aboutsummaryrefslogtreecommitdiff
path: root/semihosting/syscalls.c
blob: 42080ffdda3e61a9faaeaf393a6bc6f90f0be117 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
/*
 * Syscall implementations for semihosting.
 *
 * Copyright (c) 2022 Linaro
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 */

#include "qemu/osdep.h"
#include "cpu.h"
#include "gdbstub/syscalls.h"
#include "semihosting/guestfd.h"
#include "semihosting/syscalls.h"
#include "semihosting/console.h"
#ifdef CONFIG_USER_ONLY
#include "qemu.h"
#else
#include "semihosting/softmmu-uaccess.h"
#endif


/*
 * Validate or compute the length of the string (including terminator).
 */
static int validate_strlen(CPUState *cs, target_ulong str, target_ulong tlen)
{
    CPUArchState *env G_GNUC_UNUSED = cs->env_ptr;
    char c;

    if (tlen == 0) {
        ssize_t slen = target_strlen(str);

        if (slen < 0) {
            return -EFAULT;
        }
        if (slen >= INT32_MAX) {
            return -ENAMETOOLONG;
        }
        return slen + 1;
    }
    if (tlen > INT32_MAX) {
        return -ENAMETOOLONG;
    }
    if (get_user_u8(c, str + tlen - 1)) {
        return -EFAULT;
    }
    if (c != 0) {
        return -EINVAL;
    }
    return tlen;
}

static int validate_lock_user_string(char **pstr, CPUState *cs,
                                     target_ulong tstr, target_ulong tlen)
{
    int ret = validate_strlen(cs, tstr, tlen);
    CPUArchState *env G_GNUC_UNUSED = cs->env_ptr;
    char *str = NULL;

    if (ret > 0) {
        str = lock_user(VERIFY_READ, tstr, ret, true);
        ret = str ? 0 : -EFAULT;
    }
    *pstr = str;
    return ret;
}

/*
 * TODO: Note that gdb always stores the stat structure big-endian.
 * So far, that's ok, as the only two targets using this are also
 * big-endian.  Until we do something with gdb, also produce the
 * same big-endian result from the host.
 */
static int copy_stat_to_user(CPUState *cs, target_ulong addr,
                             const struct stat *s)
{
    CPUArchState *env G_GNUC_UNUSED = cs->env_ptr;
    struct gdb_stat *p;

    if (s->st_dev != (uint32_t)s->st_dev ||
        s->st_ino != (uint32_t)s->st_ino) {
        return -EOVERFLOW;
    }

    p = lock_user(VERIFY_WRITE, addr, sizeof(struct gdb_stat), 0);
    if (!p) {
        return -EFAULT;
    }

    p->gdb_st_dev = cpu_to_be32(s->st_dev);
    p->gdb_st_ino = cpu_to_be32(s->st_ino);
    p->gdb_st_mode = cpu_to_be32(s->st_mode);
    p->gdb_st_nlink = cpu_to_be32(s->st_nlink);
    p->gdb_st_uid = cpu_to_be32(s->st_uid);
    p->gdb_st_gid = cpu_to_be32(s->st_gid);
    p->gdb_st_rdev = cpu_to_be32(s->st_rdev);
    p->gdb_st_size = cpu_to_be64(s->st_size);
#ifdef _WIN32
    /* Windows stat is missing some fields.  */
    p->gdb_st_blksize = 0;
    p->gdb_st_blocks = 0;
#else
    p->gdb_st_blksize = cpu_to_be64(s->st_blksize);
    p->gdb_st_blocks = cpu_to_be64(s->st_blocks);
#endif
    p->gdb_st_atime = cpu_to_be32(s->st_atime);
    p->gdb_st_mtime = cpu_to_be32(s->st_mtime);
    p->gdb_st_ctime = cpu_to_be32(s->st_ctime);

