1/*
2** DynASM x86 encoding engine.
3** Copyright (C) 2005-2014 Mike Pall. All rights reserved.
4** Released under the MIT license. See dynasm.lua for full copyright notice.
5*/
6
7#include <stddef.h>
8#include <stdarg.h>
9#include <string.h>
10#include <stdlib.h>
11
12#define DASM_ARCH "x86"
13
14#ifndef DASM_EXTERN
15#define DASM_EXTERN(a,b,c,d) 0
16#endif
17
18/* Action definitions. DASM_STOP must be 255. */
19enum {
20 DASM_DISP = 233,
21 DASM_IMM_S, DASM_IMM_B, DASM_IMM_W, DASM_IMM_D, DASM_IMM_WB, DASM_IMM_DB,
22 DASM_VREG, DASM_SPACE, DASM_SETLABEL, DASM_REL_A, DASM_REL_LG, DASM_REL_PC,
23 DASM_IMM_LG, DASM_IMM_PC, DASM_LABEL_LG, DASM_LABEL_PC, DASM_ALIGN,
24 DASM_EXTERN, DASM_ESC, DASM_MARK, DASM_SECTION, DASM_STOP
25};
26
27/* Maximum number of section buffer positions for a single dasm_put() call. */
28#define DASM_MAXSECPOS 25
29
30/* DynASM encoder status codes. Action list offset or number are or'ed in. */
31#define DASM_S_OK 0x00000000
32#define DASM_S_NOMEM 0x01000000
33#define DASM_S_PHASE 0x02000000
34#define DASM_S_MATCH_SEC 0x03000000
35#define DASM_S_RANGE_I 0x11000000
36#define DASM_S_RANGE_SEC 0x12000000
37#define DASM_S_RANGE_LG 0x13000000
38#define DASM_S_RANGE_PC 0x14000000
39#define DASM_S_RANGE_VREG 0x15000000
40#define DASM_S_UNDEF_L 0x21000000
41#define DASM_S_UNDEF_PC 0x22000000
42
43/* Macros to convert positions (8 bit section + 24 bit index). */
44#define DASM_POS2IDX(pos) ((pos)&0x00ffffff)
45#define DASM_POS2BIAS(pos) ((pos)&0xff000000)
46#define DASM_SEC2POS(sec) ((sec)<<24)
47#define DASM_POS2SEC(pos) ((pos)>>24)
48#define DASM_POS2PTR(D, pos) (D->sections[DASM_POS2SEC(pos)].rbuf + (pos))
49
50/* Action list type. */
51typedef const unsigned char *dasm_ActList;
52
53/* Per-section structure. */
54typedef struct dasm_Section {
55 int *rbuf; /* Biased buffer pointer (negative section bias). */
56 int *buf; /* True buffer pointer. */
57 size_t bsize; /* Buffer size in bytes. */
58 int pos; /* Biased buffer position. */
59 int epos; /* End of biased buffer position - max single put. */
60 int ofs; /* Byte offset into section. */
61} dasm_Section;
62
63/* Core structure holding the DynASM encoding state. */
64struct dasm_State {
65 size_t psize; /* Allocated size of this structure. */
66 dasm_ActList actionlist; /* Current actionlist pointer. */
67 int *lglabels; /* Local/global chain/pos ptrs. */
68 size_t lgsize;
69 int *pclabels; /* PC label chains/pos ptrs. */
70 size_t pcsize;
71 void **globals; /* Array of globals (bias -10). */
72 dasm_Section *section; /* Pointer to active section. */
73 size_t codesize; /* Total size of all code sections. */
74 int maxsection; /* 0 <= sectionidx < maxsection. */
75 int status; /* Status code. */
76 dasm_Section sections[1]; /* All sections. Alloc-extended. */
77};
78
79/* The size of the core structure depends on the max. number of sections. */
