linux-user/arm/signal.c

   1 /*
   2  *  Emulation of Linux signals
   3  *
   4  *  Copyright (c) 2003 Fabrice Bellard
   5  *
   6  *  This program is free software; you can redistribute it and/or modify
   7  *  it under the terms of the GNU General Public License as published by
   8  *  the Free Software Foundation; either version 2 of the License, or
   9  *  (at your option) any later version.
  10  *
  11  *  This program is distributed in the hope that it will be useful,
  12  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  *  GNU General Public License for more details.
  15  *
  16  *  You should have received a copy of the GNU General Public License
  17  *  along with this program; if not, see <http://www.gnu.org/licenses/>.
  18  */
  19 #include "qemu/osdep.h"
  20 #include "qemu.h"
  21 #include "user-internals.h"
  22 #include "signal-common.h"
  23 #include "linux-user/trace.h"
  24 #include "target/arm/cpu-features.h"
  25 #include "vdso-asmoffset.h"
  26
  27 struct target_sigcontext {
  28     abi_ulong trap_no;
  29     abi_ulong error_code;
  30     abi_ulong oldmask;
  31     abi_ulong arm_r0;
  32     abi_ulong arm_r1;
  33     abi_ulong arm_r2;
  34     abi_ulong arm_r3;
  35     abi_ulong arm_r4;
  36     abi_ulong arm_r5;
  37     abi_ulong arm_r6;
  38     abi_ulong arm_r7;
  39     abi_ulong arm_r8;
  40     abi_ulong arm_r9;
  41     abi_ulong arm_r10;
  42     abi_ulong arm_fp;
  43     abi_ulong arm_ip;
  44     abi_ulong arm_sp;
  45     abi_ulong arm_lr;
  46     abi_ulong arm_pc;
  47     abi_ulong arm_cpsr;
  48     abi_ulong fault_address;
  49 };
  50
  51 struct target_ucontext {
  52     abi_ulong tuc_flags;
  53     abi_ulong tuc_link;
  54     target_stack_t tuc_stack;
  55     struct target_sigcontext tuc_mcontext;
  56     target_sigset_t  tuc_sigmask;       /* mask last for extensibility */
  57     char __unused[128 - sizeof(target_sigset_t)];
  58     abi_ulong tuc_regspace[128] __attribute__((__aligned__(8)));
  59 };
  60
  61 struct target_user_vfp {
  62     uint64_t fpregs[32];
  63     abi_ulong fpscr;
  64 };
  65
  66 struct target_user_vfp_exc {
  67     abi_ulong fpexc;
  68     abi_ulong fpinst;
  69     abi_ulong fpinst2;
  70 };
  71
  72 struct target_vfp_sigframe {
  73     abi_ulong magic;
  74     abi_ulong size;
  75     struct target_user_vfp ufp;
  76     struct target_user_vfp_exc ufp_exc;
  77 } __attribute__((__aligned__(8)));
  78
  79 struct target_iwmmxt_sigframe {
  80     abi_ulong magic;
  81     abi_ulong size;
  82     uint64_t regs[16];
  83     /* Note that not all the coprocessor control registers are stored here */
  84     uint32_t wcssf;
  85     uint32_t wcasf;
  86     uint32_t wcgr0;
  87     uint32_t wcgr1;
  88     uint32_t wcgr2;
  89     uint32_t wcgr3;
  90 } __attribute__((__aligned__(8)));
  91
  92 #define TARGET_VFP_MAGIC 0x56465001
  93 #define TARGET_IWMMXT_MAGIC 0x12ef842a
  94
  95 struct sigframe
  96 {
  97     struct target_ucontext uc;
  98     abi_ulong retcode[4];
  99 };
 100
 101 struct rt_sigframe
 102 {
 103     struct target_siginfo info;
 104     struct sigframe sig;
 105 };
 106
 107 QEMU_BUILD_BUG_ON(offsetof(struct sigframe, retcode[3])
 108                   != SIGFRAME_RC3_OFFSET);
 109 QEMU_BUILD_BUG_ON(offsetof(struct rt_sigframe, sig.retcode[3])
 110                   != RT_SIGFRAME_RC3_OFFSET);
 111
 112 static abi_ptr sigreturn_fdpic_tramp;
 113
 114 /*
 115  * Up to 3 words of 'retcode' in the sigframe are code,
 116  * with retcode[3] being used by fdpic for the function descriptor.
