LCOV - code coverage report
Current view: top level - gcc/config - host-linux.c (source / functions) Hit Total Coverage
Test: gcc.info Lines: 14 49 28.6 %
Date: 2020-03-28 11:57:23 Functions: 2 2 100.0 %
Legend: Lines: hit not hit | Branches: + taken - not taken # not executed Branches: 0 0 -

           Branch data     Line data    Source code
       1                 :            : /* Linux host-specific hook definitions.
       2                 :            :    Copyright (C) 2004-2020 Free Software Foundation, Inc.
       3                 :            : 
       4                 :            :    This file is part of GCC.
       5                 :            : 
       6                 :            :    GCC is free software; you can redistribute it and/or modify it
       7                 :            :    under the terms of the GNU General Public License as published
       8                 :            :    by the Free Software Foundation; either version 3, or (at your
       9                 :            :    option) any later version.
      10                 :            : 
      11                 :            :    GCC is distributed in the hope that it will be useful, but WITHOUT
      12                 :            :    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
      13                 :            :    or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
      14                 :            :    License for more details.
      15                 :            : 
      16                 :            :    You should have received a copy of the GNU General Public License
      17                 :            :    along with GCC; see the file COPYING3.  If not see
      18                 :            :    <http://www.gnu.org/licenses/>.  */
      19                 :            : 
      20                 :            : #include "config.h"
      21                 :            : #include "system.h"
      22                 :            : #include "coretypes.h"
      23                 :            : #include "hosthooks.h"
      24                 :            : #include "hosthooks-def.h"
      25                 :            : 
      26                 :            : 
      27                 :            : /* Linux has a feature called exec-shield-randomize that perturbs the
      28                 :            :    address of non-fixed mapped segments by a (relatively) small amount.
      29                 :            :    The feature is intended to make it harder to attack the system with
      30                 :            :    buffer overflow attacks, since every invocation of a program will
      31                 :            :    have its libraries and data segments at slightly different addresses.
      32                 :            : 
      33                 :            :    This feature causes us problems with PCH because it makes it that
      34                 :            :    much harder to acquire a stable location at which to map our PCH
      35                 :            :    data file.
      36                 :            : 
      37                 :            :    [ The feature causes other points of non-determinism within the
      38                 :            :      compiler as well, so we'd *really* like to be able to have the
      39                 :            :      driver disable exec-shield-randomize for the process group, but
      40                 :            :      that isn't possible at present.  ]
      41                 :            : 
      42                 :            :    We're going to try several things:
      43                 :            : 
      44                 :            :       * Select an architecture specific address as "likely" and see
      45                 :            :         if that's free.  For our 64-bit hosts, we can easily choose
      46                 :            :         an address in Never Never Land.
      47                 :            : 
      48                 :            :       * If exec-shield-randomize is disabled, then just use the
      49                 :            :         address chosen by mmap in step one.
      50                 :            : 
      51                 :            :       * If exec-shield-randomize is enabled, then temporarily allocate
      52                 :            :         32M of memory as a buffer, then allocate PCH memory, then
      53                 :            :         free the buffer.  The theory here is that the perturbation is
      54                 :            :         no more than 16M, and so by allocating our buffer larger than
      55                 :            :         that we make it considerably more likely that the address will
      56                 :            :         be free when we want to load the data back.
