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/* Target-dependent code for OpenBSD/i386.

   Copyright (C) 1988, 1989, 1991, 1992, 1994, 1996, 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 "arch-utils.h"

#include "frame.h"

#include "frame-unwind.h"

#include "gdbcore.h"

#include "regcache.h"

#include "regset.h"

#include "symtab.h"

#include "objfiles.h"

#include "osabi.h"

#include "target.h"

#include "trad-frame.h"

#include "gdb_assert.h"

#include "gdb_string.h"

#include "i386-tdep.h"

#include "i387-tdep.h"

#include "solib-svr4.h"

#include "bsd-uthread.h"

/* Support for signal handlers.  */

/* Since OpenBSD 3.2, the sigtramp routine is mapped at a random page

   in virtual memory.  The randomness makes it somewhat tricky to

   detect it, but fortunately we can rely on the fact that the start

   of the sigtramp routine is page-aligned.  We recognize the

   trampoline by looking for the code that invokes the sigreturn

   system call.  The offset where we can find that code varies from

   release to release.

   By the way, the mapping mentioned above is read-only, so you cannot

   place a breakpoint in the signal trampoline.  */

/* Default page size.  */

static const int i386obsd_page_size = 4096;

/* Offset for sigreturn(2).  */

static const int i386obsd_sigreturn_offset[] = {

  0x0a,                         /* OpenBSD 3.2 */

  0x14,                         /* OpenBSD 3.6 */

  0x3a,                         /* OpenBSD 3.8 */

  -1

};

/* Return whether THIS_FRAME corresponds to an OpenBSD sigtramp

   routine.  */

static int

i386obsd_sigtramp_p (struct frame_info *this_frame)

{

  CORE_ADDR pc = get_frame_pc (this_frame);

  CORE_ADDR start_pc = (pc & ~(i386obsd_page_size - 1));

  /* The call sequence invoking sigreturn(2).  */

  const gdb_byte sigreturn[] =

  {

    0xb8,

    0x67, 0x00, 0x00, 0x00,     /* movl $SYS_sigreturn, %eax */

    0xcd, 0x80                  /* int $0x80 */

  };

  size_t buflen = sizeof sigreturn;

  const int *offset;

  gdb_byte *buf;

  char *name;

  /* If the function has a valid symbol name, it isn't a

     trampoline.  */

  find_pc_partial_function (pc, &name, NULL, NULL);

  if (name != NULL)

    return 0;

  /* If the function lives in a valid section (even without a starting

     point) it isn't a trampoline.  */

  if (find_pc_section (pc) != NULL)

    return 0;

  /* Allocate buffer.  */

  buf = alloca (buflen);

  /* Loop over all offsets.  */

  for (offset = i386obsd_sigreturn_offset; *offset != -1; offset++)

    {

      /* If we can't read the instructions, return zero.  */

      if (!safe_frame_unwind_memory (this_frame, start_pc + *offset,

                                     buf, buflen))

        return 0;

      /* Check for sigreturn(2).  */

      if (memcmp (buf, sigreturn, buflen) == 0)

        return 1;

    }

  return 0;

}

/* Mapping between the general-purpose registers in `struct reg'

   format and GDB's register cache layout.  */

/* From <machine/reg.h>.  */

static int i386obsd_r_reg_offset[] =

{

  1 * 4,                        /* %ecx */

  2 * 4,                        /* %edx */

  3 * 4,                        /* %ebx */

  4 * 4,                        /* %esp */

  5 * 4,                        /* %ebp */

  6 * 4,                        /* %esi */

  7 * 4,                        /* %edi */

  8 * 4,                        /* %eip */

  9 * 4,                        /* %eflags */

  10 * 4,                       /* %cs */

  11 * 4,                       /* %ss */

  12 * 4,                       /* %ds */

  13 * 4,                       /* %es */

  14 * 4,                       /* %fs */

  15 * 4                        /* %gs */

};

static void

i386obsd_aout_supply_regset (const struct regset *regset,

                             struct regcache *regcache, int regnum,

                             const void *regs, size_t len)

{

  const struct gdbarch_tdep *tdep = gdbarch_tdep (regset->arch);

  const gdb_byte *gregs = regs;

  gdb_assert (len >= tdep->sizeof_gregset + I387_SIZEOF_FSAVE);

  i386_supply_gregset (regset, regcache, regnum, regs, tdep->sizeof_gregset);

  i387_supply_fsave (regcache, regnum, gregs + tdep->sizeof_gregset);

