semihosting/arm-compat-semi.c

   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 softmmu 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/softmmu-uaccess.h"
 212 #endif
 213
 214 static inline uint32_t get_swi_errno(CPUState *cs)
 215 {
 216 #ifdef CONFIG_USER_ONLY
 217     TaskState *ts = cs->opaque;
 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 = cs->opaque;
 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 = cs->env_ptr;
 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 = cs->env_ptr;
 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 = cs->env_ptr;
 365     target_ulong args;
 366     target_ulong arg0, arg1, arg2, arg3;
 367     target_ulong ul_ret;
 368     char * s;
 369     int nr;
 370     uint32_t ret;
 371     int64_t elapsed;
 372
 373     nr = common_semi_arg(cs, 0) & 0xffffffffU;
 374     args = common_semi_arg(cs, 1);
 375
 376     switch (nr) {
 377     case TARGET_SYS_OPEN:
 378     {
 379         int ret, err = 0;
 380         int hostfd;
 381
 382         GET_ARG(0);
 383         GET_ARG(1);
 384         GET_ARG(2);
 385         s = lock_user_string(arg0);
 386         if (!s) {
 387             goto do_fault;
 388         }
 389         if (arg1 >= 12) {
 390             unlock_user(s, arg0, 0);
 391             common_semi_cb(cs, -1, EINVAL);
 392             break;
 393         }
 394
 395         if (strcmp(s, ":tt") == 0) {
 396             /*
 397              * We implement SH_EXT_STDOUT_STDERR, so:
 398              *  open for read == stdin
 399              *  open for write == stdout
 400              *  open for append == stderr
 401              */
 402             if (arg1 < 4) {
 403                 hostfd = STDIN_FILENO;
 404             } else if (arg1 < 8) {
 405                 hostfd = STDOUT_FILENO;
 406             } else {
 407                 hostfd = STDERR_FILENO;
 408             }
 409             ret = alloc_guestfd();
 410             associate_guestfd(ret, hostfd);
 411         } else if (strcmp(s, ":semihosting-features") == 0) {
 412             /* We must fail opens for modes other than 0 ('r') or 1 ('rb') */
 413             if (arg1 != 0 && arg1 != 1) {
 414                 ret = -1;
 415                 err = EACCES;
 416             } else {
 417                 ret = alloc_guestfd();
 418                 staticfile_guestfd(ret, featurefile_data,
 419                                    sizeof(featurefile_data));
 420             }
 421         } else {
 422             unlock_user(s, arg0, 0);
 423             semihost_sys_open(cs, common_semi_cb, arg0, arg2 + 1,
 424                               gdb_open_modeflags[arg1], 0644);
 425             break;
 426         }
 427         unlock_user(s, arg0, 0);
 428         common_semi_cb(cs, ret, err);
 429         break;
 430     }
 431
 432     case TARGET_SYS_CLOSE:
 433         GET_ARG(0);
 434         semihost_sys_close(cs, common_semi_cb, arg0);
 435         break;
 436
 437     case TARGET_SYS_WRITEC:
 438         /*
 439          * FIXME: the byte to be written is in a target_ulong slot,
 440          * which means this is wrong for a big-endian guest.
