1 /*
2  *  Semihosting support for systems modeled on the Arm "Angel"
3  *  semihosting syscalls design. This includes Arm and RISC-V processors
4  *
5  *  Copyright (c) 2005, 2007 CodeSourcery.
6  *  Copyright (c) 2019 Linaro
7  *  Written by Paul Brook.
8  *
9  *  Copyright © 2020 by Keith Packard <keithp@keithp.com>
10  *  Adapted for systems other than ARM, including RISC-V, by Keith Packard
11  *
12  *  This program is free software; you can redistribute it and/or modify
13  *  it under the terms of the GNU General Public License as published by
14  *  the Free Software Foundation; either version 2 of the License, or
15  *  (at your option) any later version.
16  *
17  *  This program is distributed in the hope that it will be useful,
18  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
19  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
20  *  GNU General Public License for more details.
21  *
22  *  You should have received a copy of the GNU General Public License
23  *  along with this program; if not, see <http://www.gnu.org/licenses/>.
24  *
25  *  ARM Semihosting is documented in:
26  *     Semihosting for AArch32 and AArch64 Release 2.0
27  *     https://github.com/ARM-software/abi-aa/blob/main/semihosting/semihosting.rst
28  *
29  *  RISC-V Semihosting is documented in:
30  *     RISC-V Semihosting
31  *     https://github.com/riscv/riscv-semihosting-spec/blob/main/riscv-semihosting-spec.adoc
32  */
33 
34 #include "qemu/osdep.h"
35 #include "qemu/timer.h"
36 #include "exec/gdbstub.h"
37 #include "gdbstub/syscalls.h"
38 #include "semihosting/semihost.h"
39 #include "semihosting/console.h"
40 #include "semihosting/common-semi.h"
41 #include "semihosting/guestfd.h"
42 #include "semihosting/syscalls.h"
43 
44 #ifdef CONFIG_USER_ONLY
45 #include "qemu.h"
46 
47 #define COMMON_SEMI_HEAP_SIZE (128 * 1024 * 1024)
48 #else
49 #include "qemu/cutils.h"
50 #include "hw/loader.h"
51 #include "hw/boards.h"
52 #endif
53 
54 #define TARGET_SYS_OPEN        0x01
55 #define TARGET_SYS_CLOSE       0x02
56 #define TARGET_SYS_WRITEC      0x03
57 #define TARGET_SYS_WRITE0      0x04
58 #define TARGET_SYS_WRITE       0x05
59 #define TARGET_SYS_READ        0x06
60 #define TARGET_SYS_READC       0x07
61 #define TARGET_SYS_ISERROR     0x08
62 #define TARGET_SYS_ISTTY       0x09
63 #define TARGET_SYS_SEEK        0x0a
64 #define TARGET_SYS_FLEN        0x0c
65 #define TARGET_SYS_TMPNAM      0x0d
66 #define TARGET_SYS_REMOVE      0x0e
67 #define TARGET_SYS_RENAME      0x0f
68 #define TARGET_SYS_CLOCK       0x10
69 #define TARGET_SYS_TIME        0x11
70 #define TARGET_SYS_SYSTEM      0x12
71 #define TARGET_SYS_ERRNO       0x13
72 #define TARGET_SYS_GET_CMDLINE 0x15
73 #define TARGET_SYS_HEAPINFO    0x16
74 #define TARGET_SYS_EXIT        0x18
75 #define TARGET_SYS_SYNCCACHE   0x19
76 #define TARGET_SYS_EXIT_EXTENDED 0x20
77 #define TARGET_SYS_ELAPSED     0x30
78 #define TARGET_SYS_TICKFREQ    0x31
79 
80 /* ADP_Stopped_ApplicationExit is used for exit(0),
81  * anything else is implemented as exit(1) */
82 #define ADP_Stopped_ApplicationExit     (0x20026)
83 
84 #ifndef O_BINARY
85 #define O_BINARY 0
86 #endif
87 
88 static int gdb_open_modeflags[12] = {
89     GDB_O_RDONLY,
90     GDB_O_RDONLY,
91     GDB_O_RDWR,
92     GDB_O_RDWR,
93     GDB_O_WRONLY | GDB_O_CREAT | GDB_O_TRUNC,
94     GDB_O_WRONLY | GDB_O_CREAT | GDB_O_TRUNC,
95     GDB_O_RDWR | GDB_O_CREAT | GDB_O_TRUNC,
96     GDB_O_RDWR | GDB_O_CREAT | GDB_O_TRUNC,
97     GDB_O_WRONLY | GDB_O_CREAT | GDB_O_APPEND,
98     GDB_O_WRONLY | GDB_O_CREAT | GDB_O_APPEND,
99     GDB_O_RDWR | GDB_O_CREAT | GDB_O_APPEND,
100     GDB_O_RDWR | GDB_O_CREAT | GDB_O_APPEND,
101 };
102 
103 #ifndef CONFIG_USER_ONLY
104 
105 /**
106  * common_semi_find_bases: find information about ram and heap base
107  *
108  * This function attempts to provide meaningful numbers for RAM and
109  * HEAP base addresses. The rambase is simply the lowest addressable
110  * RAM position. For the heapbase we ask the loader to scan the
111  * address space and the largest available gap by querying the "ROM"
112  * regions.
