1/*
2** Machine code management.
3** Copyright (C) 2005-2014 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#if LJ_HASJIT
11#include "lj_gc.h"
12#include "lj_err.h"
13#include "lj_jit.h"
14#include "lj_mcode.h"
15#include "lj_trace.h"
16#include "lj_dispatch.h"
17#endif
18#if LJ_HASJIT || LJ_HASFFI
19#include "lj_vm.h"
20#endif
21
22/* -- OS-specific functions ----------------------------------------------- */
23
24#if LJ_HASJIT || LJ_HASFFI
25
26/* Define this if you want to run LuaJIT with Valgrind. */
27#ifdef LUAJIT_USE_VALGRIND
28#include <valgrind/valgrind.h>
29#endif
30
31#if LJ_TARGET_IOS
32void sys_icache_invalidate(void *start, size_t len);
33#endif
34
35/* Synchronize data/instruction cache. */
36void lj_mcode_sync(void *start, void *end)
37{
38#ifdef LUAJIT_USE_VALGRIND
39 VALGRIND_DISCARD_TRANSLATIONS(start, (char *)end-(char *)start);
40#endif
41#if LJ_TARGET_X86ORX64
42 UNUSED(start); UNUSED(end);
43#elif LJ_TARGET_IOS
44 sys_icache_invalidate(start, (char *)end-(char *)start);
45#elif LJ_TARGET_PPC
46 lj_vm_cachesync(start, end);
47#elif defined(__GNUC__)
48 __clear_cache(start, end);
49#else
50#error "Missing builtin to flush instruction cache"
51#endif
52}
53
54#endif
55
56#if LJ_HASJIT
57
58#if LJ_TARGET_WINDOWS
59
60#define WIN32_LEAN_AND_MEAN
61#include <windows.h>
62
63#define MCPROT_RW PAGE_READWRITE
64#define MCPROT_RX PAGE_EXECUTE_READ
65#define MCPROT_RWX PAGE_EXECUTE_READWRITE
66
67static void *mcode_alloc_at(jit_State *J, uintptr_t hint, size_t sz, DWORD prot)
68{
69 void *p = VirtualAlloc((void *)hint, sz,
70 MEM_RESERVE|MEM_COMMIT|MEM_TOP_DOWN, prot);
71 if (!p && !hint)
72 lj_trace_err(J, LJ_TRERR_MCODEAL);
73 return p;
74}
75
76static void mcode_free(jit_State *J, void *p, size_t sz)
77{
78 UNUSED(J); UNUSED(sz);
79 VirtualFree(p, 0, MEM_RELEASE);
80}
81
82static int mcode_setprot(void *p, size_t sz, DWORD prot)
83{
84 DWORD oprot;
85 return !VirtualProtect(p, sz, prot, &oprot);
86}
87
88#elif LJ_TARGET_POSIX
89
90#include <sys/mman.h>
91
92#ifndef MAP_ANONYMOUS
93#define MAP_ANONYMOUS MAP_ANON
94#endif
95
96#define MCPROT_RW (PROT_READ|PROT_WRITE)
97#define MCPROT_RX (PROT_READ|PROT_EXEC)
98#define MCPROT_RWX (PROT_READ|PROT_WRITE|PROT_EXEC)
99
100static void *mcode_alloc_at(jit_State *J, uintptr_t hint, size_t sz, int prot)
101{
102 void *p = mmap((void *)hint, sz, prot, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
103 if (p == MAP_FAILED) {
104 if (!hint) lj_trace_err(J, LJ_TRERR_MCODEAL);
105 p = NULL;
106 }
107 return p;
108}
109
110static void mcode_free(jit_State *J, void *p, size_t sz)
111{
112 UNUSED(J);
113 munmap(p, sz);
114}
115
116static int mcode_setprot(void *p, size_t sz, int prot)
117{
118 return mprotect(p, sz, prot);
119}
120
121#elif LJ_64
122
123#error "Missing OS support for explicit placement of executable memory"
124
125#else
126
127/* Fallback allocator. This will fail if memory is not executable by default. */
128#define LUAJIT_UNPROTECT_MCODE
129#define MCPROT_RW 0
130#define MCPROT_RX 0
131#define MCPROT_RWX 0
132
133static void *mcode_alloc_at(jit_State *J, uintptr_t hint, size_t sz, int prot)
134{
135 UNUSED(hint); UNUSED(prot);
136 return lj_mem_new(J->L, sz);
137}
138
139static void mcode_free(jit_State *J, void *p, size_t sz)
140{
141 lj_mem_free(J2G(J), p, sz);
142}
143
144#endif
145
146/* -- MCode area protection ----------------------------------------------- */
147
148/* Define this ONLY if the page protection twiddling becomes a bottleneck. */
149#ifdef LUAJIT_UNPROTECT_MCODE
150
151/* It's generally considered to be a potential security risk to have
152** pages with simultaneous write *and* execute access in a process.
