minix/servers/vm/mem_directphys.c

   1
   2 /* This file implements the methods of direct physical mapping.
   3  *
   4  * A direct physical mapping is done by accepting the physical
   5  * memory address and range from the caller and allowing direct
   6  * access to it. Most significantly, no physical memory is allocated
   7  * when it's mapped or freed when it's unmapped. E.g. device memory.
   8  */
   9
  10 #include "vm.h"
  11 #include "proto.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 phys_unreference(struct phys_region *pr);
  21 static int phys_writable(struct phys_region *pr);
  22 static int phys_pagefault(struct vmproc *vmp, struct vir_region *region,
  23         struct phys_region *ph, int write, vfs_callback_t cb, void *state,
  24         int len, int *io);
  25 static int phys_copy(struct vir_region *vr, struct vir_region *newvr);
  26 static int phys_pt_flags(struct vir_region *vr);
  27
  28 struct mem_type mem_type_directphys = {
  29         .name = "physical memory mapping",
  30         .ev_copy = phys_copy,
  31         .ev_unreference = phys_unreference,
  32         .writable = phys_writable,
  33         .ev_pagefault = phys_pagefault,
  34         .pt_flags = phys_pt_flags
  35 };
  36
  37 static int phys_pt_flags(struct vir_region *vr){
  38 #if defined(__arm__)
  39         return ARM_VM_PTE_DEVICE;
  40 #else
  41         return 0;
  42 #endif
  43 }
  44
  45 static int phys_unreference(struct phys_region *pr)
  46 {
  47         return OK;
  48 }
  49
  50 static int phys_pagefault(struct vmproc *vmp, struct vir_region *region,
  51     struct phys_region *ph, int write, vfs_callback_t cb, void *state,
  52     int len, int *io)
  53 {
  54         phys_bytes arg = region->param.phys, phmem;
  55         assert(arg != MAP_NONE);
  56         assert(ph->ph->phys == MAP_NONE);
  57         phmem = arg + ph->offset;
  58         assert(phmem != MAP_NONE);
  59         ph->ph->phys = phmem;
  60         return OK;
  61 }
  62
  63 static int phys_writable(struct phys_region *pr)
  64 {
  65         assert(pr->ph->refcount > 0);
  66         return pr->ph->phys != MAP_NONE;
  67 }
  68
  69 void phys_setphys(struct vir_region *vr, phys_bytes phys)
  70 {
  71         vr->param.phys = phys;
  72 }
  73
  74 static int phys_copy(struct vir_region *vr, struct vir_region *newvr)
  75 {
  76         newvr->param.phys = vr->param.phys;
  77
  78         return OK;
  79 }