src/arm/Ginit.c

/* libunwind - a platform-independent unwind library
   Copyright (C) 2008 CodeSourcery

This file is part of libunwind.

Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */

#include <inttypes.h>
#include <stdlib.h>
#include <string.h>

#include "unwind_i.h"

static struct unw_addr_space local_addr_space;

PROTECTED unw_addr_space_t unw_local_addr_space = &local_addr_space;

HIDDEN unw_dyn_info_list_t _U_dyn_info_list;

static inline void *
uc_addr (unw_tdep_context_t *uc, int reg)
{
  // TODO: Do we want to use mcontext_t et. al.?
  // For now this is cheating. See def in musl arm/signal.h.
  if (reg >= UNW_ARM_R0 && reg < UNW_ARM_R0 + 16)
    return &uc->uc_mcontext.arm_r0 + (reg - UNW_ARM_R0);
  else
    return NULL;
}

/* XXX fix me: there is currently no way to locate the dyn-info list
       by a remote unwinder.  On ia64, this is done via a special
       unwind-table entry.  Perhaps something similar can be done with
       DWARF2 unwind info.  */

static int
get_dyn_info_list_addr (unw_addr_space_t as, unw_word_t *dyn_info_list_addr,
                        void *arg)
{
  *dyn_info_list_addr = (unw_word_t) &_U_dyn_info_list;
  return 0;
}

#define PAGE_SIZE 4096
#define PAGE_START(a)	((a) & ~(PAGE_SIZE-1))

/* Cache of already validated addresses */
#define NLGA 4
static unw_word_t last_good_addr[NLGA];
static int lga_victim;

static int
validate_mem (unw_word_t addr)
{
  int i, victim;
  size_t len;

  if (PAGE_START(addr + sizeof (unw_word_t) - 1) == PAGE_START(addr))
    len = PAGE_SIZE;
  else
    len = PAGE_SIZE * 2;

  addr = PAGE_START(addr);

  if (addr == 0)
    return -1;

  for (i = 0; i < NLGA; i++)
    {
      if (last_good_addr[i] && (addr == last_good_addr[i]))
      return 0;
    }

  if (msync ((void *) addr, len, MS_ASYNC) == -1)
    return -1;

  victim = lga_victim;
  for (i = 0; i < NLGA; i++) {
    if (!last_good_addr[victim]) {
      last_good_addr[victim++] = addr;
      return 0;
    }
    victim = (victim + 1) % NLGA;
  }

  /* All slots full. Evict the victim. */
  last_good_addr[victim] = addr;
  victim = (victim + 1) % NLGA;
  lga_victim = victim;

  return 0;
}

static int
access_mem (unw_addr_space_t as, unw_word_t addr, unw_word_t *val, int write,
            void *arg)
{
  if (write)
    {
      Debug (16, "mem[%" PRIxPTR "x <- %" PRIxPTR "\n", addr, *val);
      *(unw_word_t *) addr = *val;
    }
  else
    {
      /* validate address */
      const struct cursor *c = (const struct cursor *) arg;
      if (c && validate_mem(addr))
        return -1;

      *val = *(unw_word_t *) addr;
      Debug (16, "mem[%" PRIxPTR "] -> %" PRIxPTR "\n", addr, *val);
    }
  return 0;
}

static int
access_reg (unw_addr_space_t as, unw_regnum_t reg, unw_word_t *val, int write,
            void *arg)
{
  unw_word_t *addr;
  unw_tdep_context_t *uc = arg;

  if (unw_is_fpreg (reg))
    goto badreg;

  if (!(addr = uc_addr (uc, reg)))
    goto badreg;

  if (write)
    {
      *(unw_word_t *) addr = *val;
      Debug (12, "%s <- %" PRIxPTR "\n", unw_regname (reg), *val);
    }
  else
    {
      *val = *(unw_word_t *) addr;
      Debug (12, "%s -> %" PRIxPTR "\n", unw_regname (reg), *val);
    }
  return 0;

 badreg:
  Debug (1, "bad register number %u\n", reg);
  return -UNW_EBADREG;
}

static int
access_fpreg (unw_addr_space_t as, unw_regnum_t reg, unw_fpreg_t *val,
              int write, void *arg)
{
  unw_tdep_context_t *uc = arg;
  unw_fpreg_t *addr;

  if (!unw_is_fpreg (reg))
    goto badreg;

  if (!(addr = uc_addr (uc, reg)))
    goto badreg;

  if (write)
    {
      Debug (12, "%s <- %08lx.%08lx.%08lx\n", unw_regname (reg),
             ((long *)val)[0], ((long *)val)[1], ((long *)val)[2]);
      *(unw_fpreg_t *) addr = *val;
    }
  else
    {
      *val = *(unw_fpreg_t *) addr;
      Debug (12, "%s -> %08lx.%08lx.%08lx\n", unw_regname (reg),
             ((long *)val)[0], ((long *)val)[1], ((long *)val)[2]);
    }
  return 0;

 badreg:
  Debug (1, "bad register number %u\n", reg);
  /* attempt to access a non-preserved register */
  return -UNW_EBADREG;
}

static int
get_static_proc_name (unw_addr_space_t as, unw_word_t ip,
                      char *buf, size_t buf_len, unw_word_t *offp,
                      void *arg)
{
  return _Uelf32_get_proc_name (as, getpid (), ip, buf, buf_len, offp);
}

HIDDEN void
arm_local_addr_space_init (void)
{
  memset (&local_addr_space, 0, sizeof (local_addr_space));
  local_addr_space.caching_policy = UNW_CACHE_GLOBAL;
  local_addr_space.acc.find_proc_info = arm_find_proc_info;
  local_addr_space.acc.put_unwind_info = arm_put_unwind_info;
  local_addr_space.acc.get_dyn_info_list_addr = get_dyn_info_list_addr;
  local_addr_space.acc.access_mem = access_mem;
  local_addr_space.acc.access_reg = access_reg;
  local_addr_space.acc.access_fpreg = access_fpreg;
  local_addr_space.acc.resume = NULL;
  local_addr_space.acc.get_proc_name = get_static_proc_name;
  local_addr_space.big_endian = (__BYTE_ORDER == __BIG_ENDIAN);
  unw_flush_cache (&local_addr_space, 0, 0);
}