1 /*
2 ** DynASM MIPS encoding engine.
3 ** Copyright (C) 2005-2021 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		"mips"
13 
14 #ifndef DASM_EXTERN
15 #define DASM_EXTERN(a,b,c,d)	0
16 #endif
17 
18 /* Action definitions. */
19 enum {
20   DASM_STOP, DASM_SECTION, DASM_ESC, DASM_REL_EXT,
21   /* The following actions need a buffer position. */
22   DASM_ALIGN, DASM_REL_LG, DASM_LABEL_LG,
23   /* The following actions also have an argument. */
24   DASM_REL_PC, DASM_LABEL_PC, DASM_IMM, DASM_IMMS,
25   DASM__MAX
26 };
27 
28 /* Maximum number of section buffer positions for a single dasm_put() call. */
29 #define DASM_MAXSECPOS		25
30 
31 /* DynASM encoder status codes. Action list offset or number are or'ed in. */
32 #define DASM_S_OK		0x00000000
33 #define DASM_S_NOMEM		0x01000000
34 #define DASM_S_PHASE		0x02000000
35 #define DASM_S_MATCH_SEC	0x03000000
36 #define DASM_S_RANGE_I		0x11000000
37 #define DASM_S_RANGE_SEC	0x12000000
38 #define DASM_S_RANGE_LG		0x13000000
39 #define DASM_S_RANGE_PC		0x14000000
40 #define DASM_S_RANGE_REL	0x15000000
41 #define DASM_S_UNDEF_LG		0x21000000
42 #define DASM_S_UNDEF_PC		0x22000000
43 
44 /* Macros to convert positions (8 bit section + 24 bit index). */
45 #define DASM_POS2IDX(pos)	((pos)&0x00ffffff)
46 #define DASM_POS2BIAS(pos)	((pos)&0xff000000)
47 #define DASM_SEC2POS(sec)	((sec)<<24)
48 #define DASM_POS2SEC(pos)	((pos)>>24)
49 #define DASM_POS2PTR(D, pos)	(D->sections[DASM_POS2SEC(pos)].rbuf + (pos))
50 
51 /* Action list type. */
52 typedef const unsigned int *dasm_ActList;
53 
54 /* Per-section structure. */
55 typedef struct dasm_Section {
56   int *rbuf;		/* Biased buffer pointer (negative section bias). */
57   int *buf;		/* True buffer pointer. */
58   size_t bsize;		/* Buffer size in bytes. */
59   int pos;		/* Biased buffer position. */
60   int epos;		/* End of biased buffer position - max single put. */
61   int ofs;		/* Byte offset into section. */
62 } dasm_Section;
63 
64 /* Core structure holding the DynASM encoding state. */
65 struct dasm_State {
66   size_t psize;			/* Allocated size of this structure. */
67   dasm_ActList actionlist;	/* Current actionlist pointer. */
68   int *lglabels;		/* Local/global chain/pos ptrs. */
69   size_t lgsize;
70   int *pclabels;		/* PC label chains/pos ptrs. */
71   size_t pcsize;
72   void **globals;		/* Array of globals (bias -10). */
73   dasm_Section *section;	/* Pointer to active section. */
74   size_t codesize;		/* Total size of all code sections. */
75   int maxsection;		/* 0 <= sectionidx < maxsection. */
76   int status;			/* Status code. */
77   dasm_Section sections[1];	/* All sections. Alloc-extended. */
78 };
79 
80 /* The size of the core structure depends on the max. number of sections. */
81 #define DASM_PSZ(ms)	(sizeof(dasm_State)+(ms-1)*sizeof(dasm_Section))
82 
83 
84 /* Initialize DynASM state. */
dasm_init(Dst_DECL,int maxsection)85 void dasm_init(Dst_DECL, int maxsection)
86 {
87   dasm_State *D;
88   size_t psz = 0;
89   int i;
90   Dst_REF = NULL;
91   DASM_M_GROW(Dst, struct dasm_State, Dst_REF, psz, DASM_PSZ(maxsection));
92   D = Dst_REF;
93   D->psize = psz;
94   D->lglabels = NULL;
95   D->lgsize = 0;
96   D->pclabels = NULL;
97   D->pcsize = 0;
98   D->globals = NULL;
99   D->maxsection = maxsection;
100   for (i = 0; i < maxsection; i++) {
101     D->sections[i].buf = NULL;  /* Need this for pass3. */
102     D->sections[i].rbuf = D->sections[i].buf - DASM_SEC2POS(i);
103     D->sections[i].bsize = 0;
