The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/compat/linux/linux_mmap.c

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    1 /*-
    2  * Copyright (c) 2004 Tim J. Robbins
    3  * Copyright (c) 2002 Doug Rabson
    4  * Copyright (c) 2000 Marcel Moolenaar
    5  * Copyright (c) 1994-1995 Søren Schmidt
    6  * All rights reserved.
    7  *
    8  * Redistribution and use in source and binary forms, with or without
    9  * modification, are permitted provided that the following conditions
   10  * are met:
   11  * 1. Redistributions of source code must retain the above copyright
   12  *    notice, this list of conditions and the following disclaimer
   13  *    in this position and unchanged.
   14  * 2. Redistributions in binary form must reproduce the above copyright
   15  *    notice, this list of conditions and the following disclaimer in the
   16  *    documentation and/or other materials provided with the distribution.
   17  * 3. The name of the author may not be used to endorse or promote products
   18  *    derived from this software without specific prior written permission.
   19  *
   20  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   21  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   22  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   23  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   24  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   25  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   26  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   27  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   28  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   29  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   30  *
   31  * $FreeBSD: releng/10.4/sys/compat/linux/linux_mmap.c 302964 2016-07-17 15:23:32Z dchagin $
   32  */
   33 
   34 #include <sys/cdefs.h>
   35 __FBSDID("$FreeBSD: releng/10.4/sys/compat/linux/linux_mmap.c 302964 2016-07-17 15:23:32Z dchagin $");
   36 
   37 #include <sys/capsicum.h>
   38 #include <sys/file.h>
   39 #include <sys/imgact.h>
   40 #include <sys/ktr.h>
   41 #include <sys/mman.h>
   42 #include <sys/proc.h>
   43 #include <sys/resourcevar.h>
   44 #include <sys/sysent.h>
   45 #include <sys/sysproto.h>
   46 
   47 #include <vm/pmap.h>
   48 #include <vm/vm_map.h>
   49 
   50 #include <compat/linux/linux_emul.h>
   51 #include <compat/linux/linux_mmap.h>
   52 #include <compat/linux/linux_persona.h>
   53 #include <compat/linux/linux_util.h>
   54 
   55 
   56 #define STACK_SIZE  (2 * 1024 * 1024)
   57 #define GUARD_SIZE  (4 * PAGE_SIZE)
   58 
   59 #if defined(__amd64__)
   60 static void linux_fixup_prot(struct thread *td, int *prot);
   61 #endif
   62 
   63 
   64 int
   65 linux_mmap_common(struct thread *td, uintptr_t addr, size_t len, int prot,
   66     int flags, int fd, off_t pos)
   67 {
   68         struct proc *p = td->td_proc;
   69         struct vmspace *vms = td->td_proc->p_vmspace;
   70         struct mmap_args /* {
   71                 caddr_t addr;
   72                 size_t len;
   73                 int prot;
   74                 int flags;
   75                 int fd;
   76                 off_t pos;
   77         } */ bsd_args;
   78         int error;
   79         struct file *fp;
   80 
   81         cap_rights_t rights;
   82         LINUX_CTR6(mmap2, "0x%lx, %ld, %ld, 0x%08lx, %ld, 0x%lx",
   83             addr, len, prot, flags, fd, pos);
   84 
   85         error = 0;
   86         bsd_args.flags = 0;
   87         fp = NULL;
   88 
   89         /*
   90          * Linux mmap(2):
   91          * You must specify exactly one of MAP_SHARED and MAP_PRIVATE
   92          */
   93         if (!((flags & LINUX_MAP_SHARED) ^ (flags & LINUX_MAP_PRIVATE)))
   94                 return (EINVAL);
   95 
   96         if (flags & LINUX_MAP_SHARED)
   97                 bsd_args.flags |= MAP_SHARED;
   98         if (flags & LINUX_MAP_PRIVATE)
   99                 bsd_args.flags |= MAP_PRIVATE;
  100         if (flags & LINUX_MAP_FIXED)
  101                 bsd_args.flags |= MAP_FIXED;
  102         if (flags & LINUX_MAP_ANON) {
  103                 /* Enforce pos to be on page boundary, then ignore. */
  104                 if ((pos & PAGE_MASK) != 0)
  105                         return (EINVAL);
  106                 pos = 0;
  107                 bsd_args.flags |= MAP_ANON;
  108         } else
  109                 bsd_args.flags |= MAP_NOSYNC;
  110         if (flags & LINUX_MAP_GROWSDOWN)
  111                 bsd_args.flags |= MAP_STACK;
  112 
  113         /*
  114          * PROT_READ, PROT_WRITE, or PROT_EXEC implies PROT_READ and PROT_EXEC
  115          * on Linux/i386 if the binary requires executable stack.
  116          * We do this only for IA32 emulation as on native i386 this is does not
  117          * make sense without PAE.
  118          *
  119          * XXX. Linux checks that the file system is not mounted with noexec.
  120          */
  121         bsd_args.prot = prot;
  122 #if defined(__amd64__)
  123         linux_fixup_prot(td, &bsd_args.prot);
  124 #endif
  125 
  126         /* Linux does not check file descriptor when MAP_ANONYMOUS is set. */
  127         bsd_args.fd = (bsd_args.flags & MAP_ANON) ? -1 : fd;
  128         if (bsd_args.fd != -1) {
  129                 /*
  130                  * Linux follows Solaris mmap(2) description:
  131                  * The file descriptor fildes is opened with
  132                  * read permission, regardless of the
  133                  * protection options specified.
