text: /* Target-dependent code for OpenBSD/amd64.
  
     Copyright (C) 2003-2021 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 "frame-unwind.h"
  #include "gdbcore.h"
  #include "symtab.h"
  #include "objfiles.h"
  #include "osabi.h"
  #include "regcache.h"
  #include "regset.h"
  #include "target.h"
  #include "trad-frame.h"
  
  #include "obsd-tdep.h"
  #include "amd64-tdep.h"
  #include "i387-tdep.h"
  #include "gdbsupport/x86-xstate.h"
  #include "solib-svr4.h"
  #include "bsd-uthread.h"
  
  /* Support for signal handlers.  */
  
  /* Default page size.  */
  static const int amd64obsd_page_size = 4096;
  
  /* Return whether THIS_FRAME corresponds to an OpenBSD sigtramp
     routine.  */
  
  static int
  amd64obsd_sigtramp_p (struct frame_info *this_frame)
  {
    CORE_ADDR pc = get_frame_pc (this_frame);
    CORE_ADDR start_pc = (pc & ~(amd64obsd_page_size - 1));
    const gdb_byte osigreturn[] =
    {
      0x48, 0xc7, 0xc0,
      0x67, 0x00, 0x00, 0x00,	/* movq $SYS_sigreturn, %rax */
      0xcd, 0x80			/* int $0x80 */
    };
    const gdb_byte sigreturn[] =
    {
      0x48, 0xc7, 0xc0,
      0x67, 0x00, 0x00, 0x00,	/* movq $SYS_sigreturn, %rax */
      0x0f, 0x05			/* syscall */
    };
    size_t buflen = (sizeof sigreturn) + 1;
    gdb_byte *buf;
    const 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;
  
    /* If we can't read the instructions at START_PC, return zero.  */
    buf = (gdb_byte *) alloca ((sizeof sigreturn) + 1);
    if (!safe_frame_unwind_memory (this_frame, start_pc + 6, {buf, buflen}))
      return 0;
  
    /* Check for sigreturn(2).  Depending on how the assembler encoded
       the `movq %rsp, %rdi' instruction, the code starts at offset 6 or
       7.  OpenBSD 5.0 and later use the `syscall' instruction.  Older
       versions use `int $0x80'.  Check for both.  */
    if (memcmp (buf, sigreturn, sizeof sigreturn)
        && memcmp (buf + 1, sigreturn, sizeof sigreturn)
        && memcmp (buf, osigreturn, sizeof osigreturn)
        && memcmp (buf + 1, osigreturn, sizeof osigreturn))
      return 0;
  
    return 1;
  }
  
  /* Assuming THIS_FRAME is for a BSD sigtramp routine, return the
     address of the associated sigcontext structure.  */
  
  static CORE_ADDR
  amd64obsd_sigcontext_addr (struct frame_info *this_frame)
  {
    CORE_ADDR pc = get_frame_pc (this_frame);
    ULONGEST offset = (pc & (amd64obsd_page_size - 1));
  
    /* The %rsp register points at `struct sigcontext' upon entry of a
       signal trampoline.  The relevant part of the trampoline is
  
  	call    *%rax
  	movq    %rsp, %rdi
  	pushq   %rdi
  	movq    $SYS_sigreturn,%rax
  	int     $0x80
  
       (see /usr/src/sys/arch/amd64/amd64/locore.S).  The `pushq'
       instruction clobbers %rsp, but its value is saved in `%rdi'.  */
  
    if (offset > 5)
      return get_frame_register_unsigned (this_frame, AMD64_RDI_REGNUM);
    else
      return get_frame_register_unsigned (this_frame, AMD64_RSP_REGNUM);
  }
  
  /* OpenBSD 3.5 or later.  */
  
  /* Mapping between the general-purpose registers in `struct reg'
     format and GDB's register cache layout.  */
  
  /* From <machine/reg.h>.  */
  int amd64obsd_r_reg_offset[] =
  {
    14 * 8,			/* %rax */
    13 * 8,			/* %rbx */
    3 * 8,			/* %rcx */
    2 * 8,			/* %rdx */
    1 * 8,			/* %rsi */
    0 * 8,			/* %rdi */
    12 * 8,			/* %rbp */
    15 * 8,			/* %rsp */
    4 * 8,			/* %r8 ..  */
    5 * 8,
    6 * 8,
    7 * 8,
    8 * 8,
    9 * 8,
    10 * 8,
    11 * 8,			/* ... %r15 */
    16 * 8,			/* %rip */
    17 * 8,			/* %eflags */
    18 * 8,			/* %cs */
    19 * 8,			/* %ss */
    20 * 8,			/* %ds */
    21 * 8,			/* %es */
    22 * 8,			/* %fs */
    23 * 8			/* %gs */
  };
  