113  *
114  * Returns: a structure with the numbers we need.
115  */
116 
117 typedef struct LayoutInfo {
118     target_ulong rambase;
119     size_t ramsize;
120     hwaddr heapbase;
121     hwaddr heaplimit;
122 } LayoutInfo;
123 
124 static bool find_ram_cb(Int128 start, Int128 len, const MemoryRegion *mr,
125                         hwaddr offset_in_region, void *opaque)
126 {
127     LayoutInfo *info = (LayoutInfo *) opaque;
128     uint64_t size = int128_get64(len);
129 
130     if (!mr->ram || mr->readonly) {
131         return false;
132     }
133 
134     if (size > info->ramsize) {
135         info->rambase = int128_get64(start);
136         info->ramsize = size;
137     }
138 
139     /* search exhaustively for largest RAM */
140     return false;
141 }
142 
143 static LayoutInfo common_semi_find_bases(CPUState *cs)
144 {
145     FlatView *fv;
146     LayoutInfo info = { 0, 0, 0, 0 };
147 
148     RCU_READ_LOCK_GUARD();
149 
150     fv = address_space_to_flatview(cs->as);
151     flatview_for_each_range(fv, find_ram_cb, &info);
152 
153     /*
154      * If we have found the RAM lets iterate through the ROM blobs to
155      * work out the best place for the remainder of RAM and split it
156      * equally between stack and heap.
157      */
158     if (info.rambase || info.ramsize > 0) {
159         RomGap gap = rom_find_largest_gap_between(info.rambase, info.ramsize);
160         info.heapbase = gap.base;
161         info.heaplimit = gap.base + gap.size;
162     }
163 
164     return info;
165 }
166 
167 #endif
168 
169 #include "common-semi-target.h"
170 
171 /*
172  * Read the input value from the argument block; fail the semihosting
173  * call if the memory read fails. Eventually we could use a generic
174  * CPUState helper function here.
175  * Note that GET_ARG() handles memory access errors by jumping to
176  * do_fault, so must be used as the first thing done in handling a
177  * semihosting call, to avoid accidentally leaking allocated resources.
178  * SET_ARG(), since it unavoidably happens late, instead returns an
179  * error indication (0 on success, non-0 for error) which the caller
180  * should check.
181  */
182 
183 #define GET_ARG(n) do {                                 \
184     if (is_64bit_semihosting(env)) {                    \
185         if (get_user_u64(arg ## n, args + (n) * 8)) {   \
186             goto do_fault;                              \
187         }                                               \
188     } else {                                            \
189         if (get_user_u32(arg ## n, args + (n) * 4)) {   \
190             goto do_fault;                              \
191         }                                               \
192     }                                                   \
193 } while (0)
194 
195 #define SET_ARG(n, val)                                 \
196     (is_64bit_semihosting(env) ?                        \
197      put_user_u64(val, args + (n) * 8) :                \
198      put_user_u32(val, args + (n) * 4))
199 
200 
201 /*
202  * The semihosting API has no concept of its errno being thread-safe,
203  * as the API design predates SMP CPUs and was intended as a simple
204  * real-hardware set of debug functionality. For QEMU, we make the
205  * errno be per-thread in linux-user mode; in system-mode it is a simple
206  * global, and we assume that the guest takes care of avoiding any races.