}

static const struct regset *

i386obsd_aout_regset_from_core_section (struct gdbarch *gdbarch,

                                        const char *sect_name,

                                        size_t sect_size)

{

  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);

  /* OpenBSD a.out core dumps don't use seperate register sets for the

     general-purpose and floating-point registers.  */

  if (strcmp (sect_name, ".reg") == 0

      && sect_size >= tdep->sizeof_gregset + I387_SIZEOF_FSAVE)

    {

      if (tdep->gregset == NULL)

        tdep->gregset =

          regset_alloc (gdbarch, i386obsd_aout_supply_regset, NULL);

      return tdep->gregset;

    }

  return NULL;

}

/* Sigtramp routine location for OpenBSD 3.1 and earlier releases.  */

CORE_ADDR i386obsd_sigtramp_start_addr = 0xbfbfdf20;

CORE_ADDR i386obsd_sigtramp_end_addr = 0xbfbfdff0;

/* From <machine/signal.h>.  */

int i386obsd_sc_reg_offset[I386_NUM_GREGS] =

{

  10 * 4,                       /* %eax */

  9 * 4,                        /* %ecx */

  8 * 4,                        /* %edx */

  7 * 4,                        /* %ebx */

  14 * 4,                       /* %esp */

  6 * 4,                        /* %ebp */

  5 * 4,                        /* %esi */

  4 * 4,                        /* %edi */

  11 * 4,                       /* %eip */

  13 * 4,                       /* %eflags */

  12 * 4,                       /* %cs */

  15 * 4,                       /* %ss */

  3 * 4,                        /* %ds */

  2 * 4,                        /* %es */

  1 * 4,                        /* %fs */

};

/* From /usr/src/lib/libpthread/arch/i386/uthread_machdep.c.  */

static int i386obsd_uthread_reg_offset[] =

{

  11 * 4,                       /* %eax */

  10 * 4,                       /* %ecx */

  9 * 4,                        /* %edx */

  8 * 4,                        /* %ebx */

  -1,                           /* %esp */

  6 * 4,                        /* %ebp */

  5 * 4,                        /* %esi */

  4 * 4,                        /* %edi */

  12 * 4,                       /* %eip */

  -1,                           /* %eflags */

  13 * 4,                       /* %cs */

  -1,                           /* %ss */

  3 * 4,                        /* %ds */

  2 * 4,                        /* %es */

  1 * 4,                        /* %fs */

};

/* Offset within the thread structure where we can find the saved

   stack pointer (%esp).  */

#define I386OBSD_UTHREAD_ESP_OFFSET     176

static void

i386obsd_supply_uthread (struct regcache *regcache,

                         int regnum, CORE_ADDR addr)

{

  struct gdbarch *gdbarch = get_regcache_arch (regcache);

  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);

  CORE_ADDR sp_addr = addr + I386OBSD_UTHREAD_ESP_OFFSET;

  CORE_ADDR sp = 0;

  gdb_byte buf[4];

  int i;

  gdb_assert (regnum >= -1);

  if (regnum == -1 || regnum == I386_ESP_REGNUM)

    {

      int offset;

      /* Fetch stack pointer from thread structure.  */

      sp = read_memory_unsigned_integer (sp_addr, 4, byte_order);

      /* Adjust the stack pointer such that it looks as if we just

         returned from _thread_machdep_switch.  */

      offset = i386obsd_uthread_reg_offset[I386_EIP_REGNUM] + 4;

      store_unsigned_integer (buf, 4, byte_order, sp + offset);

      regcache_raw_supply (regcache, I386_ESP_REGNUM, buf);

    }

  for (i = 0; i < ARRAY_SIZE (i386obsd_uthread_reg_offset); i++)

    {

      if (i386obsd_uthread_reg_offset[i] != -1

          && (regnum == -1 || regnum == i))

        {

          /* Fetch stack pointer from thread structure (if we didn't

             do so already).  */

          if (sp == 0)

            sp = read_memory_unsigned_integer (sp_addr, 4, byte_order);

          /* Read the saved register from the stack frame.  */

          read_memory (sp + i386obsd_uthread_reg_offset[i], buf, 4);

          regcache_raw_supply (regcache, i, buf);

        }

    }

}

static void

i386obsd_collect_uthread (const struct regcache *regcache,

                          int regnum, CORE_ADDR addr)

{

  struct gdbarch *gdbarch = get_regcache_arch (regcache);

  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);