 117  * This code is not actually executed, but is retained for ABI compat.
 118  *
 119  * We will create a table of 8 retcode variants in the sigtramp page.
 120  * Let each table entry use 3 words.
 121  */
 122 #define RETCODE_WORDS  3
 123 #define RETCODE_BYTES  (RETCODE_WORDS * 4)
 124
 125 static inline int valid_user_regs(CPUARMState *regs)
 126 {
 127     return 1;
 128 }
 129
 130 static void
 131 setup_sigcontext(struct target_sigcontext *sc, /*struct _fpstate *fpstate,*/
 132                  CPUARMState *env, abi_ulong mask)
 133 {
 134     __put_user(env->regs[0], &sc->arm_r0);
 135     __put_user(env->regs[1], &sc->arm_r1);
 136     __put_user(env->regs[2], &sc->arm_r2);
 137     __put_user(env->regs[3], &sc->arm_r3);
 138     __put_user(env->regs[4], &sc->arm_r4);
 139     __put_user(env->regs[5], &sc->arm_r5);
 140     __put_user(env->regs[6], &sc->arm_r6);
 141     __put_user(env->regs[7], &sc->arm_r7);
 142     __put_user(env->regs[8], &sc->arm_r8);
 143     __put_user(env->regs[9], &sc->arm_r9);
 144     __put_user(env->regs[10], &sc->arm_r10);
 145     __put_user(env->regs[11], &sc->arm_fp);
 146     __put_user(env->regs[12], &sc->arm_ip);
 147     __put_user(env->regs[13], &sc->arm_sp);
 148     __put_user(env->regs[14], &sc->arm_lr);
 149     __put_user(env->regs[15], &sc->arm_pc);
 150     __put_user(cpsr_read(env), &sc->arm_cpsr);
 151
 152     __put_user(/* current->thread.trap_no */ 0, &sc->trap_no);
 153     __put_user(/* current->thread.error_code */ 0, &sc->error_code);
 154     __put_user(/* current->thread.address */ 0, &sc->fault_address);
 155     __put_user(mask, &sc->oldmask);
 156 }
 157
 158 static inline abi_ulong
 159 get_sigframe(struct target_sigaction *ka, CPUARMState *regs, int framesize)
 160 {
 161     unsigned long sp;
 162
 163     sp = target_sigsp(get_sp_from_cpustate(regs), ka);
 164     /*
 165      * ATPCS B01 mandates 8-byte alignment
 166      */
 167     return (sp - framesize) & ~7;
 168 }
 169
 170 static void write_arm_sigreturn(uint32_t *rc, int syscall);
 171 static void write_arm_fdpic_sigreturn(uint32_t *rc, int ofs);
 172
 173 static int
 174 setup_return(CPUARMState *env, struct target_sigaction *ka, int usig,
 175              struct sigframe *frame, abi_ulong sp_addr)
 176 {
 177     abi_ulong handler = 0;
 178     abi_ulong handler_fdpic_GOT = 0;
 179     abi_ulong retcode;
 180     bool is_fdpic = info_is_fdpic(get_task_state(thread_cpu)->info);
 181     bool is_rt = ka->sa_flags & TARGET_SA_SIGINFO;
 182     bool thumb;
 183
 184     if (is_fdpic) {
 185         /* In FDPIC mode, ka->_sa_handler points to a function
 186          * descriptor (FD). The first word contains the address of the
 187          * handler. The second word contains the value of the PIC
 188          * register (r9).  */
 189         abi_ulong funcdesc_ptr = ka->_sa_handler;
 190         if (get_user_ual(handler, funcdesc_ptr)
 191             || get_user_ual(handler_fdpic_GOT, funcdesc_ptr + 4)) {
 192             return 1;
 193         }
 194     } else {
 195         handler = ka->_sa_handler;
 196     }
 197     thumb = handler & 1;
 198
 199     uint32_t cpsr = cpsr_read(env);
 200
 201     cpsr &= ~CPSR_IT;
 202     if (thumb) {
 203         cpsr |= CPSR_T;
 204     } else {
 205         cpsr &= ~CPSR_T;
 206     }
 207     if (env->cp15.sctlr_el[1] & SCTLR_E0E) {
 208         cpsr |= CPSR_E;
 209     } else {
 210         cpsr &= ~CPSR_E;
 211     }
 212
 213     /* Our vdso default_sigreturn label is a table of entry points. */
 214     retcode = default_sigreturn + (is_fdpic * 2 + is_rt) * 8;
 215
 216     /*
 217      * Put the sigreturn code on the stack no matter which return
 218      * mechanism we use in order to remain ABI compliant.