    unlock_user(p, addr, sizeof(struct gdb_stat));
    return 0;
}

/*
 * GDB semihosting syscall implementations.
 */

static gdb_syscall_complete_cb gdb_open_complete;

static void gdb_open_cb(CPUState *cs, uint64_t ret, int err)
{
    if (!err) {
        int guestfd = alloc_guestfd();
        associate_guestfd(guestfd, ret);
        ret = guestfd;
    }
    gdb_open_complete(cs, ret, err);
}

static void gdb_open(CPUState *cs, gdb_syscall_complete_cb complete,
                     target_ulong fname, target_ulong fname_len,
                     int gdb_flags, int mode)
{
    int len = validate_strlen(cs, fname, fname_len);
    if (len < 0) {
        complete(cs, -1, -len);
        return;
    }

    gdb_open_complete = complete;
    gdb_do_syscall(gdb_open_cb, "open,%s,%x,%x",
                   fname, len, (target_ulong)gdb_flags, (target_ulong)mode);
}

static void gdb_close(CPUState *cs, gdb_syscall_complete_cb complete,
                      GuestFD *gf)
{
    gdb_do_syscall(complete, "close,%x", (target_ulong)gf->hostfd);
}

static void gdb_read(CPUState *cs, gdb_syscall_complete_cb complete,
                     GuestFD *gf, target_ulong buf, target_ulong len)
{
    gdb_do_syscall(complete, "read,%x,%x,%x",
                   (target_ulong)gf->hostfd, buf, len);
}

static void gdb_write(CPUState *cs, gdb_syscall_complete_cb complete,
                      GuestFD *gf, target_ulong buf, target_ulong len)
{
    gdb_do_syscall(complete, "write,%x,%x,%x",
                   (target_ulong)gf->hostfd, buf, len);
}

static void gdb_lseek(CPUState *cs, gdb_syscall_complete_cb complete,
                      GuestFD *gf, int64_t off, int gdb_whence)
{
    gdb_do_syscall(complete, "lseek,%x,%lx,%x",
                   (target_ulong)gf->hostfd, off, (target_ulong)gdb_whence);
}

static void gdb_isatty(CPUState *cs, gdb_syscall_complete_cb complete,
                       GuestFD *gf)
{
    gdb_do_syscall(complete, "isatty,%x", (target_ulong)gf->hostfd);
}

static void gdb_fstat(CPUState *cs, gdb_syscall_complete_cb complete,
                      GuestFD *gf, target_ulong addr)
{
    gdb_do_syscall(complete, "fstat,%x,%x", (target_ulong)gf->hostfd, addr);
}

static void gdb_stat(CPUState *cs, gdb_syscall_complete_cb complete,
                     target_ulong fname, target_ulong fname_len,
                     target_ulong addr)
{
    int len = validate_strlen(cs, fname, fname_len);
    if (len < 0) {
        complete(cs, -1, -len);
        return;
    }

    gdb_do_syscall(complete, "stat,%s,%x", fname, len, addr);
}

static void gdb_remove(CPUState *cs, gdb_syscall_complete_cb complete,
                       target_ulong fname, target_ulong fname_len)
{
    int len = validate_strlen(cs, fname, fname_len);
    if (len < 0) {
        complete(cs, -1, -len);
        return;
    }

    gdb_do_syscall(complete, "unlink,%s", fname, len);
}

static void gdb_rename(CPUState *cs, gdb_syscall_complete_cb complete,
                       target_ulong oname, target_ulong oname_len,
                       target_ulong nname, target_ulong nname_len)
{
    int olen, nlen;

    olen = validate_strlen(cs, oname, oname_len);
    if (olen < 0) {
        complete(cs, -1, -olen);
        return;
    }
    nlen = validate_strlen(cs, nname, nname_len);
    if (nlen < 0) {
        complete(cs, -1, -nlen);
        return;
    }

    gdb_do_syscall(complete, "rename,%s,%s", oname, olen, nname, nlen);
}

static void gdb_system(CPUState *cs, gdb_syscall_complete_cb complete,
                       target_ulong cmd, target_ulong cmd_len)
{
    int len = validate_strlen(cs, cmd, cmd_len);
    if (len < 0) {
        complete(cs, -1, -len);
        return;
    }

    gdb_do_syscall(complete, "system,%s", cmd, len);
}

static void gdb_gettimeofday(CPUState *cs, gdb_syscall_complete_cb complete,
                             target_ulong tv_addr, target_ulong tz_addr)
{
    gdb_do_syscall(complete, "gettimeofday,%x,%x", tv_addr, tz_addr);
}

