait_for_inferior in infrun.c
   Ha!  That's not what this does at all.  wait_for_inferior in infrun.c
   calls IN_SIGTRAMP in order to detect entry into a signal trampoline
   calls IN_SIGTRAMP in order to detect entry into a signal trampoline
   just after delivery of a signal.  But on linux, signal trampolines
   just after delivery of a signal.  But on linux, signal trampolines
   are used for the return path only.  The kernel sets things up so that
   are used for the return path only.  The kernel sets things up so that
   the signal handler is called directly.
   the signal handler is called directly.
 
 
   If we use in_sigtramp2() in place of in_sigtramp() (see below)
   If we use in_sigtramp2() in place of in_sigtramp() (see below)
   we'll (often) end up with stop_pc in the trampoline and prev_pc in
   we'll (often) end up with stop_pc in the trampoline and prev_pc in
   the (now exited) handler.  The code there will cause a temporary
   the (now exited) handler.  The code there will cause a temporary
   breakpoint to be set on prev_pc which is not very likely to get hit
   breakpoint to be set on prev_pc which is not very likely to get hit
   again.
   again.
 
 
   If this is confusing, think of it this way...  the code in
   If this is confusing, think of it this way...  the code in
   wait_for_inferior() needs to be able to detect entry into a signal
   wait_for_inferior() needs to be able to detect entry into a signal
   trampoline just after a signal is delivered, not after the handler
   trampoline just after a signal is delivered, not after the handler
   has been run.
   has been run.
 
 
   So, we define in_sigtramp() below to return 1 if the following is
   So, we define in_sigtramp() below to return 1 if the following is
   true:
   true:
 
 
   1) The previous frame is a real signal trampoline.
   1) The previous frame is a real signal trampoline.
 
 
   - and -
   - and -
 
 
   2) pc is at the first or second instruction of the corresponding
   2) pc is at the first or second instruction of the corresponding
   handler.
   handler.
 
 
   Why the second instruction?  It seems that wait_for_inferior()
   Why the second instruction?  It seems that wait_for_inferior()
   never sees the first instruction when single stepping.  When a
   never sees the first instruction when single stepping.  When a
   signal is delivered while stepping, the next instruction that
   signal is delivered while stepping, the next instruction that
   would've been stepped over isn't, instead a signal is delivered and
   would've been stepped over isn't, instead a signal is delivered and
   the first instruction of the handler is stepped over instead.  That
   the first instruction of the handler is stepped over instead.  That
   puts us on the second instruction.  (I added the test for the
   puts us on the second instruction.  (I added the test for the
   first instruction long after the fact, just in case the observed
   first instruction long after the fact, just in case the observed
   behavior is ever fixed.)
   behavior is ever fixed.)
 
 
   IN_SIGTRAMP is called from blockframe.c as well in order to set
   IN_SIGTRAMP is called from blockframe.c as well in order to set
   the signal_handler_caller flag.  Because of our strange definition
   the signal_handler_caller flag.  Because of our strange definition
   of in_sigtramp below, we can't rely on signal_handler_caller getting
   of in_sigtramp below, we can't rely on signal_handler_caller getting
   set correctly from within blockframe.c.  This is why we take pains
   set correctly from within blockframe.c.  This is why we take pains
   to set it in init_extra_frame_info().  */
   to set it in init_extra_frame_info().  */
 
 
int
int
ppc_linux_in_sigtramp (CORE_ADDR pc, char *func_name)
ppc_linux_in_sigtramp (CORE_ADDR pc, char *func_name)
{
{
  CORE_ADDR lr;
  CORE_ADDR lr;
  CORE_ADDR sp;
  CORE_ADDR sp;
  CORE_ADDR tramp_sp;
  CORE_ADDR tramp_sp;
  char buf[4];
  char buf[4];
  CORE_ADDR handler;
  CORE_ADDR handler;
 
 
  lr = read_register (LR_REGNUM);
  lr = read_register (LR_REGNUM);
  if (!ppc_linux_at_sigtramp_return_path (lr))
  if (!ppc_linux_at_sigtramp_return_path (lr))
    return 0;
    return 0;
 
 
  sp = read_register (SP_REGNUM);
  sp = read_register (SP_REGNUM);
 
 
  if (target_read_memory (sp, buf, sizeof (buf)) != 0)
  if (target_read_memory (sp, buf, sizeof (buf)) != 0)
    return 0;
    return 0;
 
 
  tramp_sp = extract_unsigned_integer (buf, 4);
  tramp_sp = extract_unsigned_integer (buf, 4);
 
 
  if (target_read_memory (tramp_sp + PPC_LINUX_HANDLER_PTR_OFFSET, buf,
  if (target_read_memory (tramp_sp + PPC_LINUX_HANDLER_PTR_OFFSET, buf,
                          sizeof (buf)) != 0)
                          sizeof (buf)) != 0)
    return 0;
    return 0;
 
 
  handler = extract_unsigned_integer (buf, 4);
  handler = extract_unsigned_integer (buf, 4);
 
 
  return (pc == handler || pc == handler + 4);
  return (pc == handler || pc == handler + 4);
}
}
 
 
/*
/*
 * The signal handler trampoline is on the stack and consists of exactly
 * The signal handler trampoline is on the stack and consists of exactly
 * two instructions.  The easiest and most accurate way of determining
 * two instructions.  The easiest and most accurate way of determining
 * whether the pc is in one of these trampolines is by inspecting the
 * whether the pc is in one of these trampolines is by inspecting the
 * instructions.  It'd be faster though if we could find a way to do this
 * instructions.  It'd be faster though if we could find a way to do this
 * via some simple address comparisons.
 * via some simple address comparisons.
 */
 */
int
int
ppc_linux_at_sigtramp_return_path (CORE_ADDR pc)
ppc_linux_at_sigtramp_return_path (CORE_ADDR pc)
{
{
  char buf[12];
  char buf[12];
  unsigned long pcinsn;
  unsigned long pcinsn;
  if (target_read_memory (pc - 4, buf, sizeof (buf)) != 0)
  if (target_read_memory (pc - 4, buf, sizeof (buf)) != 0)
    return 0;
    return 0;
 