  CORE_ADDR sp_addr = addr + I386OBSD_UTHREAD_ESP_OFFSET;

  CORE_ADDR sp = 0;

  gdb_byte buf[4];

  int i;

  gdb_assert (regnum >= -1);

  if (regnum == -1 || regnum == I386_ESP_REGNUM)

    {

      int offset;

      /* Calculate the stack pointer (frame pointer) that will be

         stored into the thread structure.  */

      offset = i386obsd_uthread_reg_offset[I386_EIP_REGNUM] + 4;

      regcache_raw_collect (regcache, I386_ESP_REGNUM, buf);

      sp = extract_unsigned_integer (buf, 4, byte_order) - offset;

      /* Store the stack pointer.  */

      write_memory_unsigned_integer (sp_addr, 4, byte_order, sp);

      /* The stack pointer was (potentially) modified.  Make sure we

         build a proper stack frame.  */

      regnum = -1;

    }

  for (i = 0; i < ARRAY_SIZE (i386obsd_uthread_reg_offset); i++)

    {

      if (i386obsd_uthread_reg_offset[i] != -1

          && (regnum == -1 || regnum == i))

        {

          /* Fetch stack pointer from thread structure (if we didn't

             calculate it already).  */

          if (sp == 0)

            sp = read_memory_unsigned_integer (sp_addr, 4, byte_order);

          /* Write the register into the stack frame.  */

          regcache_raw_collect (regcache, i, buf);

          write_memory (sp + i386obsd_uthread_reg_offset[i], buf, 4);

        }

    }

}

/* Kernel debugging support.  */

/* From <machine/frame.h>.  Note that %esp and %ess are only saved in

   a trap frame when entering the kernel from user space.  */

static int i386obsd_tf_reg_offset[] =

{

  10 * 4,                       /* %eax */

  9 * 4,                        /* %ecx */

  8 * 4,                        /* %edx */

  7 * 4,                        /* %ebx */

  -1,                           /* %esp */

  6 * 4,                        /* %ebp */

  5 * 4,                        /* %esi */

  4 * 4,                        /* %edi */

  13 * 4,                       /* %eip */

  15 * 4,                       /* %eflags */

  14 * 4,                       /* %cs */

  -1,                           /* %ss */

  3 * 4,                        /* %ds */

  2 * 4,                        /* %es */

  1 * 4                         /* %gs */

};

static struct trad_frame_cache *

i386obsd_trapframe_cache (struct frame_info *this_frame, void **this_cache)

{

  struct gdbarch *gdbarch = get_frame_arch (this_frame);

  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);

  struct trad_frame_cache *cache;

  CORE_ADDR func, sp, addr;

  ULONGEST cs;

  char *name;

  int i;

  if (*this_cache)

    return *this_cache;

  cache = trad_frame_cache_zalloc (this_frame);

  *this_cache = cache;

  func = get_frame_func (this_frame);

  sp = get_frame_register_unsigned (this_frame, I386_ESP_REGNUM);

  find_pc_partial_function (func, &name, NULL, NULL);

  if (name && strncmp (name, "Xintr", 5) == 0)

    addr = sp + 8;              /* It's an interrupt frame.  */

  else

    addr = sp;

  for (i = 0; i < ARRAY_SIZE (i386obsd_tf_reg_offset); i++)

    if (i386obsd_tf_reg_offset[i] != -1)

      trad_frame_set_reg_addr (cache, i, addr + i386obsd_tf_reg_offset[i]);

  /* Read %cs from trap frame.  */

  addr += i386obsd_tf_reg_offset[I386_CS_REGNUM];

  cs = read_memory_unsigned_integer (addr, 4, byte_order);

  if ((cs & I386_SEL_RPL) == I386_SEL_UPL)

    {

      /* Trap from user space; terminate backtrace.  */

      trad_frame_set_id (cache, outer_frame_id);

    }

  else

    {

      /* Construct the frame ID using the function start.  */

      trad_frame_set_id (cache, frame_id_build (sp + 8, func));

    }

  return cache;

}

static void

i386obsd_trapframe_this_id (struct frame_info *this_frame,

                            void **this_cache, struct frame_id *this_id)

{

  struct trad_frame_cache *cache =

    i386obsd_trapframe_cache (this_frame, this_cache);

  trad_frame_get_id (cache, this_id);

}

static struct value *

i386obsd_trapframe_prev_register (struct frame_info *this_frame,

                                  void **this_cache, int regnum)