      57                 :            : */
      58                 :            : 
      59                 :            : #undef HOST_HOOKS_GT_PCH_GET_ADDRESS
      60                 :            : #define HOST_HOOKS_GT_PCH_GET_ADDRESS linux_gt_pch_get_address
      61                 :            : 
      62                 :            : #undef HOST_HOOKS_GT_PCH_USE_ADDRESS
      63                 :            : #define HOST_HOOKS_GT_PCH_USE_ADDRESS linux_gt_pch_use_address
      64                 :            : 
      65                 :            : /* For various ports, try to guess a fixed spot in the vm space
      66                 :            :    that's probably free.  */
      67                 :            : #if defined(__alpha)
      68                 :            : # define TRY_EMPTY_VM_SPACE     0x10000000000
      69                 :            : #elif defined(__ia64)
      70                 :            : # define TRY_EMPTY_VM_SPACE     0x2000000100000000
      71                 :            : #elif defined(__x86_64) && defined(__LP64__)
      72                 :            : # define TRY_EMPTY_VM_SPACE     0x1000000000
      73                 :            : #elif defined(__x86_64)
      74                 :            : # define TRY_EMPTY_VM_SPACE     0x60000000
      75                 :            : #elif defined(__i386)
      76                 :            : # define TRY_EMPTY_VM_SPACE     0x60000000
      77                 :            : #elif defined(__powerpc__)
      78                 :            : # define TRY_EMPTY_VM_SPACE     0x60000000
      79                 :            : #elif defined(__s390x__)
      80                 :            : # define TRY_EMPTY_VM_SPACE     0x8000000000
      81                 :            : #elif defined(__s390__)
      82                 :            : # define TRY_EMPTY_VM_SPACE     0x60000000
      83                 :            : #elif defined(__sparc__) && defined(__LP64__)
      84                 :            : # define TRY_EMPTY_VM_SPACE     0x8000000000
      85                 :            : #elif defined(__sparc__)
      86                 :            : # define TRY_EMPTY_VM_SPACE     0x60000000
      87                 :            : #elif defined(__mc68000__)
      88                 :            : # define TRY_EMPTY_VM_SPACE     0x40000000
      89                 :            : #elif defined(__aarch64__) && defined(__ILP32__)
      90                 :            : # define TRY_EMPTY_VM_SPACE     0x60000000
      91                 :            : #elif defined(__aarch64__)
      92                 :            : # define TRY_EMPTY_VM_SPACE     0x1000000000
      93                 :            : #elif defined(__ARM_EABI__)
      94                 :            : # define TRY_EMPTY_VM_SPACE     0x60000000
      95                 :            : #elif defined(__mips__) && defined(__LP64__)
      96                 :            : # define TRY_EMPTY_VM_SPACE     0x8000000000
      97                 :            : #elif defined(__mips__)
      98                 :            : # define TRY_EMPTY_VM_SPACE     0x60000000
      99                 :            : #else
     100                 :            : # define TRY_EMPTY_VM_SPACE     0
     101                 :            : #endif
     102                 :            : 
     103                 :            : /* Determine a location where we might be able to reliably allocate SIZE
     104                 :            :    bytes.  FD is the PCH file, though we should return with the file 
     105                 :            :    unmapped.  */
     106                 :            : 
     107                 :            : static void *
     108                 :        346 : linux_gt_pch_get_address (size_t size, int fd)
     109                 :            : {
     110                 :        346 :   size_t buffer_size = 32 * 1024 * 1024;
     111                 :        346 :   void *addr, *buffer;
     112                 :        346 :   FILE *f;
     113                 :        346 :   bool randomize_on;
     114                 :            : 
     115                 :        346 :   addr = mmap ((void *)TRY_EMPTY_VM_SPACE, size, PROT_READ | PROT_WRITE,
     116                 :            :                MAP_PRIVATE, fd, 0);
     117                 :            : 
     118                 :            :   /* If we failed the map, that means there's *no* free space.  */
     119                 :        346 :   if (addr == (void *) MAP_FAILED)
     120                 :            :     return NULL;
     121                 :            :   /* Unmap the area before returning.  */
     122                 :        346 :   munmap (addr, size);
     123                 :            : 
     124                 :            :   /* If we got the exact area we requested, then that's great.  */
     125                 :        346 :   if (TRY_EMPTY_VM_SPACE && addr == (void *) TRY_EMPTY_VM_SPACE)
     126                 :            :     return addr;
     127                 :            : 
     128                 :            :   /* If we didn't, then we need to look to see if virtual address
     129                 :            :      randomization is on.  That is recorded in
     130                 :            :      kernel.randomize_va_space.  An older implementation used
     131                 :            :      kernel.exec-shield-randomize.  */
     132                 :          0 :   f = fopen ("/proc/sys/kernel/randomize_va_space", "r");
     133                 :          0 :   if (f == NULL)
     134                 :          0 :     f = fopen ("/proc/sys/kernel/exec-shield-randomize", "r");
     135                 :          0 :   randomize_on = false;
     136                 :          0 :   if (f != NULL)
     137                 :            :     {
     138                 :          0 :       char buf[100];
     139                 :          0 :       size_t c;
     140                 :            : 
     141                 :          0 :       c = fread (buf, 1, sizeof buf - 1, f);
     142                 :          0 :       if (c > 0)
     143                 :            :         {
     144                 :          0 :           buf[c] = '\0';
     145                 :          0 :           randomize_on = (atoi (buf) > 0);
     146                 :            :         }
     147                 :          0 :       fclose (f);
     148                 :            :     }
     149                 :            : 
     150                 :            :   /* If it isn't, then accept the address that mmap selected as fine.  */
     151                 :          0 :   if (!randomize_on)
     152                 :          0 :     return addr;
     153                 :            : 
     154                 :            :   /* Otherwise, we need to try again with buffer space.  */
     155                 :          0 :   buffer = mmap (0, buffer_size, PROT_NONE, MAP_PRIVATE | MAP_ANON, -1, 0);
     156                 :          0 :   addr = mmap (0, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
     157                 :          0 :   if (buffer != (void *) MAP_FAILED)
     158                 :          0 :     munmap (buffer, buffer_size);
     159                 :          0 :   if (addr == (void *) MAP_FAILED)
     160                 :            :     return NULL;
     161                 :          0 :   munmap (addr, size);
     162                 :            : 
     163                 :          0 :   return addr;
     164                 :            : }
     165                 :            : 
     166                 :            : /* Map SIZE bytes of FD+OFFSET at BASE.  Return 1 if we succeeded at
     167                 :            :    mapping the data at BASE, -1 if we couldn't.