153**
154** Do not even think about using this mode for server processes or
155** apps handling untrusted external data (such as a browser).
156**
157** The security risk is not in LuaJIT itself -- but if an adversary finds
158** any *other* flaw in your C application logic, then any RWX memory page
159** simplifies writing an exploit considerably.
160*/
161#define MCPROT_GEN MCPROT_RWX
162#define MCPROT_RUN MCPROT_RWX
163
164static void mcode_protect(jit_State *J, int prot)
165{
166 UNUSED(J); UNUSED(prot);
167}
168
169#else
170
171/* This is the default behaviour and much safer:
172**
173** Most of the time the memory pages holding machine code are executable,
174** but NONE of them is writable.
175**
176** The current memory area is marked read-write (but NOT executable) only
177** during the short time window while the assembler generates machine code.
178*/
179#define MCPROT_GEN MCPROT_RW
180#define MCPROT_RUN MCPROT_RX
181
182/* Protection twiddling failed. Probably due to kernel security. */
183static LJ_NOINLINE void mcode_protfail(jit_State *J)
184{
185 lua_CFunction panic = J2G(J)->panic;
186 if (panic) {
187 lua_State *L = J->L;
188 setstrV(L, L->top++, lj_err_str(L, LJ_ERR_JITPROT));
189 panic(L);
190 }
191}
192
193/* Change protection of MCode area. */
194static void mcode_protect(jit_State *J, int prot)
195{
196 if (J->mcprot != prot) {
197 if (LJ_UNLIKELY(mcode_setprot(J->mcarea, J->szmcarea, prot)))
198 mcode_protfail(J);
199 J->mcprot = prot;
200 }
201}
202
203#endif
204
205/* -- MCode area allocation ----------------------------------------------- */
206
207#if LJ_TARGET_X64
208#define mcode_validptr(p) ((p) && (uintptr_t)(p) < (uintptr_t)1<<47)
209#else
210#define mcode_validptr(p) ((p) && (uintptr_t)(p) < 0xffff0000)
211#endif
212
213#ifdef LJ_TARGET_JUMPRANGE
214
215/* Get memory within relative jump distance of our code in 64 bit mode. */
216static void *mcode_alloc(jit_State *J, size_t sz)
217{
218 /* Target an address in the static assembler code (64K aligned).
219 ** Try addresses within a distance of target-range/2+1MB..target+range/2-1MB.
220 ** Use half the jump range so every address in the range can reach any other.
221 */
222#if LJ_TARGET_MIPS
223 /* Use the middle of the 256MB-aligned region. */
224 uintptr_t target = ((uintptr_t)(void *)lj_vm_exit_handler & 0xf0000000u) +
225 0x08000000u;
226#else
227 uintptr_t target = (uintptr_t)(void *)lj_vm_exit_handler & ~(uintptr_t)0xffff;
228#endif
229 const uintptr_t range = (1u << (LJ_TARGET_JUMPRANGE-1)) - (1u << 21);
230 /* First try a contiguous area below the last one. */
231 uintptr_t hint = J->mcarea ? (uintptr_t)J->mcarea - sz : 0;
232 int i;
233 for (i = 0; i < 32; i++) { /* 32 attempts ought to be enough ... */
234 if (mcode_validptr(hint)) {
235 void *p = mcode_alloc_at(J, hint, sz, MCPROT_GEN);
236
237 if (mcode_validptr(p) &&
238 ((uintptr_t)p + sz - target < range || target - (uintptr_t)p < range))
239 return p;
240 if (p) mcode_free(J, p, sz); /* Free badly placed area. */
241 }
242 /* Next try probing pseudo-random addresses. */
243 do {
244 hint = (0x78fb ^ LJ_PRNG_BITS(J, 15)) << 16; /* 64K aligned. */
245 } while (!(hint + sz < range));
246 hint = target + hint - (range>>1);
247 }
248 lj_trace_err(J, LJ_TRERR_MCODEAL); /* Give up. OS probably ignores hints? */
249 return NULL;
250}
251
252#else
253
254/* All memory addresses are reachable by relative jumps. */
255#define mcode_alloc(J, sz) mcode_alloc_at((J), 0, (sz), MCPROT_GEN)
