xref: /openbmc/qemu/accel/tcg/translator.c (revision 646b5378)
1 /*
2  * Generic intermediate code generation.
3  *
4  * Copyright (C) 2016-2017 Lluís Vilanova <vilanova@ac.upc.edu>
5  *
6  * This work is licensed under the terms of the GNU GPL, version 2 or later.
7  * See the COPYING file in the top-level directory.
8  */
9 
10 #include "qemu/osdep.h"
11 #include "qemu/log.h"
12 #include "qemu/error-report.h"
13 #include "exec/exec-all.h"
14 #include "exec/translator.h"
15 #include "exec/cpu_ldst.h"
16 #include "exec/plugin-gen.h"
17 #include "exec/cpu_ldst.h"
18 #include "tcg/tcg-op-common.h"
19 #include "internal-target.h"
20 #include "disas/disas.h"
21 
22 static void set_can_do_io(DisasContextBase *db, bool val)
23 {
24     QEMU_BUILD_BUG_ON(sizeof_field(CPUState, neg.can_do_io) != 1);
25     tcg_gen_st8_i32(tcg_constant_i32(val), tcg_env,
26                     offsetof(ArchCPU, parent_obj.neg.can_do_io) -
27                     offsetof(ArchCPU, env));
28 }
29 
30 bool translator_io_start(DisasContextBase *db)
31 {
32     /*
33      * Ensure that this instruction will be the last in the TB.
34      * The target may override this to something more forceful.
35      */
36     if (db->is_jmp == DISAS_NEXT) {
37         db->is_jmp = DISAS_TOO_MANY;
38     }
39     return true;
40 }
41 
42 static TCGOp *gen_tb_start(DisasContextBase *db, uint32_t cflags)
43 {
44     TCGv_i32 count = NULL;
45     TCGOp *icount_start_insn = NULL;
46 
47     if ((cflags & CF_USE_ICOUNT) || !(cflags & CF_NOIRQ)) {
48         count = tcg_temp_new_i32();
49         tcg_gen_ld_i32(count, tcg_env,
50                        offsetof(ArchCPU, parent_obj.neg.icount_decr.u32)
51                        - offsetof(ArchCPU, env));
52     }
53 
54     if (cflags & CF_USE_ICOUNT) {
55         /*
56          * We emit a sub with a dummy immediate argument. Keep the insn index
57          * of the sub so that we later (when we know the actual insn count)
58          * can update the argument with the actual insn count.
59          */
60         tcg_gen_sub_i32(count, count, tcg_constant_i32(0));
61         icount_start_insn = tcg_last_op();
62     }
63 
64     /*
65      * Emit the check against icount_decr.u32 to see if we should exit
66      * unless we suppress the check with CF_NOIRQ. If we are using
67      * icount and have suppressed interruption the higher level code
68      * should have ensured we don't run more instructions than the
69      * budget.
70      */
71     if (cflags & CF_NOIRQ) {
72         tcg_ctx->exitreq_label = NULL;
73     } else {
74         tcg_ctx->exitreq_label = gen_new_label();
75         tcg_gen_brcondi_i32(TCG_COND_LT, count, 0, tcg_ctx->exitreq_label);
76     }
77 
78     if (cflags & CF_USE_ICOUNT) {
79         tcg_gen_st16_i32(count, tcg_env,
80                          offsetof(ArchCPU, parent_obj.neg.icount_decr.u16.low)
81                          - offsetof(ArchCPU, env));
82     }
83 
84     return icount_start_insn;
85 }
86 
87 static void gen_tb_end(const TranslationBlock *tb, uint32_t cflags,
88                        TCGOp *icount_start_insn, int num_insns)
89 {
90     if (cflags & CF_USE_ICOUNT) {
91         /*
92          * Update the num_insn immediate parameter now that we know
93          * the actual insn count.