 
  /* extract the instruction at the pc */
  /* extract the instruction at the pc */
  pcinsn = extract_unsigned_integer (buf + 4, 4);
  pcinsn = extract_unsigned_integer (buf + 4, 4);
 
 
  return (
  return (
           (pcinsn == INSTR_LI_R0_0x7777
           (pcinsn == INSTR_LI_R0_0x7777
            && extract_unsigned_integer (buf + 8, 4) == INSTR_SC)
            && extract_unsigned_integer (buf + 8, 4) == INSTR_SC)
           ||
           ||
           (pcinsn == INSTR_SC
           (pcinsn == INSTR_SC
            && extract_unsigned_integer (buf, 4) == INSTR_LI_R0_0x7777));
            && extract_unsigned_integer (buf, 4) == INSTR_LI_R0_0x7777));
}
}
 
 
CORE_ADDR
CORE_ADDR
ppc_linux_skip_trampoline_code (CORE_ADDR pc)
ppc_linux_skip_trampoline_code (CORE_ADDR pc)
{
{
  char buf[4];
  char buf[4];
  struct obj_section *sect;
  struct obj_section *sect;
  struct objfile *objfile;
  struct objfile *objfile;
  unsigned long insn;
  unsigned long insn;
  CORE_ADDR plt_start = 0;
  CORE_ADDR plt_start = 0;
  CORE_ADDR symtab = 0;
  CORE_ADDR symtab = 0;
  CORE_ADDR strtab = 0;
  CORE_ADDR strtab = 0;
  int num_slots = -1;
  int num_slots = -1;
  int reloc_index = -1;
  int reloc_index = -1;
  CORE_ADDR plt_table;
  CORE_ADDR plt_table;
  CORE_ADDR reloc;
  CORE_ADDR reloc;
  CORE_ADDR sym;
  CORE_ADDR sym;
  long symidx;
  long symidx;
  char symname[1024];
  char symname[1024];
  struct minimal_symbol *msymbol;
  struct minimal_symbol *msymbol;
 
 
  /* Find the section pc is in; return if not in .plt */
  /* Find the section pc is in; return if not in .plt */
  sect = find_pc_section (pc);
  sect = find_pc_section (pc);
  if (!sect || strcmp (sect->the_bfd_section->name, ".plt") != 0)
  if (!sect || strcmp (sect->the_bfd_section->name, ".plt") != 0)
    return 0;
    return 0;
 
 
  objfile = sect->objfile;
  objfile = sect->objfile;
 
 
  /* Pick up the instruction at pc.  It had better be of the
  /* Pick up the instruction at pc.  It had better be of the
     form
     form
     li r11, IDX
     li r11, IDX
 
 
     where IDX is an index into the plt_table.  */
     where IDX is an index into the plt_table.  */
 
 
  if (target_read_memory (pc, buf, 4) != 0)
  if (target_read_memory (pc, buf, 4) != 0)
    return 0;
    return 0;
  insn = extract_unsigned_integer (buf, 4);
  insn = extract_unsigned_integer (buf, 4);
 
 
  if ((insn & 0xffff0000) != 0x39600000 /* li r11, VAL */ )
  if ((insn & 0xffff0000) != 0x39600000 /* li r11, VAL */ )
    return 0;
    return 0;
 
 
  reloc_index = (insn << 16) >> 16;
  reloc_index = (insn << 16) >> 16;
 
 
  /* Find the objfile that pc is in and obtain the information
  /* Find the objfile that pc is in and obtain the information
     necessary for finding the symbol name. */
     necessary for finding the symbol name. */
  for (sect = objfile->sections; sect < objfile->sections_end; ++sect)
  for (sect = objfile->sections; sect < objfile->sections_end; ++sect)
    {
    {
      const char *secname = sect->the_bfd_section->name;
      const char *secname = sect->the_bfd_section->name;
      if (strcmp (secname, ".plt") == 0)
      if (strcmp (secname, ".plt") == 0)
        plt_start = sect->addr;
        plt_start = sect->addr;
      else if (strcmp (secname, ".rela.plt") == 0)
      else if (strcmp (secname, ".rela.plt") == 0)
        num_slots = ((int) sect->endaddr - (int) sect->addr) / 12;
        num_slots = ((int) sect->endaddr - (int) sect->addr) / 12;
      else if (strcmp (secname, ".dynsym") == 0)
      else if (strcmp (secname, ".dynsym") == 0)
        symtab = sect->addr;
        symtab = sect->addr;
      else if (strcmp (secname, ".dynstr") == 0)
      else if (strcmp (secname, ".dynstr") == 0)
        strtab = sect->addr;
        strtab = sect->addr;
    }
    }
 
 
  /* Make sure we have all the information we need. */
  /* Make sure we have all the information we need. */
  if (plt_start == 0 || num_slots == -1 || symtab == 0 || strtab == 0)
  if (plt_start == 0 || num_slots == -1 || symtab == 0 || strtab == 0)
    return 0;
    return 0;
 
 
  /* Compute the value of the plt table */
  /* Compute the value of the plt table */
  plt_table = plt_start + 72 + 8 * num_slots;
  plt_table = plt_start + 72 + 8 * num_slots;
 