/*
 * Host semihosting syscall implementations.
 */

static void host_open(CPUState *cs, gdb_syscall_complete_cb complete,
                      target_ulong fname, target_ulong fname_len,
                      int gdb_flags, int mode)
{
    CPUArchState *env G_GNUC_UNUSED = cs->env_ptr;
    char *p;
    int ret, host_flags = O_BINARY;

    ret = validate_lock_user_string(&p, cs, fname, fname_len);
    if (ret < 0) {
        complete(cs, -1, -ret);
        return;
    }

    if (gdb_flags & GDB_O_WRONLY) {
        host_flags |= O_WRONLY;
    } else if (gdb_flags & GDB_O_RDWR) {
        host_flags |= O_RDWR;
    } else {
        host_flags |= O_RDONLY;
    }
    if (gdb_flags & GDB_O_CREAT) {
        host_flags |= O_CREAT;
    }
    if (gdb_flags & GDB_O_TRUNC) {
        host_flags |= O_TRUNC;
    }
    if (gdb_flags & GDB_O_EXCL) {
        host_flags |= O_EXCL;
    }

    ret = open(p, host_flags, mode);
    if (ret < 0) {
        complete(cs, -1, errno);
    } else {
        int guestfd = alloc_guestfd();
        associate_guestfd(guestfd, ret);
        complete(cs, guestfd, 0);
    }
    unlock_user(p, fname, 0);
}

static void host_close(CPUState *cs, gdb_syscall_complete_cb complete,
                       GuestFD *gf)
{
    /*
     * Only close the underlying host fd if it's one we opened on behalf
     * of the guest in SYS_OPEN.
     */
    if (gf->hostfd != STDIN_FILENO &&
        gf->hostfd != STDOUT_FILENO &&
        gf->hostfd != STDERR_FILENO &&
        close(gf->hostfd) < 0) {
        complete(cs, -1, errno);
    } else {
        complete(cs, 0, 0);
    }
}

static void host_read(CPUState *cs, gdb_syscall_complete_cb complete,
                      GuestFD *gf, target_ulong buf, target_ulong len)
{
    CPUArchState *env G_GNUC_UNUSED = cs->env_ptr;
    void *ptr = lock_user(VERIFY_WRITE, buf, len, 0);
    ssize_t ret;

    if (!ptr) {
        complete(cs, -1, EFAULT);
        return;
    }
    ret = RETRY_ON_EINTR(read(gf->hostfd, ptr, len));
    if (ret == -1) {
        unlock_user(ptr, buf, 0);
        complete(cs, -1, errno);
    } else {
        unlock_user(ptr, buf, ret);
        complete(cs, ret, 0);
    }
}

static void host_write(CPUState *cs, gdb_syscall_complete_cb complete,
                       GuestFD *gf, target_ulong buf, target_ulong len)
{
    CPUArchState *env G_GNUC_UNUSED = cs->env_ptr;
    void *ptr = lock_user(VERIFY_READ, buf, len, 1);
    ssize_t ret;

    if (!ptr) {
        complete(cs, -1, EFAULT);
        return;
    }
    ret = write(gf->hostfd, ptr, len);
    unlock_user(ptr, buf, 0);
    complete(cs, ret, ret == -1 ? errno : 0);
}