207  */
208 #ifndef CONFIG_USER_ONLY
209 static target_ulong syscall_err;
210 
211 #include "semihosting/uaccess.h"
212 #endif
213 
214 static inline uint32_t get_swi_errno(CPUState *cs)
215 {
216 #ifdef CONFIG_USER_ONLY
217     TaskState *ts = get_task_state(cs);
218 
219     return ts->swi_errno;
220 #else
221     return syscall_err;
222 #endif
223 }
224 
225 static void common_semi_cb(CPUState *cs, uint64_t ret, int err)
226 {
227     if (err) {
228 #ifdef CONFIG_USER_ONLY
229         TaskState *ts = get_task_state(cs);
230         ts->swi_errno = err;
231 #else
232         syscall_err = err;
233 #endif
234     }
235     common_semi_set_ret(cs, ret);
236 }
237 
238 /*
239  * Use 0xdeadbeef as the return value when there isn't a defined
240  * return value for the call.
241  */
242 static void common_semi_dead_cb(CPUState *cs, uint64_t ret, int err)
243 {
244     common_semi_set_ret(cs, 0xdeadbeef);
245 }
246 
247 /*
248  * SYS_READ and SYS_WRITE always return the number of bytes not read/written.
249  * There is no error condition, other than returning the original length.
250  */
251 static void common_semi_rw_cb(CPUState *cs, uint64_t ret, int err)
252 {
253     /* Recover the original length from the third argument. */
254     CPUArchState *env G_GNUC_UNUSED = cpu_env(cs);
255     target_ulong args = common_semi_arg(cs, 1);
256     target_ulong arg2;
257     GET_ARG(2);
258 
259     if (err) {
260  do_fault:
261         ret = 0; /* error: no bytes transmitted */
262     }
263     common_semi_set_ret(cs, arg2 - ret);
264 }
265 
266 /*
267  * Convert from Posix ret+errno to Arm SYS_ISTTY return values.
268  * With gdbstub, err is only ever set for protocol errors to EIO.
269  */
270 static void common_semi_istty_cb(CPUState *cs, uint64_t ret, int err)
271 {
272     if (err) {
273         ret = (err == ENOTTY ? 0 : -1);
274     }
275     common_semi_cb(cs, ret, err);
276 }
277 
278 /*
279  * SYS_SEEK returns 0 on success, not the resulting offset.
280  */
281 static void common_semi_seek_cb(CPUState *cs, uint64_t ret, int err)
282 {
283     if (!err) {
284         ret = 0;
285     }
286     common_semi_cb(cs, ret, err);
287 }
288 
289 /*
290  * Return an address in target memory of 64 bytes where the remote
291  * gdb should write its stat struct. (The format of this structure
292  * is defined by GDB's remote protocol and is not target-specific.)
293  * We put this on the guest's stack just below SP.