 
  /* Get address of the relocation entry (Elf32_Rela) */
  /* Get address of the relocation entry (Elf32_Rela) */
  if (target_read_memory (plt_table + reloc_index, buf, 4) != 0)
  if (target_read_memory (plt_table + reloc_index, buf, 4) != 0)
    return 0;
    return 0;
  reloc = extract_address (buf, 4);
  reloc = extract_address (buf, 4);
 
 
  sect = find_pc_section (reloc);
  sect = find_pc_section (reloc);
  if (!sect)
  if (!sect)
    return 0;
    return 0;
 
 
  if (strcmp (sect->the_bfd_section->name, ".text") == 0)
  if (strcmp (sect->the_bfd_section->name, ".text") == 0)
    return reloc;
    return reloc;
 
 
  /* Now get the r_info field which is the relocation type and symbol
  /* Now get the r_info field which is the relocation type and symbol
     index. */
     index. */
  if (target_read_memory (reloc + 4, buf, 4) != 0)
  if (target_read_memory (reloc + 4, buf, 4) != 0)
    return 0;
    return 0;
  symidx = extract_unsigned_integer (buf, 4);
  symidx = extract_unsigned_integer (buf, 4);
 
 
  /* Shift out the relocation type leaving just the symbol index */
  /* Shift out the relocation type leaving just the symbol index */
  /* symidx = ELF32_R_SYM(symidx); */
  /* symidx = ELF32_R_SYM(symidx); */
  symidx = symidx >> 8;
  symidx = symidx >> 8;
 
 
  /* compute the address of the symbol */
  /* compute the address of the symbol */
  sym = symtab + symidx * 4;
  sym = symtab + symidx * 4;
 
 
  /* Fetch the string table index */
  /* Fetch the string table index */
  if (target_read_memory (sym, buf, 4) != 0)
  if (target_read_memory (sym, buf, 4) != 0)
    return 0;
    return 0;
  symidx = extract_unsigned_integer (buf, 4);
  symidx = extract_unsigned_integer (buf, 4);
 
 
  /* Fetch the string; we don't know how long it is.  Is it possible
  /* Fetch the string; we don't know how long it is.  Is it possible
     that the following will fail because we're trying to fetch too
     that the following will fail because we're trying to fetch too
     much? */
     much? */
  if (target_read_memory (strtab + symidx, symname, sizeof (symname)) != 0)
  if (target_read_memory (strtab + symidx, symname, sizeof (symname)) != 0)
    return 0;
    return 0;
 
 
  /* This might not work right if we have multiple symbols with the
  /* This might not work right if we have multiple symbols with the
     same name; the only way to really get it right is to perform
     same name; the only way to really get it right is to perform
     the same sort of lookup as the dynamic linker. */
     the same sort of lookup as the dynamic linker. */
  msymbol = lookup_minimal_symbol_text (symname, NULL, NULL);
  msymbol = lookup_minimal_symbol_text (symname, NULL, NULL);
  if (!msymbol)
  if (!msymbol)
    return 0;
    return 0;
 
 
  return SYMBOL_VALUE_ADDRESS (msymbol);
  return SYMBOL_VALUE_ADDRESS (msymbol);
}
}
 
 
/* The rs6000 version of FRAME_SAVED_PC will almost work for us.  The
/* The rs6000 version of FRAME_SAVED_PC will almost work for us.  The
   signal handler details are different, so we'll handle those here
   signal handler details are different, so we'll handle those here
   and call the rs6000 version to do the rest. */
   and call the rs6000 version to do the rest. */
unsigned long
unsigned long
ppc_linux_frame_saved_pc (struct frame_info *fi)
ppc_linux_frame_saved_pc (struct frame_info *fi)
{
{
  if (fi->signal_handler_caller)
  if (fi->signal_handler_caller)
    {
    {
      CORE_ADDR regs_addr =
      CORE_ADDR regs_addr =
        read_memory_integer (fi->frame + PPC_LINUX_REGS_PTR_OFFSET, 4);
        read_memory_integer (fi->frame + PPC_LINUX_REGS_PTR_OFFSET, 4);
      /* return the NIP in the regs array */
      /* return the NIP in the regs array */
      return read_memory_integer (regs_addr + 4 * PPC_LINUX_PT_NIP, 4);
      return read_memory_integer (regs_addr + 4 * PPC_LINUX_PT_NIP, 4);
    }
    }
  else if (fi->next && fi->next->signal_handler_caller)
  else if (fi->next && fi->next->signal_handler_caller)
    {
    {
      CORE_ADDR regs_addr =
      CORE_ADDR regs_addr =
        read_memory_integer (fi->next->frame + PPC_LINUX_REGS_PTR_OFFSET, 4);
        read_memory_integer (fi->next->frame + PPC_LINUX_REGS_PTR_OFFSET, 4);
      /* return LNK in the regs array */
      /* return LNK in the regs array */
      return read_memory_integer (regs_addr + 4 * PPC_LINUX_PT_LNK, 4);
      return read_memory_integer (regs_addr + 4 * PPC_LINUX_PT_LNK, 4);
    }
    }
  else
  else
    return rs6000_frame_saved_pc (fi);
    return rs6000_frame_saved_pc (fi);
}
}
 
 
void
void
ppc_linux_init_extra_frame_info (int fromleaf, struct frame_info *fi)
ppc_linux_init_extra_frame_info (int fromleaf, struct frame_info *fi)
{
{
  rs6000_init_extra_frame_info (fromleaf, fi);
  rs6000_init_extra_frame_info (fromleaf, fi);
 
 
  if (fi->next != 0)
  if (fi->next != 0)
    {
    {
      /* We're called from get_prev_frame_info; check to see if
      /* We're called from get_prev_frame_info; check to see if
         this is a signal frame by looking to see if the pc points
         this is a signal frame by looking to see if the pc points
         at trampoline code */
         at trampoline code */
      if (ppc_linux_at_sigtramp_return_path (fi->pc))
      if (ppc_linux_at_sigtramp_return_path (fi->pc))
        fi->signal_handler_caller = 1;
        fi->signal_handler_caller = 1;
      else
      else
        fi->signal_handler_caller = 0;
        fi->signal_handler_caller = 0;
    }
    }
}
}
 