 219      * Because this is about ABI, always use the A32 instructions,
 220      * despite the fact that our actual vdso trampoline is T16.
 221      */
 222     if (is_fdpic) {
 223         write_arm_fdpic_sigreturn(frame->retcode,
 224                                   is_rt ? RT_SIGFRAME_RC3_OFFSET
 225                                         : SIGFRAME_RC3_OFFSET);
 226     } else {
 227         write_arm_sigreturn(frame->retcode,
 228                             is_rt ? TARGET_NR_rt_sigreturn
 229                                   : TARGET_NR_sigreturn);
 230     }
 231
 232     if (ka->sa_flags & TARGET_SA_RESTORER) {
 233         if (is_fdpic) {
 234             /* Place the function descriptor in slot 3. */
 235             __put_user((abi_ulong)ka->sa_restorer, &frame->retcode[3]);
 236         } else {
 237             retcode = ka->sa_restorer;
 238         }
 239     }
 240
 241     env->regs[0] = usig;
 242     if (is_fdpic) {
 243         env->regs[9] = handler_fdpic_GOT;
 244     }
 245     env->regs[13] = sp_addr;
 246     env->regs[14] = retcode;
 247     env->regs[15] = handler & (thumb ? ~1 : ~3);
 248     cpsr_write(env, cpsr, CPSR_IT | CPSR_T | CPSR_E, CPSRWriteByInstr);
 249
 250     return 0;
 251 }
 252
 253 static abi_ulong *setup_sigframe_vfp(abi_ulong *regspace, CPUARMState *env)
 254 {
 255     int i;
 256     struct target_vfp_sigframe *vfpframe;
 257     vfpframe = (struct target_vfp_sigframe *)regspace;
 258     __put_user(TARGET_VFP_MAGIC, &vfpframe->magic);
 259     __put_user(sizeof(*vfpframe), &vfpframe->size);
 260     for (i = 0; i < 32; i++) {
 261         __put_user(*aa32_vfp_dreg(env, i), &vfpframe->ufp.fpregs[i]);
 262     }
 263     __put_user(vfp_get_fpscr(env), &vfpframe->ufp.fpscr);
 264     __put_user(env->vfp.xregs[ARM_VFP_FPEXC], &vfpframe->ufp_exc.fpexc);
 265     __put_user(env->vfp.xregs[ARM_VFP_FPINST], &vfpframe->ufp_exc.fpinst);
 266     __put_user(env->vfp.xregs[ARM_VFP_FPINST2], &vfpframe->ufp_exc.fpinst2);
 267     return (abi_ulong*)(vfpframe+1);
 268 }
 269
 270 static abi_ulong *setup_sigframe_iwmmxt(abi_ulong *regspace, CPUARMState *env)
 271 {
 272     int i;
 273     struct target_iwmmxt_sigframe *iwmmxtframe;
 274     iwmmxtframe = (struct target_iwmmxt_sigframe *)regspace;
 275     __put_user(TARGET_IWMMXT_MAGIC, &iwmmxtframe->magic);
 276     __put_user(sizeof(*iwmmxtframe), &iwmmxtframe->size);
 277     for (i = 0; i < 16; i++) {
 278         __put_user(env->iwmmxt.regs[i], &iwmmxtframe->regs[i]);
 279     }
 280     __put_user(env->vfp.xregs[ARM_IWMMXT_wCSSF], &iwmmxtframe->wcssf);
 281     __put_user(env->vfp.xregs[ARM_IWMMXT_wCASF], &iwmmxtframe->wcssf);
 282     __put_user(env->vfp.xregs[ARM_IWMMXT_wCGR0], &iwmmxtframe->wcgr0);
 283     __put_user(env->vfp.xregs[ARM_IWMMXT_wCGR1], &iwmmxtframe->wcgr1);
 284     __put_user(env->vfp.xregs[ARM_IWMMXT_wCGR2], &iwmmxtframe->wcgr2);
 285     __put_user(env->vfp.xregs[ARM_IWMMXT_wCGR3], &iwmmxtframe->wcgr3);
 286     return (abi_ulong*)(iwmmxtframe+1);
 287 }
 288
 289 static void setup_sigframe(struct target_ucontext *uc,
 290                            target_sigset_t *set, CPUARMState *env)
 291 {
 292     struct target_sigaltstack stack;
