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/kern/imgact_gzip.c

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    1 /*-
    2  * SPDX-License-Identifier: Beerware
    3  *
    4  * ----------------------------------------------------------------------------
    5  * "THE BEER-WARE LICENSE" (Revision 42):
    6  * <phk@FreeBSD.org> wrote this file.  As long as you retain this notice you
    7  * can do whatever you want with this stuff. If we meet some day, and you think
    8  * this stuff is worth it, you can buy me a beer in return.   Poul-Henning Kamp
    9  * ----------------------------------------------------------------------------
   10  */
   11 
   12 /*
   13  * This module handles execution of a.out files which have been run through
   14  * "gzip".  This saves diskspace, but wastes cpu-cycles and VM.
   15  *
   16  * TODO:
   17  *      text-segments should be made R/O after being filled
   18  *      is the vm-stuff safe ?
   19  *      should handle the entire header of gzip'ed stuff.
   20  *      inflate isn't quite reentrant yet...
   21  *      error-handling is a mess...
   22  *      so is the rest...
   23  *      tidy up unnecessary includes
   24  */
   25 
   26 #include <sys/cdefs.h>
   27 __FBSDID("$FreeBSD: releng/12.0/sys/kern/imgact_gzip.c 330842 2018-03-13 13:09:10Z emaste $");
   28 
   29 #include <sys/param.h>
   30 #include <sys/exec.h>
   31 #include <sys/imgact.h>
   32 #include <sys/imgact_aout.h>
   33 #include <sys/kernel.h>
   34 #include <sys/lock.h>
   35 #include <sys/mman.h>
   36 #include <sys/mutex.h>
   37 #include <sys/proc.h>
   38 #include <sys/racct.h>
   39 #include <sys/resourcevar.h>
   40 #include <sys/sysent.h>
   41 #include <sys/systm.h>
   42 #include <sys/vnode.h>
   43 #include <sys/inflate.h>
   44 
   45 #include <vm/vm.h>
   46 #include <vm/vm_param.h>
   47 #include <vm/pmap.h>
   48 #include <vm/vm_map.h>
   49 #include <vm/vm_kern.h>
   50 #include <vm/vm_extern.h>
   51 
   52 struct imgact_gzip {
   53         struct image_params *ip;
   54         struct exec     a_out;
   55         int             error;
   56         int             gotheader;
   57         int             where;
   58         u_char         *inbuf;
   59         u_long          offset;
   60         u_long          output;
   61         u_long          len;
   62         int             idx;
   63         u_long          virtual_offset, file_offset, file_end, bss_size;
   64 };
   65 
   66 static int exec_gzip_imgact(struct image_params *imgp);
   67 static int NextByte(void *vp);
   68 static int do_aout_hdr(struct imgact_gzip *);
   69 static int Flush(void *vp, u_char *, u_long siz);
   70 
   71 static int
   72 exec_gzip_imgact(struct image_params *imgp)
   73 {
   74         int             error;
   75         const u_char   *p = (const u_char *) imgp->image_header;
   76         struct imgact_gzip igz;
   77         struct inflate  infl;
   78         struct vmspace *vmspace;
   79 
   80         /* If these four are not OK, it isn't a gzip file */
   81         if (p[0] != 0x1f)
   82                 return -1;      /* 0    Simply magic     */
   83         if (p[1] != 0x8b)
   84                 return -1;      /* 1    Simply magic     */
   85         if (p[2] != 0x08)
   86                 return -1;      /* 2    Compression method       */
   87         if (p[9] != 0x03)
   88                 return -1;      /* 9    OS compressed on         */
   89 
   90         /*
   91          * If this one contains anything but a comment or a filename marker,
   92          * we don't want to chew on it
   93          */
   94         if (p[3] & ~(0x18))
   95                 return ENOEXEC; /* 3    Flags            */
   96 
   97         /* These are of no use to us */
   98         /* 4-7  Timestamp                */
   99         /* 8    Extra flags              */
  100 
  101         bzero(&igz, sizeof igz);
  102         bzero(&infl, sizeof infl);
  103         infl.gz_private = (void *) &igz;
  104         infl.gz_input = NextByte;
  105         infl.gz_output = Flush;
  106 
  107         igz.ip = imgp;
  108         igz.idx = 10;
  109 
  110         if (p[3] & 0x08) {      /* skip a filename */
  111                 while (p[igz.idx++])
  112                         if (igz.idx >= PAGE_SIZE)
  113                                 return ENOEXEC;
  114         }
  115         if (p[3] & 0x10) {      /* skip a comment */
  116                 while (p[igz.idx++])
  117                         if (igz.idx >= PAGE_SIZE)
  118                                 return ENOEXEC;
  119         }
  120         igz.len = imgp->attr->va_size;
  121 
  122         error = inflate(&infl);
  123 
  124         /*
  125          * The unzipped file may not even have been long enough to contain
  126          * a header giving Flush() a chance to return error.  Check for this.