static void host_lseek(CPUState *cs, gdb_syscall_complete_cb complete,
                       GuestFD *gf, int64_t off, int whence)
{
    /* So far, all hosts use the same values. */
    QEMU_BUILD_BUG_ON(GDB_SEEK_SET != SEEK_SET);
    QEMU_BUILD_BUG_ON(GDB_SEEK_CUR != SEEK_CUR);
    QEMU_BUILD_BUG_ON(GDB_SEEK_END != SEEK_END);

    off_t ret = off;
    int err = 0;

    if (ret == off) {
        ret = lseek(gf->hostfd, ret, whence);
        if (ret == -1) {
            err = errno;
        }
    } else {
        ret = -1;
        err = EINVAL;
    }
    complete(cs, ret, err);
}

static void host_isatty(CPUState *cs, gdb_syscall_complete_cb complete,
                        GuestFD *gf)
{
    int ret = isatty(gf->hostfd);
    complete(cs, ret, ret ? 0 : errno);
}

static void host_flen(CPUState *cs, gdb_syscall_complete_cb complete,
                      GuestFD *gf)
{
    struct stat buf;

    if (fstat(gf->hostfd, &buf) < 0) {
        complete(cs, -1, errno);
    } else {
        complete(cs, buf.st_size, 0);
    }
}

static void host_fstat(CPUState *cs, gdb_syscall_complete_cb complete,
                       GuestFD *gf, target_ulong addr)
{
    struct stat buf;
    int ret;

    ret = fstat(gf->hostfd, &buf);
    if (ret) {
        complete(cs, -1, errno);
        return;
    }
    ret = copy_stat_to_user(cs, addr, &buf);
    complete(cs, ret ? -1 : 0, ret ? -ret : 0);
}

static void host_stat(CPUState *cs, gdb_syscall_complete_cb complete,
                      target_ulong fname, target_ulong fname_len,
                      target_ulong addr)
{
    CPUArchState *env G_GNUC_UNUSED = cs->env_ptr;
    struct stat buf;
    char *name;
    int ret, err;

    ret = validate_lock_user_string(&name, cs, fname, fname_len);
    if (ret < 0) {
        complete(cs, -1, -ret);
        return;
    }

    ret = stat(name, &buf);
    if (ret) {
        err = errno;
    } else {
        ret = copy_stat_to_user(cs, addr, &buf);
        err = 0;
        if (ret < 0) {
            err = -ret;
            ret = -1;
        }
    }
    unlock_user(name, fname, 0);
    complete(cs, ret, err);
}

static void host_remove(CPUState *cs, gdb_syscall_complete_cb complete,
                        target_ulong fname, target_ulong fname_len)
{
    CPUArchState *env G_GNUC_UNUSED = cs->env_ptr;
    char *p;
    int ret;

    ret = validate_lock_user_string(&p, cs, fname, fname_len);
    if (ret < 0) {
        complete(cs, -1, -ret);
        return;
    }

    ret = remove(p);
    unlock_user(p, fname, 0);
    complete(cs, ret, ret ? errno : 0);
}

static void host_rename(CPUState *cs, gdb_syscall_complete_cb complete,
                        target_ulong oname, target_ulong oname_len,
                        target_ulong nname, target_ulong nname_len)
{
    CPUArchState *env G_GNUC_UNUSED = cs->env_ptr;
    char *ostr, *nstr;
    int ret;

    ret = validate_lock_user_string(&ostr, cs, oname, oname_len);
    if (ret < 0) {
        complete(cs, -1, -ret);
        return;
    }
    ret = validate_lock_user_string(&nstr, cs, nname, nname_len);
    if (ret < 0) {
        unlock_user(ostr, oname, 0);
        complete(cs, -1, -ret);
        return;
    }

    ret = rename(ostr, nstr);
    unlock_user(ostr, oname, 0);
    unlock_user(nstr, nname, 0);
    complete(cs, ret, ret ? errno : 0);
}

