Restartable sequences: powerpc architecture support
[deliverable/linux.git] / arch / powerpc / kernel / signal.c
1 /*
2 * Common signal handling code for both 32 and 64 bits
3 *
4 * Copyright (c) 2007 Benjamin Herrenschmidt, IBM Corporation
5 * Extracted from signal_32.c and signal_64.c
6 *
7 * This file is subject to the terms and conditions of the GNU General
8 * Public License. See the file README.legal in the main directory of
9 * this archive for more details.
10 */
11
12 #include <linux/tracehook.h>
13 #include <linux/signal.h>
14 #include <linux/uprobes.h>
15 #include <linux/key.h>
16 #include <linux/context_tracking.h>
17 #include <asm/hw_breakpoint.h>
18 #include <asm/uaccess.h>
19 #include <asm/unistd.h>
20 #include <asm/debug.h>
21 #include <asm/tm.h>
22
23 #include "signal.h"
24
25 /* Log an error when sending an unhandled signal to a process. Controlled
26 * through debug.exception-trace sysctl.
27 */
28
29 int show_unhandled_signals = 1;
30
31 /*
32 * Allocate space for the signal frame
33 */
34 void __user *get_sigframe(struct ksignal *ksig, unsigned long sp,
35 size_t frame_size, int is_32)
36 {
37 unsigned long oldsp, newsp;
38
39 /* Default to using normal stack */
40 oldsp = get_clean_sp(sp, is_32);
41 oldsp = sigsp(oldsp, ksig);
42 newsp = (oldsp - frame_size) & ~0xFUL;
43
44 /* Check access */
45 if (!access_ok(VERIFY_WRITE, (void __user *)newsp, oldsp - newsp))
46 return NULL;
47
48 return (void __user *)newsp;
49 }
50
51 static void check_syscall_restart(struct pt_regs *regs, struct k_sigaction *ka,
52 int has_handler)
53 {
54 unsigned long ret = regs->gpr[3];
55 int restart = 1;
56
57 /* syscall ? */
58 if (TRAP(regs) != 0x0C00)
59 return;
60
61 /* error signalled ? */
62 if (!(regs->ccr & 0x10000000))
63 return;
64
65 switch (ret) {
66 case ERESTART_RESTARTBLOCK:
67 case ERESTARTNOHAND:
68 /* ERESTARTNOHAND means that the syscall should only be
69 * restarted if there was no handler for the signal, and since
70 * we only get here if there is a handler, we dont restart.
71 */
72 restart = !has_handler;
73 break;
74 case ERESTARTSYS:
75 /* ERESTARTSYS means to restart the syscall if there is no
76 * handler or the handler was registered with SA_RESTART
77 */
78 restart = !has_handler || (ka->sa.sa_flags & SA_RESTART) != 0;
79 break;
80 case ERESTARTNOINTR:
81 /* ERESTARTNOINTR means that the syscall should be
82 * called again after the signal handler returns.
83 */
84 break;
85 default:
86 return;
87 }
88 if (restart) {
89 if (ret == ERESTART_RESTARTBLOCK)
90 regs->gpr[0] = __NR_restart_syscall;
91 else
92 regs->gpr[3] = regs->orig_gpr3;
93 regs->nip -= 4;
94 regs->result = 0;
95 } else {
96 regs->result = -EINTR;
97 regs->gpr[3] = EINTR;
98 regs->ccr |= 0x10000000;
99 }
100 }
101
102 static void do_signal(struct pt_regs *regs)
103 {
104 sigset_t *oldset = sigmask_to_save();
105 struct ksignal ksig;
106 int ret;
107 int is32 = is_32bit_task();
108
109 get_signal(&ksig);
110
111 /* Is there any syscall restart business here ? */
112 check_syscall_restart(regs, &ksig.ka, ksig.sig > 0);
113
114 if (ksig.sig <= 0) {
115 /* No signal to deliver -- put the saved sigmask back */
116 restore_saved_sigmask();
117 regs->trap = 0;
118 return; /* no signals delivered */
119 }
120
121 #ifndef CONFIG_PPC_ADV_DEBUG_REGS
122 /*
123 * Reenable the DABR before delivering the signal to
124 * user space. The DABR will have been cleared if it
125 * triggered inside the kernel.
126 */
127 if (current->thread.hw_brk.address &&
128 current->thread.hw_brk.type)
129 __set_breakpoint(&current->thread.hw_brk);
130 #endif
131 /* Re-enable the breakpoints for the signal stack */
132 thread_change_pc(current, regs);
133
134 rseq_signal_deliver(regs);
135
136 if (is32) {
137 if (ksig.ka.sa.sa_flags & SA_SIGINFO)
138 ret = handle_rt_signal32(&ksig, oldset, regs);
139 else
140 ret = handle_signal32(&ksig, oldset, regs);
141 } else {
142 ret = handle_rt_signal64(&ksig, oldset, regs);
143 }
144
145 regs->trap = 0;
146 signal_setup_done(ret, &ksig, test_thread_flag(TIF_SINGLESTEP));
147 }
148
149 void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags)
150 {
151 user_exit();
152
153 if (thread_info_flags & _TIF_UPROBE)
154 uprobe_notify_resume(regs);
155
156 if (thread_info_flags & _TIF_SIGPENDING)
157 do_signal(regs);
158
159 if (thread_info_flags & _TIF_NOTIFY_RESUME) {
160 clear_thread_flag(TIF_NOTIFY_RESUME);
161 tracehook_notify_resume(regs);
162 rseq_handle_notify_resume(regs);
163 }
164
165 user_enter();
166 }
167
168 unsigned long get_tm_stackpointer(struct pt_regs *regs)
169 {
170 /* When in an active transaction that takes a signal, we need to be
171 * careful with the stack. It's possible that the stack has moved back
172 * up after the tbegin. The obvious case here is when the tbegin is
173 * called inside a function that returns before a tend. In this case,
174 * the stack is part of the checkpointed transactional memory state.
175 * If we write over this non transactionally or in suspend, we are in
176 * trouble because if we get a tm abort, the program counter and stack
177 * pointer will be back at the tbegin but our in memory stack won't be
178 * valid anymore.
179 *
180 * To avoid this, when taking a signal in an active transaction, we
181 * need to use the stack pointer from the checkpointed state, rather
182 * than the speculated state. This ensures that the signal context
183 * (written tm suspended) will be written below the stack required for
184 * the rollback. The transaction is aborted because of the treclaim,
185 * so any memory written between the tbegin and the signal will be
186 * rolled back anyway.
187 *
188 * For signals taken in non-TM or suspended mode, we use the
189 * normal/non-checkpointed stack pointer.
190 */
191
192 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
193 if (MSR_TM_ACTIVE(regs->msr)) {
194 tm_reclaim_current(TM_CAUSE_SIGNAL);
195 if (MSR_TM_TRANSACTIONAL(regs->msr))
196 return current->thread.ckpt_regs.gpr[1];
197 }
198 #endif
199 return regs->gpr[1];
200 }
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