294  */
295 static target_ulong common_semi_flen_buf(CPUState *cs)
296 {
297     target_ulong sp = common_semi_stack_bottom(cs);
298     return sp - 64;
299 }
300 
301 static void
302 common_semi_flen_fstat_cb(CPUState *cs, uint64_t ret, int err)
303 {
304     if (!err) {
305         /* The size is always stored in big-endian order, extract the value. */
306         uint64_t size;
307         if (cpu_memory_rw_debug(cs, common_semi_flen_buf(cs) +
308                                 offsetof(struct gdb_stat, gdb_st_size),
309                                 &size, 8, 0)) {
310             ret = -1, err = EFAULT;
311         } else {
312             size = be64_to_cpu(size);
313             if (ret != size) {
314                 ret = -1, err = EOVERFLOW;
315             }
316         }
317     }
318     common_semi_cb(cs, ret, err);
319 }
320 
321 static void
322 common_semi_readc_cb(CPUState *cs, uint64_t ret, int err)
323 {
324     if (!err) {
325         CPUArchState *env G_GNUC_UNUSED = cpu_env(cs);
326         uint8_t ch;
327 
328         if (get_user_u8(ch, common_semi_stack_bottom(cs) - 1)) {
329             ret = -1, err = EFAULT;
330         } else {
331             ret = ch;
332         }
333     }
334     common_semi_cb(cs, ret, err);
335 }
336 
337 #define SHFB_MAGIC_0 0x53
338 #define SHFB_MAGIC_1 0x48
339 #define SHFB_MAGIC_2 0x46
340 #define SHFB_MAGIC_3 0x42
341 
342 /* Feature bits reportable in feature byte 0 */
343 #define SH_EXT_EXIT_EXTENDED (1 << 0)
344 #define SH_EXT_STDOUT_STDERR (1 << 1)
345 
346 static const uint8_t featurefile_data[] = {
347     SHFB_MAGIC_0,
348     SHFB_MAGIC_1,
349     SHFB_MAGIC_2,
350     SHFB_MAGIC_3,
351     SH_EXT_EXIT_EXTENDED | SH_EXT_STDOUT_STDERR, /* Feature byte 0 */
352 };
353 
354 /*
355  * Do a semihosting call.
356  *
357  * The specification always says that the "return register" either
358  * returns a specific value or is corrupted, so we don't need to
359  * report to our caller whether we are returning a value or trying to
360  * leave the register unchanged.
361  */
362 void do_common_semihosting(CPUState *cs)
363 {
364     CPUArchState *env = cpu_env(cs);
365     target_ulong args;
366     target_ulong arg0, arg1, arg2, arg3;
367     target_ulong ul_ret;
368     char * s;
369     int nr;
370     int64_t elapsed;
371 
372     nr = common_semi_arg(cs, 0) & 0xffffffffU;
373     args = common_semi_arg(cs, 1);
374 
375     switch (nr) {
376     case TARGET_SYS_OPEN:
377     {
378         int ret, err = 0;
379         int hostfd;
380 
381         GET_ARG(0);
382         GET_ARG(1);
383         GET_ARG(2);
384         s = lock_user_string(arg0);
385         if (!s) {
386             goto do_fault;
387         }
388         if (arg1 >= 12) {
389             unlock_user(s, arg0, 0);
390             common_semi_cb(cs, -1, EINVAL);
391             break;
392         }
393 
394         if (strcmp(s, ":tt") == 0) {
395             /*
396              * We implement SH_EXT_STDOUT_STDERR, so:
397              *  open for read == stdin
398              *  open for write == stdout
399              *  open for append == stderr
400              */
401             if (arg1 < 4) {
402                 hostfd = STDIN_FILENO;
403             } else if (arg1 < 8) {
404                 hostfd = STDOUT_FILENO;
405             } else {
406                 hostfd = STDERR_FILENO;
407             }
408             ret = alloc_guestfd();
409             associate_guestfd(ret, hostfd);
410         } else if (strcmp(s, ":semihosting-features") == 0) {
411             /* We must fail opens for modes other than 0 ('r') or 1 ('rb') */
412             if (arg1 != 0 && arg1 != 1) {
413                 ret = -1;
414                 err = EACCES;
415             } else {
416                 ret = alloc_guestfd();
417                 staticfile_guestfd(ret, featurefile_data,
418                                    sizeof(featurefile_data));
419             }
420         } else {
421             unlock_user(s, arg0, 0);
422             semihost_sys_open(cs, common_semi_cb, arg0, arg2 + 1,
423                               gdb_open_modeflags[arg1], 0644);
424             break;
425         }
426         unlock_user(s, arg0, 0);
427         common_semi_cb(cs, ret, err);
428         break;
429     }
430 
431     case TARGET_SYS_CLOSE:
432         GET_ARG(0);
433         semihost_sys_close(cs, common_semi_cb, arg0);
434         break;
435 
436     case TARGET_SYS_WRITEC:
437         /*
438          * FIXME: the byte to be written is in a target_ulong slot,
439          * which means this is wrong for a big-endian guest.