104     D->sections[i].epos = 0;  /* Wrong, but is recalculated after resize. */
105   }
106 }
107 
108 /* Free DynASM state. */
dasm_free(Dst_DECL)109 void dasm_free(Dst_DECL)
110 {
111   dasm_State *D = Dst_REF;
112   int i;
113   for (i = 0; i < D->maxsection; i++)
114     if (D->sections[i].buf)
115       DASM_M_FREE(Dst, D->sections[i].buf, D->sections[i].bsize);
116   if (D->pclabels) DASM_M_FREE(Dst, D->pclabels, D->pcsize);
117   if (D->lglabels) DASM_M_FREE(Dst, D->lglabels, D->lgsize);
118   DASM_M_FREE(Dst, D, D->psize);
119 }
120 
121 /* Setup global label array. Must be called before dasm_setup(). */
dasm_setupglobal(Dst_DECL,void ** gl,unsigned int maxgl)122 void dasm_setupglobal(Dst_DECL, void **gl, unsigned int maxgl)
123 {
124   dasm_State *D = Dst_REF;
125   D->globals = gl - 10;  /* Negative bias to compensate for locals. */
126   DASM_M_GROW(Dst, int, D->lglabels, D->lgsize, (10+maxgl)*sizeof(int));
127 }
128 
129 /* Grow PC label array. Can be called after dasm_setup(), too. */
dasm_growpc(Dst_DECL,unsigned int maxpc)130 void dasm_growpc(Dst_DECL, unsigned int maxpc)
131 {
132   dasm_State *D = Dst_REF;
133   size_t osz = D->pcsize;
134   DASM_M_GROW(Dst, int, D->pclabels, D->pcsize, maxpc*sizeof(int));
135   memset((void *)(((unsigned char *)D->pclabels)+osz), 0, D->pcsize-osz);
136 }
137 
138 /* Setup encoder. */
dasm_setup(Dst_DECL,const void * actionlist)139 void dasm_setup(Dst_DECL, const void *actionlist)
140 {
141   dasm_State *D = Dst_REF;
142   int i;
143   D->actionlist = (dasm_ActList)actionlist;
144   D->status = DASM_S_OK;
145   D->section = &D->sections[0];
146   memset((void *)D->lglabels, 0, D->lgsize);
147   if (D->pclabels) memset((void *)D->pclabels, 0, D->pcsize);
148   for (i = 0; i < D->maxsection; i++) {
149     D->sections[i].pos = DASM_SEC2POS(i);
150     D->sections[i].ofs = 0;
151   }
152 }
153 
154 
155 #ifdef DASM_CHECKS
156 #define CK(x, st) \
157   do { if (!(x)) { \
158     D->status = DASM_S_##st|(p-D->actionlist-1); return; } } while (0)
159 #define CKPL(kind, st) \
160   do { if ((size_t)((char *)pl-(char *)D->kind##labels) >= D->kind##size) { \
161     D->status = DASM_S_RANGE_##st|(p-D->actionlist-1); return; } } while (0)
162 #else
163 #define CK(x, st)	((void)0)
164 #define CKPL(kind, st)	((void)0)
165 #endif
166 
167 /* Pass 1: Store actions and args, link branches/labels, estimate offsets. */
dasm_put(Dst_DECL,int start,...)168 void dasm_put(Dst_DECL, int start, ...)
169 {
170   va_list ap;
171   dasm_State *D = Dst_REF;
172   dasm_ActList p = D->actionlist + start;
173   dasm_Section *sec = D->section;
174   int pos = sec->pos, ofs = sec->ofs;
175   int *b;
176 
177   if (pos >= sec->epos) {
178     DASM_M_GROW(Dst, int, sec->buf, sec->bsize,
179       sec->bsize + 2*DASM_MAXSECPOS*sizeof(int));
180     sec->rbuf = sec->buf - DASM_POS2BIAS(pos);
181     sec->epos = (int)sec->bsize/sizeof(int) - DASM_MAXSECPOS+DASM_POS2BIAS(pos);
182   }
183 
184   b = sec->rbuf;
185   b[pos++] = start;
186 
187   va_start(ap, start);
188   while (1) {
189     unsigned int ins = *p++;
190     unsigned int action = (ins >> 16) - 0xff00;
191     if (action >= DASM__MAX) {
192       ofs += 4;
193     } else {
194       int *pl, n = action >= DASM_REL_PC ? va_arg(ap, int) : 0;
195       switch (action) {
196       case DASM_STOP: goto stop;
197       case DASM_SECTION:
198 	n = (ins & 255); CK(n < D->maxsection, RANGE_SEC);
199 	D->section = &D->sections[n]; goto stop;
200       case DASM_ESC: p++; ofs += 4; break;
201       case DASM_REL_EXT: break;
