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) 2000-2013 Julian Seward
11     jseward@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)
80ML_(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
881:	/* 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. */
1142:	int	$0x80
1153:	/* 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
1204:	/* 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
1315:	/* now safe from signals */
132	movl	$0, %eax	/* SUCCESS */
133	popl	%ebp
134	popl	%ebx
135	popl	%edi
136	popl	%esi
137	ret
138
1397:	/* 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)
161ML_(blksys_setup):	.long 1b
162ML_(blksys_restart):	.long 2b
163ML_(blksys_complete):	.long 3b
164ML_(blksys_committed):	.long 4b
165ML_(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