440          */
441         semihost_sys_write_gf(cs, common_semi_dead_cb,
442                               &console_out_gf, args, 1);
443         break;
444 
445     case TARGET_SYS_WRITE0:
446         {
447             ssize_t len = target_strlen(args);
448             if (len < 0) {
449                 common_semi_dead_cb(cs, -1, EFAULT);
450             } else {
451                 semihost_sys_write_gf(cs, common_semi_dead_cb,
452                                       &console_out_gf, args, len);
453             }
454         }
455         break;
456 
457     case TARGET_SYS_WRITE:
458         GET_ARG(0);
459         GET_ARG(1);
460         GET_ARG(2);
461         semihost_sys_write(cs, common_semi_rw_cb, arg0, arg1, arg2);
462         break;
463 
464     case TARGET_SYS_READ:
465         GET_ARG(0);
466         GET_ARG(1);
467         GET_ARG(2);
468         semihost_sys_read(cs, common_semi_rw_cb, arg0, arg1, arg2);
469         break;
470 
471     case TARGET_SYS_READC:
472         semihost_sys_read_gf(cs, common_semi_readc_cb, &console_in_gf,
473                              common_semi_stack_bottom(cs) - 1, 1);
474         break;
475 
476     case TARGET_SYS_ISERROR:
477         GET_ARG(0);
478         common_semi_set_ret(cs, (target_long)arg0 < 0);
479         break;
480 
481     case TARGET_SYS_ISTTY:
482         GET_ARG(0);
483         semihost_sys_isatty(cs, common_semi_istty_cb, arg0);
484         break;
485 
486     case TARGET_SYS_SEEK:
487         GET_ARG(0);
488         GET_ARG(1);
489         semihost_sys_lseek(cs, common_semi_seek_cb, arg0, arg1, GDB_SEEK_SET);
490         break;
491 
492     case TARGET_SYS_FLEN:
493         GET_ARG(0);
494         semihost_sys_flen(cs, common_semi_flen_fstat_cb, common_semi_cb,
495                           arg0, common_semi_flen_buf(cs));
496         break;
497 
498     case TARGET_SYS_TMPNAM:
499     {
500         int len;
501         char *p;
502 
503         GET_ARG(0);
504         GET_ARG(1);
505         GET_ARG(2);
506         len = asprintf(&s, "%s/qemu-%x%02x", g_get_tmp_dir(),
507                        getpid(), (int)arg1 & 0xff);
508         if (len < 0) {
509             common_semi_set_ret(cs, -1);
510             break;
511         }
512 
513         /* Allow for trailing NUL */
514         len++;
515         /* Make sure there's enough space in the buffer */
516         if (len > arg2) {
517             free(s);
518             common_semi_set_ret(cs, -1);
519             break;
520         }
521         p = lock_user(VERIFY_WRITE, arg0, len, 0);
522         if (!p) {
523             free(s);
524             goto do_fault;
525         }
526         memcpy(p, s, len);
527         unlock_user(p, arg0, len);
528         free(s);
529         common_semi_set_ret(cs, 0);
530         break;
531     }
532 
533     case TARGET_SYS_REMOVE:
534         GET_ARG(0);
535         GET_ARG(1);
536         semihost_sys_remove(cs, common_semi_cb, arg0, arg1 + 1);
537         break;
538 
539     case TARGET_SYS_RENAME:
540         GET_ARG(0);
541         GET_ARG(1);
542         GET_ARG(2);
543         GET_ARG(3);
544         semihost_sys_rename(cs, common_semi_cb, arg0, arg1 + 1, arg2, arg3 + 1);
545         break;
546 
547     case TARGET_SYS_CLOCK:
548         common_semi_set_ret(cs, clock() / (CLOCKS_PER_SEC / 100));
549         break;
550 
551     case TARGET_SYS_TIME:
552         ul_ret = time(NULL);
553         common_semi_cb(cs, ul_ret, ul_ret == -1 ? errno : 0);
554         break;
555 
556     case TARGET_SYS_SYSTEM:
557         GET_ARG(0);
558         GET_ARG(1);
559         semihost_sys_system(cs, common_semi_cb, arg0, arg1 + 1);
560         break;
561 
562     case TARGET_SYS_ERRNO:
563         common_semi_set_ret(cs, get_swi_errno(cs));
564         break;
565 
566     case TARGET_SYS_GET_CMDLINE:
567         {
568             /* Build a command-line from the original argv.
