servers/vm/mem_anon.c

   1
   2 /* This file implements the methods of anonymous memory.
   3  *
   4  * Anonymous memory is memory that is for private use to a process
   5  * and can not be related to a file (hence anonymous).
   6  */
   7
   8 #include <assert.h>
   9
  10 #include "proto.h"
  11 #include "vm.h"
  12 #include "region.h"
  13 #include "glo.h"
  14
  15 /* These functions are static so as to not pollute the
  16  * global namespace, and are accessed through their function
  17  * pointers.
  18  */
  19
  20 static int anon_reference(struct phys_region *pr);
  21 static int anon_unreference(struct phys_region *pr);
  22 static int anon_pagefault(struct vmproc *vmp, struct vir_region *region,
  23         struct phys_region *ph, int write);
  24 static int anon_sanitycheck(struct phys_region *pr, char *file, int line);
  25 static int anon_writable(struct phys_region *pr);
  26 static int anon_resize(struct vmproc *vmp, struct vir_region *vr, vir_bytes l);
  27 static u32_t anon_regionid(struct vir_region *region);
  28 static int anon_refcount(struct vir_region *vr);
  29
  30 struct mem_type mem_type_anon = {
  31         .name = "anonymous memory",
  32         .ev_reference = anon_reference,
  33         .ev_unreference = anon_unreference,
  34         .ev_pagefault = anon_pagefault,
  35         .ev_resize = anon_resize,
  36         .ev_sanitycheck = anon_sanitycheck,
  37         .regionid = anon_regionid,
  38         .writable = anon_writable,
  39         .refcount = anon_refcount
  40 };
  41
  42 static int anon_reference(struct phys_region *pr)
  43 {
  44         return OK;
  45 }
  46
  47 static int anon_unreference(struct phys_region *pr)
  48 {
  49         assert(pr->ph->refcount == 0);
  50         if(pr->ph->phys != MAP_NONE)
  51                 free_mem(ABS2CLICK(pr->ph->phys), 1);
  52         return OK;
  53 }
  54
  55 static int anon_pagefault(struct vmproc *vmp, struct vir_region *region,
  56         struct phys_region *ph, int write)
  57 {
  58         phys_bytes new_page, new_page_cl;
  59         struct phys_block *pb;
  60         u32_t allocflags;
  61
  62         allocflags = vrallocflags(region->flags);
  63
  64         assert(ph->ph->refcount > 0);
  65
  66         if((new_page_cl = alloc_mem(1, allocflags)) == NO_MEM)
  67                 return ENOMEM;
  68         new_page = CLICK2ABS(new_page_cl);
  69
  70         /* Totally new block? Create it. */
  71         if(ph->ph->phys == MAP_NONE) {
  72                 ph->ph->phys = new_page;
  73                 assert(ph->ph->phys != MAP_NONE);
  74
  75                 return OK;
  76         }
  77
  78         if(ph->ph->refcount < 2 || !write) {
  79                 printf("anon_pagefault: %d refcount, %d write - not handling pagefault\n",
  80                         ph->ph->refcount, write);
  81                 return OK;
  82         }
  83
  84         assert(region->flags & VR_WRITABLE);
  85
  86         if(sys_abscopy(ph->ph->phys, new_page, VM_PAGE_SIZE) != OK) {
  87                 panic("VM: abscopy failed\n");
  88                 return EFAULT;
  89         }
  90
  91         if(!(pb = pb_new(new_page))) {
  92                 free_mem(new_page_cl, 1);
  93                 return ENOMEM;
  94         }
  95
  96         pb_unreferenced(region, ph, 0);
  97         pb_link(ph, pb, ph->offset, region);
  98
  99         return OK;
 100 }
 101
 102 static int anon_sanitycheck(struct phys_region *pr, char *file, int line)
 103 {
 104         MYASSERT(usedpages_add(pr->ph->phys, VM_PAGE_SIZE) == OK);
 105         return OK;
 106 }
 107
 108 static int anon_writable(struct phys_region *pr)
 109 {
 110         assert(pr->ph->refcount > 0);
 111         if(pr->parent->remaps > 0)
 112                 return 1;
 113         return pr->ph->phys != MAP_NONE && pr->ph->refcount == 1;
 114 }
 115
 116 static int anon_resize(struct vmproc *vmp, struct vir_region *vr, vir_bytes l)
 117 {
 118         /* Shrinking not implemented; silently ignored.
 119          * (Which is ok for brk().)
 120          */
 121         if(l <= vr->length)
 122                 return OK;
 123
 124         assert(vr);
 125         assert(vr->flags & VR_ANON);
 126         assert(!(l % VM_PAGE_SIZE));
 127
 128         USE(vr, vr->length = l;);
 129
 130         return OK;
 131 }
 132
 133 static u32_t anon_regionid(struct vir_region *region)
 134 {
 135         return region->id;
 136 }
 137
 138 static int anon_refcount(struct vir_region *vr)
 139 {
 140         return 1 + vr->remaps;
 141 }
 142