256
257#endif
258
259/* -- MCode area management ----------------------------------------------- */
260
261/* Linked list of MCode areas. */
262typedef struct MCLink {
263 MCode *next; /* Next area. */
264 size_t size; /* Size of current area. */
265} MCLink;
266
267/* Allocate a new MCode area. */
268static void mcode_allocarea(jit_State *J)
269{
270 MCode *oldarea = J->mcarea;
271 size_t sz = (size_t)J->param[JIT_P_sizemcode] << 10;
272 sz = (sz + LJ_PAGESIZE-1) & ~(size_t)(LJ_PAGESIZE - 1);
273 J->mcarea = (MCode *)mcode_alloc(J, sz);
274 J->szmcarea = sz;
275 J->mcprot = MCPROT_GEN;
276 J->mctop = (MCode *)((char *)J->mcarea + J->szmcarea);
277 J->mcbot = (MCode *)((char *)J->mcarea + sizeof(MCLink));
278 ((MCLink *)J->mcarea)->next = oldarea;
279 ((MCLink *)J->mcarea)->size = sz;
280 J->szallmcarea += sz;
281}
282
283/* Free all MCode areas. */
284void lj_mcode_free(jit_State *J)
285{
286 MCode *mc = J->mcarea;
287 J->mcarea = NULL;
288 J->szallmcarea = 0;
289 while (mc) {
290 MCode *next = ((MCLink *)mc)->next;
291 mcode_free(J, mc, ((MCLink *)mc)->size);
292 mc = next;
293 }
294}
295
296/* -- MCode transactions -------------------------------------------------- */
297
298/* Reserve the remainder of the current MCode area. */
299MCode *lj_mcode_reserve(jit_State *J, MCode **lim)
300{
301 if (!J->mcarea)
302 mcode_allocarea(J);
303 else
304 mcode_protect(J, MCPROT_GEN);
305 *lim = J->mcbot;
306 return J->mctop;
307}
308
309/* Commit the top part of the current MCode area. */
310void lj_mcode_commit(jit_State *J, MCode *top)
311{
312 J->mctop = top;
313 mcode_protect(J, MCPROT_RUN);
314}
315
316/* Abort the reservation. */
317void lj_mcode_abort(jit_State *J)
318{
319 if (J->mcarea)
320 mcode_protect(J, MCPROT_RUN);
321}
322
323/* Set/reset protection to allow patching of MCode areas. */
324MCode *lj_mcode_patch(jit_State *J, MCode *ptr, int finish)
325{
326#ifdef LUAJIT_UNPROTECT_MCODE
327 UNUSED(J); UNUSED(ptr); UNUSED(finish);
328 return NULL;
329#else
330 if (finish) {
331 if (J->mcarea == ptr)
332 mcode_protect(J, MCPROT_RUN);
333 else if (LJ_UNLIKELY(mcode_setprot(ptr, ((MCLink *)ptr)->size, MCPROT_RUN)))
334 mcode_protfail(J);
335 return NULL;
336 } else {
337 MCode *mc = J->mcarea;
338 /* Try current area first to use the protection cache. */
339 if (ptr >= mc && ptr < (MCode *)((char *)mc + J->szmcarea)) {
340 mcode_protect(J, MCPROT_GEN);
341 return mc;
342 }
343 /* Otherwise search through the list of MCode areas. */
344 for (;;) {
345 mc = ((MCLink *)mc)->next;
346 lua_assert(mc != NULL);
347 if (ptr >= mc && ptr < (MCode *)((char *)mc + ((MCLink *)mc)->size)) {
348 if (LJ_UNLIKELY(mcode_setprot(mc, ((MCLink *)mc)->size, MCPROT_GEN)))
349 mcode_protfail(J);
350 return mc;
351 }
352 }
353 }
354#endif
355}
356
357/* Limit of MCode reservation reached. */
358void lj_mcode_limiterr(jit_State *J, size_t need)
359{
360 size_t sizemcode, maxmcode;
361 lj_mcode_abort(J);
362 sizemcode = (size_t)J->param[JIT_P_sizemcode] << 10;
363 sizemcode = (sizemcode + LJ_PAGESIZE-1) & ~(size_t)(LJ_PAGESIZE - 1);
364 maxmcode = (size_t)J->param[JIT_P_maxmcode] << 10;
365 if ((size_t)need > sizemcode)
366 lj_trace_err(J, LJ_TRERR_MCODEOV); /* Too long for any area. */
367 if (J->szallmcarea + sizemcode > maxmcode)
368 lj_trace_err(J, LJ_TRERR_MCODEAL);
369 mcode_allocarea(J);
370 lj_trace_err(J, LJ_TRERR_MCODELM); /* Retry with new area. */
371}
372
373#endif
374