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Diffstat (limited to '')
-rw-r--r-- | src/lj_mcode.c | 260 |
1 files changed, 260 insertions, 0 deletions
diff --git a/src/lj_mcode.c b/src/lj_mcode.c new file mode 100644 index 00000000..e5791e9f --- /dev/null +++ b/src/lj_mcode.c | |||
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1 | /* | ||
2 | ** Machine code management. | ||
3 | ** Copyright (C) 2005-2009 Mike Pall. See Copyright Notice in luajit.h | ||
4 | */ | ||
5 | |||
6 | #define lj_mcode_c | ||
7 | #define LUA_CORE | ||
8 | |||
9 | #include "lj_obj.h" | ||
10 | |||
11 | #if LJ_HASJIT | ||
12 | |||
13 | #include "lj_gc.h" | ||
14 | #include "lj_jit.h" | ||
15 | #include "lj_mcode.h" | ||
16 | #include "lj_trace.h" | ||
17 | #include "lj_dispatch.h" | ||
18 | |||
19 | /* -- OS-specific functions ----------------------------------------------- */ | ||
20 | |||
21 | #if defined(LUA_USE_WIN) | ||
22 | |||
23 | #define WIN32_LEAN_AND_MEAN | ||
24 | #include <windows.h> | ||
25 | |||
26 | #define MCPROT_RW PAGE_READWRITE | ||
27 | #define MCPROT_RX PAGE_EXECUTE_READ | ||
28 | #define MCPROT_RWX PAGE_EXECUTE_READWRITE | ||
29 | |||
30 | static LJ_AINLINE void *mcode_alloc(jit_State *J, size_t sz, DWORD prot) | ||
31 | { | ||
32 | void *p = VirtualAlloc(NULL, sz, MEM_RESERVE|MEM_COMMIT|MEM_TOP_DOWN, prot); | ||
33 | if (!p) | ||
34 | lj_trace_err(J, LJ_TRERR_MCODEAL); | ||
35 | return p; | ||
36 | } | ||
37 | |||
38 | static LJ_AINLINE void mcode_free(jit_State *J, void *p, size_t sz) | ||
39 | { | ||
40 | UNUSED(J); UNUSED(sz); | ||
41 | VirtualFree(p, 0, MEM_RELEASE); | ||
42 | } | ||
43 | |||
44 | static LJ_AINLINE void mcode_setprot(void *p, size_t sz, DWORD prot) | ||
45 | { | ||
46 | DWORD oprot; | ||
47 | VirtualProtect(p, sz, prot, &oprot); | ||
48 | } | ||
49 | |||
50 | #elif defined(LUA_USE_POSIX) | ||
51 | |||
52 | #include <sys/mman.h> | ||
53 | |||
54 | #ifndef MAP_ANONYMOUS | ||
55 | #define MAP_ANONYMOUS MAP_ANON | ||
56 | #endif | ||
57 | |||
58 | #define MCPROT_RW (PROT_READ|PROT_WRITE) | ||
59 | #define MCPROT_RX (PROT_READ|PROT_EXEC) | ||
60 | #define MCPROT_RWX (PROT_READ|PROT_WRITE|PROT_EXEC) | ||
61 | |||
62 | static LJ_AINLINE void *mcode_alloc(jit_State *J, size_t sz, int prot) | ||
63 | { | ||
64 | void *p = mmap(NULL, sz, prot, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0); | ||
65 | if (p == MAP_FAILED) | ||
66 | lj_trace_err(J, LJ_TRERR_MCODEAL); | ||
67 | return p; | ||
68 | } | ||
69 | |||
70 | static LJ_AINLINE void mcode_free(jit_State *J, void *p, size_t sz) | ||
71 | { | ||
72 | UNUSED(J); | ||
73 | munmap(p, sz); | ||
74 | } | ||
75 | |||
76 | static LJ_AINLINE void mcode_setprot(void *p, size_t sz, int prot) | ||
77 | { | ||
78 | mprotect(p, sz, prot); | ||
79 | } | ||
80 | |||
81 | #else | ||
82 | |||
83 | /* Fallback allocator. This will fail if memory is not executable by default. */ | ||
84 | #define LUAJIT_UNPROTECT_MCODE | ||
85 | #define MCPROT_RW 0 | ||
86 | #define MCPROT_RX 0 | ||
87 | #define MCPROT_RWX 0 | ||
88 | |||
89 | static LJ_AINLINE void *mcode_alloc(jit_State *J, size_t sz, int prot) | ||