202       case DASM_ALIGN: ofs += (ins & 255); b[pos++] = ofs; break;
203       case DASM_REL_LG:
204 	n = (ins & 2047) - 10; pl = D->lglabels + n;
205 	/* Bkwd rel or global. */
206 	if (n >= 0) { CK(n>=10||*pl<0, RANGE_LG); CKPL(lg, LG); goto putrel; }
207 	pl += 10; n = *pl;
208 	if (n < 0) n = 0;  /* Start new chain for fwd rel if label exists. */
209 	goto linkrel;
210       case DASM_REL_PC:
211 	pl = D->pclabels + n; CKPL(pc, PC);
212       putrel:
213 	n = *pl;
214 	if (n < 0) {  /* Label exists. Get label pos and store it. */
215 	  b[pos] = -n;
216 	} else {
217       linkrel:
218 	  b[pos] = n;  /* Else link to rel chain, anchored at label. */
219 	  *pl = pos;
220 	}
221 	pos++;
222 	break;
223       case DASM_LABEL_LG:
224 	pl = D->lglabels + (ins & 2047) - 10; CKPL(lg, LG); goto putlabel;
225       case DASM_LABEL_PC:
226 	pl = D->pclabels + n; CKPL(pc, PC);
227       putlabel:
228 	n = *pl;  /* n > 0: Collapse rel chain and replace with label pos. */
229 	while (n > 0) { int *pb = DASM_POS2PTR(D, n); n = *pb; *pb = pos;
230 	}
231 	*pl = -pos;  /* Label exists now. */
232 	b[pos++] = ofs;  /* Store pass1 offset estimate. */
233 	break;
234       case DASM_IMM: case DASM_IMMS:
235 #ifdef DASM_CHECKS
236 	CK((n & ((1<<((ins>>10)&31))-1)) == 0, RANGE_I);
237 #endif
238 	n >>= ((ins>>10)&31);
239 #ifdef DASM_CHECKS
240 	if (ins & 0x8000)
241 	  CK(((n + (1<<(((ins>>5)&31)-1)))>>((ins>>5)&31)) == 0, RANGE_I);
242 	else
243 	  CK((n>>((ins>>5)&31)) == 0, RANGE_I);
244 #endif
245 	b[pos++] = n;
246 	break;
247       }
248     }
249   }
250 stop:
251   va_end(ap);
252   sec->pos = pos;
253   sec->ofs = ofs;
254 }
255 #undef CK
256 
257 /* Pass 2: Link sections, shrink aligns, fix label offsets. */
dasm_link(Dst_DECL,size_t * szp)258 int dasm_link(Dst_DECL, size_t *szp)
259 {
260   dasm_State *D = Dst_REF;
261   int secnum;
262   int ofs = 0;
263 
264 #ifdef DASM_CHECKS
265   *szp = 0;
266   if (D->status != DASM_S_OK) return D->status;
267   {
268     int pc;
269     for (pc = 0; pc*sizeof(int) < D->pcsize; pc++)
270       if (D->pclabels[pc] > 0) return DASM_S_UNDEF_PC|pc;
271   }
272 #endif
273 
274   { /* Handle globals not defined in this translation unit. */
275     int idx;
276     for (idx = 20; idx*sizeof(int) < D->lgsize; idx++) {
277       int n = D->lglabels[idx];
278       /* Undefined label: Collapse rel chain and replace with marker (< 0). */
279       while (n > 0) { int *pb = DASM_POS2PTR(D, n); n = *pb; *pb = -idx; }
280     }
281   }
282 
283   /* Combine all code sections. No support for data sections (yet). */
284   for (secnum = 0; secnum < D->maxsection; secnum++) {
285     dasm_Section *sec = D->sections + secnum;
286     int *b = sec->rbuf;
287     int pos = DASM_SEC2POS(secnum);
288     int lastpos = sec->pos;
289 
290     while (pos != lastpos) {
291       dasm_ActList p = D->actionlist + b[pos++];
292       while (1) {
293 	unsigned int ins = *p++;
294 	unsigned int action = (ins >> 16) - 0xff00;
295 	switch (action) {
296 	case DASM_STOP: case DASM_SECTION: goto stop;
297 	case DASM_ESC: p++; break;
298 	case DASM_REL_EXT: break;
299 	case DASM_ALIGN: ofs -= (b[pos++] + ofs) & (ins & 255); break;
300 	case DASM_REL_LG: case DASM_REL_PC: pos++; break;
301 	case DASM_LABEL_LG: case DASM_LABEL_PC: b[pos++] += ofs; break;
302 	case DASM_IMM: case DASM_IMMS: pos++; break;
303 	}
304       }
305       stop: (void)0;
306     }
307     ofs += sec->ofs;  /* Next section starts right after current section. */
308   }
309 