 
int
int
ppc_linux_frameless_function_invocation (struct frame_info *fi)
ppc_linux_frameless_function_invocation (struct frame_info *fi)
{
{
  /* We'll find the wrong thing if we let
  /* We'll find the wrong thing if we let
     rs6000_frameless_function_invocation () search for a signal trampoline */
     rs6000_frameless_function_invocation () search for a signal trampoline */
  if (ppc_linux_at_sigtramp_return_path (fi->pc))
  if (ppc_linux_at_sigtramp_return_path (fi->pc))
    return 0;
    return 0;
  else
  else
    return rs6000_frameless_function_invocation (fi);
    return rs6000_frameless_function_invocation (fi);
}
}
 
 
void
void
ppc_linux_frame_init_saved_regs (struct frame_info *fi)
ppc_linux_frame_init_saved_regs (struct frame_info *fi)
{
{
  if (fi->signal_handler_caller)
  if (fi->signal_handler_caller)
    {
    {
      CORE_ADDR regs_addr;
      CORE_ADDR regs_addr;
      int i;
      int i;
      if (fi->saved_regs)
      if (fi->saved_regs)
        return;
        return;
 
 
      frame_saved_regs_zalloc (fi);
      frame_saved_regs_zalloc (fi);
 
 
      regs_addr =
      regs_addr =
        read_memory_integer (fi->frame + PPC_LINUX_REGS_PTR_OFFSET, 4);
        read_memory_integer (fi->frame + PPC_LINUX_REGS_PTR_OFFSET, 4);
      fi->saved_regs[PC_REGNUM] = regs_addr + 4 * PPC_LINUX_PT_NIP;
      fi->saved_regs[PC_REGNUM] = regs_addr + 4 * PPC_LINUX_PT_NIP;
      fi->saved_regs[PS_REGNUM] = regs_addr + 4 * PPC_LINUX_PT_MSR;
      fi->saved_regs[PS_REGNUM] = regs_addr + 4 * PPC_LINUX_PT_MSR;
      fi->saved_regs[CR_REGNUM] = regs_addr + 4 * PPC_LINUX_PT_CCR;
      fi->saved_regs[CR_REGNUM] = regs_addr + 4 * PPC_LINUX_PT_CCR;
      fi->saved_regs[LR_REGNUM] = regs_addr + 4 * PPC_LINUX_PT_LNK;
      fi->saved_regs[LR_REGNUM] = regs_addr + 4 * PPC_LINUX_PT_LNK;
      fi->saved_regs[CTR_REGNUM] = regs_addr + 4 * PPC_LINUX_PT_CTR;
      fi->saved_regs[CTR_REGNUM] = regs_addr + 4 * PPC_LINUX_PT_CTR;
      fi->saved_regs[XER_REGNUM] = regs_addr + 4 * PPC_LINUX_PT_XER;
      fi->saved_regs[XER_REGNUM] = regs_addr + 4 * PPC_LINUX_PT_XER;
      fi->saved_regs[MQ_REGNUM] = regs_addr + 4 * PPC_LINUX_PT_MQ;
      fi->saved_regs[MQ_REGNUM] = regs_addr + 4 * PPC_LINUX_PT_MQ;
      for (i = 0; i < 32; i++)
      for (i = 0; i < 32; i++)
        fi->saved_regs[GP0_REGNUM + i] = regs_addr + 4 * PPC_LINUX_PT_R0 + 4 * i;
        fi->saved_regs[GP0_REGNUM + i] = regs_addr + 4 * PPC_LINUX_PT_R0 + 4 * i;
      for (i = 0; i < 32; i++)
      for (i = 0; i < 32; i++)
        fi->saved_regs[FP0_REGNUM + i] = regs_addr + 4 * PPC_LINUX_PT_FPR0 + 8 * i;
        fi->saved_regs[FP0_REGNUM + i] = regs_addr + 4 * PPC_LINUX_PT_FPR0 + 8 * i;
    }
    }
  else
  else
    rs6000_frame_init_saved_regs (fi);
    rs6000_frame_init_saved_regs (fi);
}
}
 
 
CORE_ADDR
CORE_ADDR
ppc_linux_frame_chain (struct frame_info *thisframe)
ppc_linux_frame_chain (struct frame_info *thisframe)
{
{
  /* Kernel properly constructs the frame chain for the handler */
  /* Kernel properly constructs the frame chain for the handler */
  if (thisframe->signal_handler_caller)
  if (thisframe->signal_handler_caller)
    return read_memory_integer ((thisframe)->frame, 4);
    return read_memory_integer ((thisframe)->frame, 4);
  else
  else
    return rs6000_frame_chain (thisframe);
    return rs6000_frame_chain (thisframe);
}
}
 
 
/* FIXME: Move the following to rs6000-tdep.c (or some other file where
/* FIXME: Move the following to rs6000-tdep.c (or some other file where
   it may be used generically by ports which use either the SysV ABI or
   it may be used generically by ports which use either the SysV ABI or
   the EABI */
   the EABI */
 
 
/* round2 rounds x up to the nearest multiple of s assuming that s is a
/* round2 rounds x up to the nearest multiple of s assuming that s is a
   power of 2 */
   power of 2 */
 
 
#undef round2
#undef round2
#define round2(x,s) ((((long) (x) - 1) & ~(long)((s)-1)) + (s))
#define round2(x,s) ((((long) (x) - 1) & ~(long)((s)-1)) + (s))
 
 
/* Pass the arguments in either registers, or in the stack. Using the
/* Pass the arguments in either registers, or in the stack. Using the
   ppc sysv ABI, the first eight words of the argument list (that might
   ppc sysv ABI, the first eight words of the argument list (that might
   be less than eight parameters if some parameters occupy more than one
   be less than eight parameters if some parameters occupy more than one
   word) are passed in r3..r10 registers.  float and double parameters are
   word) are passed in r3..r10 registers.  float and double parameters are
   passed in fpr's, in addition to that. Rest of the parameters if any
   passed in fpr's, in addition to that. Rest of the parameters if any
   are passed in user stack.
   are passed in user stack.
 
