gdb/aarch64-nat.c

/* Native-dependent code for AArch64.

   Copyright (C) 2011-2022 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 "gdbarch.h"
#include "inferior.h"
#include "cli/cli-cmds.h"
#include "aarch64-nat.h"

#include <unordered_map>

/* Hash table storing per-process data.  We don't bind this to a
   per-inferior registry because of targets like x86 GNU/Linux that
   need to keep track of processes that aren't bound to any inferior
   (e.g., fork children, checkpoints).  */

static std::unordered_map<pid_t, aarch64_debug_reg_state>
aarch64_debug_process_state;

/* See aarch64-nat.h.  */

struct aarch64_debug_reg_state *
aarch64_lookup_debug_reg_state (pid_t pid)
{
  auto it = aarch64_debug_process_state.find (pid);
  if (it != aarch64_debug_process_state.end ())
    return &it->second;

  return nullptr;
}

/* See aarch64-nat.h.  */

struct aarch64_debug_reg_state *
aarch64_get_debug_reg_state (pid_t pid)
{
  return &aarch64_debug_process_state[pid];
}

/* See aarch64-nat.h.  */

void
aarch64_remove_debug_reg_state (pid_t pid)
{
  aarch64_debug_process_state.erase (pid);
}

/* Returns the number of hardware watchpoints of type TYPE that we can
   set.  Value is positive if we can set CNT watchpoints, zero if
   setting watchpoints of type TYPE is not supported, and negative if
   CNT is more than the maximum number of watchpoints of type TYPE
   that we can support.  TYPE is one of bp_hardware_watchpoint,
   bp_read_watchpoint, bp_write_watchpoint, or bp_hardware_breakpoint.
   CNT is the number of such watchpoints used so far (including this
   one).  OTHERTYPE is non-zero if other types of watchpoints are
   currently enabled.  */

int
aarch64_can_use_hw_breakpoint (enum bptype type, int cnt, int othertype)
{
  if (type == bp_hardware_watchpoint || type == bp_read_watchpoint
      || type == bp_access_watchpoint || type == bp_watchpoint)
    {
      if (aarch64_num_wp_regs == 0)
	return 0;
    }
  else if (type == bp_hardware_breakpoint)
    {
      if (aarch64_num_bp_regs == 0)
	return 0;
    }
  else
    gdb_assert_not_reached ("unexpected breakpoint type");

  /* We always return 1 here because we don't have enough information
     about possible overlap of addresses that they want to watch.  As an
     extreme example, consider the case where all the watchpoints watch
     the same address and the same region length: then we can handle a
     virtually unlimited number of watchpoints, due to debug register
     sharing implemented via reference counts.  */
  return 1;
}

/* Insert a hardware-assisted breakpoint at BP_TGT->reqstd_address.
   Return 0 on success, -1 on failure.  */

int
aarch64_insert_hw_breakpoint (struct gdbarch *gdbarch,
			      struct bp_target_info *bp_tgt)
{
  int ret;
  CORE_ADDR addr = bp_tgt->placed_address = bp_tgt->reqstd_address;
  int len;
  const enum target_hw_bp_type type = hw_execute;
  struct aarch64_debug_reg_state *state
    = aarch64_get_debug_reg_state (inferior_ptid.pid ());

  gdbarch_breakpoint_from_pc (gdbarch, &addr, &len);

  if (show_debug_regs)
    gdb_printf (gdb_stdlog,
		"insert_hw_breakpoint on entry (addr=0x%08lx, len=%d))\n",
		(unsigned long) addr, len);

  ret = aarch64_handle_breakpoint (type, addr, len, 1 /* is_insert */,
				   inferior_ptid, state);

  if (show_debug_regs)
    {
      aarch64_show_debug_reg_state (state,
				    "insert_hw_breakpoint", addr, len, type);
    }

  return ret;
}

/* Remove a hardware-assisted breakpoint at BP_TGT->placed_address.
   Return 0 on success, -1 on failure.  */

int
aarch64_remove_hw_breakpoint (struct gdbarch *gdbarch,
			      struct bp_target_info *bp_tgt)
{
  int ret;
  CORE_ADDR addr = bp_tgt->placed_address;
  int len = 4;
  const enum target_hw_bp_type type = hw_execute;
  struct aarch64_debug_reg_state *state
    = aarch64_get_debug_reg_state (inferior_ptid.pid ());

  gdbarch_breakpoint_from_pc (gdbarch, &addr, &len);

  if (show_debug_regs)
    gdb_printf (gdb_stdlog,
		"remove_hw_breakpoint on entry (addr=0x%08lx, len=%d))\n",
		(unsigned long) addr, len);

  ret = aarch64_handle_breakpoint (type, addr, len, 0 /* is_insert */,
				   inferior_ptid, state);

  if (show_debug_regs)
    {
      aarch64_show_debug_reg_state (state,
				    "remove_hw_watchpoint", addr, len, type);
    }