80#define DASM_PSZ(ms) (sizeof(dasm_State)+(ms-1)*sizeof(dasm_Section))
81
82
83/* Initialize DynASM state. */
84void dasm_init(Dst_DECL, int maxsection)
85{
86 dasm_State *D;
87 size_t psz = 0;
88 int i;
89 Dst_REF = NULL;
90 DASM_M_GROW(Dst, struct dasm_State, Dst_REF, psz, DASM_PSZ(maxsection));
91 D = Dst_REF;
92 D->psize = psz;
93 D->lglabels = NULL;
94 D->lgsize = 0;
95 D->pclabels = NULL;
96 D->pcsize = 0;
97 D->globals = NULL;
98 D->maxsection = maxsection;
99 for (i = 0; i < maxsection; i++) {
100 D->sections[i].buf = NULL; /* Need this for pass3. */
101 D->sections[i].rbuf = D->sections[i].buf - DASM_SEC2POS(i);
102 D->sections[i].bsize = 0;
103 D->sections[i].epos = 0; /* Wrong, but is recalculated after resize. */
104 }
105}
106
107/* Free DynASM state. */
108void dasm_free(Dst_DECL)
109{
110 dasm_State *D = Dst_REF;
111 int i;
112 for (i = 0; i < D->maxsection; i++)
113 if (D->sections[i].buf)
114 DASM_M_FREE(Dst, D->sections[i].buf, D->sections[i].bsize);
115 if (D->pclabels) DASM_M_FREE(Dst, D->pclabels, D->pcsize);
116 if (D->lglabels) DASM_M_FREE(Dst, D->lglabels, D->lgsize);
117 DASM_M_FREE(Dst, D, D->psize);
118}
119
120/* Setup global label array. Must be called before dasm_setup(). */
121void dasm_setupglobal(Dst_DECL, void **gl, unsigned int maxgl)
122{
123 dasm_State *D = Dst_REF;
124 D->globals = gl - 10; /* Negative bias to compensate for locals. */
125 DASM_M_GROW(Dst, int, D->lglabels, D->lgsize, (10+maxgl)*sizeof(int));
126}
127
128/* Grow PC label array. Can be called after dasm_setup(), too. */
129void dasm_growpc(Dst_DECL, unsigned int maxpc)
130{
131 dasm_State *D = Dst_REF;
132 size_t osz = D->pcsize;
133 DASM_M_GROW(Dst, int, D->pclabels, D->pcsize, maxpc*sizeof(int));
134 memset((void *)(((unsigned char *)D->pclabels)+osz), 0, D->pcsize-osz);
135}
136
137/* Setup encoder. */
138void dasm_setup(Dst_DECL, const void *actionlist)
139{
140 dasm_State *D = Dst_REF;
141 int i;
142 D->actionlist = (dasm_ActList)actionlist;
143 D->status = DASM_S_OK;
144 D->section = &D->sections[0];
145 memset((void *)D->lglabels, 0, D->lgsize);
146 if (D->pclabels) memset((void *)D->pclabels, 0, D->pcsize);
147 for (i = 0; i < D->maxsection; i++) {
148 D->sections[i].pos = DASM_SEC2POS(i);
149 D->sections[i].ofs = 0;
150 }
151}
152
153
154#ifdef DASM_CHECKS
155#define CK(x, st) \
156 do { if (!(x)) { \
157 D->status = DASM_S_##st|(int)(p-D->actionlist-1); return; } } while (0)
158#define CKPL(kind, st) \
159 do { if ((size_t)((char *)pl-(char *)D->kind##labels) >= D->kind##size) { \
160 D->status=DASM_S_RANGE_##st|(int)(p-D->actionlist-1); return; } } while (0)
161#else
162#define CK(x, st) ((void)0)
163#define CKPL(kind, st) ((void)0)
164#endif
165
166/* Pass 1: Store actions and args, link branches/labels, estimate offsets. */
167void dasm_put(Dst_DECL, int start, ...)