  134                  */
  135 
  136                 error = fget(td, bsd_args.fd,
  137                     cap_rights_init(&rights, CAP_MMAP), &fp);
  138                 if (error != 0)
  139                         return (error);
  140                 if (fp->f_type != DTYPE_VNODE) {
  141                         fdrop(fp, td);
  142                         return (EINVAL);
  143                 }
  144 
  145                 /* Linux mmap() just fails for O_WRONLY files */
  146                 if (!(fp->f_flag & FREAD)) {
  147                         fdrop(fp, td);
  148                         return (EACCES);
  149                 }
  150 
  151                 fdrop(fp, td);
  152         }
  153 
  154         if (flags & LINUX_MAP_GROWSDOWN) {
  155                 /*
  156                  * The Linux MAP_GROWSDOWN option does not limit auto
  157                  * growth of the region.  Linux mmap with this option
  158                  * takes as addr the initial BOS, and as len, the initial
  159                  * region size.  It can then grow down from addr without
  160                  * limit.  However, Linux threads has an implicit internal
  161                  * limit to stack size of STACK_SIZE.  Its just not
  162                  * enforced explicitly in Linux.  But, here we impose
  163                  * a limit of (STACK_SIZE - GUARD_SIZE) on the stack
  164                  * region, since we can do this with our mmap.
  165                  *
  166                  * Our mmap with MAP_STACK takes addr as the maximum
  167                  * downsize limit on BOS, and as len the max size of
  168                  * the region.  It then maps the top SGROWSIZ bytes,
  169                  * and auto grows the region down, up to the limit
  170                  * in addr.
  171                  *
  172                  * If we don't use the MAP_STACK option, the effect
  173                  * of this code is to allocate a stack region of a
  174                  * fixed size of (STACK_SIZE - GUARD_SIZE).
  175                  */
  176 
  177                 if ((caddr_t)addr + len > vms->vm_maxsaddr) {
  178                         /*
  179                          * Some Linux apps will attempt to mmap
  180                          * thread stacks near the top of their
  181                          * address space.  If their TOS is greater
  182                          * than vm_maxsaddr, vm_map_growstack()
  183                          * will confuse the thread stack with the
  184                          * process stack and deliver a SEGV if they
  185                          * attempt to grow the thread stack past their
  186                          * current stacksize rlimit.  To avoid this,
  187                          * adjust vm_maxsaddr upwards to reflect
  188                          * the current stacksize rlimit rather
  189                          * than the maximum possible stacksize.
  190                          * It would be better to adjust the
  191                          * mmap'ed region, but some apps do not check
  192                          * mmap's return value.
  193                          */
  194                         PROC_LOCK(p);
  195                         vms->vm_maxsaddr = (char *)p->p_sysent->sv_usrstack -
  196                             lim_cur(p, RLIMIT_STACK);
  197                         PROC_UNLOCK(p);
  198                 }
  199 
  200                 /*
  201                  * This gives us our maximum stack size and a new BOS.
  202                  * If we're using VM_STACK, then mmap will just map
  203                  * the top SGROWSIZ bytes, and let the stack grow down
  204                  * to the limit at BOS.  If we're not using VM_STACK
  205                  * we map the full stack, since we don't have a way
  206                  * to autogrow it.
  207                  */
  208                 if (len > STACK_SIZE - GUARD_SIZE) {
  209                         bsd_args.addr = (caddr_t)addr;
  210                         bsd_args.len = len;
  211                 } else {
  212                         bsd_args.addr = (caddr_t)addr -
  213                             (STACK_SIZE - GUARD_SIZE - len);
  214                         bsd_args.len = STACK_SIZE - GUARD_SIZE;
  215                 }
  216         } else {
  217                 bsd_args.addr = (caddr_t)addr;
  218                 bsd_args.len  = len;
  219         }
  220         bsd_args.pos = pos;
  221 
  222         error = sys_mmap(td, &bsd_args);
  223 
  224         LINUX_CTR2(mmap2, "return: %d (%p)", error, td->td_retval[0]);
  225 
  226         return (error);
  227 }
  228 
  229 int
  230 linux_mprotect_common(struct thread *td, uintptr_t addr, size_t len, int prot)
  231 {
  232         struct mprotect_args bsd_args;
  233 
  234         bsd_args.addr = (void *)addr;
  235         bsd_args.len = len;
  236         bsd_args.prot = prot;
  237 
  238 #if defined(__amd64__)
  239         linux_fixup_prot(td, &bsd_args.prot);
  240 #endif
  241         return (sys_mprotect(td, &bsd_args));
  242 }
  243 
  244 #if defined(__amd64__)
  245 static void
  246 linux_fixup_prot(struct thread *td, int *prot)
  247 {
  248         struct linux_pemuldata *pem;
  249 
  250         if (SV_PROC_FLAG(td->td_proc, SV_ILP32) && *prot & PROT_READ) {
  251                 pem = pem_find(td->td_proc);
  252                 if (pem->persona & LINUX_READ_IMPLIES_EXEC)
  253                         *prot |= PROT_EXEC;
  254         }
  255 
  256 }
  257 #endif

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