569              *
570              * The inputs are:
571              *     * arg0, pointer to a buffer of at least the size
572              *               specified in arg1.
573              *     * arg1, size of the buffer pointed to by arg0 in
574              *               bytes.
575              *
576              * The outputs are:
577              *     * arg0, pointer to null-terminated string of the
578              *               command line.
579              *     * arg1, length of the string pointed to by arg0.
580              */
581 
582             char *output_buffer;
583             size_t input_size;
584             size_t output_size;
585             int status = 0;
586 #if !defined(CONFIG_USER_ONLY)
587             const char *cmdline;
588 #else
589             TaskState *ts = get_task_state(cs);
590 #endif
591             GET_ARG(0);
592             GET_ARG(1);
593             input_size = arg1;
594             /* Compute the size of the output string.  */
595 #if !defined(CONFIG_USER_ONLY)
596             cmdline = semihosting_get_cmdline();
597             if (cmdline == NULL) {
598                 cmdline = ""; /* Default to an empty line. */
599             }
600             output_size = strlen(cmdline) + 1; /* Count terminating 0. */
601 #else
602             unsigned int i;
603 
604             output_size = ts->info->env_strings - ts->info->arg_strings;
605             if (!output_size) {
606                 /*
607                  * We special-case the "empty command line" case (argc==0).
608                  * Just provide the terminating 0.
609                  */
610                 output_size = 1;
611             }
612 #endif
613 
614             if (output_size > input_size) {
615                 /* Not enough space to store command-line arguments.  */
616                 common_semi_cb(cs, -1, E2BIG);
617                 break;
618             }
619 
620             /* Adjust the command-line length.  */
621             if (SET_ARG(1, output_size - 1)) {
622                 /* Couldn't write back to argument block */
623                 goto do_fault;
624             }
625 
626             /* Lock the buffer on the ARM side.  */
627             output_buffer = lock_user(VERIFY_WRITE, arg0, output_size, 0);
628             if (!output_buffer) {
629                 goto do_fault;
630             }
631 
632             /* Copy the command-line arguments.  */
633 #if !defined(CONFIG_USER_ONLY)
634             pstrcpy(output_buffer, output_size, cmdline);
635 #else
636             if (output_size == 1) {
637                 /* Empty command-line.  */
638                 output_buffer[0] = '\0';
639                 goto out;
640             }
641 
642             if (copy_from_user(output_buffer, ts->info->arg_strings,
643                                output_size)) {
644                 unlock_user(output_buffer, arg0, 0);
645                 goto do_fault;
646             }
647 
648             /* Separate arguments by white spaces.  */
649             for (i = 0; i < output_size - 1; i++) {
650                 if (output_buffer[i] == 0) {
651                     output_buffer[i] = ' ';
652                 }
653             }
654         out:
655 #endif
656             /* Unlock the buffer on the ARM side.  */
657             unlock_user(output_buffer, arg0, output_size);
658             common_semi_cb(cs, status, 0);
659         }
660         break;
661 
662     case TARGET_SYS_HEAPINFO:
663         {
664             target_ulong retvals[4];
665             int i;
666 #ifdef CONFIG_USER_ONLY
667             TaskState *ts = get_task_state(cs);
668             target_ulong limit;
669 #else
670             LayoutInfo info = common_semi_find_bases(cs);
671 #endif
672 
673             GET_ARG(0);
674 
675 #ifdef CONFIG_USER_ONLY
676             /*
677              * Some C libraries assume the heap immediately follows .bss, so
678              * allocate it using sbrk.
