minix/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 void anon_split(struct vmproc *vmp, struct vir_region *vr,
  21                         struct vir_region *r1, struct vir_region *r2);
  22 static int anon_lowshrink(struct vir_region *vr, vir_bytes len);
  23 static int anon_unreference(struct phys_region *pr);
  24 static int anon_pagefault(struct vmproc *vmp, struct vir_region *region,
  25         struct phys_region *ph, int write, vfs_callback_t cb, void *state,
  26         int len, int *io);
  27 static int anon_sanitycheck(struct phys_region *pr, const char *file, int line);
  28 static int anon_writable(struct phys_region *pr);
  29 static int anon_resize(struct vmproc *vmp, struct vir_region *vr, vir_bytes l);
  30 static u32_t anon_regionid(struct vir_region *region);
  31 static int anon_refcount(struct vir_region *vr);
  32 static int anon_pt_flags(struct vir_region *vr);
  33
  34 struct mem_type mem_type_anon = {
  35         .name = "anonymous memory",
  36         .ev_unreference = anon_unreference,
  37         .ev_pagefault = anon_pagefault,
  38         .ev_resize = anon_resize,
  39         .ev_sanitycheck = anon_sanitycheck,
  40         .ev_lowshrink = anon_lowshrink,
  41         .ev_split = anon_split,
  42         .regionid = anon_regionid,
  43         .writable = anon_writable,
  44         .refcount = anon_refcount,
  45         .pt_flags = anon_pt_flags,
  46 };
  47
  48 static int anon_pt_flags(struct vir_region *vr){
  49 #if defined(__arm__)
  50         return ARM_VM_PTE_CACHED;
  51 #else
  52         return 0;
  53 #endif
  54 }
  55
  56 static int anon_unreference(struct phys_region *pr)
  57 {
  58         assert(pr->ph->refcount == 0);
  59         if(pr->ph->phys != MAP_NONE)
  60                 free_mem(ABS2CLICK(pr->ph->phys), 1);
  61         return OK;
  62 }
  63
  64 static int anon_pagefault(struct vmproc *vmp, struct vir_region *region,
  65         struct phys_region *ph, int write, vfs_callback_t cb, void *state,
  66         int len, int *io)
  67 {
  68         phys_bytes new_page, new_page_cl;
  69         u32_t allocflags;
  70
  71         allocflags = vrallocflags(region->flags);
  72
  73         assert(ph->ph->refcount > 0);
  74
  75         if((new_page_cl = alloc_mem(1, allocflags)) == NO_MEM) {
  76                 printf("anon_pagefault: out of memory\n");
  77                 return ENOMEM;
  78         }
  79         new_page = CLICK2ABS(new_page_cl);
  80
  81         /* Totally new block? Create it. */
  82         if(ph->ph->phys == MAP_NONE) {
  83                 ph->ph->phys = new_page;
  84                 assert(ph->ph->phys != MAP_NONE);
  85
  86                 return OK;
  87         }
  88
  89         if(ph->ph->refcount < 2 || !write) {
  90                 /* memory is ready already */
  91                 return OK;
  92         }
  93
  94         assert(region->flags & VR_WRITABLE);
  95
  96         return mem_cow(region, ph, new_page_cl, new_page);
  97 }
  98
  99 static int anon_sanitycheck(struct phys_region *pr, const char *file, int line)
 100 {
 101         MYASSERT(usedpages_add(pr->ph->phys, VM_PAGE_SIZE) == OK);
 102         return OK;
 103 }
 104
 105 static int anon_writable(struct phys_region *pr)
 106 {
 107         assert(pr->ph->refcount > 0);
 108         if(pr->ph->phys == MAP_NONE)
 109                 return 0;
 110         if(pr->parent->remaps > 0)
 111                 return 1;
 112         return pr->ph->refcount == 1;
 113 }
 114
 115 static int anon_resize(struct vmproc *vmp, struct vir_region *vr, vir_bytes l)
 116 {
 117         /* Shrinking not implemented; silently ignored.
 118          * (Which is ok for brk().)
 119          */
 120         if(l <= vr->length)
 121                 return OK;
 122
 123         assert(vr);
 124         assert(vr->flags & VR_ANON);
 125         assert(!(l % VM_PAGE_SIZE));
 126
 127         USE(vr, vr->length = l;);
 128
 129         return OK;
 130 }
 131
 132 static u32_t anon_regionid(struct vir_region *region)
 133 {
 134         return region->id;
 135 }
 136
 137 static int anon_lowshrink(struct vir_region *vr, vir_bytes len)
 138 {
 139         return OK;
 140 }
 141
 142 static int anon_refcount(struct vir_region *vr)
 143 {
 144         return 1 + vr->remaps;
 145 }
 146
 147 static void anon_split(struct vmproc *vmp, struct vir_region *vr,
 148                         struct vir_region *r1, struct vir_region *r2)
 149 {
 150         return;
 151 }