     168                 :            : 
     169                 :            :    It's not possibly to reliably mmap a file using MAP_PRIVATE to
     170                 :            :    a specific START address on either hpux or linux.  First we see
     171                 :            :    if mmap with MAP_PRIVATE works.  If it does, we are off to the
     172                 :            :    races.  If it doesn't, we try an anonymous private mmap since the
     173                 :            :    kernel is more likely to honor the BASE address in anonymous maps.
     174                 :            :    We then copy the data to the anonymous private map.  This assumes
     175                 :            :    of course that we don't need to change the data in the PCH file
     176                 :            :    after it is created.
     177                 :            : 
     178                 :            :    This approach obviously causes a performance penalty but there is
     179                 :            :    little else we can do given the current PCH implementation.  */
     180                 :            : 
     181                 :            : static int
     182                 :     154897 : linux_gt_pch_use_address (void *base, size_t size, int fd, size_t offset)
     183                 :            : {
     184                 :     154897 :   void *addr;
     185                 :            : 
     186                 :            :   /* We're called with size == 0 if we're not planning to load a PCH
     187                 :            :      file at all.  This allows the hook to free any static space that
     188                 :            :      we might have allocated at link time.  */
     189                 :     154897 :   if (size == 0)
     190                 :            :     return -1;
     191                 :            : 
     192                 :            :   /* Try to map the file with MAP_PRIVATE.  */
     193                 :       6399 :   addr = mmap (base, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, offset);
     194                 :            : 
     195                 :       6399 :   if (addr == base)
     196                 :            :     return 1;
     197                 :            : 
     198                 :          0 :   if (addr != (void *) MAP_FAILED)
     199                 :          0 :     munmap (addr, size);
     200                 :            : 
     201                 :            :   /* Try to make an anonymous private mmap at the desired location.  */
     202                 :          0 :   addr = mmap (base, size, PROT_READ | PROT_WRITE,
     203                 :            :                MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
     204                 :            : 
     205                 :          0 :   if (addr != base)
     206                 :            :     {
     207                 :          0 :       if (addr != (void *) MAP_FAILED)
     208                 :          0 :         munmap (addr, size);
     209                 :          0 :       return -1;
     210                 :            :     }
     211                 :            : 
     212                 :          0 :   if (lseek (fd, offset, SEEK_SET) == (off_t)-1)
     213                 :            :     return -1;
     214                 :            : 
     215                 :          0 :   while (size)
     216                 :            :     {
     217                 :          0 :       ssize_t nbytes;
     218                 :            : 
     219                 :          0 :       nbytes = read (fd, base, MIN (size, (size_t)-1 >> 1));
     220                 :          0 :       if (nbytes <= 0)
     221                 :            :         return -1;
     222                 :          0 :       base = (char *) base + nbytes;
     223                 :          0 :       size -= nbytes;
     224                 :            :     }
     225                 :            : 
     226                 :            :   return 1;
     227                 :            : }
     228                 :            : 
     229                 :            : 
     230                 :            : const struct host_hooks host_hooks = HOST_HOOKS_INITIALIZER;

Generated by: LCOV version 1.0

LCOV profile is generated on x86_64 machine using following configure options: configure --disable-bootstrap --enable-coverage=opt --enable-languages=c,c++,fortran,go,jit,lto --enable-host-shared. GCC test suite is run with the built compiler.