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1ab3bf1b JG |
1 | /* GDB support for an sbrk-like function that uses mmap. |
2 | Copyright 1992 Free Software Foundation, Inc. | |
3 | Contributed by Cygnus Support, using pieces from other GDB modules. | |
4 | ||
5 | This file is part of GDB. | |
6 | ||
7 | This program is free software; you can redistribute it and/or modify | |
8 | it under the terms of the GNU General Public License as published by | |
9 | the Free Software Foundation; either version 2 of the License, or | |
10 | (at your option) any later version. | |
11 | ||
12 | This program is distributed in the hope that it will be useful, | |
13 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
15 | GNU General Public License for more details. | |
16 | ||
17 | You should have received a copy of the GNU General Public License | |
18 | along with this program; if not, write to the Free Software | |
19 | Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ | |
20 | ||
1ab3bf1b JG |
21 | #include "defs.h" |
22 | ||
23 | #ifdef HAVE_MMAP | |
24 | ||
25 | #include <fcntl.h> | |
26 | #include <sys/mman.h> | |
27 | ||
28 | #ifdef i386 | |
29 | #define MMAP_BASE ((caddr_t) 0x81000000) | |
30 | #define MMAP_PGSZ 0x00002000 /* Must be multiple of real page size */ | |
31 | #else | |
32 | #define MMAP_BASE ((caddr_t) 0xC2000000) | |
33 | #define MMAP_PGSZ 0x00002000 /* Must be multiple of real page size */ | |
34 | #endif | |
35 | ||
36 | #define PAGE_ALIGN(addr) (caddr_t) (((long)(addr) + MMAP_PGSZ - 1) & \ | |
37 | ~(MMAP_PGSZ - 1)) | |
38 | ||
39 | static caddr_t mbase = MMAP_BASE; /* Current base of mmap'd region */ | |
40 | static caddr_t mbreak = MMAP_BASE; /* Current "break" address */ | |
41 | static caddr_t mtop = MMAP_BASE; /* Current top of mmap'd region */ | |
42 | ||
43 | static int fd = -1; /* Open fd for /dev/zero */ | |
44 | ||
45 | ||
46 | /* Provide a utility routine for other modules to obtain compatible | |
47 | page alignment. */ | |
48 | ||
49 | PTR | |
50 | mmap_page_align (addr) | |
51 | PTR addr; | |
52 | { | |
53 | return (PAGE_ALIGN (addr)); | |
54 | } | |
55 | ||
56 | /* Return the base address of the start of the mmap'd region. Note that | |
57 | we can find the end of the region at anytime by calling mmap_sbrk(0) */ | |
58 | ||
59 | PTR | |
60 | mmap_base () | |
61 | { | |
62 | return (mbase); | |
63 | } | |
64 | ||
65 | /* Works like sbrk(), but uses mmap to add to or subtract from a | |
66 | memory region. */ | |
67 | ||
68 | PTR | |
69 | mmap_sbrk (size) | |
70 | int size; | |
71 | { | |
72 | PTR result = NULL; | |
73 | int minc; | |
74 | caddr_t moveto; | |
75 | ||
76 | if (size == 0) | |
77 | { | |
78 | /* Just return the current "break" value. */ | |
79 | result = mbreak; | |
80 | } | |
81 | else if (size < 0) | |
82 | { | |
83 | /* We are deallocating memory. If the amount requested would cause | |
84 | us to try to deallocate back past the base of the mmap'd region | |
85 | then do nothing, and return NULL. Otherwise, deallocate the | |
86 | memory and return the old break value. */ | |
87 | if (mbreak + size >= mbase) | |
88 | { | |
89 | result = (PTR) mbreak; | |
90 | mbreak += size; | |
91 | moveto = PAGE_ALIGN (mbreak); | |
92 | munmap (moveto, (size_t) (mtop - moveto)); | |
93 | mtop = moveto; | |
94 | } | |
95 | } | |
96 | else | |
97 | { | |
98 | /* We are allocating memory. Make sure we have an open file | |
99 | descriptor and then go on to get the memory. */ | |
100 | if ((fd == -1) && (fd = open ("/dev/zero", O_RDONLY)) < 0) | |
101 | { | |
102 | result = NULL; | |
103 | } | |
104 | else if (mbreak + size > mtop) | |
105 | { | |
106 | /* The request would move us past the end of the currently | |
107 | mapped memory, so map in enough more memory to satisfy | |
108 | the request. */ | |
109 | moveto = PAGE_ALIGN (mbreak + size); | |
110 | if (mmap (mtop, moveto - mtop, PROT_READ | PROT_WRITE, | |
111 | MAP_PRIVATE | MAP_FIXED, fd, 0) == mtop) | |
112 | { | |
113 | mtop = moveto; | |
114 | result = (PTR) mbreak; | |
115 | mbreak += size; | |
116 | } | |
117 | } | |
118 | else | |
119 | { | |
120 | result = (PTR) mbreak; | |
121 | mbreak += size; | |
122 | } | |
123 | } | |
124 | return (result); | |
125 | } | |
126 | ||
127 | PTR | |
128 | mmap_remap (base, mapsize, fd, foffset) | |
129 | PTR base; | |
130 | long mapsize; | |
131 | int fd; | |
132 | long foffset; | |
133 | { | |
134 | /* FIXME: Quick hack, needs error checking and other attention. */ | |
135 | munmap (mbase, (size_t) (mtop - mbase)); | |
136 | mbase = base; | |
137 | mtop = mbase + mapsize; | |
138 | base = mmap (base, mapsize, PROT_READ | PROT_WRITE, | |
139 | MAP_PRIVATE | MAP_FIXED, dup (fd), foffset); | |
140 | return (base); | |
141 | } | |
142 | ||
143 | ||
144 | #endif /* HAVE_MMAP */ |