 
   If the function is returning a structure, then the return address is passed
   If the function is returning a structure, then the return address is passed
   in r3, then the first 7 words of the parametes can be passed in registers,
   in r3, then the first 7 words of the parametes can be passed in registers,
   starting from r4. */
   starting from r4. */
 
 
CORE_ADDR
CORE_ADDR
ppc_sysv_abi_push_arguments (nargs, args, sp, struct_return, struct_addr)
ppc_sysv_abi_push_arguments (nargs, args, sp, struct_return, struct_addr)
     int nargs;
     int nargs;
     value_ptr *args;
     value_ptr *args;
     CORE_ADDR sp;
     CORE_ADDR sp;
     int struct_return;
     int struct_return;
     CORE_ADDR struct_addr;
     CORE_ADDR struct_addr;
{
{
  int argno;
  int argno;
  int greg, freg;
  int greg, freg;
  int argstkspace;
  int argstkspace;
  int structstkspace;
  int structstkspace;
  int argoffset;
  int argoffset;
  int structoffset;
  int structoffset;
  value_ptr arg;
  value_ptr arg;
  struct type *type;
  struct type *type;
  int len;
  int len;
  char old_sp_buf[4];
  char old_sp_buf[4];
  CORE_ADDR saved_sp;
  CORE_ADDR saved_sp;
 
 
  greg = struct_return ? 4 : 3;
  greg = struct_return ? 4 : 3;
  freg = 1;
  freg = 1;
  argstkspace = 0;
  argstkspace = 0;
  structstkspace = 0;
  structstkspace = 0;
 
 
  /* Figure out how much new stack space is required for arguments
  /* Figure out how much new stack space is required for arguments
     which don't fit in registers.  Unlike the PowerOpen ABI, the
     which don't fit in registers.  Unlike the PowerOpen ABI, the
     SysV ABI doesn't reserve any extra space for parameters which
     SysV ABI doesn't reserve any extra space for parameters which
     are put in registers. */
     are put in registers. */
  for (argno = 0; argno < nargs; argno++)
  for (argno = 0; argno < nargs; argno++)
    {
    {
      arg = args[argno];
      arg = args[argno];
      type = check_typedef (VALUE_TYPE (arg));
      type = check_typedef (VALUE_TYPE (arg));
      len = TYPE_LENGTH (type);
      len = TYPE_LENGTH (type);
 
 
      if (TYPE_CODE (type) == TYPE_CODE_FLT)
      if (TYPE_CODE (type) == TYPE_CODE_FLT)
        {
        {
          if (freg <= 8)
          if (freg <= 8)
            freg++;
            freg++;
          else
          else
            {
            {
              /* SysV ABI converts floats to doubles when placed in
              /* SysV ABI converts floats to doubles when placed in
                 memory and requires 8 byte alignment */
                 memory and requires 8 byte alignment */
              if (argstkspace & 0x4)
              if (argstkspace & 0x4)
                argstkspace += 4;
                argstkspace += 4;
              argstkspace += 8;
              argstkspace += 8;
            }
            }
        }
        }
      else if (TYPE_CODE (type) == TYPE_CODE_INT && len == 8)   /* long long */
      else if (TYPE_CODE (type) == TYPE_CODE_INT && len == 8)   /* long long */
        {
        {
          if (greg > 9)
          if (greg > 9)
            {
            {
              greg = 11;
              greg = 11;
              if (argstkspace & 0x4)
              if (argstkspace & 0x4)
                argstkspace += 4;
                argstkspace += 4;
              argstkspace += 8;
              argstkspace += 8;
            }
            }
          else
          else
            {
            {
              if ((greg & 1) == 0)
              if ((greg & 1) == 0)
                greg++;
                greg++;
              greg += 2;
              greg += 2;
            }
            }
        }
        }
      else
      else
        {
        {
          if (len > 4
          if (len > 4
              || TYPE_CODE (type) == TYPE_CODE_STRUCT
              || TYPE_CODE (type) == TYPE_CODE_STRUCT
              || TYPE_CODE (type) == TYPE_CODE_UNION)
              || TYPE_CODE (type) == TYPE_CODE_UNION)
            {
            {
              /* Rounding to the nearest multiple of 8 may not be necessary,
              /* Rounding to the nearest multiple of 8 may not be necessary,
                 but it is safe.  Particularly since we don't know the
                 but it is safe.  Particularly since we don't know the
                 field types of the structure */
                 field types of the structure */
              structstkspace += round2 (len, 8);
              structstkspace += round2 (len, 8);
            }
            }
          if (greg <= 10)
          if (greg <= 10)
            greg++;
            greg++;
          else
          else
            argstkspace += 4;
            argstkspace += 4;
        }
        }
    }
    }
 
 
  /* Get current SP location */
  /* Get current SP location */
  saved_sp = read_sp ();
  saved_sp = read_sp ();
 
 
  sp -= argstkspace + structstkspace;
  sp -= argstkspace + structstkspace;
 
 
  /* Allocate space for backchain and callee's saved lr */
  /* Allocate space for backchain and callee's saved lr */
  sp -= 8;
  sp -= 8;
 
 
  /* Make sure that we maintain 16 byte alignment */
  /* Make sure that we maintain 16 byte alignment */
  sp &= ~0x0f;
  sp &= ~0x0f;
 
 
  /* Update %sp before proceeding any further */
  /* Update %sp before proceeding any further */
  write_register (SP_REGNUM, sp);
  write_register (SP_REGNUM, sp);
 