94          */
95         tcg_set_insn_param(icount_start_insn, 2,
96                            tcgv_i32_arg(tcg_constant_i32(num_insns)));
97     }
98 
99     if (tcg_ctx->exitreq_label) {
100         gen_set_label(tcg_ctx->exitreq_label);
101         tcg_gen_exit_tb(tb, TB_EXIT_REQUESTED);
102     }
103 }
104 
105 bool translator_use_goto_tb(DisasContextBase *db, vaddr dest)
106 {
107     /* Suppress goto_tb if requested. */
108     if (tb_cflags(db->tb) & CF_NO_GOTO_TB) {
109         return false;
110     }
111 
112     /* Check for the dest on the same page as the start of the TB.  */
113     return ((db->pc_first ^ dest) & TARGET_PAGE_MASK) == 0;
114 }
115 
116 void translator_loop(CPUState *cpu, TranslationBlock *tb, int *max_insns,
117                      vaddr pc, void *host_pc, const TranslatorOps *ops,
118                      DisasContextBase *db)
119 {
120     uint32_t cflags = tb_cflags(tb);
121     TCGOp *icount_start_insn;
122     TCGOp *first_insn_start = NULL;
123     bool plugin_enabled;
124 
125     /* Initialize DisasContext */
126     db->tb = tb;
127     db->pc_first = pc;
128     db->pc_next = pc;
129     db->is_jmp = DISAS_NEXT;
130     db->num_insns = 0;
131     db->max_insns = *max_insns;
132     db->insn_start = NULL;
133     db->fake_insn = false;
134     db->host_addr[0] = host_pc;
135     db->host_addr[1] = NULL;
136     db->record_start = 0;
137     db->record_len = 0;
138 
139     ops->init_disas_context(db, cpu);
140     tcg_debug_assert(db->is_jmp == DISAS_NEXT);  /* no early exit */
141 
142     /* Start translating.  */
143     icount_start_insn = gen_tb_start(db, cflags);
144     ops->tb_start(db, cpu);
145     tcg_debug_assert(db->is_jmp == DISAS_NEXT);  /* no early exit */
146 
147     plugin_enabled = plugin_gen_tb_start(cpu, db);
148     db->plugin_enabled = plugin_enabled;
149 
150     while (true) {
151         *max_insns = ++db->num_insns;
152         ops->insn_start(db, cpu);
153         db->insn_start = tcg_last_op();
154         if (first_insn_start == NULL) {
155             first_insn_start = db->insn_start;
156         }
157         tcg_debug_assert(db->is_jmp == DISAS_NEXT);  /* no early exit */
158 
159         if (plugin_enabled) {
160             plugin_gen_insn_start(cpu, db);
161         }
162 
163         /*
164          * Disassemble one instruction.  The translate_insn hook should
165          * update db->pc_next and db->is_jmp to indicate what should be
166          * done next -- either exiting this loop or locate the start of
167          * the next instruction.
168          */
169         ops->translate_insn(db, cpu);
170 
171         /*
172          * We can't instrument after instructions that change control
173          * flow although this only really affects post-load operations.
174          *
175          * Calling plugin_gen_insn_end() before we possibly stop translation
176          * is important. Even if this ends up as dead code, plugin generation
177          * needs to see a matching plugin_gen_insn_{start,end}() pair in order
178          * to accurately track instrumented helpers that might access memory.
179          */
180         if (plugin_enabled) {
181             plugin_gen_insn_end();
182         }
183 
184         /* Stop translation if translate_insn so indicated.  */
185         if (db->is_jmp != DISAS_NEXT) {
186             break;
187         }
188 
189         /* Stop translation if the output buffer is full,
190            or we have executed all of the allowed instructions.  */
191         if (tcg_op_buf_full() || db->num_insns >= db->max_insns) {
192             db->is_jmp = DISAS_TOO_MANY;
193             break;
194         }
195     }
196 
197     /* Emit code to exit the TB, as indicated by db->is_jmp.  */
198     ops->tb_stop(db, cpu);
199     gen_tb_end(tb, cflags, icount_start_insn, db->num_insns);
200 
201     /*
202      * Manage can_do_io for the translation block: set to false before
203      * the first insn and set to true before the last insn.