 441          */
 442         semihost_sys_write_gf(cs, common_semi_dead_cb,
 443                               &console_out_gf, args, 1);
 444         break;
 445
 446     case TARGET_SYS_WRITE0:
 447         {
 448             ssize_t len = target_strlen(args);
 449             if (len < 0) {
 450                 common_semi_dead_cb(cs, -1, EFAULT);
 451             } else {
 452                 semihost_sys_write_gf(cs, common_semi_dead_cb,
 453                                       &console_out_gf, args, len);
 454             }
 455         }
 456         break;
 457
 458     case TARGET_SYS_WRITE:
 459         GET_ARG(0);
 460         GET_ARG(1);
 461         GET_ARG(2);
 462         semihost_sys_write(cs, common_semi_rw_cb, arg0, arg1, arg2);
 463         break;
 464
 465     case TARGET_SYS_READ:
 466         GET_ARG(0);
 467         GET_ARG(1);
 468         GET_ARG(2);
 469         semihost_sys_read(cs, common_semi_rw_cb, arg0, arg1, arg2);
 470         break;
 471
 472     case TARGET_SYS_READC:
 473         semihost_sys_read_gf(cs, common_semi_readc_cb, &console_in_gf,
 474                              common_semi_stack_bottom(cs) - 1, 1);
 475         break;
 476
 477     case TARGET_SYS_ISERROR:
 478         GET_ARG(0);
 479         common_semi_set_ret(cs, (target_long)arg0 < 0);
 480         break;
 481
 482     case TARGET_SYS_ISTTY:
 483         GET_ARG(0);
 484         semihost_sys_isatty(cs, common_semi_istty_cb, arg0);
 485         break;
 486
 487     case TARGET_SYS_SEEK:
 488         GET_ARG(0);
 489         GET_ARG(1);
 490         semihost_sys_lseek(cs, common_semi_seek_cb, arg0, arg1, GDB_SEEK_SET);
 491         break;
 492
 493     case TARGET_SYS_FLEN:
 494         GET_ARG(0);
 495         semihost_sys_flen(cs, common_semi_flen_fstat_cb, common_semi_cb,
 496                           arg0, common_semi_flen_buf(cs));
 497         break;
 498
 499     case TARGET_SYS_TMPNAM:
 500     {
 501         int len;
 502         char *p;
 503
 504         GET_ARG(0);
 505         GET_ARG(1);
 506         GET_ARG(2);
 507         len = asprintf(&s, "%s/qemu-%x%02x", g_get_tmp_dir(),
 508                        getpid(), (int)arg1 & 0xff);
 509         if (len < 0) {
 510             common_semi_set_ret(cs, -1);
 511             break;
 512         }
 513
 514         /* Allow for trailing NUL */
 515         len++;
 516         /* Make sure there's enough space in the buffer */
 517         if (len > arg2) {
 518             free(s);
 519             common_semi_set_ret(cs, -1);
 520             break;
 521         }
 522         p = lock_user(VERIFY_WRITE, arg0, len, 0);
 523         if (!p) {
 524             free(s);
 525             goto do_fault;
 526         }
 527         memcpy(p, s, len);
 528         unlock_user(p, arg0, len);
 529         free(s);
 530         common_semi_set_ret(cs, 0);
 531         break;
 532     }
 533
 534     case TARGET_SYS_REMOVE:
 535         GET_ARG(0);
 536         GET_ARG(1);
 537         semihost_sys_remove(cs, common_semi_cb, arg0, arg1 + 1);
 538         break;
 539
 540     case TARGET_SYS_RENAME:
 541         GET_ARG(0);
 542         GET_ARG(1);
 543         GET_ARG(2);
 544         GET_ARG(3);
 545         semihost_sys_rename(cs, common_semi_cb, arg0, arg1 + 1, arg2, arg3 + 1);
 546         break;
 547
 548     case TARGET_SYS_CLOCK:
 549         common_semi_set_ret(cs, clock() / (CLOCKS_PER_SEC / 100));
 550         break;
 551
 552     case TARGET_SYS_TIME:
 553         ul_ret = time(NULL);
 554         common_semi_cb(cs, ul_ret, ul_ret == -1 ? errno : 0);
 555         break;
 556
 557     case TARGET_SYS_SYSTEM:
 558         GET_ARG(0);
 559         GET_ARG(1);
 560         semihost_sys_system(cs, common_semi_cb, arg0, arg1 + 1);
 561         break;
 562
 563     case TARGET_SYS_ERRNO:
 564         common_semi_set_ret(cs, get_swi_errno(cs));
 565         break;
 566
 567     case TARGET_SYS_GET_CMDLINE:
 568         {
 569             /* Build a command-line from the original argv.
 570              *
 571              * The inputs are:
 572              *     * arg0, pointer to a buffer of at least the size
 573              *               specified in arg1.
