1 /* 2 * linux/mm/mmap.c 3 * 4 * Written by obz. 5 */ 6 #include <linux/stat.h>
7 #include <linux/sched.h>
8 #include <linux/kernel.h>
9 #include <linux/mm.h>
10 #include <linux/errno.h>
11 #include <linux/mman.h>
12 #include <linux/string.h>
13
14 #include <asm/segment.h>
15 #include <asm/system.h>
16
17 /* 18 * description of effects of mapping type and prot in current implementation. 19 * this is due to the current handling of page faults in memory.c. the expected 20 * behavior is in parens: 21 * 22 * map_type prot 23 * PROT_NONE PROT_READ PROT_WRITE PROT_EXEC 24 * MAP_SHARED r: (no) yes r: (yes) yes r: (no) yes r: (no) no 25 * w: (no) yes w: (no) copy w: (yes) yes w: (no) no 26 * x: (no) no x: (no) no x: (no) no x: (yes) no 27 * 28 * MAP_PRIVATE r: (no) yes r: (yes) yes r: (no) yes r: (no) no 29 * w: (no) copy w: (no) copy w: (copy) copy w: (no) no 30 * x: (no) no x: (no) no x: (no) no x: (yes) no 31 * 32 */ 33
34 #defineCODE_SPACE(addr) ((((addr)+4095)&~4095) < \
35 current->start_code + current->end_code)
36
37 intsys_mmap(unsignedlong *buffer)
/* */ 38 { 39 unsignedlongbase, addr;
40 unsignedlonglen, limit, off;
41 intprot, flags, mask, fd, error;
42 structfile *file;
43
44 addr = (unsignedlong) get_fs_long(buffer); /* user address space*/ 45 len = (size_t) get_fs_long(buffer+1); /* nbytes of mapping */ 46 prot = (int) get_fs_long(buffer+2); /* protection */ 47 flags = (int) get_fs_long(buffer+3); /* mapping type */ 48 fd = (int) get_fs_long(buffer+4); /* object to map */ 49 off = (unsignedlong) get_fs_long(buffer+5); /* offset in object */ 50
51 if (fd >= NR_OPEN || fd < 0 || !(file = current->filp[fd]))
52 return -EBADF;
53 if (addr > TASK_SIZE || len > TASK_SIZE || addr > TASK_SIZE-len)
54 return -EINVAL;
55
56 /* 57 * do simple checking here so the lower-level routines won't have 58 * to. we assume access permissions have been handled by the open 59 * of the memory object, so we don't do any here. 60 */ 61
62 switch (flags & MAP_TYPE) { 63 caseMAP_SHARED:
64 if ((prot & PROT_WRITE) && !(file->f_mode & 2))
65 return -EINVAL;
66 /* fall through */ 67 caseMAP_PRIVATE:
68 if (!(file->f_mode & 1))
69 return -EINVAL;
70 break;
71
72 default:
73 return -EINVAL;
74 } 75
76 /* 77 * obtain the address to map to. we verify (or select) it and ensure 78 * that it represents a valid section of the address space. we assume 79 * that if PROT_EXEC is specified this should be in the code segment. 80 */ 81 base = 0;
82 limit = TASK_SIZE;
83
84 if (flags & MAP_FIXED) { 85 /* 86 * if MAP_FIXED is specified, we have to map exactly at this 87 * address. it must be page aligned and not ambiguous. 88 */ 89 if ((addr & 0xfff) || addr > 0x7fffffff || addr == 0 ||
90 (off & 0xfff))
91 return -EINVAL;
92 if (addr + len > limit)
93 return -ENOMEM;
94 }else{ 95 /* 96 * we're given a hint as to where to put the address. 97 * that we still need to search for a range of pages which 98 * are not mapped and which won't impact the stack or data 99 * segment. 100 * in linux, we only have a code segment and data segment. 101 * since data grows up and stack grows down, we're sort of 102 * stuck. placing above the data will break malloc, below 103 * the stack will cause stack overflow. because of this 104 * we don't allow nonspecified mappings... 105 */ 106 return -ENOMEM;
107 } 108
109 /* 110 * determine the object being mapped and call the appropriate 111 * specific mapper. the address has already been validated, but 112 * not unmapped 113 */ 114 if (!file->f_op || !file->f_op->mmap)
115 return -ENODEV;
116 mask = 0;
117 if (prot & (PROT_READ | PROT_EXEC))
118 mask |= PAGE_READONLY;
119 if (prot & PROT_WRITE)
120 mask |= PAGE_RW;
121 if (!mask)
122 return -EINVAL;
123 if ((flags & MAP_TYPE) == MAP_PRIVATE) { 124 mask |= PAGE_COW;
125 mask &= ~PAGE_RW;
126 } 127 error = file->f_op->mmap(file->f_inode, file, base + addr, len, mask, off);
128 if (error)
129 returnerror;
130 returnaddr;
131 } 132
133 intsys_munmap(unsignedlongaddr, size_tlen)
/* */ 134 { 135 unsignedlongbase, limit;
136
137 base = 0;
138 limit = TASK_SIZE;
139
140 if ((addr & 0xfff) || addr > 0x7fffffff || addr == 0 ||
141 addr + len > limit)
142 return -EINVAL;
143 if (unmap_page_range(base + addr, len))
144 return -EAGAIN; /* should never happen */ 145 return 0;
146 }