![[BACK]](/cvsweb/icons/back.gif){kind=icon}
Return to mmap.c CVS log ![[TXT]](/cvsweb/icons/text.gif){kind=icon}
![[DIR]](/cvsweb/icons/dir.gif){kind=icon}
Up to [Early Linux] / linux / mm|
Return to mmap.c CVS log | Up to [Early Linux] / linux / mm |
1.1 root 1: /*
2: * linux/mm/mmap.c
3: *
4: * Written by obz.
5: */
1.1.1.2 root 6: #include <linux/stat.h>
1.1 root 7: #include <linux/sched.h>
8: #include <linux/kernel.h>
1.1.1.3 root 9: #include <linux/mm.h>
1.1.1.4 ! root 10: #include <linux/errno.h>
! 11:
1.1 root 12: #include <asm/segment.h>
13: #include <asm/system.h>
1.1.1.4 ! root 14:
1.1 root 15: #include <sys/mman.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: * the permissions are encoded as cxwr (copy,exec,write,read)
33: */
34: #define MTYP(T) ((T) & MAP_TYPE)
35: #define PREAD(T,P) (((P) & PROT_READ) ? 1 : 0)
36: #define PWRITE(T,P) (((P) & PROT_WRITE) ? (MTYP(T) == MAP_SHARED ? 2 : 10) : 0)
37: #define PEXEC(T,P) (((P) & PROT_EXEC) ? 4 : 0)
38: #define PERMISS(T,P) (PREAD(T,P)|PWRITE(T,P)|PEXEC(T,P))
39:
40: #define CODE_SPACE(addr) ((((addr)+4095)&~4095) < \
41: current->start_code + current->end_code)
42:
43: static caddr_t
44: mmap_chr(unsigned long addr, size_t len, int prot, int flags,
45: struct inode *inode, unsigned long off)
46: {
47: int major, minor;
48:
49: major = MAJOR(inode->i_rdev);
50: minor = MINOR(inode->i_rdev);
51:
52: /*
53: * for character devices, only /dev/mem may be mapped. when the
54: * swapping code is modified to allow arbitrary sources of pages,
55: * then we can open it up to regular files.
56: */
57:
58: if (major != 1 || minor != 1)
59: return (caddr_t)-ENODEV;
60:
61: /*
1.1.1.4 ! root 62: * we only allow mappings from address 0 to high_memory, since thats
1.1 root 63: * the range of our memory [actually this is a lie. the buffer cache
64: * and ramdisk occupy higher memory, but the paging stuff won't
65: * let us map to it anyway, so we break it here].
66: *
67: * this call is very dangerous! because of the lack of adequate
68: * tagging of frames, it is possible to mmap over a frame belonging
69: * to another (innocent) process. with MAP_SHARED|MAP_WRITE, this
70: * rogue process can trample over the other's data! we ignore this :{
71: * for now, we hope people will malloc the required amount of space,
72: * then mmap over it. the mm needs serious work before this can be
73: * truly useful.
74: */
75:
1.1.1.4 ! root 76: if (len > high_memory || off > high_memory - len) /* avoid overflow */
1.1 root 77: return (caddr_t)-ENXIO;
78:
79: if (remap_page_range(addr, off, len, PERMISS(flags, prot)))
80: return (caddr_t)-EAGAIN;
81:
82: return (caddr_t)addr;
83: }
84:
85: caddr_t
86: sys_mmap(unsigned long *buffer)
87: {
88: unsigned long base, addr;
89: unsigned long len, limit, off;
90: int prot, flags, fd;
91: struct file *file;
92: struct inode *inode;
93:
94: addr = (unsigned long) get_fs_long(buffer); /* user address space*/
95: len = (size_t) get_fs_long(buffer+1); /* nbytes of mapping */
96: prot = (int) get_fs_long(buffer+2); /* protection */
97: flags = (int) get_fs_long(buffer+3); /* mapping type */
98: fd = (int) get_fs_long(buffer+4); /* object to map */
99: off = (unsigned long) get_fs_long(buffer+5); /* offset in object */
100:
101: if (fd >= NR_OPEN || fd < 0 || !(file = current->filp[fd]))
102: return (caddr_t) -EBADF;
103: if (addr > TASK_SIZE || (addr+(unsigned long) len) > TASK_SIZE)
104: return (caddr_t) -EINVAL;
105: inode = file->f_inode;
106:
107: /*
108: * do simple checking here so the lower-level routines won't have
109: * to. we assume access permissions have been handled by the open
110: * of the memory object, so we don't do any here.
111: */
112:
113: switch (flags & MAP_TYPE) {
114: case MAP_SHARED:
115: if ((prot & PROT_WRITE) && !(file->f_mode & 2))
116: return (caddr_t)-EINVAL;
117: /* fall through */
118: case MAP_PRIVATE:
119: if (!(file->f_mode & 1))
120: return (caddr_t)-EINVAL;
121: break;
122:
123: default:
124: return (caddr_t)-EINVAL;
125: }
126:
127: /*
128: * obtain the address to map to. we verify (or select) it and ensure
129: * that it represents a valid section of the address space. we assume
130: * that if PROT_EXEC is specified this should be in the code segment.
131: */
132: if (prot & PROT_EXEC) {
133: base = get_base(current->ldt[1]); /* cs */
134: limit = get_limit(0x0f); /* cs limit */
135: } else {
136: base = get_base(current->ldt[2]); /* ds */
137: limit = get_limit(0x17); /* ds limit */
138: }
139:
140: if (flags & MAP_FIXED) {
141: /*
142: * if MAP_FIXED is specified, we have to map exactly at this
143: * address. it must be page aligned and not ambiguous.
144: */
145: if ((addr & 0xfff) || addr > 0x7fffffff || addr == 0 ||
146: (off & 0xfff))
147: return (caddr_t)-EINVAL;
148: if (addr + len > limit)
149: return (caddr_t)-ENOMEM;
150: } else {
151: /*
152: * we're given a hint as to where to put the address.
153: * that we still need to search for a range of pages which
154: * are not mapped and which won't impact the stack or data
155: * segment.
156: * in linux, we only have a code segment and data segment.
157: * since data grows up and stack grows down, we're sort of
158: * stuck. placing above the data will break malloc, below
159: * the stack will cause stack overflow. because of this
160: * we don't allow nonspecified mappings...
161: */
162: return (caddr_t)-ENOMEM;
163: }
164:
165: /*
166: * determine the object being mapped and call the appropriate
167: * specific mapper. the address has already been validated, but
168: * not unmapped
169: */
170: if (S_ISCHR(inode->i_mode))
171: addr = (unsigned long)mmap_chr(base + addr, len, prot, flags,
172: inode, off);
173: else
174: addr = (unsigned long)-ENODEV;
175: if ((long)addr > 0)
176: addr -= base;
177:
178: return (caddr_t)addr;
179: }
180:
181: int sys_munmap(unsigned long addr, size_t len)
182: {
183: unsigned long base, limit;
184:
185: base = get_base(current->ldt[2]); /* map into ds */
186: limit = get_limit(0x17); /* ds limit */
187:
188: if ((addr & 0xfff) || addr > 0x7fffffff || addr == 0 ||
189: addr + len > limit)
190: return -EINVAL;
191: if (unmap_page_range(base + addr, len))
192: return -EAGAIN; /* should never happen */
193: return 0;
194: }
This archive runs on limited infrastructure. Preserving old code on modern bandwidth. Automated agents are requested to crawl responsibly.