  /* From <machine/signal.h>.  */
  static int amd64obsd_sc_reg_offset[] =
  {
    14 * 8,			/* %rax */
    13 * 8,			/* %rbx */
    3 * 8,			/* %rcx */
    2 * 8,			/* %rdx */
    1 * 8,			/* %rsi */
    0 * 8,			/* %rdi */
    12 * 8,			/* %rbp */
    24 * 8,			/* %rsp */
    4 * 8,			/* %r8 ...  */
    5 * 8,
    6 * 8,
    7 * 8,
    8 * 8,
    9 * 8,
    10 * 8,
    11 * 8,			/* ... %r15 */
    21 * 8,			/* %rip */
    23 * 8,			/* %eflags */
    22 * 8,			/* %cs */
    25 * 8,			/* %ss */
    18 * 8,			/* %ds */
    17 * 8,			/* %es */
    16 * 8,			/* %fs */
    15 * 8			/* %gs */
  };
  
  /* From /usr/src/lib/libpthread/arch/amd64/uthread_machdep.c.  */
  static int amd64obsd_uthread_reg_offset[] =
  {
    19 * 8,			/* %rax */
    16 * 8,			/* %rbx */
    18 * 8,			/* %rcx */
    17 * 8,			/* %rdx */
    14 * 8,			/* %rsi */
    13 * 8,			/* %rdi */
    15 * 8,			/* %rbp */
    -1,				/* %rsp */
    12 * 8,			/* %r8 ...  */
    11 * 8,
    10 * 8,
    9 * 8,
    8 * 8,
    7 * 8,
    6 * 8,
    5 * 8,			/* ... %r15 */
    20 * 8,			/* %rip */
    4 * 8,			/* %eflags */
    21 * 8,			/* %cs */
    -1,				/* %ss */
    3 * 8,			/* %ds */
    2 * 8,			/* %es */
    1 * 8,			/* %fs */
    0 * 8				/* %gs */
  };
  
  /* Offset within the thread structure where we can find the saved
     stack pointer (%esp).  */
  #define AMD64OBSD_UTHREAD_RSP_OFFSET	400
  
  static void
  amd64obsd_supply_uthread (struct regcache *regcache,
  			  int regnum, CORE_ADDR addr)
  {
    struct gdbarch *gdbarch = regcache->arch ();
    enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
    CORE_ADDR sp_addr = addr + AMD64OBSD_UTHREAD_RSP_OFFSET;
    CORE_ADDR sp = 0;
    gdb_byte buf[8];
    int i;
  
    gdb_assert (regnum >= -1);
  
    if (regnum == -1 || regnum == AMD64_RSP_REGNUM)
      {
        int offset;
  
        /* Fetch stack pointer from thread structure.  */
        sp = read_memory_unsigned_integer (sp_addr, 8, byte_order);
  
        /* Adjust the stack pointer such that it looks as if we just
  	 returned from _thread_machdep_switch.  */
        offset = amd64obsd_uthread_reg_offset[AMD64_RIP_REGNUM] + 8;
        store_unsigned_integer (buf, 8, byte_order, sp + offset);
        regcache->raw_supply (AMD64_RSP_REGNUM, buf);
      }
  
    for (i = 0; i < ARRAY_SIZE (amd64obsd_uthread_reg_offset); i++)
      {
        if (amd64obsd_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, 8, byte_order);
  
  	  /* Read the saved register from the stack frame.  */
  	  read_memory (sp + amd64obsd_uthread_reg_offset[i], buf, 8);
  	  regcache->raw_supply (i, buf);
  	}
      }
  }
  
  static void
  amd64obsd_collect_uthread (const struct regcache *regcache,
  			   int regnum, CORE_ADDR addr)
  {
    struct gdbarch *gdbarch = regcache->arch ();
    enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
    CORE_ADDR sp_addr = addr + AMD64OBSD_UTHREAD_RSP_OFFSET;
    CORE_ADDR sp = 0;
    gdb_byte buf[8];
    int i;
  
    gdb_assert (regnum >= -1);
  
    if (regnum == -1 || regnum == AMD64_RSP_REGNUM)
      {
        int offset;
  
        /* Calculate the stack pointer (frame pointer) that will be
  	 stored into the thread structure.  */
        offset = amd64obsd_uthread_reg_offset[AMD64_RIP_REGNUM] + 8;
        regcache->raw_collect (AMD64_RSP_REGNUM, buf);
        sp = extract_unsigned_integer (buf, 8, byte_order) - offset;
  
        /* Store the stack pointer.  */
        write_memory_unsigned_integer (sp_addr, 8, 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 (amd64obsd_uthread_reg_offset); i++)
      {
        if (amd64obsd_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, 8, byte_order);
  