  127          */
  128         if ( !igz.gotheader )
  129                 return ENOEXEC;
  130 
  131         if ( !error ) {
  132                 vmspace = imgp->proc->p_vmspace;
  133                 error = vm_map_protect(&vmspace->vm_map,
  134                         (vm_offset_t) vmspace->vm_taddr,
  135                         (vm_offset_t) (vmspace->vm_taddr + 
  136                                       (vmspace->vm_tsize << PAGE_SHIFT)) ,
  137                         VM_PROT_READ|VM_PROT_EXECUTE,0);
  138         }
  139 
  140         if (igz.inbuf)
  141                 kmap_free_wakeup(exec_map, (vm_offset_t)igz.inbuf, PAGE_SIZE);
  142         if (igz.error || error) {
  143                 printf("Output=%lu ", igz.output);
  144                 printf("Inflate_error=%d igz.error=%d where=%d\n",
  145                        error, igz.error, igz.where);
  146         }
  147         if (igz.error)
  148                 return igz.error;
  149         if (error)
  150                 return ENOEXEC;
  151         return 0;
  152 }
  153 
  154 static int
  155 do_aout_hdr(struct imgact_gzip * gz)
  156 {
  157         int             error;
  158         struct vmspace *vmspace;
  159         vm_offset_t     vmaddr;
  160 
  161         /*
  162          * Set file/virtual offset based on a.out variant. We do two cases:
  163          * host byte order and network byte order (for NetBSD compatibility)
  164          */
  165         switch ((int) (gz->a_out.a_midmag & 0xffff)) {
  166         case ZMAGIC:
  167                 gz->virtual_offset = 0;
  168                 if (gz->a_out.a_text) {
  169                         gz->file_offset = PAGE_SIZE;
  170                 } else {
  171                         /* Bill's "screwball mode" */
  172                         gz->file_offset = 0;
  173                 }
  174                 break;
  175         case QMAGIC:
  176                 gz->virtual_offset = PAGE_SIZE;
  177                 gz->file_offset = 0;
  178                 break;
  179         default:
  180                 /* NetBSD compatibility */
  181                 switch ((int) (ntohl(gz->a_out.a_midmag) & 0xffff)) {
  182                 case ZMAGIC:
  183                 case QMAGIC:
  184                         gz->virtual_offset = PAGE_SIZE;
  185                         gz->file_offset = 0;
  186                         break;
  187                 default:
  188                         gz->where = __LINE__;
  189                         return (-1);
  190                 }
  191         }
  192 
  193         gz->bss_size = roundup(gz->a_out.a_bss, PAGE_SIZE);
  194 
  195         /*
  196          * Check various fields in header for validity/bounds.
