linux-aarch64-ipa.c

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/* GNU/Linux/AArch64 specific low level interface, for the in-process
   agent library for GDB.

   Copyright (C) 2015-2018 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 "server.h"
#include <sys/mman.h>
#include "tracepoint.h"
#include <elf.h>
#ifdef HAVE_GETAUXVAL
#include <sys/auxv.h>
#endif
#include "linux-aarch64-tdesc.h"

/* Each register saved by the jump pad is in a 16 byte cell.  */
#define FT_CR_SIZE 16

#define FT_CR_FPCR  0
#define FT_CR_FPSR  1
#define FT_CR_CPSR  2
#define FT_CR_PC    3
#define FT_CR_SP    4
#define FT_CR_X0    5
#define FT_CR_GPR(n)    (FT_CR_X0 + (n))
#define FT_CR_FPR(n)    (FT_CR_GPR (31) + (n))

/* Mapping between registers collected by the jump pad and GDB's register
   array layout used by regcache.

   See linux-aarch64-low.c (aarch64_install_fast_tracepoint_jump_pad) for
   more details.  */

static const int aarch64_ft_collect_regmap[] = {
  FT_CR_GPR (0),
  FT_CR_GPR (1),
  FT_CR_GPR (2),
  FT_CR_GPR (3),
  FT_CR_GPR (4),
  FT_CR_GPR (5),
  FT_CR_GPR (6),
  FT_CR_GPR (7),
  FT_CR_GPR (8),
  FT_CR_GPR (9),
  FT_CR_GPR (10),
  FT_CR_GPR (11),
  FT_CR_GPR (12),
  FT_CR_GPR (13),
  FT_CR_GPR (14),
  FT_CR_GPR (15),
  FT_CR_GPR (16),
  FT_CR_GPR (17),
  FT_CR_GPR (18),
  FT_CR_GPR (19),
  FT_CR_GPR (20),
  FT_CR_GPR (21),
  FT_CR_GPR (22),
  FT_CR_GPR (23),
  FT_CR_GPR (24),
  FT_CR_GPR (25),
  FT_CR_GPR (26),
  FT_CR_GPR (27),
  FT_CR_GPR (28),
  /* FP */
  FT_CR_GPR (29),
  /* LR */
  FT_CR_GPR (30),
  FT_CR_SP,
  FT_CR_PC,
  FT_CR_CPSR,
  FT_CR_FPR (0),
  FT_CR_FPR (1),
  FT_CR_FPR (2),
  FT_CR_FPR (3),
  FT_CR_FPR (4),
  FT_CR_FPR (5),
  FT_CR_FPR (6),
  FT_CR_FPR (7),
  FT_CR_FPR (8),
  FT_CR_FPR (9),
  FT_CR_FPR (10),
  FT_CR_FPR (11),
  FT_CR_FPR (12),
  FT_CR_FPR (13),
  FT_CR_FPR (14),
  FT_CR_FPR (15),
  FT_CR_FPR (16),
  FT_CR_FPR (17),
  FT_CR_FPR (18),
  FT_CR_FPR (19),
  FT_CR_FPR (20),
  FT_CR_FPR (21),
  FT_CR_FPR (22),
  FT_CR_FPR (23),
  FT_CR_FPR (24),
  FT_CR_FPR (25),
  FT_CR_FPR (26),
  FT_CR_FPR (27),
  FT_CR_FPR (28),
  FT_CR_FPR (29),
  FT_CR_FPR (30),
  FT_CR_FPR (31),
  FT_CR_FPSR,
  FT_CR_FPCR
};

#define AARCH64_NUM_FT_COLLECT_GREGS \
  (sizeof (aarch64_ft_collect_regmap) / sizeof(aarch64_ft_collect_regmap[0]))

/* Fill in REGCACHE with registers saved by the jump pad in BUF.  */

void
supply_fast_tracepoint_registers (struct regcache *regcache,
                  const unsigned char *buf)
{
  int i;

  for (i = 0; i < AARCH64_NUM_FT_COLLECT_GREGS; i++)
    supply_register (regcache, i,
             ((char *) buf)
             + (aarch64_ft_collect_regmap[i] * FT_CR_SIZE));
}

ULONGEST
get_raw_reg (const unsigned char *raw_regs, int regnum)
{
  if (regnum >= AARCH64_NUM_FT_COLLECT_GREGS)
    return 0;

  return *(ULONGEST *) (raw_regs
            + aarch64_ft_collect_regmap[regnum] * FT_CR_SIZE);
}

/* Return target_desc to use for IPA, given the tdesc index passed by
   gdbserver.  Index is ignored, since we have only one tdesc
   at the moment.  */

const struct target_desc *
get_ipa_tdesc (int idx)
{
  return aarch64_linux_read_description ();
}

/* Allocate buffer for the jump pads.  The branch instruction has a reach
   of +/- 128MiB, and the executable is loaded at 0x400000 (4MiB).
   To maximize the area of executable that can use tracepoints, try
   allocating at 0x400000 - size initially, decreasing until we hit
   a free area.  */

void *
alloc_jump_pad_buffer (size_t size)
{
  uintptr_t addr;
  uintptr_t exec_base = getauxval (AT_PHDR);
  int pagesize;
  void *res;

  if (exec_base == 0)
    exec_base = 0x400000;

  pagesize = sysconf (_SC_PAGE_SIZE);
  if (pagesize == -1)
    perror_with_name ("sysconf");

  addr = exec_base - size;

  /* size should already be page-aligned, but this can't hurt.  */
  addr &= ~(pagesize - 1);

  /* Search for a free area.  If we hit 0, we're out of luck.  */
  for (; addr; addr -= pagesize)
    {
      /* No MAP_FIXED - we don't want to zap someone's mapping.  */
      res = mmap ((void *) addr, size,
          PROT_READ | PROT_WRITE | PROT_EXEC,
          MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);

      /* If we got what we wanted, return.  */
      if ((uintptr_t) res == addr)
    return res;

      /* If we got a mapping, but at a wrong address, undo it.  */
      if (res != MAP_FAILED)
    munmap (res, size);
    }

  return NULL;
}

void
initialize_low_tracepoint (void)
{
  aarch64_linux_read_description ();
}