static void host_system(CPUState *cs, gdb_syscall_complete_cb complete,
                        target_ulong cmd, target_ulong cmd_len)
{
    CPUArchState *env G_GNUC_UNUSED = cs->env_ptr;
    char *p;
    int ret;

    ret = validate_lock_user_string(&p, cs, cmd, cmd_len);
    if (ret < 0) {
        complete(cs, -1, -ret);
        return;
    }

    ret = system(p);
    unlock_user(p, cmd, 0);
    complete(cs, ret, ret == -1 ? errno : 0);
}

static void host_gettimeofday(CPUState *cs, gdb_syscall_complete_cb complete,
                              target_ulong tv_addr, target_ulong tz_addr)
{
    CPUArchState *env G_GNUC_UNUSED = cs->env_ptr;
    struct gdb_timeval *p;
    int64_t rt;

    /* GDB fails on non-null TZ, so be consistent. */
    if (tz_addr != 0) {
        complete(cs, -1, EINVAL);
        return;
    }

    p = lock_user(VERIFY_WRITE, tv_addr, sizeof(struct gdb_timeval), 0);
    if (!p) {
        complete(cs, -1, EFAULT);
        return;
    }

    /* TODO: Like stat, gdb always produces big-endian results; match it. */
    rt = g_get_real_time();
    p->tv_sec = cpu_to_be32(rt / G_USEC_PER_SEC);
    p->tv_usec = cpu_to_be64(rt % G_USEC_PER_SEC);
    unlock_user(p, tv_addr, sizeof(struct gdb_timeval));
}

#ifndef CONFIG_USER_ONLY
static void host_poll_one(CPUState *cs, gdb_syscall_complete_cb complete,
                          GuestFD *gf, GIOCondition cond, int timeout)
{
    /*
     * Since this is only used by xtensa in system mode, and stdio is
     * handled through GuestFDConsole, and there are no semihosting
     * system calls for sockets and the like, that means this descriptor
     * must be a normal file.  Normal files never block and are thus
     * always ready.
     */
    complete(cs, cond & (G_IO_IN | G_IO_OUT), 0);
}
#endif

/*
 * Static file semihosting syscall implementations.
 */

static void staticfile_read(CPUState *cs, gdb_syscall_complete_cb complete,
                            GuestFD *gf, target_ulong buf, target_ulong len)
{
    CPUArchState *env G_GNUC_UNUSED = cs->env_ptr;
    target_ulong rest = gf->staticfile.len - gf->staticfile.off;
    void *ptr;

    if (len > rest) {
        len = rest;
    }
    ptr = lock_user(VERIFY_WRITE, buf, len, 0);
    if (!ptr) {
        complete(cs, -1, EFAULT);
        return;
    }
    memcpy(ptr, gf->staticfile.data + gf->staticfile.off, len);
    gf->staticfile.off += len;
    unlock_user(ptr, buf, len);
    complete(cs, len, 0);
}

static void staticfile_lseek(CPUState *cs, gdb_syscall_complete_cb complete,
                             GuestFD *gf, int64_t off, int gdb_whence)
{
    int64_t ret;

    switch (gdb_whence) {
    case GDB_SEEK_SET:
        ret = off;
        break;
    case GDB_SEEK_CUR:
        ret = gf->staticfile.off + off;
        break;
    case GDB_SEEK_END:
        ret = gf->staticfile.len + off;
        break;
    default:
        ret = -1;
        break;
    }
    if (ret >= 0 && ret <= gf->staticfile.len) {
        gf->staticfile.off = ret;
        complete(cs, ret, 0);
    } else {
        complete(cs, -1, EINVAL);
    }
}

static void staticfile_flen(CPUState *cs, gdb_syscall_complete_cb complete,
                            GuestFD *gf)
{
    complete(cs, gf->staticfile.len, 0);
}