  197          */
  198         if (                    /* entry point must lay with text region */
  199             gz->a_out.a_entry < gz->virtual_offset ||
  200             gz->a_out.a_entry >= gz->virtual_offset + gz->a_out.a_text ||
  201 
  202         /* text and data size must each be page rounded */
  203             gz->a_out.a_text & PAGE_MASK || gz->a_out.a_data & PAGE_MASK) {
  204                 gz->where = __LINE__;
  205                 return (-1);
  206         }
  207         /*
  208          * text/data/bss must not exceed limits
  209          */
  210         PROC_LOCK(gz->ip->proc);
  211         if (                    /* text can't exceed maximum text size */
  212             gz->a_out.a_text > maxtsiz ||
  213 
  214         /* data + bss can't exceed rlimit */
  215             gz->a_out.a_data + gz->bss_size >
  216             lim_cur_proc(gz->ip->proc, RLIMIT_DATA) ||
  217             racct_set(gz->ip->proc, RACCT_DATA,
  218             gz->a_out.a_data + gz->bss_size) != 0) {
  219                 PROC_UNLOCK(gz->ip->proc);
  220                 gz->where = __LINE__;
  221                 return (ENOMEM);
  222         }
  223         PROC_UNLOCK(gz->ip->proc);
  224         /* Find out how far we should go */
  225         gz->file_end = gz->file_offset + gz->a_out.a_text + gz->a_out.a_data;
  226 
  227         /*
  228          * Avoid a possible deadlock if the current address space is destroyed
  229          * and that address space maps the locked vnode.  In the common case,
  230          * the locked vnode's v_usecount is decremented but remains greater
  231          * than zero.  Consequently, the vnode lock is not needed by vrele().
  232          * However, in cases where the vnode lock is external, such as nullfs,
  233          * v_usecount may become zero.
  234          */
  235         VOP_UNLOCK(gz->ip->vp, 0);
  236 
  237         /*
  238          * Destroy old process VM and create a new one (with a new stack)
  239          */
  240         error = exec_new_vmspace(gz->ip, &aout_sysvec);
  241 
  242         vn_lock(gz->ip->vp, LK_EXCLUSIVE | LK_RETRY);
  243         if (error) {
  244                 gz->where = __LINE__;
  245                 return (error);
  246         }
  247 
  248         vmspace = gz->ip->proc->p_vmspace;
  249 
  250         vmaddr = gz->virtual_offset;
  251 
  252         error = vm_mmap(&vmspace->vm_map,
  253                         &vmaddr,
  254                         gz->a_out.a_text + gz->a_out.a_data,
  255                         VM_PROT_ALL, VM_PROT_ALL, MAP_ANON | MAP_FIXED,
  256                         OBJT_DEFAULT,
  257                         NULL,
  258                         0);
  259 
  260         if (error) {
  261                 gz->where = __LINE__;
  262                 return (error);
  263         }
  264 
  265         if (gz->bss_size != 0) {
  266                 /*
  267                  * Allocate demand-zeroed area for uninitialized data.
  268                  * "bss" = 'block started by symbol' - named after the 
  269                  * IBM 7090 instruction of the same name.
  270                  */
  271                 vmaddr = gz->virtual_offset + gz->a_out.a_text + 
  272                         gz->a_out.a_data;
  273                 error = vm_map_find(&vmspace->vm_map, NULL, 0, &vmaddr,
  274                     gz->bss_size, 0, VMFS_NO_SPACE, VM_PROT_ALL, VM_PROT_ALL,
  275                     0);
  276                 if (error) {
  277                         gz->where = __LINE__;
  278                         return (error);
  279                 }
  280         }
  281         /* Fill in process VM information */
  282         vmspace->vm_tsize = gz->a_out.a_text >> PAGE_SHIFT;
  283         vmspace->vm_dsize = (gz->a_out.a_data + gz->bss_size) >> PAGE_SHIFT;
  284         vmspace->vm_taddr = (caddr_t) (uintptr_t) gz->virtual_offset;
  285         vmspace->vm_daddr = (caddr_t) (uintptr_t)
  286                             (gz->virtual_offset + gz->a_out.a_text);
  287 
  288         /* Fill in image_params */
  289         gz->ip->interpreted = 0;
  290         gz->ip->entry_addr = gz->a_out.a_entry;
  291 