204      */
205     if (db->num_insns == 1) {
206         tcg_debug_assert(first_insn_start == db->insn_start);
207     } else {
208         tcg_debug_assert(first_insn_start != db->insn_start);
209         tcg_ctx->emit_before_op = first_insn_start;
210         set_can_do_io(db, false);
211     }
212     tcg_ctx->emit_before_op = db->insn_start;
213     set_can_do_io(db, true);
214     tcg_ctx->emit_before_op = NULL;
215 
216     /* May be used by disas_log or plugin callbacks. */
217     tb->size = db->pc_next - db->pc_first;
218     tb->icount = db->num_insns;
219 
220     if (plugin_enabled) {
221         plugin_gen_tb_end(cpu, db->num_insns);
222     }
223 
224     if (qemu_loglevel_mask(CPU_LOG_TB_IN_ASM)
225         && qemu_log_in_addr_range(db->pc_first)) {
226         FILE *logfile = qemu_log_trylock();
227         if (logfile) {
228             fprintf(logfile, "----------------\n");
229 
230             if (!ops->disas_log ||
231                 !ops->disas_log(db, cpu, logfile)) {
232                 fprintf(logfile, "IN: %s\n", lookup_symbol(db->pc_first));
233                 target_disas(logfile, cpu, db);
234             }
235             fprintf(logfile, "\n");
236             qemu_log_unlock(logfile);
237         }
238     }
239 }
240 
241 static bool translator_ld(CPUArchState *env, DisasContextBase *db,
242                           void *dest, vaddr pc, size_t len)
243 {
244     TranslationBlock *tb = db->tb;
245     vaddr last = pc + len - 1;
246     void *host;
247     vaddr base;
248 
249     /* Use slow path if first page is MMIO. */
250     if (unlikely(tb_page_addr0(tb) == -1)) {
251         /* We capped translation with first page MMIO in tb_gen_code. */
252         tcg_debug_assert(db->max_insns == 1);
253         return false;
254     }
255 
256     host = db->host_addr[0];
257     base = db->pc_first;
258 
259     if (likely(((base ^ last) & TARGET_PAGE_MASK) == 0)) {
260         /* Entire read is from the first page. */
261         memcpy(dest, host + (pc - base), len);
262         return true;
263     }
264 
265     if (unlikely(((base ^ pc) & TARGET_PAGE_MASK) == 0)) {
266         /* Read begins on the first page and extends to the second. */
267         size_t len0 = -(pc | TARGET_PAGE_MASK);
268         memcpy(dest, host + (pc - base), len0);
269         pc += len0;
270         dest += len0;
271         len -= len0;
272     }
273 
274     /*
275      * The read must conclude on the second page and not extend to a third.
276      *
277      * TODO: We could allow the two pages to be virtually discontiguous,
278      * since we already allow the two pages to be physically discontiguous.
279      * The only reasonable use case would be executing an insn at the end
280      * of the address space wrapping around to the beginning.  For that,
281      * we would need to know the current width of the address space.
282      * In the meantime, assert.
283      */
284     base = (base & TARGET_PAGE_MASK) + TARGET_PAGE_SIZE;
285     assert(((base ^ pc) & TARGET_PAGE_MASK) == 0);
286     assert(((base ^ last) & TARGET_PAGE_MASK) == 0);
287     host = db->host_addr[1];
288 
289     if (host == NULL) {
290         tb_page_addr_t page0, old_page1, new_page1;
291 
292         new_page1 = get_page_addr_code_hostp(env, base, &db->host_addr[1]);
293 
294         /*
295          * If the second page is MMIO, treat as if the first page
296          * was MMIO as well, so that we do not cache the TB.
297          */
298         if (unlikely(new_page1 == -1)) {
299             tb_unlock_pages(tb);
300             tb_set_page_addr0(tb, -1);
301             /* Require that this be the final insn. */
302             db->max_insns = db->num_insns;
303             return false;
304         }
305 
306         /*
307          * If this is not the first time around, and page1 matches,
308          * then we already have the page locked.  Alternately, we're
309          * not doing anything to prevent the PTE from changing, so
310          * we might wind up with a different page, requiring us to
311          * re-do the locking.
312          */
313         old_page1 = tb_page_addr1(tb);
314         if (likely(new_page1 != old_page1)) {
315             page0 = tb_page_addr0(tb);
316             if (unlikely(old_page1 != -1)) {
317                 tb_unlock_page1(page0, old_page1);
318             }
319             tb_set_page_addr1(tb, new_page1);
320             tb_lock_page1(page0, new_page1);
321         }
322         host = db->host_addr[1];
323     }
324 
325     memcpy(dest, host + (pc - base), len);
326     return true;
327 }
328 
329 static void record_save(DisasContextBase *db, vaddr pc,
330                         const void *from, int size)
331 {
332     int offset;
333 
334     /* Do not record probes before the start of TB. */
335     if (pc < db->pc_first) {
336         return;
337     }
338 
339     /*
340      * In translator_access, we verified that pc is within 2 pages
341      * of pc_first, thus this will never overflow.