 
  /* write the backchain */
  /* write the backchain */
  store_address (old_sp_buf, 4, saved_sp);
  store_address (old_sp_buf, 4, saved_sp);
  write_memory (sp, old_sp_buf, 4);
  write_memory (sp, old_sp_buf, 4);
 
 
  argoffset = 8;
  argoffset = 8;
  structoffset = argoffset + argstkspace;
  structoffset = argoffset + argstkspace;
  freg = 1;
  freg = 1;
  greg = 3;
  greg = 3;
  /* Fill in r3 with the return structure, if any */
  /* Fill in r3 with the return structure, if any */
  if (struct_return)
  if (struct_return)
    {
    {
      char val_buf[4];
      char val_buf[4];
      store_address (val_buf, 4, struct_addr);
      store_address (val_buf, 4, struct_addr);
      memcpy (&registers[REGISTER_BYTE (greg)], val_buf, 4);
      memcpy (&registers[REGISTER_BYTE (greg)], val_buf, 4);
      greg++;
      greg++;
    }
    }
  /* Now fill in the registers and stack... */
  /* Now fill in the registers and stack... */
  for (argno = 0; argno < nargs; argno++)
  for (argno = 0; argno < nargs; argno++)
    {
    {
      arg = args[argno];
      arg = args[argno];
      type = check_typedef (VALUE_TYPE (arg));
      type = check_typedef (VALUE_TYPE (arg));
      len = TYPE_LENGTH (type);
      len = TYPE_LENGTH (type);
 
 
      if (TYPE_CODE (type) == TYPE_CODE_FLT)
      if (TYPE_CODE (type) == TYPE_CODE_FLT)
        {
        {
          if (freg <= 8)
          if (freg <= 8)
            {
            {
              if (len > 8)
              if (len > 8)
                printf_unfiltered (
                printf_unfiltered (
                                    "Fatal Error: a floating point parameter #%d with a size > 8 is found!\n", argno);
                                    "Fatal Error: a floating point parameter #%d with a size > 8 is found!\n", argno);
              memcpy (&registers[REGISTER_BYTE (FP0_REGNUM + freg)],
              memcpy (&registers[REGISTER_BYTE (FP0_REGNUM + freg)],
                      VALUE_CONTENTS (arg), len);
                      VALUE_CONTENTS (arg), len);
              freg++;
              freg++;
            }
            }
          else
          else
            {
            {
              /* SysV ABI converts floats to doubles when placed in
              /* SysV ABI converts floats to doubles when placed in
                 memory and requires 8 byte alignment */
                 memory and requires 8 byte alignment */
              /* FIXME: Convert floats to doubles */
              /* FIXME: Convert floats to doubles */
              if (argoffset & 0x4)
              if (argoffset & 0x4)
                argoffset += 4;
                argoffset += 4;
              write_memory (sp + argoffset, (char *) VALUE_CONTENTS (arg), len);
              write_memory (sp + argoffset, (char *) VALUE_CONTENTS (arg), len);
              argoffset += 8;
              argoffset += 8;
            }
            }
        }
        }
      else if (TYPE_CODE (type) == TYPE_CODE_INT && len == 8)   /* long long */
      else if (TYPE_CODE (type) == TYPE_CODE_INT && len == 8)   /* long long */
        {
        {
          if (greg > 9)
          if (greg > 9)
            {
            {
              greg = 11;
              greg = 11;
              if (argoffset & 0x4)
              if (argoffset & 0x4)
                argoffset += 4;
                argoffset += 4;
              write_memory (sp + argoffset, (char *) VALUE_CONTENTS (arg), len);
              write_memory (sp + argoffset, (char *) VALUE_CONTENTS (arg), len);
              argoffset += 8;
              argoffset += 8;
            }
            }
          else
          else
            {
            {
              if ((greg & 1) == 0)
              if ((greg & 1) == 0)
                greg++;
                greg++;
 
 
              memcpy (&registers[REGISTER_BYTE (greg)],
              memcpy (&registers[REGISTER_BYTE (greg)],
                      VALUE_CONTENTS (arg), 4);
                      VALUE_CONTENTS (arg), 4);
              memcpy (&registers[REGISTER_BYTE (greg + 1)],
              memcpy (&registers[REGISTER_BYTE (greg + 1)],
                      VALUE_CONTENTS (arg) + 4, 4);
                      VALUE_CONTENTS (arg) + 4, 4);
              greg += 2;
              greg += 2;
            }
            }
        }
        }
      else
      else
        {
        {
          char val_buf[4];
          char val_buf[4];
          if (len > 4
          if (len > 4
              || TYPE_CODE (type) == TYPE_CODE_STRUCT
              || TYPE_CODE (type) == TYPE_CODE_STRUCT
              || TYPE_CODE (type) == TYPE_CODE_UNION)
              || TYPE_CODE (type) == TYPE_CODE_UNION)
            {
            {
              write_memory (sp + structoffset, VALUE_CONTENTS (arg), len);
              write_memory (sp + structoffset, VALUE_CONTENTS (arg), len);
              store_address (val_buf, 4, sp + structoffset);
              store_address (val_buf, 4, sp + structoffset);
              structoffset += round2 (len, 8);
              structoffset += round2 (len, 8);
            }
            }
          else
          else
            {
            {
              memset (val_buf, 0, 4);
              memset (val_buf, 0, 4);
              memcpy (val_buf, VALUE_CONTENTS (arg), len);
              memcpy (val_buf, VALUE_CONTENTS (arg), len);
            }
            }
          if (greg <= 10)
          if (greg <= 10)
            {
            {
              *(int *) &registers[REGISTER_BYTE (greg)] = 0;
              *(int *) &registers[REGISTER_BYTE (greg)] = 0;
              memcpy (&registers[REGISTER_BYTE (greg)], val_buf, 4);
              memcpy (&registers[REGISTER_BYTE (greg)], val_buf, 4);
              greg++;
              greg++;
            }
            }
          else
          else
            {
            {
              write_memory (sp + argoffset, val_buf, 4);
              write_memory (sp + argoffset, val_buf, 4);
              argoffset += 4;
              argoffset += 4;
            }
            }
        }
        }
    }
    }
 
 
  target_store_registers (-1);
  target_store_registers (-1);
  return sp;
  return sp;
}
}
 