  	  /* Write the register into the stack frame.  */
  	  regcache->raw_collect (i, buf);
  	  write_memory (sp + amd64obsd_uthread_reg_offset[i], buf, 8);
  	}
      }
  }
  /* Kernel debugging support.  */
  
  /* From <machine/frame.h>.  Easy since `struct trapframe' matches
     `struct sigcontext'.  */
  #define amd64obsd_tf_reg_offset amd64obsd_sc_reg_offset
  
  static struct trad_frame_cache *
  amd64obsd_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;
    const char *name;
    int i;
  
    if (*this_cache)
      return (struct trad_frame_cache *) *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, AMD64_RSP_REGNUM);
  
    find_pc_partial_function (func, &name, NULL, NULL);
    if (name && startswith (name, "Xintr"))
      addr = sp + 8;		/* It's an interrupt frame.  */
    else
      addr = sp;
  
    for (i = 0; i < ARRAY_SIZE (amd64obsd_tf_reg_offset); i++)
      if (amd64obsd_tf_reg_offset[i] != -1)
        trad_frame_set_reg_addr (cache, i, addr + amd64obsd_tf_reg_offset[i]);
  
    /* Read %cs from trap frame.  */
    addr += amd64obsd_tf_reg_offset[AMD64_CS_REGNUM];
    cs = read_memory_unsigned_integer (addr, 8, 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 + 16, func));
      }
  
    return cache;
  }
  
  static void
  amd64obsd_trapframe_this_id (struct frame_info *this_frame,
  			     void **this_cache, struct frame_id *this_id)
  {
    struct trad_frame_cache *cache =
      amd64obsd_trapframe_cache (this_frame, this_cache);
    
    trad_frame_get_id (cache, this_id);
  }
  
  static struct value *
  amd64obsd_trapframe_prev_register (struct frame_info *this_frame,
  				   void **this_cache, int regnum)
  {
    struct trad_frame_cache *cache =
      amd64obsd_trapframe_cache (this_frame, this_cache);
  
    return trad_frame_get_register (cache, this_frame, regnum);
  }
  
  static int
  amd64obsd_trapframe_sniffer (const struct frame_unwind *self,
  			     struct frame_info *this_frame,
  			     void **this_prologue_cache)
  {
    ULONGEST cs;
    const char *name;
  
    /* Check Current Privilege Level and bail out if we're not executing
       in kernel space.  */
    cs = get_frame_register_unsigned (this_frame, AMD64_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, "osyscall1") == 0)
  		   || (strcmp (name, "Xsyscall") == 0)
  		   || (startswith (name, "Xintr"))));
  }
  
  static const struct frame_unwind amd64obsd_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,
    default_frame_unwind_stop_reason,
    amd64obsd_trapframe_this_id,
    amd64obsd_trapframe_prev_register,
    NULL,
    amd64obsd_trapframe_sniffer
  };
  
  
  static void
  amd64obsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
  {
    struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
  
    amd64_init_abi (info, gdbarch,
  		  amd64_target_description (X86_XSTATE_SSE_MASK, true));
    obsd_init_abi (info, gdbarch);
  
    /* Initialize general-purpose register set details.  */
    tdep->gregset_reg_offset = amd64obsd_r_reg_offset;
    tdep->gregset_num_regs = ARRAY_SIZE (amd64obsd_r_reg_offset);
    tdep->sizeof_gregset = 24 * 8;
  
    tdep->jb_pc_offset = 7 * 8;
  
    tdep->sigtramp_p = amd64obsd_sigtramp_p;
    tdep->sigcontext_addr = amd64obsd_sigcontext_addr;
    tdep->sc_reg_offset = amd64obsd_sc_reg_offset;
    tdep->sc_num_regs = ARRAY_SIZE (amd64obsd_sc_reg_offset);
  
    /* OpenBSD provides a user-level threads implementation.  */
    bsd_uthread_set_supply_uthread (gdbarch, amd64obsd_supply_uthread);
    bsd_uthread_set_collect_uthread (gdbarch, amd64obsd_collect_uthread);
  
    /* OpenBSD uses SVR4-style shared libraries.  */
    set_solib_svr4_fetch_link_map_offsets
      (gdbarch, svr4_lp64_fetch_link_map_offsets);
  
    /* Unwind kernel trap frames correctly.  */
    frame_unwind_prepend_unwinder (gdbarch, &amd64obsd_trapframe_unwind);
  }
  
  void _initialize_amd64obsd_tdep ();
  void
  _initialize_amd64obsd_tdep ()
  {
    /* The OpenBSD/amd64 native dependent code makes this assumption.  */
    gdb_assert (ARRAY_SIZE (amd64obsd_r_reg_offset) == AMD64_NUM_GREGS);
  
    gdbarch_register_osabi (bfd_arch_i386, bfd_mach_x86_64,
  			  GDB_OSABI_OPENBSD, amd64obsd_init_abi);
  }
  