  return ret;
}

/* Insert a watchpoint to watch a memory region which starts at
   address ADDR and whose length is LEN bytes.  Watch memory accesses
   of the type TYPE.  Return 0 on success, -1 on failure.  */

int
aarch64_insert_watchpoint (CORE_ADDR addr, int len, enum target_hw_bp_type type,
			   struct expression *cond)
{
  int ret;
  struct aarch64_debug_reg_state *state
    = aarch64_get_debug_reg_state (inferior_ptid.pid ());

  if (show_debug_regs)
    gdb_printf (gdb_stdlog,
		"insert_watchpoint on entry (addr=0x%08lx, len=%d)\n",
		(unsigned long) addr, len);

  gdb_assert (type != hw_execute);

  ret = aarch64_handle_watchpoint (type, addr, len, 1 /* is_insert */,
				   inferior_ptid, state);

  if (show_debug_regs)
    {
      aarch64_show_debug_reg_state (state,
				    "insert_watchpoint", addr, len, type);
    }

  return ret;
}

/* Remove a watchpoint that watched the memory region which starts at
   address ADDR, whose length is LEN bytes, and for accesses of the
   type TYPE.  Return 0 on success, -1 on failure.  */

int
aarch64_remove_watchpoint (CORE_ADDR addr, int len, enum target_hw_bp_type type,
			   struct expression *cond)
{
  int ret;
  struct aarch64_debug_reg_state *state
    = aarch64_get_debug_reg_state (inferior_ptid.pid ());

  if (show_debug_regs)
    gdb_printf (gdb_stdlog,
		"remove_watchpoint on entry (addr=0x%08lx, len=%d)\n",
		(unsigned long) addr, len);

  gdb_assert (type != hw_execute);

  ret = aarch64_handle_watchpoint (type, addr, len, 0 /* is_insert */,
				   inferior_ptid, state);

  if (show_debug_regs)
    {
      aarch64_show_debug_reg_state (state,
				    "remove_watchpoint", addr, len, type);
    }

  return ret;
}

/* See aarch64-nat.h.  */

bool
aarch64_stopped_data_address (const struct aarch64_debug_reg_state *state,
			      CORE_ADDR addr_trap, CORE_ADDR *addr_p)
{
  int i;

  for (i = aarch64_num_wp_regs - 1; i >= 0; --i)
    {
      const unsigned int offset
	= aarch64_watchpoint_offset (state->dr_ctrl_wp[i]);
      const unsigned int len = aarch64_watchpoint_length (state->dr_ctrl_wp[i]);
      const CORE_ADDR addr_watch = state->dr_addr_wp[i] + offset;
      const CORE_ADDR addr_watch_aligned = align_down (state->dr_addr_wp[i], 8);
      const CORE_ADDR addr_orig = state->dr_addr_orig_wp[i];

      if (state->dr_ref_count_wp[i]
	  && DR_CONTROL_ENABLED (state->dr_ctrl_wp[i])
	  && addr_trap >= addr_watch_aligned
	  && addr_trap < addr_watch + len)
	{
	  /* ADDR_TRAP reports the first address of the memory range
	     accessed by the CPU, regardless of what was the memory
	     range watched.  Thus, a large CPU access that straddles
	     the ADDR_WATCH..ADDR_WATCH+LEN range may result in an
	     ADDR_TRAP that is lower than the
	     ADDR_WATCH..ADDR_WATCH+LEN range.  E.g.:

	     addr: |   4   |   5   |   6   |   7   |   8   |
				   |---- range watched ----|
		   |----------- range accessed ------------|

	     In this case, ADDR_TRAP will be 4.

	     To match a watchpoint known to GDB core, we must never
	     report *ADDR_P outside of any ADDR_WATCH..ADDR_WATCH+LEN
	     range.  ADDR_WATCH <= ADDR_TRAP < ADDR_ORIG is a false
	     positive on kernels older than 4.10.  See PR
	     external/20207.  */
	  *addr_p = addr_orig;
	  return true;
	}
    }

  return false;
}

/* Define AArch64 maintenance commands.  */

static void
add_show_debug_regs_command (void)
{
  /* A maintenance command to enable printing the internal DRi mirror
     variables.  */
  add_setshow_boolean_cmd ("show-debug-regs", class_maintenance,
			   &show_debug_regs, _("\
Set whether to show variables that mirror the AArch64 debug registers."), _("\
Show whether to show variables that mirror the AArch64 debug registers."), _("\
Use \"on\" to enable, \"off\" to disable.\n\
If enabled, the debug registers values are shown when GDB inserts\n\
or removes a hardware breakpoint or watchpoint, and when the inferior\n\
triggers a breakpoint or watchpoint."),
			   NULL,
			   NULL,
			   &maintenance_set_cmdlist,
			   &maintenance_show_cmdlist);
}

void
aarch64_initialize_hw_point ()
{
  add_show_debug_regs_command ();
}