310   D->codesize = ofs;  /* Total size of all code sections */
311   *szp = ofs;
312   return DASM_S_OK;
313 }
314 
315 #ifdef DASM_CHECKS
316 #define CK(x, st) \
317   do { if (!(x)) return DASM_S_##st|(p-D->actionlist-1); } while (0)
318 #else
319 #define CK(x, st)	((void)0)
320 #endif
321 
322 /* Pass 3: Encode sections. */
dasm_encode(Dst_DECL,void * buffer)323 int dasm_encode(Dst_DECL, void *buffer)
324 {
325   dasm_State *D = Dst_REF;
326   char *base = (char *)buffer;
327   unsigned int *cp = (unsigned int *)buffer;
328   int secnum;
329 
330   /* Encode all code sections. No support for data sections (yet). */
331   for (secnum = 0; secnum < D->maxsection; secnum++) {
332     dasm_Section *sec = D->sections + secnum;
333     int *b = sec->buf;
334     int *endb = sec->rbuf + sec->pos;
335 
336     while (b != endb) {
337       dasm_ActList p = D->actionlist + *b++;
338       while (1) {
339 	unsigned int ins = *p++;
340 	unsigned int action = (ins >> 16) - 0xff00;
341 	int n = (action >= DASM_ALIGN && action < DASM__MAX) ? *b++ : 0;
342 	switch (action) {
343 	case DASM_STOP: case DASM_SECTION: goto stop;
344 	case DASM_ESC: *cp++ = *p++; break;
345 	case DASM_REL_EXT:
346 	  n = DASM_EXTERN(Dst, (unsigned char *)cp, (ins & 2047), 1);
347 	  goto patchrel;
348 	case DASM_ALIGN:
349 	  ins &= 255; while ((((char *)cp - base) & ins)) *cp++ = 0x60000000;
350 	  break;
351 	case DASM_REL_LG:
352 	  CK(n >= 0, UNDEF_LG);
353 	  /* fallthrough */
354 	case DASM_REL_PC:
355 	  CK(n >= 0, UNDEF_PC);
356 	  n = *DASM_POS2PTR(D, n);
357 	  if (ins & 2048)
358 	    n = (n + (int)(size_t)base) & 0x0fffffff;
359 	  else
360 	    n = n - (int)((char *)cp - base);
361 	patchrel: {
362 	  unsigned int e = 16 + ((ins >> 12) & 15);
363 	  CK((n & 3) == 0 &&
364 	     ((n + ((ins & 2048) ? 0 : (1<<(e+1)))) >> (e+2)) == 0, RANGE_REL);
365 	  cp[-1] |= ((n>>2) & ((1<<e)-1));
366 	  }
367 	  break;
368 	case DASM_LABEL_LG:
369 	  ins &= 2047; if (ins >= 20) D->globals[ins-10] = (void *)(base + n);
370 	  break;
371 	case DASM_LABEL_PC: break;
372 	case DASM_IMMS:
373 	  cp[-1] |= ((n>>3) & 4); n &= 0x1f;
374 	  /* fallthrough */
375 	case DASM_IMM:
376 	  cp[-1] |= (n & ((1<<((ins>>5)&31))-1)) << (ins&31);
377 	  break;
378 	default: *cp++ = ins; break;
379 	}
380       }
381       stop: (void)0;
382     }
383   }
384 
385   if (base + D->codesize != (char *)cp)  /* Check for phase errors. */
386     return DASM_S_PHASE;
387   return DASM_S_OK;
388 }
389 #undef CK
390 
391 /* Get PC label offset. */
dasm_getpclabel(Dst_DECL,unsigned int pc)392 int dasm_getpclabel(Dst_DECL, unsigned int pc)
393 {
394   dasm_State *D = Dst_REF;
395   if (pc*sizeof(int) < D->pcsize) {
396     int pos = D->pclabels[pc];
397     if (pos < 0) return *DASM_POS2PTR(D, -pos);
398     if (pos > 0) return -1;  /* Undefined. */
399   }
400   return -2;  /* Unused or out of range. */
401 }
402 
403 #ifdef DASM_CHECKS
404 /* Optional sanity checker to call between isolated encoding steps. */
dasm_checkstep(Dst_DECL,int secmatch)405 int dasm_checkstep(Dst_DECL, int secmatch)
406 {
407   dasm_State *D = Dst_REF;
408   if (D->status == DASM_S_OK) {
409     int i;
410     for (i = 1; i <= 9; i++) {
411       if (D->lglabels[i] > 0) { D->status = DASM_S_UNDEF_LG|i; break; }
412       D->lglabels[i] = 0;
413     }
414   }
415   if (D->status == DASM_S_OK && secmatch >= 0 &&
416       D->section != &D->sections[secmatch])
417     D->status = DASM_S_MATCH_SEC|(D->section-D->sections);
418   return D->status;
419 }
420 #endif
421 
422