text: /* libunwind - a platform-independent unwind library
     Copyright (C) 2002 Hewlett-Packard Co
     Copyright (C) 2007 David Mosberger-Tang
          Contributed by David Mosberger-Tang <dmosberger@gmail.com>
  
     Modified for x86_64 by Max Asbock <masbock@us.ibm.com>
  
  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.  */
  
  #ifdef HAVE_CONFIG_H
  #include <config.h>
  #endif
  
  #include <errno.h>
  #include <stdlib.h>
  #include <string.h>
  #include <sys/mman.h>
  #include <sys/syscall.h>
  
  #include "unwind_i.h"
  
  #ifdef UNW_REMOTE_ONLY
  
  /* unw_local_addr_space is a NULL pointer in this case.  */
  unw_addr_space_t unw_local_addr_space;
  
  #else /* !UNW_REMOTE_ONLY */
  
  static struct unw_addr_space local_addr_space;
  
  unw_addr_space_t unw_local_addr_space = &local_addr_space;
  
  HIDDEN unw_dyn_info_list_t _U_dyn_info_list;
  
  /* 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 void
  put_unwind_info (unw_addr_space_t as, unw_proc_info_t *proc_info, void *arg)
  {
    /* it's a no-op */
  }
  
  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))
  
  static int mem_validate_pipe[2] = {-1, -1};
  
  static inline void
  open_pipe (void)
  {
    /* ignore errors for closing invalid fd's */
    close (mem_validate_pipe[0]);
    close (mem_validate_pipe[1]);
  
    pipe2 (mem_validate_pipe, O_CLOEXEC | O_NONBLOCK);
  }
  
  ALWAYS_INLINE
  static int
  write_validate (void *addr)
  {
    int ret = -1;
    ssize_t bytes = 0;
  
    do
      {
        char buf;
        bytes = read (mem_validate_pipe[0], &buf, 1);
      }
    while ( errno == EINTR );
  
    int valid_read = (bytes > 0 || errno == EAGAIN || errno == EWOULDBLOCK);
    if (!valid_read)
      {
        // re-open closed pipe
        open_pipe ();
      }
  
    do
      {
        /* use syscall insteadof write() so that ASAN does not complain */
        ret = syscall (SYS_write, mem_validate_pipe[1], addr, 1);
      }
    while ( errno == EINTR );
  
    return ret;
  }
  
  static int (*mem_validate_func) (void *addr, size_t len);
  static int msync_validate (void *addr, size_t len)
  {
    if (msync (addr, len, MS_ASYNC) != 0)
      {
        return -1;
      }
  
    return write_validate (addr);
  }
  
  #ifdef HAVE_MINCORE
  static int mincore_validate (void *addr, size_t len)
  {
    unsigned char mvec[2]; /* Unaligned access may cross page boundary */
    size_t i;
  
    /* mincore could fail with EAGAIN but we conservatively return -1
       instead of looping. */
    if (mincore (addr, len, mvec) != 0)
      {
        return -1;
      }
  
    return write_validate (addr);
  }
  #endif
  
  /* Initialise memory validation method. On linux kernels <2.6.21,
     mincore() returns incorrect value for MAP_PRIVATE mappings,
     such as stacks. If mincore() was available at compile time,
     check if we can actually use it. If not, use msync() instead. */
  HIDDEN void
  tdep_init_mem_validate (void)
  {
    open_pipe ();
  
  #ifdef HAVE_MINCORE
    unsigned char present = 1;
    unw_word_t addr = PAGE_START((unw_word_t)&present);
    unsigned char mvec[1];
    int ret;
    while ((ret = mincore ((void*)addr, PAGE_SIZE, mvec)) == -1 &&
           errno == EAGAIN) {}
    if (ret == 0)
      {
        Debug(1, "using mincore to validate memory\n");
        mem_validate_func = mincore_validate;
      }
    else
  #endif
      {
        Debug(1, "using msync to validate memory\n");
        mem_validate_func = msync_validate;
      }
  }
  
  /* 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 (mem_validate_func ((void *) addr, len) == -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 (unlikely (write))
      {
        Debug (16, "mem[%016lx] <- %lx\n", addr, *val);
        *(unw_word_t *) addr = *val;
      }
    else
      {
        /* validate address */
        const struct cursor *c = (const struct cursor *)arg;
        if (likely (c != NULL) && unlikely (c->validate)
            && unlikely (validate_mem (addr))) {
          Debug (16, "mem[%016lx] -> invalid\n", addr);
          return -1;
        }
        *val = *(unw_word_t *) addr;
        Debug (16, "mem[%016lx] -> %lx\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;
    ucontext_t *uc = ((struct cursor *)arg)->uc;
  
    if (unw_is_fpreg (reg))
      goto badreg;
  
    if (!(addr = x86_64_r_uc_addr (uc, reg)))
      goto badreg;
  
    if (write)
      {
        *(unw_word_t *) addr = *val;
        Debug (12, "%s <- 0x%016lx\n", unw_regname (reg), *val);
      }
    else
      {
        *val = *(unw_word_t *) addr;
        Debug (12, "%s -> 0x%016lx\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)
  {
    ucontext_t *uc = ((struct cursor *)arg)->uc;
    unw_fpreg_t *addr;
  
    if (!unw_is_fpreg (reg))
      goto badreg;
  
    if (!(addr = x86_64_r_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 _Uelf64_get_proc_name (as, getpid (), ip, buf, buf_len, offp);
  }
  
  HIDDEN void
  x86_64_local_addr_space_init (void)
  {
    memset (&local_addr_space, 0, sizeof (local_addr_space));
    local_addr_space.caching_policy = UNWI_DEFAULT_CACHING_POLICY;
    local_addr_space.acc.find_proc_info = dwarf_find_proc_info;
    local_addr_space.acc.put_unwind_info = 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 = x86_64_local_resume;
    local_addr_space.acc.get_proc_name = get_static_proc_name;
    unw_flush_cache (&local_addr_space, 0, 0);
  
    memset (last_good_addr, 0, sizeof (unw_word_t) * NLGA);
    lga_victim = 0;
  }
  
  #endif /* !UNW_REMOTE_ONLY */
  