 574              *     * arg1, size of the buffer pointed to by arg0 in
 575              *               bytes.
 576              *
 577              * The outputs are:
 578              *     * arg0, pointer to null-terminated string of the
 579              *               command line.
 580              *     * arg1, length of the string pointed to by arg0.
 581              */
 582
 583             char *output_buffer;
 584             size_t input_size;
 585             size_t output_size;
 586             int status = 0;
 587 #if !defined(CONFIG_USER_ONLY)
 588             const char *cmdline;
 589 #else
 590             TaskState *ts = cs->opaque;
 591 #endif
 592             GET_ARG(0);
 593             GET_ARG(1);
 594             input_size = arg1;
 595             /* Compute the size of the output string.  */
 596 #if !defined(CONFIG_USER_ONLY)
 597             cmdline = semihosting_get_cmdline();
 598             if (cmdline == NULL) {
 599                 cmdline = ""; /* Default to an empty line. */
 600             }
 601             output_size = strlen(cmdline) + 1; /* Count terminating 0. */
 602 #else
 603             unsigned int i;
 604
 605             output_size = ts->info->env_strings - ts->info->arg_strings;
 606             if (!output_size) {
 607                 /*
 608                  * We special-case the "empty command line" case (argc==0).
 609                  * Just provide the terminating 0.
 610                  */
 611                 output_size = 1;
 612             }
 613 #endif
 614
 615             if (output_size > input_size) {
 616                 /* Not enough space to store command-line arguments.  */
 617                 common_semi_cb(cs, -1, E2BIG);
 618                 break;
 619             }
 620
 621             /* Adjust the command-line length.  */
 622             if (SET_ARG(1, output_size - 1)) {
 623                 /* Couldn't write back to argument block */
 624                 goto do_fault;
 625             }
 626
 627             /* Lock the buffer on the ARM side.  */
 628             output_buffer = lock_user(VERIFY_WRITE, arg0, output_size, 0);
 629             if (!output_buffer) {
 630                 goto do_fault;
 631             }
 632
 633             /* Copy the command-line arguments.  */
 634 #if !defined(CONFIG_USER_ONLY)
 635             pstrcpy(output_buffer, output_size, cmdline);
 636 #else
 637             if (output_size == 1) {
 638                 /* Empty command-line.  */
 639                 output_buffer[0] = '\0';
 640                 goto out;
 641             }
 642
 643             if (copy_from_user(output_buffer, ts->info->arg_strings,
 644                                output_size)) {
 645                 unlock_user(output_buffer, arg0, 0);
 646                 goto do_fault;
 647             }
 648
 649             /* Separate arguments by white spaces.  */
 650             for (i = 0; i < output_size - 1; i++) {
 651                 if (output_buffer[i] == 0) {
 652                     output_buffer[i] = ' ';
 653                 }
 654             }
 655         out:
 656 #endif
 657             /* Unlock the buffer on the ARM side.  */
 658             unlock_user(output_buffer, arg0, output_size);
 659             common_semi_cb(cs, status, 0);
 660         }
 661         break;
 662
 663     case TARGET_SYS_HEAPINFO:
 664         {
 665             target_ulong retvals[4];
 666             int i;
 667 #ifdef CONFIG_USER_ONLY
 668             TaskState *ts = cs->opaque;
 669             target_ulong limit;
 670 #else
 671             LayoutInfo info = common_semi_find_bases(cs);
 672 #endif
 673
 674             GET_ARG(0);
 675
 676 #ifdef CONFIG_USER_ONLY
 677             /*
 678              * Some C libraries assume the heap immediately follows .bss, so
 679              * allocate it using sbrk.