168{
169 va_list ap;
170 dasm_State *D = Dst_REF;
171 dasm_ActList p = D->actionlist + start;
172 dasm_Section *sec = D->section;
173 int pos = sec->pos, ofs = sec->ofs, mrm = 4;
174 int *b;
175
176 if (pos >= sec->epos) {
177 DASM_M_GROW(Dst, int, sec->buf, sec->bsize,
178 sec->bsize + 2*DASM_MAXSECPOS*sizeof(int));
179 sec->rbuf = sec->buf - DASM_POS2BIAS(pos);
180 sec->epos = (int)sec->bsize/sizeof(int) - DASM_MAXSECPOS+DASM_POS2BIAS(pos);
181 }
182
183 b = sec->rbuf;
184 b[pos++] = start;
185
186 va_start(ap, start);
187 while (1) {
188 int action = *p++;
189 if (action < DASM_DISP) {
190 ofs++;
191 } else if (action <= DASM_REL_A) {
192 int n = va_arg(ap, int);
193 b[pos++] = n;
194 switch (action) {
195 case DASM_DISP:
196 if (n == 0) { if ((mrm&7) == 4) mrm = p[-2]; if ((mrm&7) != 5) break; }
197 case DASM_IMM_DB: if (((n+128)&-256) == 0) goto ob;
198 case DASM_REL_A: /* Assumes ptrdiff_t is int. !x64 */
199 case DASM_IMM_D: ofs += 4; break;
200 case DASM_IMM_S: CK(((n+128)&-256) == 0, RANGE_I); goto ob;
201 case DASM_IMM_B: CK((n&-256) == 0, RANGE_I); ob: ofs++; break;
202 case DASM_IMM_WB: if (((n+128)&-256) == 0) goto ob;
203 case DASM_IMM_W: CK((n&-65536) == 0, RANGE_I); ofs += 2; break;
204 case DASM_SPACE: p++; ofs += n; break;
205 case DASM_SETLABEL: b[pos-2] = -0x40000000; break; /* Neg. label ofs. */
206 case DASM_VREG: CK((n&-8) == 0 && (n != 4 || (*p&1) == 0), RANGE_VREG);
207 if (*p++ == 1 && *p == DASM_DISP) mrm = n; continue;
208 }
209 mrm = 4;
210 } else {
211 int *pl, n;
212 switch (action) {
213 case DASM_REL_LG:
214 case DASM_IMM_LG:
215 n = *p++; pl = D->lglabels + n;
216 /* Bkwd rel or global. */
217 if (n <= 246) { CK(n>=10||*pl<0, RANGE_LG); CKPL(lg, LG); goto putrel; }
218 pl -= 246; n = *pl;
219 if (n < 0) n = 0; /* Start new chain for fwd rel if label exists. */
220 goto linkrel;
221 case DASM_REL_PC:
222 case DASM_IMM_PC: pl = D->pclabels + va_arg(ap, int); CKPL(pc, PC);
223 putrel:
224 n = *pl;
225 if (n < 0) { /* Label exists. Get label pos and store it. */
226 b[pos] = -n;
227 } else {
228 linkrel:
229 b[pos] = n; /* Else link to rel chain, anchored at label. */
230 *pl = pos;
231 }
232 pos++;
233 ofs += 4; /* Maximum offset needed. */
234 if (action == DASM_REL_LG || action == DASM_REL_PC)
235 b[pos++] = ofs; /* Store pass1 offset estimate. */
236 break;
237 case DASM_LABEL_LG: pl = D->lglabels + *p++; CKPL(lg, LG); goto putlabel;
238 case DASM_LABEL_PC: pl = D->pclabels + va_arg(ap, int); CKPL(pc, PC);
239 putlabel:
240 n = *pl; /* n > 0: Collapse rel chain and replace with label pos. */
241 while (n > 0) { int *pb = DASM_POS2PTR(D, n); n = *pb; *pb = pos; }
242 *pl = -pos; /* Label exists now. */
243 b[pos++] = ofs; /* Store pass1 offset estimate. */
244 break;
245 case DASM_ALIGN:
246 ofs += *p++; /* Maximum alignment needed (arg is 2**n-1). */
247 b[pos++] = ofs; /* Store pass1 offset estimate. */
248 break;
249 case DASM_EXTERN: p += 2; ofs += 4; break;
250 case DASM_ESC: p++; ofs++; break;
251 case DASM_MARK: mrm = p[-2]; break;
252 case DASM_SECTION:
253 n = *p; CK(n < D->maxsection, RANGE_SEC); D->section = &D->sections[n];
254 case DASM_STOP: goto stop;
255 }
256 }
257 }
258stop:
259 va_end(ap);
260 sec->pos = pos;
261 sec->ofs = ofs;
262}
263#undef CK
264
265/* Pass 2: Link sections, shrink branches/aligns, fix label offsets. */
266int dasm_link(Dst_DECL, size_t *szp)
267{
268 dasm_State *D = Dst_REF;