90 | { | ||
91 | UNUSED(prot); | ||
92 | return lj_mem_new(J->L, sz); | ||
93 | } | ||
94 | |||
95 | static LJ_AINLINE void mcode_free(jit_State *J, void *p, size_t sz) | ||
96 | { | ||
97 | lj_mem_free(J2G(J), p, sz); | ||
98 | } | ||
99 | |||
100 | #define mcode_setprot(p, sz, prot) UNUSED(p) | ||
101 | |||
102 | #endif | ||
103 | |||
104 | /* -- MCode area management ----------------------------------------------- */ | ||
105 | |||
106 | /* Define this ONLY if the page protection twiddling becomes a bottleneck. */ | ||
107 | #ifdef LUAJIT_UNPROTECT_MCODE | ||
108 | |||
109 | /* It's generally considered to be a potential security risk to have | ||
110 | ** pages with simultaneous write *and* execute access in a process. | ||
111 | ** | ||
112 | ** Do not even think about using this mode for server processes or | ||
113 | ** apps handling untrusted external data (such as a browser). | ||
114 | ** | ||
115 | ** The security risk is not in LuaJIT itself -- but if an adversary finds | ||
116 | ** any *other* flaw in your C application logic, then any RWX memory page | ||
117 | ** simplifies writing an exploit considerably. | ||
118 | */ | ||
119 | #define MCPROT_GEN MCPROT_RWX | ||
120 | #define MCPROT_RUN MCPROT_RWX | ||
121 | |||
122 | #else | ||
123 | |||
124 | /* This is the default behaviour and much safer: | ||
125 | ** | ||
126 | ** Most of the time the memory pages holding machine code are executable, | ||
127 | ** but NONE of them is writable. | ||
128 | ** | ||
129 | ** The current memory area is marked read-write (but NOT executable) only | ||
130 | ** during the short time window while the assembler generates machine code. | ||
131 | */ | ||
132 | #define MCPROT_GEN MCPROT_RW | ||
133 | #define MCPROT_RUN MCPROT_RX | ||
134 | |||
135 | #endif | ||
136 | |||
137 | /* Change protection of MCode area. */ | ||
138 | static void mcode_protect(jit_State *J, int prot) | ||
139 | { | ||
140 | #ifdef LUAJIT_UNPROTECT_MCODE | ||
141 | UNUSED(J); UNUSED(prot); | ||
142 | #else | ||
143 | if (J->mcprot != prot) { | ||
144 | mcode_setprot(J->mcarea, J->szmcarea, prot); | ||
145 | J->mcprot = prot; | ||
146 | } | ||
147 | #endif | ||
148 | } | ||
149 | |||
150 | /* Linked list of MCode areas. */ | ||
151 | typedef struct MCLink { | ||
152 | MCode *next; /* Next area. */ | ||
153 | size_t size; /* Size of current area. */ | ||
154 | } MCLink; | ||
155 | |||
156 | /* Allocate a new MCode area. */ | ||
157 | static void mcode_allocarea(jit_State *J) | ||
158 | { | ||
159 | MCode *oldarea = J->mcarea; | ||
160 | size_t sz = (size_t)J->param[JIT_P_sizemcode] << 10; | ||
161 | sz = (sz + LJ_PAGESIZE-1) & ~(size_t)(LJ_PAGESIZE - 1); | ||
162 | J->mcarea = (MCode *)mcode_alloc(J, sz, MCPROT_GEN); | ||
163 | J->szmcarea = sz; | ||
164 | J->mcprot = MCPROT_GEN; | ||
165 | J->mctop = (MCode *)((char *)J->mcarea + J->szmcarea); | ||
166 | J->mcbot = (MCode *)((char *)J->mcarea + sizeof(MCLink)); | ||
167 | ((MCLink *)J->mcarea)->next = oldarea; | ||
168 | ((MCLink *)J->mcarea)->size = sz; | ||
169 | J->szallmcarea += sz; | ||
170 | } | ||