/*
 * Console semihosting syscall implementations.
 */

static void console_read(CPUState *cs, gdb_syscall_complete_cb complete,
                         GuestFD *gf, target_ulong buf, target_ulong len)
{
    CPUArchState *env G_GNUC_UNUSED = cs->env_ptr;
    char *ptr;
    int ret;

    ptr = lock_user(VERIFY_WRITE, buf, len, 0);
    if (!ptr) {
        complete(cs, -1, EFAULT);
        return;
    }
    ret = qemu_semihosting_console_read(cs, ptr, len);
    unlock_user(ptr, buf, ret);
    complete(cs, ret, 0);
}

static void console_write(CPUState *cs, gdb_syscall_complete_cb complete,
                          GuestFD *gf, target_ulong buf, target_ulong len)
{
    CPUArchState *env G_GNUC_UNUSED = cs->env_ptr;
    char *ptr = lock_user(VERIFY_READ, buf, len, 1);
    int ret;

    if (!ptr) {
        complete(cs, -1, EFAULT);
        return;
    }
    ret = qemu_semihosting_console_write(ptr, len);
    unlock_user(ptr, buf, 0);
    complete(cs, ret ? ret : -1, ret ? 0 : EIO);
}

static void console_fstat(CPUState *cs, gdb_syscall_complete_cb complete,
                          GuestFD *gf, target_ulong addr)
{
    static const struct stat tty_buf = {
        .st_mode = 020666,  /* S_IFCHR, ugo+rw */
        .st_rdev = 5,       /* makedev(5, 0) -- linux /dev/tty */
    };
    int ret;

    ret = copy_stat_to_user(cs, addr, &tty_buf);
    complete(cs, ret ? -1 : 0, ret ? -ret : 0);
}

#ifndef CONFIG_USER_ONLY
static void console_poll_one(CPUState *cs, gdb_syscall_complete_cb complete,
                             GuestFD *gf, GIOCondition cond, int timeout)
{
    /* The semihosting console does not support urgent data or errors. */
    cond &= G_IO_IN | G_IO_OUT;

    /*
     * Since qemu_semihosting_console_write never blocks, we can
     * consider output always ready -- leave G_IO_OUT alone.
     * All that remains is to conditionally signal input ready.
     * Since output ready causes an immediate return, only block
     * for G_IO_IN alone.
     *
     * TODO: Implement proper timeout.  For now, only support
     * indefinite wait or immediate poll.
     */
    if (cond == G_IO_IN && timeout < 0) {
        qemu_semihosting_console_block_until_ready(cs);
        /* We returned -- input must be ready. */
    } else if ((cond & G_IO_IN) && !qemu_semihosting_console_ready()) {
        cond &= ~G_IO_IN;
    }

    complete(cs, cond, 0);
}
#endif

/*
 * Syscall entry points.
 */

void semihost_sys_open(CPUState *cs, gdb_syscall_complete_cb complete,
                       target_ulong fname, target_ulong fname_len,
                       int gdb_flags, int mode)
{
    if (use_gdb_syscalls()) {
        gdb_open(cs, complete, fname, fname_len, gdb_flags, mode);
    } else {
        host_open(cs, complete, fname, fname_len, gdb_flags, mode);
    }
}

void semihost_sys_close(CPUState *cs, gdb_syscall_complete_cb complete, int fd)
{
    GuestFD *gf = get_guestfd(fd);

    if (!gf) {
        complete(cs, -1, EBADF);
        return;
    }
    switch (gf->type) {
    case GuestFDGDB:
        gdb_close(cs, complete, gf);
        break;
    case GuestFDHost:
        host_close(cs, complete, gf);
        break;
    case GuestFDStatic:
    case GuestFDConsole:
        complete(cs, 0, 0);
        break;
    default:
        g_assert_not_reached();
    }
    dealloc_guestfd(fd);
}