269 int secnum;
270 int ofs = 0;
271
272#ifdef DASM_CHECKS
273 *szp = 0;
274 if (D->status != DASM_S_OK) return D->status;
275 {
276 int pc;
277 for (pc = 0; pc*sizeof(int) < D->pcsize; pc++)
278 if (D->pclabels[pc] > 0) return DASM_S_UNDEF_PC|pc;
279 }
280#endif
281
282 { /* Handle globals not defined in this translation unit. */
283 int idx;
284 for (idx = 10; idx*sizeof(int) < D->lgsize; idx++) {
285 int n = D->lglabels[idx];
286 /* Undefined label: Collapse rel chain and replace with marker (< 0). */
287 while (n > 0) { int *pb = DASM_POS2PTR(D, n); n = *pb; *pb = -idx; }
288 }
289 }
290
291 /* Combine all code sections. No support for data sections (yet). */
292 for (secnum = 0; secnum < D->maxsection; secnum++) {
293 dasm_Section *sec = D->sections + secnum;
294 int *b = sec->rbuf;
295 int pos = DASM_SEC2POS(secnum);
296 int lastpos = sec->pos;
297
298 while (pos != lastpos) {
299 dasm_ActList p = D->actionlist + b[pos++];
300 while (1) {
301 int op, action = *p++;
302 switch (action) {
303 case DASM_REL_LG: p++; op = p[-3]; goto rel_pc;
304 case DASM_REL_PC: op = p[-2]; rel_pc: {
305 int shrink = op == 0xe9 ? 3 : ((op&0xf0) == 0x80 ? 4 : 0);
306 if (shrink) { /* Shrinkable branch opcode? */
307 int lofs, lpos = b[pos];
308 if (lpos < 0) goto noshrink; /* Ext global? */
309 lofs = *DASM_POS2PTR(D, lpos);
310 if (lpos > pos) { /* Fwd label: add cumulative section offsets. */
311 int i;
312 for (i = secnum; i < DASM_POS2SEC(lpos); i++)
313 lofs += D->sections[i].ofs;
314 } else {
315 lofs -= ofs; /* Bkwd label: unfix offset. */
316 }
317 lofs -= b[pos+1]; /* Short branch ok? */
318 if (lofs >= -128-shrink && lofs <= 127) ofs -= shrink; /* Yes. */
319 else { noshrink: shrink = 0; } /* No, cannot shrink op. */
320 }
321 b[pos+1] = shrink;
322 pos += 2;
323 break;
324 }
325 case DASM_SPACE: case DASM_IMM_LG: case DASM_VREG: p++;
326 case DASM_DISP: case DASM_IMM_S: case DASM_IMM_B: case DASM_IMM_W:
327 case DASM_IMM_D: case DASM_IMM_WB: case DASM_IMM_DB:
328 case DASM_SETLABEL: case DASM_REL_A: case DASM_IMM_PC: pos++; break;
329 case DASM_LABEL_LG: p++;
330 case DASM_LABEL_PC: b[pos++] += ofs; break; /* Fix label offset. */
331 case DASM_ALIGN: ofs -= (b[pos++]+ofs)&*p++; break; /* Adjust ofs. */
332 case DASM_EXTERN: p += 2; break;
333 case DASM_ESC: p++; break;
334 case DASM_MARK: break;
335 case DASM_SECTION: case DASM_STOP: goto stop;
336 }
337 }
338 stop: (void)0;
339 }
340 ofs += sec->ofs; /* Next section starts right after current section. */
341 }
342
343 D->codesize = ofs; /* Total size of all code sections */
344 *szp = ofs;
345 return DASM_S_OK;
346}
347
348#define dasmb(x) *cp++ = (unsigned char)(x)
349#ifndef DASM_ALIGNED_WRITES
350#define dasmw(x) \
351 do { *((unsigned short *)cp) = (unsigned short)(x); cp+=2; } while (0)
352#define dasmd(x) \
353 do { *((unsigned int *)cp) = (unsigned int)(x); cp+=4; } while (0)
354#else
355#define dasmw(x) do { dasmb(x); dasmb((x)>>8); } while (0)
356#define dasmd(x) do { dasmw(x); dasmw((x)>>16); } while (0)
357#endif
358
359/* Pass 3: Encode sections. */
360int dasm_encode(Dst_DECL, void *buffer)
361{
362 dasm_State *D = Dst_REF;
363 unsigned char *base = (unsigned char *)buffer;
364 unsigned char *cp = base;
365 int secnum;
366
367 /* Encode all code sections. No support for data sections (yet). */
368 for (secnum = 0; secnum < D->maxsection; secnum++) {
369 dasm_Section *sec = D->sections + secnum;