{

  struct trad_frame_cache *cache =

    i386obsd_trapframe_cache (this_frame, this_cache);

  return trad_frame_get_register (cache, this_frame, regnum);

}

static int

i386obsd_trapframe_sniffer (const struct frame_unwind *self,

                            struct frame_info *this_frame,

                            void **this_prologue_cache)

{

  ULONGEST cs;

  char *name;

  /* Check Current Privilege Level and bail out if we're not executing

     in kernel space.  */

  cs = get_frame_register_unsigned (this_frame, I386_CS_REGNUM);

  if ((cs & I386_SEL_RPL) == I386_SEL_UPL)

    return 0;

  find_pc_partial_function (get_frame_pc (this_frame), &name, NULL, NULL);

  return (name && (strcmp (name, "calltrap") == 0

                   || strcmp (name, "syscall1") == 0

                   || strncmp (name, "Xintr", 5) == 0

                   || strncmp (name, "Xsoft", 5) == 0));

}

static const struct frame_unwind i386obsd_trapframe_unwind = {

  /* FIXME: kettenis/20051219: This really is more like an interrupt

     frame, but SIGTRAMP_FRAME would print <signal handler called>,

     which really is not what we want here.  */

  NORMAL_FRAME,

  i386obsd_trapframe_this_id,

  i386obsd_trapframe_prev_register,

  NULL,

  i386obsd_trapframe_sniffer

};

static void

i386obsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)

{

  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);

  /* Obviously OpenBSD is BSD-based.  */

  i386bsd_init_abi (info, gdbarch);

  /* OpenBSD has a different `struct reg'.  */

  tdep->gregset_reg_offset = i386obsd_r_reg_offset;

  tdep->gregset_num_regs = ARRAY_SIZE (i386obsd_r_reg_offset);

  tdep->sizeof_gregset = 16 * 4;

  /* OpenBSD uses -freg-struct-return by default.  */

  tdep->struct_return = reg_struct_return;

  /* OpenBSD uses a different memory layout.  */

  tdep->sigtramp_start = i386obsd_sigtramp_start_addr;

  tdep->sigtramp_end = i386obsd_sigtramp_end_addr;

  tdep->sigtramp_p = i386obsd_sigtramp_p;

  /* OpenBSD has a `struct sigcontext' that's different from the

     original 4.3 BSD.  */

  tdep->sc_reg_offset = i386obsd_sc_reg_offset;

  tdep->sc_num_regs = ARRAY_SIZE (i386obsd_sc_reg_offset);

  /* OpenBSD provides a user-level threads implementation.  */

  bsd_uthread_set_supply_uthread (gdbarch, i386obsd_supply_uthread);

  bsd_uthread_set_collect_uthread (gdbarch, i386obsd_collect_uthread);

  /* Unwind kernel trap frames correctly.  */

  frame_unwind_prepend_unwinder (gdbarch, &i386obsd_trapframe_unwind);

}

/* OpenBSD a.out.  */

static void

i386obsd_aout_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)

{

  i386obsd_init_abi (info, gdbarch);

  /* OpenBSD a.out has a single register set.  */

  set_gdbarch_regset_from_core_section

    (gdbarch, i386obsd_aout_regset_from_core_section);

}

/* OpenBSD ELF.  */

static void

i386obsd_elf_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)

{

  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);

  /* It's still OpenBSD.  */

  i386obsd_init_abi (info, gdbarch);

  /* But ELF-based.  */

  i386_elf_init_abi (info, gdbarch);

  /* OpenBSD ELF uses SVR4-style shared libraries.  */

  set_solib_svr4_fetch_link_map_offsets

    (gdbarch, svr4_ilp32_fetch_link_map_offsets);

}

/* Provide a prototype to silence -Wmissing-prototypes.  */

void _initialize_i386obsd_tdep (void);

void

_initialize_i386obsd_tdep (void)

{

  /* FIXME: kettenis/20021020: Since OpenBSD/i386 binaries are

     indistingushable from NetBSD/i386 a.out binaries, building a GDB

     that should support both these targets will probably not work as

     expected.  */

#define GDB_OSABI_OPENBSD_AOUT GDB_OSABI_NETBSD_AOUT

  gdbarch_register_osabi (bfd_arch_i386, 0, GDB_OSABI_OPENBSD_AOUT,

                          i386obsd_aout_init_abi);

  gdbarch_register_osabi (bfd_arch_i386, 0, GDB_OSABI_OPENBSD_ELF,

                          i386obsd_elf_init_abi);

}