 
/* ppc_linux_memory_remove_breakpoints attempts to remove a breakpoint
/* ppc_linux_memory_remove_breakpoints attempts to remove a breakpoint
   in much the same fashion as memory_remove_breakpoint in mem-break.c,
   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
   but is careful not to write back the previous contents if the code
   in question has changed in between inserting the breakpoint and
   in question has changed in between inserting the breakpoint and
   removing it.
   removing it.
 
 
   Here is the problem that we're trying to solve...
   Here is the problem that we're trying to solve...
 
 
   Once upon a time, before introducing this function to remove
   Once upon a time, before introducing this function to remove
   breakpoints from the inferior, setting a breakpoint on a shared
   breakpoints from the inferior, setting a breakpoint on a shared
   library function prior to running the program would not work
   library function prior to running the program would not work
   properly.  In order to understand the problem, it is first
   properly.  In order to understand the problem, it is first
   necessary to understand a little bit about dynamic linking on
   necessary to understand a little bit about dynamic linking on
   this platform.
   this platform.
 
 
   A call to a shared library function is accomplished via a bl
   A call to a shared library function is accomplished via a bl
   (branch-and-link) instruction whose branch target is an entry
   (branch-and-link) instruction whose branch target is an entry
   in the procedure linkage table (PLT).  The PLT in the object
   in the procedure linkage table (PLT).  The PLT in the object
   file is uninitialized.  To gdb, prior to running the program, the
   file is uninitialized.  To gdb, prior to running the program, the
   entries in the PLT are all zeros.
   entries in the PLT are all zeros.
 
 
   Once the program starts running, the shared libraries are loaded
   Once the program starts running, the shared libraries are loaded
   and the procedure linkage table is initialized, but the entries in
   and the procedure linkage table is initialized, but the entries in
   the table are not (necessarily) resolved.  Once a function is
   the table are not (necessarily) resolved.  Once a function is
   actually called, the code in the PLT is hit and the 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
   resolved.  In order to better illustrate this, an example is in
   order; the following example is from the gdb testsuite.
   order; the following example is from the gdb testsuite.
 
 
        We start the program shmain.
        We start the program shmain.
 
 
            [kev@arroyo testsuite]$ ../gdb gdb.base/shmain
            [kev@arroyo testsuite]$ ../gdb gdb.base/shmain
            [...]
            [...]
 
 
        We place two breakpoints, one on shr1 and the other on main.
        We place two breakpoints, one on shr1 and the other on main.
 
 
            (gdb) b shr1
            (gdb) b shr1
            Breakpoint 1 at 0x100409d4
            Breakpoint 1 at 0x100409d4
            (gdb) b main
            (gdb) b main
            Breakpoint 2 at 0x100006a0: file gdb.base/shmain.c, line 44.
            Breakpoint 2 at 0x100006a0: file gdb.base/shmain.c, line 44.
 
 
        Examine the instruction (and the immediatly following instruction)
        Examine the instruction (and the immediatly following instruction)
        upon which the breakpoint was placed.  Note that the PLT entry
        upon which the breakpoint was placed.  Note that the PLT entry
        for shr1 contains zeros.
        for shr1 contains zeros.
 
 
            (gdb) x/2i 0x100409d4
            (gdb) x/2i 0x100409d4
            0x100409d4 <shr1>:      .long 0x0
            0x100409d4 <shr1>:      .long 0x0
            0x100409d8 <shr1+4>:    .long 0x0
            0x100409d8 <shr1+4>:    .long 0x0
 
 
        Now run 'til main.
        Now run 'til main.
 
 
            (gdb) r
            (gdb) r
            Starting program: gdb.base/shmain
            Starting program: gdb.base/shmain
            Breakpoint 1 at 0xffaf790: file gdb.base/shr1.c, line 19.
            Breakpoint 1 at 0xffaf790: file gdb.base/shr1.c, line 19.
 
 
            Breakpoint 2, main ()
            Breakpoint 2, main ()
                at gdb.base/shmain.c:44
                at gdb.base/shmain.c:44
            44        g = 1;
            44        g = 1;
 
 
        Examine the PLT again.  Note that the loading of the shared
        Examine the PLT again.  Note that the loading of the shared
        library has initialized the PLT to code which loads a constant
        library has initialized the PLT to code which loads a constant
        (which I think is an index into the GOT) into r11 and then
        (which I think is an index into the GOT) into r11 and then
        branchs a short distance to the code which actually does the
        branchs a short distance to the code which actually does the
        resolving.
        resolving.
 
 
            (gdb) x/2i 0x100409d4
            (gdb) x/2i 0x100409d4
            0x100409d4 <shr1>:      li      r11,4
            0x100409d4 <shr1>:      li      r11,4
            0x100409d8 <shr1+4>:    b       0x10040984 <sg+4>
            0x100409d8 <shr1+4>:    b       0x10040984 <sg+4>
            (gdb) c
            (gdb) c
            Continuing.
            Continuing.
 
