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 <linux/livepatch.h>
18 #include <linux/syscalls.h>
19 #include <asm/hw_breakpoint.h>
20 #include <linux/uaccess.h>
21 #include <asm/unistd.h>
22 #include <asm/debug.h>
23 #include <asm/tm.h>
24
25 #include "signal.h"
26
27 /* Log an error when sending an unhandled signal to a process. Controlled
28 * through debug.exception-trace sysctl.
29 */
30
31 int show_unhandled_signals = 1;
32
33 /*
34 * Allocate space for the signal frame
35 */
36 void __user *get_sigframe(struct ksignal *ksig, unsigned long sp,
37 size_t frame_size, int is_32)
38 {
39 unsigned long oldsp, newsp;
40
41 /* Default to using normal stack */
42 oldsp = get_clean_sp(sp, is_32);
43 oldsp = sigsp(oldsp, ksig);
44 newsp = (oldsp - frame_size) & ~0xFUL;
45
46 /* Check access */
47 if (!access_ok((void __user *)newsp, oldsp - newsp))
48 return NULL;
49
50 return (void __user *)newsp;
51 }
52
53 static void check_syscall_restart(struct pt_regs *regs, struct k_sigaction *ka,
54 int has_handler)
55 {
56 unsigned long ret = regs->gpr[3];
57 int restart = 1;
58
59 /* syscall ? */
60 if (TRAP(regs) != 0x0C00)
61 return;
62
63 /* error signalled ? */
64 if (!(regs->ccr & 0x10000000))
65 return;
66
67 switch (ret) {
68 case ERESTART_RESTARTBLOCK:
69 case ERESTARTNOHAND:
70 /* ERESTARTNOHAND means that the syscall should only be
71 * restarted if there was no handler for the signal, and since
72 * we only get here if there is a handler, we dont restart.
73 */
74 restart = !has_handler;
75 break;
76 case ERESTARTSYS:
77 /* ERESTARTSYS means to restart the syscall if there is no
78 * handler or the handler was registered with SA_RESTART
79 */
80 restart = !has_handler || (ka->sa.sa_flags & SA_RESTART) != 0;
81 break;
82 case ERESTARTNOINTR:
83 /* ERESTARTNOINTR means that the syscall should be
84 * called again after the signal handler returns.
85 */
86 break;
87 default:
88 return;
89 }
90 if (restart) {
91 if (ret == ERESTART_RESTARTBLOCK)
92 regs->gpr[0] = __NR_restart_syscall;
93 else
94 regs->gpr[3] = regs->orig_gpr3;
95 regs->nip -= 4;
96 regs->result = 0;
97 } else {
98 regs->result = -EINTR;
99 regs->gpr[3] = EINTR;
100 regs->ccr |= 0x10000000;
101 }
102 }
103
104 static void do_signal(struct task_struct *tsk)
105 {
106 sigset_t *oldset = sigmask_to_save();
107 struct ksignal ksig = { .sig = 0 };
108 int ret;
109 int is32 = is_32bit_task();
110
111 BUG_ON(tsk != current);
112
113 get_signal(&ksig);
114
115 /* Is there any syscall restart business here ? */
116 check_syscall_restart(tsk->thread.regs, &ksig.ka, ksig.sig > 0);
117
118 if (ksig.sig <= 0) {
119 /* No signal to deliver -- put the saved sigmask back */
120 restore_saved_sigmask();
121 tsk->thread.regs->trap = 0;
122 return; /* no signals delivered */
123 }
124
125 #ifndef CONFIG_PPC_ADV_DEBUG_REGS
126 /*
127 * Reenable the DABR before delivering the signal to
128 * user space. The DABR will have been cleared if it
129 * triggered inside the kernel.
130 */
131 if (tsk->thread.hw_brk.address && tsk->thread.hw_brk.type)
132 __set_breakpoint(&tsk->thread.hw_brk);
133 #endif
134 /* Re-enable the breakpoints for the signal stack */
135 thread_change_pc(tsk, tsk->thread.regs);
136
137 rseq_signal_deliver(&ksig, tsk->thread.regs);
138
139 if (is32) {
140 if (ksig.ka.sa.sa_flags & SA_SIGINFO)
141 ret = handle_rt_signal32(&ksig, oldset, tsk);
142 else
143 ret = handle_signal32(&ksig, oldset, tsk);
144 } else {
145 ret = handle_rt_signal64(&ksig, oldset, tsk);
146 }
147
148 tsk->thread.regs->trap = 0;
149 signal_setup_done(ret, &ksig, test_thread_flag(TIF_SINGLESTEP));
150 }
151
152 void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags)
153 {
154 user_exit();
155
156 /* Check valid addr_limit, TIF check is done there */
157 addr_limit_user_check();
158
159 if (thread_info_flags & _TIF_UPROBE)
160 uprobe_notify_resume(regs);
161
162 if (thread_info_flags & _TIF_PATCH_PENDING)
163 klp_update_patch_state(current);
164
165 if (thread_info_flags & _TIF_SIGPENDING) {
166 BUG_ON(regs != current->thread.regs);
167 do_signal(current);
168 }
169
170 if (thread_info_flags & _TIF_NOTIFY_RESUME) {
171 clear_thread_flag(TIF_NOTIFY_RESUME);
172 tracehook_notify_resume(regs);
173 rseq_handle_notify_resume(NULL, regs);
174 }
175
176 user_enter();
177 }
178
179 unsigned long get_tm_stackpointer(struct task_struct *tsk)
180 {
181 /* When in an active transaction that takes a signal, we need to be
182 * careful with the stack. It's possible that the stack has moved back
183 * up after the tbegin. The obvious case here is when the tbegin is
184 * called inside a function that returns before a tend. In this case,
185 * the stack is part of the checkpointed transactional memory state.
186 * If we write over this non transactionally or in suspend, we are in
187 * trouble because if we get a tm abort, the program counter and stack
188 * pointer will be back at the tbegin but our in memory stack won't be
189 * valid anymore.
190 *
191 * To avoid this, when taking a signal in an active transaction, we
192 * need to use the stack pointer from the checkpointed state, rather
193 * than the speculated state. This ensures that the signal context
194 * (written tm suspended) will be written below the stack required for
195 * the rollback. The transaction is aborted because of the treclaim,
196 * so any memory written between the tbegin and the signal will be
197 * rolled back anyway.
198 *
199 * For signals taken in non-TM or suspended mode, we use the
200 * normal/non-checkpointed stack pointer.
201 */
202
203 unsigned long ret = tsk->thread.regs->gpr[1];
204
205 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
206 BUG_ON(tsk != current);
207
208 if (MSR_TM_ACTIVE(tsk->thread.regs->msr)) {
209 preempt_disable();
210 tm_reclaim_current(TM_CAUSE_SIGNAL);
211 if (MSR_TM_TRANSACTIONAL(tsk->thread.regs->msr))
212 ret = tsk->thread.ckpt_regs.gpr[1];
213
214 /*
215 * If we treclaim, we must clear the current thread's TM bits
216 * before re-enabling preemption. Otherwise we might be
217 * preempted and have the live MSR[TS] changed behind our back
218 * (tm_recheckpoint_new_task() would recheckpoint). Besides, we
219 * enter the signal handler in non-transactional state.
220 */
221 tsk->thread.regs->msr &= ~MSR_TS_MASK;
222 preempt_enable();
223 }
224 #endif
225 return ret;
226 }