 293     int i;
 294     abi_ulong *regspace;
 295
 296     /* Clear all the bits of the ucontext we don't use.  */
 297     memset(uc, 0, offsetof(struct target_ucontext, tuc_mcontext));
 298
 299     memset(&stack, 0, sizeof(stack));
 300     target_save_altstack(&stack, env);
 301     memcpy(&uc->tuc_stack, &stack, sizeof(stack));
 302
 303     setup_sigcontext(&uc->tuc_mcontext, env, set->sig[0]);
 304     /* Save coprocessor signal frame.  */
 305     regspace = uc->tuc_regspace;
 306     if (cpu_isar_feature(aa32_vfp_simd, env_archcpu(env))) {
 307         regspace = setup_sigframe_vfp(regspace, env);
 308     }
 309     if (arm_feature(env, ARM_FEATURE_IWMMXT)) {
 310         regspace = setup_sigframe_iwmmxt(regspace, env);
 311     }
 312
 313     /* Write terminating magic word */
 314     __put_user(0, regspace);
 315
 316     for(i = 0; i < TARGET_NSIG_WORDS; i++) {
 317         __put_user(set->sig[i], &uc->tuc_sigmask.sig[i]);
 318     }
 319 }
 320
 321 void setup_frame(int usig, struct target_sigaction *ka,
 322                  target_sigset_t *set, CPUARMState *regs)
 323 {
 324     struct sigframe *frame;
 325     abi_ulong frame_addr = get_sigframe(ka, regs, sizeof(*frame));
 326
 327     trace_user_setup_frame(regs, frame_addr);
 328     if (!lock_user_struct(VERIFY_WRITE, frame, frame_addr, 0)) {
 329         goto sigsegv;
 330     }
 331
 332     setup_sigframe(&frame->uc, set, regs);
 333
 334     if (setup_return(regs, ka, usig, frame, frame_addr)) {
 335         goto sigsegv;
 336     }
 337
 338     unlock_user_struct(frame, frame_addr, 1);
 339     return;
 340 sigsegv:
 341     unlock_user_struct(frame, frame_addr, 1);
 342     force_sigsegv(usig);
 343 }
 344
 345 void setup_rt_frame(int usig, struct target_sigaction *ka,
 346                     target_siginfo_t *info,
 347                     target_sigset_t *set, CPUARMState *env)
 348 {
 349     struct rt_sigframe *frame;
 350     abi_ulong frame_addr = get_sigframe(ka, env, sizeof(*frame));
 351     abi_ulong info_addr, uc_addr;
 352
 353     trace_user_setup_rt_frame(env, frame_addr);
 354     if (!lock_user_struct(VERIFY_WRITE, frame, frame_addr, 0)) {
 355         goto sigsegv;
 356     }
 357
 358     info_addr = frame_addr + offsetof(struct rt_sigframe, info);
 359     uc_addr = frame_addr + offsetof(struct rt_sigframe, sig.uc);
 360     frame->info = *info;
 361
 362     setup_sigframe(&frame->sig.uc, set, env);
 363
 364     if (setup_return(env, ka, usig, &frame->sig, frame_addr)) {
 365         goto sigsegv;
 366     }
 367
 368     env->regs[1] = info_addr;
 369     env->regs[2] = uc_addr;
 370
 371     unlock_user_struct(frame, frame_addr, 1);
 372     return;
 373 sigsegv:
 374     unlock_user_struct(frame, frame_addr, 1);
 375     force_sigsegv(usig);
 376 }
 377
 378 static int
 379 restore_sigcontext(CPUARMState *env, struct target_sigcontext *sc)
 380 {
 381     int err = 0;
 382     uint32_t cpsr;
 383
 384     __get_user(env->regs[0], &sc->arm_r0);
 385     __get_user(env->regs[1], &sc->arm_r1);
 386     __get_user(env->regs[2], &sc->arm_r2);
 387     __get_user(env->regs[3], &sc->arm_r3);
 388     __get_user(env->regs[4], &sc->arm_r4);