void semihost_sys_read_gf(CPUState *cs, gdb_syscall_complete_cb complete,
                          GuestFD *gf, target_ulong buf, target_ulong len)
{
    /*
     * Bound length for 64-bit guests on 32-bit hosts, not overlowing ssize_t.
     * Note the Linux kernel does this with MAX_RW_COUNT, so it's not a bad
     * idea to do this unconditionally.
     */
    if (len > INT32_MAX) {
        len = INT32_MAX;
    }
    switch (gf->type) {
    case GuestFDGDB:
        gdb_read(cs, complete, gf, buf, len);
        break;
    case GuestFDHost:
        host_read(cs, complete, gf, buf, len);
        break;
    case GuestFDStatic:
        staticfile_read(cs, complete, gf, buf, len);
        break;
    case GuestFDConsole:
        console_read(cs, complete, gf, buf, len);
        break;
    default:
        g_assert_not_reached();
    }
}

void semihost_sys_read(CPUState *cs, gdb_syscall_complete_cb complete,
                       int fd, target_ulong buf, target_ulong len)
{
    GuestFD *gf = get_guestfd(fd);

    if (gf) {
        semihost_sys_read_gf(cs, complete, gf, buf, len);
    } else {
        complete(cs, -1, EBADF);
    }
}

void semihost_sys_write_gf(CPUState *cs, gdb_syscall_complete_cb complete,
                           GuestFD *gf, target_ulong buf, target_ulong len)
{
    /*
     * Bound length for 64-bit guests on 32-bit hosts, not overlowing ssize_t.
     * Note the Linux kernel does this with MAX_RW_COUNT, so it's not a bad
     * idea to do this unconditionally.
     */
    if (len > INT32_MAX) {
        len = INT32_MAX;
    }
    switch (gf->type) {
    case GuestFDGDB:
        gdb_write(cs, complete, gf, buf, len);
        break;
    case GuestFDHost:
        host_write(cs, complete, gf, buf, len);
        break;
    case GuestFDConsole:
        console_write(cs, complete, gf, buf, len);
        break;
    case GuestFDStatic:
        /* Static files are never open for writing: EBADF. */
        complete(cs, -1, EBADF);
        break;
    default:
        g_assert_not_reached();
    }
}

void semihost_sys_write(CPUState *cs, gdb_syscall_complete_cb complete,
                        int fd, target_ulong buf, target_ulong len)
{
    GuestFD *gf = get_guestfd(fd);

    if (gf) {
        semihost_sys_write_gf(cs, complete, gf, buf, len);
    } else {
        complete(cs, -1, EBADF);
    }
}

void semihost_sys_lseek(CPUState *cs, gdb_syscall_complete_cb complete,
                        int fd, int64_t off, int gdb_whence)
{
    GuestFD *gf = get_guestfd(fd);

    if (!gf) {
        complete(cs, -1, EBADF);
        return;
    }
    switch (gf->type) {
    case GuestFDGDB:
        gdb_lseek(cs, complete, gf, off, gdb_whence);
        return;
    case GuestFDHost:
        host_lseek(cs, complete, gf, off, gdb_whence);
        break;
    case GuestFDStatic:
        staticfile_lseek(cs, complete, gf, off, gdb_whence);
        break;
    case GuestFDConsole:
        complete(cs, -1, ESPIPE);
        break;
    default:
        g_assert_not_reached();
    }
}

void semihost_sys_isatty(CPUState *cs, gdb_syscall_complete_cb complete, int fd)
{
    GuestFD *gf = get_guestfd(fd);

    if (!gf) {
        complete(cs, 0, EBADF);
        return;
    }
    switch (gf->type) {
    case GuestFDGDB:
        gdb_isatty(cs, complete, gf);
        break;
    case GuestFDHost:
        host_isatty(cs, complete, gf);
        break;
    case GuestFDStatic:
        complete(cs, 0, ENOTTY);
        break;
    case GuestFDConsole:
        complete(cs, 1, 0);
        break;
    default:
        g_assert_not_reached();
    }
}