 
            Breakpoint 1, shr1 (x=1)
            Breakpoint 1, shr1 (x=1)
                at gdb.base/shr1.c:19
                at gdb.base/shr1.c:19
            19        l = 1;
            19        l = 1;
 
 
        Now we've hit the breakpoint at shr1.  (The breakpoint was
        Now we've hit the breakpoint at shr1.  (The breakpoint was
        reset from the PLT entry to the actual shr1 function after the
        reset from the PLT entry to the actual shr1 function after the
        shared library was loaded.) Note that the PLT entry has been
        shared library was loaded.) Note that the PLT entry has been
        resolved to contain a branch that takes us directly to shr1.
        resolved to contain a branch that takes us directly to shr1.
        (The real one, not the PLT entry.)
        (The real one, not the PLT entry.)
 
 
            (gdb) x/2i 0x100409d4
            (gdb) x/2i 0x100409d4
            0x100409d4 <shr1>:      b       0xffaf76c <shr1>
            0x100409d4 <shr1>:      b       0xffaf76c <shr1>
            0x100409d8 <shr1+4>:    b       0x10040984 <sg+4>
            0x100409d8 <shr1+4>:    b       0x10040984 <sg+4>
 
 
   The thing to note here is that the PLT entry for shr1 has been
   The thing to note here is that the PLT entry for shr1 has been
   changed twice.
   changed twice.
 
 
   Now the problem should be obvious.  GDB places a breakpoint (a
   Now the problem should be obvious.  GDB places a breakpoint (a
   trap instruction) on the zero value of the PLT entry for shr1.
   trap instruction) on the zero value of the PLT entry for shr1.
   Later on, after the shared library had been loaded and the PLT
   Later on, after the shared library had been loaded and the PLT
   initialized, GDB gets a signal indicating this fact and attempts
   initialized, GDB gets a signal indicating this fact and attempts
   (as it always does when it stops) to remove all the breakpoints.
   (as it always does when it stops) to remove all the breakpoints.
 
 
   The breakpoint removal was causing the former contents (a zero
   The breakpoint removal was causing the former contents (a zero
   word) to be written back to the now initialized PLT entry thus
   word) to be written back to the now initialized PLT entry thus
   destroying a portion of the initialization that had occurred only a
   destroying a portion of the initialization that had occurred only a
   short time ago.  When execution continued, the zero word would be
   short time ago.  When execution continued, the zero word would be
   executed as an instruction an an illegal instruction trap was
   executed as an instruction an an illegal instruction trap was
   generated instead.  (0 is not a legal instruction.)
   generated instead.  (0 is not a legal instruction.)
 
 
   The fix for this problem was fairly straightforward.  The function
   The fix for this problem was fairly straightforward.  The function
   memory_remove_breakpoint from mem-break.c was copied to this file,
   memory_remove_breakpoint from mem-break.c was copied to this file,
   modified slightly, and renamed to ppc_linux_memory_remove_breakpoint.
   modified slightly, and renamed to ppc_linux_memory_remove_breakpoint.
   In tm-linux.h, MEMORY_REMOVE_BREAKPOINT is defined to call this new
   In tm-linux.h, MEMORY_REMOVE_BREAKPOINT is defined to call this new
   function.
   function.
 
 
   The differences between ppc_linux_memory_remove_breakpoint () and
   The differences between ppc_linux_memory_remove_breakpoint () and
   memory_remove_breakpoint () are minor.  All that the former does
   memory_remove_breakpoint () are minor.  All that the former does
   that the latter does not is check to make sure that the breakpoint
   that the latter does not is check to make sure that the breakpoint
   location actually contains a breakpoint (trap instruction) prior
   location actually contains a breakpoint (trap instruction) prior
   to attempting to write back the old contents.  If it does contain
   to attempting to write back the old contents.  If it does contain
   a trap instruction, we allow the old contents to be written back.
   a trap instruction, we allow the old contents to be written back.
   Otherwise, we silently do nothing.
   Otherwise, we silently do nothing.
 
 
   The big question is whether memory_remove_breakpoint () should be
   The big question is whether memory_remove_breakpoint () should be
   changed to have the same functionality.  The downside is that more
   changed to have the same functionality.  The downside is that more
   traffic is generated for remote targets since we'll have an extra
   traffic is generated for remote targets since we'll have an extra
   fetch of a memory word each time a breakpoint is removed.
   fetch of a memory word each time a breakpoint is removed.
 
 
   For the time being, we'll leave this self-modifying-code-friendly
   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
   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
   else in the event that some other platform has similar needs with
   regard to removing breakpoints in some potentially self modifying
   regard to removing breakpoints in some potentially self modifying
   code.  */
   code.  */
int
int
ppc_linux_memory_remove_breakpoint (CORE_ADDR addr, char *contents_cache)
ppc_linux_memory_remove_breakpoint (CORE_ADDR addr, char *contents_cache)
{
{
  unsigned char *bp;
  unsigned char *bp;
  int val;
  int val;
  int bplen;
  int bplen;
  char old_contents[BREAKPOINT_MAX];
  char old_contents[BREAKPOINT_MAX];
 
 
  /* Determine appropriate breakpoint contents and size for this address.  */
  /* Determine appropriate breakpoint contents and size for this address.  */
  bp = BREAKPOINT_FROM_PC (&addr, &bplen);
  bp = BREAKPOINT_FROM_PC (&addr, &bplen);
  if (bp == NULL)
  if (bp == NULL)
    error ("Software breakpoints not implemented for this target.");
    error ("Software breakpoints not implemented for this target.");
 
 
  val = target_read_memory (addr, old_contents, bplen);
  val = target_read_memory (addr, old_contents, bplen);
 
 
  /* If our breakpoint is no longer at the address, this means that the
  /* 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
     program modified the code on us, so it is wrong to put back the
     old value */
     old value */
  if (val == 0 && memcmp (bp, old_contents, bplen) == 0)
  if (val == 0 && memcmp (bp, old_contents, bplen) == 0)
    val = target_write_memory (addr, contents_cache, bplen);
    val = target_write_memory (addr, contents_cache, bplen);
 
 
  return val;
  return val;
}
}
 
 

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