 389     __get_user(env->regs[5], &sc->arm_r5);
 390     __get_user(env->regs[6], &sc->arm_r6);
 391     __get_user(env->regs[7], &sc->arm_r7);
 392     __get_user(env->regs[8], &sc->arm_r8);
 393     __get_user(env->regs[9], &sc->arm_r9);
 394     __get_user(env->regs[10], &sc->arm_r10);
 395     __get_user(env->regs[11], &sc->arm_fp);
 396     __get_user(env->regs[12], &sc->arm_ip);
 397     __get_user(env->regs[13], &sc->arm_sp);
 398     __get_user(env->regs[14], &sc->arm_lr);
 399     __get_user(env->regs[15], &sc->arm_pc);
 400     __get_user(cpsr, &sc->arm_cpsr);
 401     cpsr_write(env, cpsr, CPSR_USER | CPSR_EXEC, CPSRWriteByInstr);
 402
 403     err |= !valid_user_regs(env);
 404
 405     return err;
 406 }
 407
 408 static abi_ulong *restore_sigframe_vfp(CPUARMState *env, abi_ulong *regspace)
 409 {
 410     int i;
 411     abi_ulong magic, sz;
 412     uint32_t fpscr, fpexc;
 413     struct target_vfp_sigframe *vfpframe;
 414     vfpframe = (struct target_vfp_sigframe *)regspace;
 415
 416     __get_user(magic, &vfpframe->magic);
 417     __get_user(sz, &vfpframe->size);
 418     if (magic != TARGET_VFP_MAGIC || sz != sizeof(*vfpframe)) {
 419         return 0;
 420     }
 421     for (i = 0; i < 32; i++) {
 422         __get_user(*aa32_vfp_dreg(env, i), &vfpframe->ufp.fpregs[i]);
 423     }
 424     __get_user(fpscr, &vfpframe->ufp.fpscr);
 425     vfp_set_fpscr(env, fpscr);
 426     __get_user(fpexc, &vfpframe->ufp_exc.fpexc);
 427     /* Sanitise FPEXC: ensure VFP is enabled, FPINST2 is invalid
 428      * and the exception flag is cleared
 429      */
 430     fpexc |= (1 << 30);
 431     fpexc &= ~((1 << 31) | (1 << 28));
 432     env->vfp.xregs[ARM_VFP_FPEXC] = fpexc;
 433     __get_user(env->vfp.xregs[ARM_VFP_FPINST], &vfpframe->ufp_exc.fpinst);
 434     __get_user(env->vfp.xregs[ARM_VFP_FPINST2], &vfpframe->ufp_exc.fpinst2);
 435     return (abi_ulong*)(vfpframe + 1);
 436 }
 437
 438 static abi_ulong *restore_sigframe_iwmmxt(CPUARMState *env,
 439                                           abi_ulong *regspace)
 440 {
 441     int i;
 442     abi_ulong magic, sz;
 443     struct target_iwmmxt_sigframe *iwmmxtframe;
 444     iwmmxtframe = (struct target_iwmmxt_sigframe *)regspace;
 445
 446     __get_user(magic, &iwmmxtframe->magic);
 447     __get_user(sz, &iwmmxtframe->size);
 448     if (magic != TARGET_IWMMXT_MAGIC || sz != sizeof(*iwmmxtframe)) {
 449         return 0;
 450     }
 451     for (i = 0; i < 16; i++) {
 452         __get_user(env->iwmmxt.regs[i], &iwmmxtframe->regs[i]);
 453     }
 454     __get_user(env->vfp.xregs[ARM_IWMMXT_wCSSF], &iwmmxtframe->wcssf);
 455     __get_user(env->vfp.xregs[ARM_IWMMXT_wCASF], &iwmmxtframe->wcssf);
 456     __get_user(env->vfp.xregs[ARM_IWMMXT_wCGR0], &iwmmxtframe->wcgr0);
 457     __get_user(env->vfp.xregs[ARM_IWMMXT_wCGR1], &iwmmxtframe->wcgr1);
 458     __get_user(env->vfp.xregs[ARM_IWMMXT_wCGR2], &iwmmxtframe->wcgr2);
 459     __get_user(env->vfp.xregs[ARM_IWMMXT_wCGR3], &iwmmxtframe->wcgr3);
 460     return (abi_ulong*)(iwmmxtframe + 1);
 461 }
 462
 463 static int do_sigframe_return(CPUARMState *env,
 464                               target_ulong context_addr,
 465                               struct target_ucontext *uc)