void semihost_sys_flen(CPUState *cs, gdb_syscall_complete_cb fstat_cb,
                       gdb_syscall_complete_cb flen_cb, int fd,
                       target_ulong fstat_addr)
{
    GuestFD *gf = get_guestfd(fd);

    if (!gf) {
        flen_cb(cs, -1, EBADF);
        return;
    }
    switch (gf->type) {
    case GuestFDGDB:
        gdb_fstat(cs, fstat_cb, gf, fstat_addr);
        break;
    case GuestFDHost:
        host_flen(cs, flen_cb, gf);
        break;
    case GuestFDStatic:
        staticfile_flen(cs, flen_cb, gf);
        break;
    case GuestFDConsole:
    default:
        g_assert_not_reached();
    }
}

void semihost_sys_fstat(CPUState *cs, gdb_syscall_complete_cb complete,
                        int fd, target_ulong addr)
{
    GuestFD *gf = get_guestfd(fd);

    if (!gf) {
        complete(cs, -1, EBADF);
        return;
    }
    switch (gf->type) {
    case GuestFDGDB:
        gdb_fstat(cs, complete, gf, addr);
        break;
    case GuestFDHost:
        host_fstat(cs, complete, gf, addr);
        break;
    case GuestFDConsole:
        console_fstat(cs, complete, gf, addr);
        break;
    case GuestFDStatic:
    default:
        g_assert_not_reached();
    }
}

void semihost_sys_stat(CPUState *cs, gdb_syscall_complete_cb complete,
                       target_ulong fname, target_ulong fname_len,
                       target_ulong addr)
{
    if (use_gdb_syscalls()) {
        gdb_stat(cs, complete, fname, fname_len, addr);
    } else {
        host_stat(cs, complete, fname, fname_len, addr);
    }
}

void semihost_sys_remove(CPUState *cs, gdb_syscall_complete_cb complete,
                         target_ulong fname, target_ulong fname_len)
{
    if (use_gdb_syscalls()) {
        gdb_remove(cs, complete, fname, fname_len);
    } else {
        host_remove(cs, complete, fname, fname_len);
    }
}

void semihost_sys_rename(CPUState *cs, gdb_syscall_complete_cb complete,
                         target_ulong oname, target_ulong oname_len,
                         target_ulong nname, target_ulong nname_len)
{
    if (use_gdb_syscalls()) {
        gdb_rename(cs, complete, oname, oname_len, nname, nname_len);
    } else {
        host_rename(cs, complete, oname, oname_len, nname, nname_len);
    }
}

void semihost_sys_system(CPUState *cs, gdb_syscall_complete_cb complete,
                         target_ulong cmd, target_ulong cmd_len)
{
    if (use_gdb_syscalls()) {
        gdb_system(cs, complete, cmd, cmd_len);
    } else {
        host_system(cs, complete, cmd, cmd_len);
    }
}

void semihost_sys_gettimeofday(CPUState *cs, gdb_syscall_complete_cb complete,
                               target_ulong tv_addr, target_ulong tz_addr)
{
    if (use_gdb_syscalls()) {
        gdb_gettimeofday(cs, complete, tv_addr, tz_addr);
    } else {
        host_gettimeofday(cs, complete, tv_addr, tz_addr);
    }
}

#ifndef CONFIG_USER_ONLY
void semihost_sys_poll_one(CPUState *cs, gdb_syscall_complete_cb complete,
                           int fd, GIOCondition cond, int timeout)
{
    GuestFD *gf = get_guestfd(fd);

    if (!gf) {
        complete(cs, G_IO_NVAL, 1);
        return;
    }
    switch (gf->type) {
    case GuestFDGDB:
        complete(cs, G_IO_NVAL, 1);
        break;
    case GuestFDHost:
        host_poll_one(cs, complete, gf, cond, timeout);
        break;
    case GuestFDConsole:
        console_poll_one(cs, complete, gf, cond, timeout);
        break;
    case GuestFDStatic:
    default:
        g_assert_not_reached();
    }
}
#endif