370 int *b = sec->buf;
371 int *endb = sec->rbuf + sec->pos;
372
373 while (b != endb) {
374 dasm_ActList p = D->actionlist + *b++;
375 unsigned char *mark = NULL;
376 while (1) {
377 int action = *p++;
378 int n = (action >= DASM_DISP && action <= DASM_ALIGN) ? *b++ : 0;
379 switch (action) {
380 case DASM_DISP: if (!mark) mark = cp; {
381 unsigned char *mm = mark;
382 if (*p != DASM_IMM_DB && *p != DASM_IMM_WB) mark = NULL;
383 if (n == 0) { int mrm = mm[-1]&7; if (mrm == 4) mrm = mm[0]&7;
384 if (mrm != 5) { mm[-1] -= 0x80; break; } }
385 if (((n+128) & -256) != 0) goto wd; else mm[-1] -= 0x40;
386 }
387 case DASM_IMM_S: case DASM_IMM_B: wb: dasmb(n); break;
388 case DASM_IMM_DB: if (((n+128)&-256) == 0) {
389 db: if (!mark) mark = cp; mark[-2] += 2; mark = NULL; goto wb;
390 } else mark = NULL;
391 case DASM_IMM_D: wd: dasmd(n); break;
392 case DASM_IMM_WB: if (((n+128)&-256) == 0) goto db; else mark = NULL;
393 case DASM_IMM_W: dasmw(n); break;
394 case DASM_VREG: { int t = *p++; if (t >= 2) n<<=3; cp[-1] |= n; break; }
395 case DASM_REL_LG: p++; if (n >= 0) goto rel_pc;
396 b++; n = (int)(ptrdiff_t)D->globals[-n];
397 case DASM_REL_A: rel_a: n -= (int)(ptrdiff_t)(cp+4); goto wd; /* !x64 */
398 case DASM_REL_PC: rel_pc: {
399 int shrink = *b++;
400 int *pb = DASM_POS2PTR(D, n); if (*pb < 0) { n = pb[1]; goto rel_a; }
401 n = *pb - ((int)(cp-base) + 4-shrink);
402 if (shrink == 0) goto wd;
403 if (shrink == 4) { cp--; cp[-1] = *cp-0x10; } else cp[-1] = 0xeb;
404 goto wb;
405 }
406 case DASM_IMM_LG:
407 p++; if (n < 0) { n = (int)(ptrdiff_t)D->globals[-n]; goto wd; }
408 case DASM_IMM_PC: {
409 int *pb = DASM_POS2PTR(D, n);
410 n = *pb < 0 ? pb[1] : (*pb + (int)(ptrdiff_t)base);
411 goto wd;
412 }
413 case DASM_LABEL_LG: {
414 int idx = *p++;
415 if (idx >= 10)
416 D->globals[idx] = (void *)(base + (*p == DASM_SETLABEL ? *b : n));
417 break;
418 }
419 case DASM_LABEL_PC: case DASM_SETLABEL: break;
420 case DASM_SPACE: { int fill = *p++; while (n--) *cp++ = fill; break; }
421 case DASM_ALIGN:
422 n = *p++;
423 while (((cp-base) & n)) *cp++ = 0x90; /* nop */
424 break;
425 case DASM_EXTERN: n = DASM_EXTERN(Dst, cp, p[1], *p); p += 2; goto wd;
426 case DASM_MARK: mark = cp; break;
427 case DASM_ESC: action = *p++;
428 default: *cp++ = action; break;
429 case DASM_SECTION: case DASM_STOP: goto stop;
430 }
431 }
432 stop: (void)0;
433 }
434 }
435
436 if (base + D->codesize != cp) /* Check for phase errors. */
437 return DASM_S_PHASE;
438 return DASM_S_OK;
439}
440
441/* Get PC label offset. */
442int dasm_getpclabel(Dst_DECL, unsigned int pc)
443{
444 dasm_State *D = Dst_REF;
445 if (pc*sizeof(int) < D->pcsize) {
446 int pos = D->pclabels[pc];
447 if (pos < 0) return *DASM_POS2PTR(D, -pos);
448 if (pos > 0) return -1; /* Undefined. */
449 }
450 return -2; /* Unused or out of range. */
451}
452
453#ifdef DASM_CHECKS
454/* Optional sanity checker to call between isolated encoding steps. */
455int dasm_checkstep(Dst_DECL, int secmatch)
456{
457 dasm_State *D = Dst_REF;
458 if (D->status == DASM_S_OK) {
459 int i;
460 for (i = 1; i <= 9; i++) {
461 if (D->lglabels[i] > 0) { D->status = DASM_S_UNDEF_L|i; break; }
462 D->lglabels[i] = 0;
463 }
464 }
465 if (D->status == DASM_S_OK && secmatch >= 0 &&
466 D->section != &D->sections[secmatch])
467 D->status = DASM_S_MATCH_SEC|(int)(D->section-D->sections);
468 return D->status;
469}
470#endif
471
472