 680              */
 681             if (!ts->heap_limit) {
 682                 abi_ulong ret;
 683
 684                 ts->heap_base = do_brk(0);
 685                 limit = ts->heap_base + COMMON_SEMI_HEAP_SIZE;
 686                 /* Try a big heap, and reduce the size if that fails.  */
 687                 for (;;) {
 688                     ret = do_brk(limit);
 689                     if (ret >= limit) {
 690                         break;
 691                     }
 692                     limit = (ts->heap_base >> 1) + (limit >> 1);
 693                 }
 694                 ts->heap_limit = limit;
 695             }
 696
 697             retvals[0] = ts->heap_base;
 698             retvals[1] = ts->heap_limit;
 699             retvals[2] = ts->stack_base;
 700             retvals[3] = 0; /* Stack limit.  */
 701 #else
 702             retvals[0] = info.heapbase;  /* Heap Base */
 703             retvals[1] = info.heaplimit; /* Heap Limit */
 704             retvals[2] = info.heaplimit; /* Stack base */
 705             retvals[3] = info.heapbase;  /* Stack limit.  */
 706 #endif
 707
 708             for (i = 0; i < ARRAY_SIZE(retvals); i++) {
 709                 bool fail;
 710
 711                 if (is_64bit_semihosting(env)) {
 712                     fail = put_user_u64(retvals[i], arg0 + i * 8);
 713                 } else {
 714                     fail = put_user_u32(retvals[i], arg0 + i * 4);
 715                 }
 716
 717                 if (fail) {
 718                     /* Couldn't write back to argument block */
 719                     goto do_fault;
 720                 }
 721             }
 722             common_semi_set_ret(cs, 0);
 723         }
 724         break;
 725
 726     case TARGET_SYS_EXIT:
 727     case TARGET_SYS_EXIT_EXTENDED:
 728         if (common_semi_sys_exit_extended(cs, nr)) {
 729             /*
 730              * The A64 version of SYS_EXIT takes a parameter block,
 731              * so the application-exit type can return a subcode which
 732              * is the exit status code from the application.
 733              * SYS_EXIT_EXTENDED is an a new-in-v2.0 optional function
 734              * which allows A32/T32 guests to also provide a status code.
 735              */
 736             GET_ARG(0);
 737             GET_ARG(1);
 738
 739             if (arg0 == ADP_Stopped_ApplicationExit) {
 740                 ret = arg1;
 741             } else {
 742                 ret = 1;
 743             }
 744         } else {
 745             /*
 746              * The A32/T32 version of SYS_EXIT specifies only
 747              * Stopped_ApplicationExit as normal exit, but does not
 748              * allow the guest to specify the exit status code.
 749              * Everything else is considered an error.
 750              */
 751             ret = (args == ADP_Stopped_ApplicationExit) ? 0 : 1;
 752         }
 753         gdb_exit(ret);
 754         exit(ret);
 755
 756     case TARGET_SYS_ELAPSED:
 757         elapsed = get_clock() - clock_start;
 758         if (sizeof(target_ulong) == 8) {
 759             if (SET_ARG(0, elapsed)) {
 760                 goto do_fault;
 761             }
 762         } else {
 763             if (SET_ARG(0, (uint32_t) elapsed) ||
 764                 SET_ARG(1, (uint32_t) (elapsed >> 32))) {
 765                 goto do_fault;
 766             }
 767         }
 768         common_semi_set_ret(cs, 0);
 769         break;
 770
 771     case TARGET_SYS_TICKFREQ:
 772         /* qemu always uses nsec */
 773         common_semi_set_ret(cs, 1000000000);
 774         break;
 775
 776     case TARGET_SYS_SYNCCACHE:
 777         /*
 778          * Clean the D-cache and invalidate the I-cache for the specified
 779          * virtual address range. This is a nop for us since we don't
 780          * implement caches. This is only present on A64.
 781          */
 782         if (common_semi_has_synccache(env)) {
 783             common_semi_set_ret(cs, 0);
 784             break;
 785         }
 786         /* fall through */
 787     default:
 788         fprintf(stderr, "qemu: Unsupported SemiHosting SWI 0x%02x\n", nr);
 789         cpu_dump_state(cs, stderr, 0);
 790         abort();
 791
 792     do_fault:
 793         common_semi_cb(cs, -1, EFAULT);
 794         break;
 795     }
 796 }