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      1 
      2 /*--------------------------------------------------------------------*/
      3 /*--- Support for doing system calls.          syscall-x86-linux.S ---*/
      4 /*--------------------------------------------------------------------*/
      5 
      6 /*
      7   This file is part of Valgrind, a dynamic binary instrumentation
      8   framework.
      9 
     10   Copyright (C) 2000-2012 Julian Seward
     11      jseward (at) acm.org
     12 
     13   This program is free software; you can redistribute it and/or
     14   modify it under the terms of the GNU General Public License as
     15   published by the Free Software Foundation; either version 2 of the
     16   License, or (at your option) any later version.
     17 
     18   This program is distributed in the hope that it will be useful, but
     19   WITHOUT ANY WARRANTY; without even the implied warranty of
     20   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     21   General Public License for more details.
     22 
     23   You should have received a copy of the GNU General Public License
     24   along with this program; if not, write to the Free Software
     25   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
     26   02111-1307, USA.
     27 
     28   The GNU General Public License is contained in the file COPYING.
     29 */
     30 
     31 #if defined(VGP_x86_linux)
     32 
     33 #include "pub_core_basics_asm.h"
     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 %eip 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_eax.  The syscall result is written
     53 	back to regs->m_eax 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,		// 0
     69 				  void* guest_state,		// 4
     70 				  const vki_sigset_t *sysmask,	// 8
     71 				  const vki_sigset_t *postmask,	// 12
     72 				  Int sigsetSzB)		// 16
     73 
     74 */
     75 
     76 /* from vki_arch.h */
     77 #define VKI_SIG_SETMASK	2
     78 
     79 .globl ML_(do_syscall_for_client_WRK)
     80 ML_(do_syscall_for_client_WRK):
     81 	/* save callee-saved regs */
     82 	push	%esi
     83 	push	%edi
     84 	push	%ebx
     85 	push	%ebp
     86 #define FSZ	((4+1)*4)	/* 4 args + ret addr */
     87 
     88 1:	/* Even though we can't take a signal until the sigprocmask completes,
     89 	   start the range early.
     90 	   If eip is in the range [1,2), the syscall hasn't been started yet */
     91 
     92 	/* Set the signal mask which should be current during the syscall. */
     93 	movl	$ __NR_rt_sigprocmask, %eax
     94 	movl	$ VKI_SIG_SETMASK, %ebx
     95 	movl	8+FSZ(%esp), %ecx
     96 	movl	12+FSZ(%esp), %edx
     97 	movl	16+FSZ(%esp), %esi
     98 	int	$0x80
     99 	testl	%eax, %eax
    100 	js	7f	/* sigprocmask failed */
    101 
    102 	movl	 4+FSZ(%esp), %eax	/* eax == ThreadState * */
    103 
    104 	movl	 OFFSET_x86_EBX(%eax), %ebx
    105 	movl	 OFFSET_x86_ECX(%eax), %ecx
    106 	movl	 OFFSET_x86_EDX(%eax), %edx
    107 	movl	 OFFSET_x86_ESI(%eax), %esi
    108 	movl	 OFFSET_x86_EDI(%eax), %edi
    109 	movl	 OFFSET_x86_EBP(%eax), %ebp
    110 	movl	 0+FSZ(%esp), %eax	/* use syscallno argument rather than thread EAX */
    111 
    112 	/* If eip==2, then the syscall was either just about to start,
    113 	   or was interrupted and the kernel was restarting it. */
    114 2:	int	$0x80
    115 3:	/* In the range [3, 4), the syscall result is in %eax, but hasn't been
    116 	   committed to EAX. */
    117 	movl	4+FSZ(%esp), %ebx
    118 	movl	%eax, OFFSET_x86_EAX(%ebx)	/* save back to EAX */
    119 
    120 4:	/* Re-block signals.  If eip is in [4,5), then the syscall is complete and
    121 	   we needn't worry about it. */
    122 	movl	$ __NR_rt_sigprocmask, %eax
    123 	movl	$ VKI_SIG_SETMASK, %ebx
    124 	movl	12+FSZ(%esp), %ecx
    125 	xorl	%edx, %edx
    126 	movl	16+FSZ(%esp), %esi
    127 	int	$0x80
    128 	testl	%eax, %eax
    129 	js	7f	/* sigprocmask failed */
    130 
    131 5:	/* now safe from signals */
    132 	movl	$0, %eax	/* SUCCESS */
    133 	popl	%ebp
    134 	popl	%ebx
    135 	popl	%edi
    136 	popl	%esi
    137 	ret
    138 
    139 7:	/* failure: return 0x8000 | error code */
    140 	negl	%eax
    141 	andl	$0x7FFF, %eax
    142 	orl	$0x8000, %eax
    143 	popl	%ebp
    144 	popl	%ebx
    145 	popl	%edi
    146 	popl	%esi
    147 	ret
    148 #undef FSZ
    149 
    150 
    151 .section .rodata
    152 /* export the ranges so that
    153    VG_(fixup_guest_state_after_syscall_interrupted) can do the
    154    right thing */
    155 
    156 .globl ML_(blksys_setup)
    157 .globl ML_(blksys_restart)
    158 .globl ML_(blksys_complete)
    159 .globl ML_(blksys_committed)
    160 .globl ML_(blksys_finished)
    161 ML_(blksys_setup):	.long 1b
    162 ML_(blksys_restart):	.long 2b
    163 ML_(blksys_complete):	.long 3b
    164 ML_(blksys_committed):	.long 4b
    165 ML_(blksys_finished):	.long 5b
    166 .previous
    167 
    168 /* Let the linker know we don't need an executable stack */
    169 .section .note.GNU-stack,"",@progbits
    170 
    171 #endif // defined(VGP_x86_linux)
    172 
    173 /*--------------------------------------------------------------------*/
    174 /*--- end                                                          ---*/
    175 /*--------------------------------------------------------------------*/
    176