679              */
680             if (!ts->heap_limit) {
681                 abi_ulong ret;
682 
683                 ts->heap_base = do_brk(0);
684                 limit = ts->heap_base + COMMON_SEMI_HEAP_SIZE;
685                 /* Try a big heap, and reduce the size if that fails.  */
686                 for (;;) {
687                     ret = do_brk(limit);
688                     if (ret >= limit) {
689                         break;
690                     }
691                     limit = (ts->heap_base >> 1) + (limit >> 1);
692                 }
693                 ts->heap_limit = limit;
694             }
695 
696             retvals[0] = ts->heap_base;
697             retvals[1] = ts->heap_limit;
698             retvals[2] = ts->stack_base;
699             retvals[3] = 0; /* Stack limit.  */
700 #else
701             retvals[0] = info.heapbase;  /* Heap Base */
702             retvals[1] = info.heaplimit; /* Heap Limit */
703             retvals[2] = info.heaplimit; /* Stack base */
704             retvals[3] = info.heapbase;  /* Stack limit.  */
705 #endif
706 
707             for (i = 0; i < ARRAY_SIZE(retvals); i++) {
708                 bool fail;
709 
710                 if (is_64bit_semihosting(env)) {
711                     fail = put_user_u64(retvals[i], arg0 + i * 8);
712                 } else {
713                     fail = put_user_u32(retvals[i], arg0 + i * 4);
714                 }
715 
716                 if (fail) {
717                     /* Couldn't write back to argument block */
718                     goto do_fault;
719                 }
720             }
721             common_semi_set_ret(cs, 0);
722         }
723         break;
724 
725     case TARGET_SYS_EXIT:
726     case TARGET_SYS_EXIT_EXTENDED:
727     {
728         uint32_t ret;
729 
730         if (common_semi_sys_exit_extended(cs, nr)) {
731             /*
732              * The A64 version of SYS_EXIT takes a parameter block,
733              * so the application-exit type can return a subcode which
734              * is the exit status code from the application.
735              * SYS_EXIT_EXTENDED is an a new-in-v2.0 optional function
736              * which allows A32/T32 guests to also provide a status code.
737              */
738             GET_ARG(0);
739             GET_ARG(1);
740 
741             if (arg0 == ADP_Stopped_ApplicationExit) {
742                 ret = arg1;
743             } else {
744                 ret = 1;
745             }
746         } else {
747             /*
748              * The A32/T32 version of SYS_EXIT specifies only
749              * Stopped_ApplicationExit as normal exit, but does not
750              * allow the guest to specify the exit status code.
751              * Everything else is considered an error.
752              */
753             ret = (args == ADP_Stopped_ApplicationExit) ? 0 : 1;
754         }
755         gdb_exit(ret);
756         exit(ret);
757     }
758 
759     case TARGET_SYS_ELAPSED:
760         elapsed = get_clock() - clock_start;
761         if (sizeof(target_ulong) == 8) {
762             if (SET_ARG(0, elapsed)) {
763                 goto do_fault;
764             }
765         } else {
766             if (SET_ARG(0, (uint32_t) elapsed) ||
767                 SET_ARG(1, (uint32_t) (elapsed >> 32))) {
768                 goto do_fault;
769             }
770         }
771         common_semi_set_ret(cs, 0);
772         break;
773 
774     case TARGET_SYS_TICKFREQ:
775         /* qemu always uses nsec */
776         common_semi_set_ret(cs, 1000000000);
777         break;
778 
779     case TARGET_SYS_SYNCCACHE:
780         /*
781          * Clean the D-cache and invalidate the I-cache for the specified
782          * virtual address range. This is a nop for us since we don't
783          * implement caches. This is only present on A64.
784          */
785         if (common_semi_has_synccache(env)) {
786             common_semi_set_ret(cs, 0);
787             break;
788         }
789         /* fall through */
790     default:
791         fprintf(stderr, "qemu: Unsupported SemiHosting SWI 0x%02x\n", nr);
792         cpu_dump_state(cs, stderr, 0);
793         abort();
794 
795     do_fault:
796         common_semi_cb(cs, -1, EFAULT);
797         break;
798     }
799 }
800