 466 {
 467     sigset_t host_set;
 468     abi_ulong *regspace;
 469
 470     target_to_host_sigset(&host_set, &uc->tuc_sigmask);
 471     set_sigmask(&host_set);
 472
 473     if (restore_sigcontext(env, &uc->tuc_mcontext)) {
 474         return 1;
 475     }
 476
 477     /* Restore coprocessor signal frame */
 478     regspace = uc->tuc_regspace;
 479     if (cpu_isar_feature(aa32_vfp_simd, env_archcpu(env))) {
 480         regspace = restore_sigframe_vfp(env, regspace);
 481         if (!regspace) {
 482             return 1;
 483         }
 484     }
 485     if (arm_feature(env, ARM_FEATURE_IWMMXT)) {
 486         regspace = restore_sigframe_iwmmxt(env, regspace);
 487         if (!regspace) {
 488             return 1;
 489         }
 490     }
 491
 492     target_restore_altstack(&uc->tuc_stack, env);
 493
 494 #if 0
 495     /* Send SIGTRAP if we're single-stepping */
 496     if (ptrace_cancel_bpt(current))
 497         send_sig(SIGTRAP, current, 1);
 498 #endif
 499
 500     return 0;
 501 }
 502
 503 long do_sigreturn(CPUARMState *env)
 504 {
 505     abi_ulong frame_addr;
 506     struct sigframe *frame = NULL;
 507
 508     /*
 509      * Since we stacked the signal on a 64-bit boundary,
 510      * then 'sp' should be word aligned here.  If it's
 511      * not, then the user is trying to mess with us.
 512      */
 513     frame_addr = env->regs[13];
 514     trace_user_do_sigreturn(env, frame_addr);
 515     if (frame_addr & 7) {
 516         goto badframe;
 517     }
 518
 519     if (!lock_user_struct(VERIFY_READ, frame, frame_addr, 1)) {
 520         goto badframe;
 521     }
 522
 523     if (do_sigframe_return(env,
 524                            frame_addr + offsetof(struct sigframe, uc),
 525                            &frame->uc)) {
 526         goto badframe;
 527     }
 528
 529     unlock_user_struct(frame, frame_addr, 0);
 530     return -QEMU_ESIGRETURN;
 531
 532 badframe:
 533     unlock_user_struct(frame, frame_addr, 0);
 534     force_sig(TARGET_SIGSEGV);
 535     return -QEMU_ESIGRETURN;
 536 }
 537
 538 long do_rt_sigreturn(CPUARMState *env)
 539 {
 540     abi_ulong frame_addr;
 541     struct rt_sigframe *frame = NULL;
 542
 543     /*
 544      * Since we stacked the signal on a 64-bit boundary,
 545      * then 'sp' should be word aligned here.  If it's
 546      * not, then the user is trying to mess with us.
 547      */
 548     frame_addr = env->regs[13];
 549     trace_user_do_rt_sigreturn(env, frame_addr);
 550     if (frame_addr & 7) {
 551         goto badframe;
 552     }
 553
 554     if (!lock_user_struct(VERIFY_READ, frame, frame_addr, 1)) {
 555         goto badframe;
 556     }
 557
 558     if (do_sigframe_return(env,
 559                            frame_addr + offsetof(struct rt_sigframe, sig.uc),
 560                            &frame->sig.uc)) {
 561         goto badframe;
 562     }
 563
 564     unlock_user_struct(frame, frame_addr, 0);
 565     return -QEMU_ESIGRETURN;
 566
 567 badframe:
 568     unlock_user_struct(frame, frame_addr, 0);
 569     force_sig(TARGET_SIGSEGV);
 570     return -QEMU_ESIGRETURN;
 571 }
 572
 573 /*
 574  * EABI syscalls pass the number via r7.