342      */
343     offset = pc - db->pc_first;
344 
345     /*
346      * Either the first or second page may be I/O.  If it is the second,
347      * then the first byte we need to record will be at a non-zero offset.
348      * In either case, we should not need to record but a single insn.
349      */
350     if (db->record_len == 0) {
351         db->record_start = offset;
352         db->record_len = size;
353     } else {
354         assert(offset == db->record_start + db->record_len);
355         assert(db->record_len + size <= sizeof(db->record));
356         db->record_len += size;
357     }
358 
359     memcpy(db->record + (offset - db->record_start), from, size);
360 }
361 
362 size_t translator_st_len(const DisasContextBase *db)
363 {
364     return db->fake_insn ? db->record_len : db->tb->size;
365 }
366 
367 bool translator_st(const DisasContextBase *db, void *dest,
368                    vaddr addr, size_t len)
369 {
370     size_t offset, offset_end;
371 
372     if (addr < db->pc_first) {
373         return false;
374     }
375     offset = addr - db->pc_first;
376     offset_end = offset + len;
377     if (offset_end > translator_st_len(db)) {
378         return false;
379     }
380 
381     if (!db->fake_insn) {
382         size_t offset_page1 = -(db->pc_first | TARGET_PAGE_MASK);
383 
384         /* Get all the bytes from the first page. */
385         if (db->host_addr[0]) {
386             if (offset_end <= offset_page1) {
387                 memcpy(dest, db->host_addr[0] + offset, len);
388                 return true;
389             }
390             if (offset < offset_page1) {
391                 size_t len0 = offset_page1 - offset;
392                 memcpy(dest, db->host_addr[0] + offset, len0);
393                 offset += len0;
394                 dest += len0;
395             }
396         }
397 
398         /* Get any bytes from the second page. */
399         if (db->host_addr[1] && offset >= offset_page1) {
400             memcpy(dest, db->host_addr[1] + (offset - offset_page1),
401                    offset_end - offset);
402             return true;
403         }
404     }
405 
406     /* Else get recorded bytes. */
407     if (db->record_len != 0 &&
408         offset >= db->record_start &&
409         offset_end <= db->record_start + db->record_len) {
410         memcpy(dest, db->record + (offset - db->record_start),
411                offset_end - offset);
412         return true;
413     }
414     return false;
415 }
416 
417 uint8_t translator_ldub(CPUArchState *env, DisasContextBase *db, vaddr pc)
418 {
419     uint8_t raw;
420 
421     if (!translator_ld(env, db, &raw, pc, sizeof(raw))) {
422         raw = cpu_ldub_code(env, pc);
423         record_save(db, pc, &raw, sizeof(raw));
424     }
425     return raw;
426 }
427 
428 uint16_t translator_lduw(CPUArchState *env, DisasContextBase *db, vaddr pc)
429 {
430     uint16_t raw, tgt;
431 
432     if (translator_ld(env, db, &raw, pc, sizeof(raw))) {
433         tgt = tswap16(raw);
434     } else {
435         tgt = cpu_lduw_code(env, pc);
436         raw = tswap16(tgt);
437         record_save(db, pc, &raw, sizeof(raw));
438     }
439     return tgt;
440 }
441 
442 uint32_t translator_ldl(CPUArchState *env, DisasContextBase *db, vaddr pc)
443 {
444     uint32_t raw, tgt;
445 
446     if (translator_ld(env, db, &raw, pc, sizeof(raw))) {
447         tgt = tswap32(raw);
448     } else {
449         tgt = cpu_ldl_code(env, pc);
450         raw = tswap32(tgt);
451         record_save(db, pc, &raw, sizeof(raw));
452     }
453     return tgt;
454 }
455 
456 uint64_t translator_ldq(CPUArchState *env, DisasContextBase *db, vaddr pc)
457 {
458     uint64_t raw, tgt;
459 
460     if (translator_ld(env, db, &raw, pc, sizeof(raw))) {
461         tgt = tswap64(raw);
462     } else {
463         tgt = cpu_ldq_code(env, pc);
464         raw = tswap64(tgt);
465         record_save(db, pc, &raw, sizeof(raw));
466     }
467     return tgt;
468 }
469 
470 void translator_fake_ld(DisasContextBase *db, const void *data, size_t len)
471 {
472     db->fake_insn = true;
473     record_save(db, db->pc_first, data, len);
474 }
475