  292         gz->ip->proc->p_sysent = &aout_sysvec;
  293 
  294         return 0;
  295 }
  296 
  297 static int
  298 NextByte(void *vp)
  299 {
  300         int             error;
  301         struct imgact_gzip *igz = (struct imgact_gzip *) vp;
  302 
  303         if (igz->idx >= igz->len) {
  304                 igz->where = __LINE__;
  305                 return GZ_EOF;
  306         }
  307         if (igz->inbuf && igz->idx < (igz->offset + PAGE_SIZE)) {
  308                 return igz->inbuf[(igz->idx++) - igz->offset];
  309         }
  310         if (igz->inbuf)
  311                 kmap_free_wakeup(exec_map, (vm_offset_t)igz->inbuf, PAGE_SIZE);
  312         igz->offset = igz->idx & ~PAGE_MASK;
  313 
  314         error = vm_mmap(exec_map,       /* map */
  315                         (vm_offset_t *) & igz->inbuf,   /* address */
  316                         PAGE_SIZE,      /* size */
  317                         VM_PROT_READ,   /* protection */
  318                         VM_PROT_READ,   /* max protection */
  319                         0,      /* flags */
  320                         OBJT_VNODE,     /* handle type */
  321                         igz->ip->vp,    /* vnode */
  322                         igz->offset);   /* offset */
  323         if (error) {
  324                 igz->where = __LINE__;
  325                 igz->error = error;
  326                 return GZ_EOF;
  327         }
  328         return igz->inbuf[(igz->idx++) - igz->offset];
  329 }
  330 
  331 static int
  332 Flush(void *vp, u_char * ptr, u_long siz)
  333 {
  334         struct imgact_gzip *gz = (struct imgact_gzip *) vp;
  335         u_char         *p = ptr, *q;
  336         int             i;
  337 
  338         /* First, find an a.out-header. */
  339         if (gz->output < sizeof gz->a_out) {
  340                 q = (u_char *) & gz->a_out;
  341                 i = min(siz, sizeof gz->a_out - gz->output);
  342                 bcopy(p, q + gz->output, i);
  343                 gz->output += i;
  344                 p += i;
  345                 siz -= i;
  346                 if (gz->output == sizeof gz->a_out) {
  347                         gz->gotheader = 1;
  348                         i = do_aout_hdr(gz);
  349                         if (i == -1) {
  350                                 if (!gz->where)
  351                                         gz->where = __LINE__;
  352                                 gz->error = ENOEXEC;
  353                                 return ENOEXEC;
  354                         } else if (i) {
  355                                 gz->where = __LINE__;
  356                                 gz->error = i;
  357                                 return ENOEXEC;
  358                         }
  359                         if (gz->file_offset == 0) {
  360                                 q = (u_char *) (uintptr_t) gz->virtual_offset;
  361                                 copyout(&gz->a_out, q, sizeof gz->a_out);
  362                         }
  363                 }
  364         }
  365         /* Skip over zero-padded first PAGE if needed */
  366         if (gz->output < gz->file_offset &&
  367             gz->output + siz > gz->file_offset) {
  368                 i = min(siz, gz->file_offset - gz->output);
  369                 gz->output += i;
  370                 p += i;
  371                 siz -= i;
  372         }
  373         if (gz->output >= gz->file_offset && gz->output < gz->file_end) {
  374                 i = min(siz, gz->file_end - gz->output);
  375                 q = (u_char *) (uintptr_t)
  376                     (gz->virtual_offset + gz->output - gz->file_offset);
  377                 copyout(p, q, i);
  378                 gz->output += i;
  379                 p += i;
  380                 siz -= i;
  381         }
  382         gz->output += siz;
  383         return 0;
  384 }
  385 
  386 
  387 /*
  388  * Tell kern_execve.c about it, with a little help from the linker.
  389  */
  390 static struct execsw gzip_execsw = {
  391         .ex_imgact = exec_gzip_imgact,
  392         .ex_name = "gzip"
  393 };
  394 EXEC_SET(execgzip, gzip_execsw);

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