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      1 
      2 /*--------------------------------------------------------------------*/
      3 /*--- Support for doing system calls.        syscall-arm-linux.S ---*/
      4 /*--------------------------------------------------------------------*/
      5 
      6 /*
      7   This file is part of Valgrind, a dynamic binary instrumentation
      8   framework.
      9 
     10   Copyright (C) 2008-2017 Evan Geller (gaze (at) bea.ms)
     11 
     12   This program is free software; you can redistribute it and/or
     13   modify it under the terms of the GNU General Public License as
     14   published by the Free Software Foundation; either version 2 of the
     15   License, or (at your option) any later version.
     16 
     17   This program is distributed in the hope that it will be useful, but
     18   WITHOUT ANY WARRANTY; without even the implied warranty of
     19   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     20   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, write to the Free Software
     24   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
     25   02111-1307, USA.
     26 
     27   The GNU General Public License is contained in the file COPYING.
     28 */
     29 
     30 #include "pub_core_basics_asm.h"
     31 
     32 #if defined(VGP_arm_linux)
     33 
     34 #include "pub_core_vkiscnums_asm.h"
     35 #include "libvex_guest_offsets.h"
     36 
     37 
     38 /*----------------------------------------------------------------*/
     39 /*
     40         Perform a syscall for the client.  This will run a syscall
     41         with the client's specific per-thread signal mask.
     42 
     43         The structure of this function is such that, if the syscall is
     44         interrupted by a signal, we can determine exactly what
     45         execution state we were in with respect to the execution of
     46         the syscall by examining the value of IP in the signal
     47         handler.  This means that we can always do the appropriate
     48         thing to precisely emulate the kernel's signal/syscall
     49         interactions.
     50 
     51         The syscall number is taken from the argument, even though it
     52         should also be in regs->m_R7.  The syscall result is written
     53         back to regs->m_R0 on completion.
     54 
     55         Returns 0 if the syscall was successfully called (even if the
     56         syscall itself failed), or a nonzero error code in the lowest
     57         8 bits if one of the sigprocmasks failed (there's no way to
     58         determine which one failed).  And there's no obvious way to
     59         recover from that either, but nevertheless we want to know.
     60 
     61         VG_(fixup_guest_state_after_syscall_interrupted) does the
     62         thread state fixup in the case where we were interrupted by a
     63         signal.
     64 
     65         Prototype:
     66 
     67    UWord ML_(do_syscall_for_client_WRK)(
     68               Int syscallno,                 // r0
     69               void* guest_state,             // r1
     70               const vki_sigset_t *sysmask,   // r2
     71               const vki_sigset_t *postmask,  // r3
     72               Int nsigwords)                 // [sp, #0]
     73 */
     74 /* from vki_arch.h */
     75 #define VKI_SIG_SETMASK 2
     76 
     77 .globl ML_(do_syscall_for_client_WRK)
     78 ML_(do_syscall_for_client_WRK):
     79 
     80    /* Stash callee-saves and our args on the stack */
     81    push {r0, r1, r3, r4, r5, r7, fp, lr}
     82 
     83 1:
     84 
     85    mov r7, #__NR_rt_sigprocmask
     86    mov r0, #VKI_SIG_SETMASK
     87    mov r1, r2 /* sysmask */
     88    mov r2, r3 /* postmask */
     89    ldr r3, [sp, #32] /* nsigwords */
     90    svc 0x00000000
     91 
     92 
     93    ldr r5, [sp, #4] /* guest_state */
     94 
     95    ldr r7, [sp, #0] /* syscall# */
     96    ldr r0, [r5, #OFFSET_arm_R0]
     97    ldr r1, [r5, #OFFSET_arm_R1]
     98    ldr r2, [r5, #OFFSET_arm_R2]
     99    ldr r3, [r5, #OFFSET_arm_R3]
    100    ldr r4, [r5, #OFFSET_arm_R4]
    101    ldr r5, [r5, #OFFSET_arm_R5]
    102 
    103 2: svc 0x00000000
    104 3:
    105    ldr r5, [sp, #4] /* guest_state */
    106    str r0, [r5, #OFFSET_arm_R0]
    107 
    108 4:
    109    mov r7, #__NR_rt_sigprocmask
    110    mov r0, #VKI_SIG_SETMASK
    111    ldr r1, [sp, #8] /* postmask */
    112    mov r2, #0
    113    ldr r3, [sp, #32] /* nsigwords */
    114    svc 0x00000000
    115 
    116    cmp r0, #0
    117    blt 7f
    118    add sp, sp, #4 /* r0 contains return value */
    119 
    120 5: /* Success */
    121    mov r0, #0
    122    pop {r1, r3, r4, r5, r7, fp, pc}
    123 
    124 7: /* Failure: return 0x8000 | error code */
    125    orr r0, r0, #0x8000
    126    pop {r1, r3, r4, r5, r7, fp, pc}
    127 
    128 
    129 .section .rodata
    130 /* export the ranges so that
    131    VG_(fixup_guest_state_after_syscall_interrupted) can do the
    132    right thing */
    133 
    134 .globl ML_(blksys_setup)
    135 .globl ML_(blksys_restart)
    136 .globl ML_(blksys_complete)
    137 .globl ML_(blksys_committed)
    138 .globl ML_(blksys_finished)
    139 ML_(blksys_setup):      .long 1b
    140 ML_(blksys_restart):    .long 2b
    141 ML_(blksys_complete):   .long 3b
    142 ML_(blksys_committed):  .long 4b
    143 ML_(blksys_finished):   .long 5b
    144 
    145 #endif // defined(VGP_arm_linux)
    146 
    147 /* Let the linker know we don't need an executable stack */
    148 MARK_STACK_NO_EXEC
    149 
    150 /*--------------------------------------------------------------------*/
    151 /*--- end                                                          ---*/
    152 /*--------------------------------------------------------------------*/
    153