 575  * Note that the kernel still adds the OABI syscall number to the trap,
 576  * presumably for backward ABI compatibility with unwinders.
 577  */
 578 #define ARM_MOV_R7_IMM(X)       (0xe3a07000 | (X))
 579 #define ARM_SWI_SYS(X)          (0xef000000 | (X) | ARM_SYSCALL_BASE)
 580
 581 #define THUMB_MOVS_R7_IMM(X)    (0x2700 | (X))
 582 #define THUMB_SWI_SYS           0xdf00
 583
 584 static void write_arm_sigreturn(uint32_t *rc, int syscall)
 585 {
 586     __put_user(ARM_MOV_R7_IMM(syscall), rc);
 587     __put_user(ARM_SWI_SYS(syscall), rc + 1);
 588     /* Wrote 8 of 12 bytes */
 589 }
 590
 591 static void write_thm_sigreturn(uint32_t *rc, int syscall)
 592 {
 593     __put_user(THUMB_SWI_SYS << 16 | THUMB_MOVS_R7_IMM(syscall), rc);
 594     /* Wrote 4 of 12 bytes */
 595 }
 596
 597 /*
 598  * Stub needed to make sure the FD register (r9) contains the right value.
 599  * Use the same instruction sequence as the kernel.
 600  */
 601 static void write_arm_fdpic_sigreturn(uint32_t *rc, int ofs)
 602 {
 603     assert(ofs <= 0xfff);
 604     __put_user(0xe59d3000 | ofs, rc + 0);   /* ldr r3, [sp, #ofs] */
 605     __put_user(0xe8930908, rc + 1);         /* ldm r3, { r3, r9 } */
 606     __put_user(0xe12fff13, rc + 2);         /* bx  r3 */
 607     /* Wrote 12 of 12 bytes */
 608 }
 609
 610 static void write_thm_fdpic_sigreturn(void *vrc, int ofs)
 611 {
 612     uint16_t *rc = vrc;
 613
 614     assert((ofs & ~0x3fc) == 0);
 615     __put_user(0x9b00 | (ofs >> 2), rc + 0);      /* ldr r3, [sp, #ofs] */
 616     __put_user(0xcb0c, rc + 1);                   /* ldm r3, { r2, r3 } */
 617     __put_user(0x4699, rc + 2);                   /* mov r9, r3 */
 618     __put_user(0x4710, rc + 3);                   /* bx  r2 */
 619     /* Wrote 8 of 12 bytes */
 620 }
 621
 622 void setup_sigtramp(abi_ulong sigtramp_page)
 623 {
 624     uint32_t total_size = 8 * RETCODE_BYTES;
 625     uint32_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, total_size, 0);
 626
 627     assert(tramp != NULL);
 628
 629     default_sigreturn = sigtramp_page;
 630     write_arm_sigreturn(&tramp[0 * RETCODE_WORDS], TARGET_NR_sigreturn);
 631     write_thm_sigreturn(&tramp[1 * RETCODE_WORDS], TARGET_NR_sigreturn);
 632     write_arm_sigreturn(&tramp[2 * RETCODE_WORDS], TARGET_NR_rt_sigreturn);
 633     write_thm_sigreturn(&tramp[3 * RETCODE_WORDS], TARGET_NR_rt_sigreturn);
 634
 635     sigreturn_fdpic_tramp = sigtramp_page + 4 * RETCODE_BYTES;
 636     write_arm_fdpic_sigreturn(tramp + 4 * RETCODE_WORDS,
 637                               offsetof(struct sigframe, retcode[3]));
 638     write_thm_fdpic_sigreturn(tramp + 5 * RETCODE_WORDS,
 639                                 offsetof(struct sigframe, retcode[3]));
 640     write_arm_fdpic_sigreturn(tramp + 6 * RETCODE_WORDS,
 641                               offsetof(struct rt_sigframe, sig.retcode[3]));
 642     write_thm_fdpic_sigreturn(tramp + 7 * RETCODE_WORDS,
 643                               offsetof(struct rt_sigframe, sig.retcode[3]));
 644
 645     unlock_user(tramp, sigtramp_page, total_size);
 646 }