171 | |||
172 | /* Free all MCode areas. */ | ||
173 | void lj_mcode_free(jit_State *J) | ||
174 | { | ||
175 | MCode *mc = J->mcarea; | ||
176 | J->mcarea = NULL; | ||
177 | J->szallmcarea = 0; | ||
178 | while (mc) { | ||
179 | MCode *next = ((MCLink *)mc)->next; | ||
180 | mcode_free(J, mc, ((MCLink *)mc)->size); | ||
181 | mc = next; | ||
182 | } | ||
183 | } | ||
184 | |||
185 | /* -- MCode transactions -------------------------------------------------- */ | ||
186 | |||
187 | /* Reserve the remainder of the current MCode area. */ | ||
188 | MCode *lj_mcode_reserve(jit_State *J, MCode **lim) | ||
189 | { | ||
190 | if (!J->mcarea) | ||
191 | mcode_allocarea(J); | ||
192 | else | ||
193 | mcode_protect(J, MCPROT_GEN); | ||
194 | *lim = J->mcbot; | ||
195 | return J->mctop; | ||
196 | } | ||
197 | |||
198 | /* Commit the top part of the current MCode area. */ | ||
199 | void lj_mcode_commit(jit_State *J, MCode *top) | ||
200 | { | ||
201 | J->mctop = top; | ||
202 | mcode_protect(J, MCPROT_RUN); | ||
203 | } | ||
204 | |||
205 | /* Abort the reservation. */ | ||
206 | void lj_mcode_abort(jit_State *J) | ||
207 | { | ||
208 | mcode_protect(J, MCPROT_RUN); | ||
209 | } | ||
210 | |||
211 | /* Set/reset protection to allow patching of MCode areas. */ | ||
212 | MCode *lj_mcode_patch(jit_State *J, MCode *ptr, int finish) | ||
213 | { | ||
214 | #ifdef LUAJIT_UNPROTECT_MCODE | ||
215 | UNUSED(J); UNUSED(ptr); UNUSED(finish); | ||
216 | return NULL; | ||
217 | #else | ||
218 | if (finish) { | ||
219 | if (J->mcarea == ptr) | ||
220 | mcode_protect(J, MCPROT_RUN); | ||
221 | else | ||
222 | mcode_setprot(ptr, ((MCLink *)ptr)->size, MCPROT_RUN); | ||
223 | return NULL; | ||
224 | } else { | ||
225 | MCode *mc = J->mcarea; | ||
226 | /* Try current area first to use the protection cache. */ | ||
227 | if (ptr >= mc && ptr < mc + J->szmcarea) { | ||
228 | mcode_protect(J, MCPROT_GEN); | ||
229 | return mc; | ||
230 | } | ||
231 | /* Otherwise search through the list of MCode areas. */ | ||
232 | for (;;) { | ||
233 | mc = ((MCLink *)mc)->next; | ||
234 | lua_assert(mc != NULL); | ||
235 | if (ptr >= mc && ptr < mc + ((MCLink *)mc)->size) { | ||
236 | mcode_setprot(mc, ((MCLink *)mc)->size, MCPROT_GEN); | ||
237 | return mc; | ||
238 | } | ||
239 | } | ||
240 | } | ||
241 | #endif | ||
242 | } | ||
243 | |||
244 | /* Limit of MCode reservation reached. */ | ||
245 | void lj_mcode_limiterr(jit_State *J, size_t need) | ||
246 | { | ||
247 | size_t sizemcode, maxmcode; | ||
248 | lj_mcode_abort(J); | ||
249 | sizemcode = (size_t)J->param[JIT_P_sizemcode] << 10; | ||
250 | sizemcode = (sizemcode + LJ_PAGESIZE-1) & ~(size_t)(LJ_PAGESIZE - 1); | ||
251 | maxmcode = (size_t)J->param[JIT_P_maxmcode] << 10; | ||
252 | if ((size_t)need > sizemcode) | ||
253 | lj_trace_err(J, LJ_TRERR_MCODEOV); /* Too long for any area. */ | ||
254 | if (J->szallmcarea + sizemcode > maxmcode) | ||
255 | lj_trace_err(J, LJ_TRERR_MCODEAL); | ||
256 | mcode_allocarea(J); | ||
257 | lj_trace_err(J, LJ_TRERR_MCODELM); /* Retry with new area. */ | ||
258 | } | ||
259 | |||
260 | #endif | ||