1/*
2 * Common signal handling code for both 32 and 64 bits
3 *
4 *    Copyright (c) 2007 Benjamin Herrenschmidt, IBM Coproration
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
29int show_unhandled_signals = 1;
30
31/*
32 * Allocate space for the signal frame
33 */
34void __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
51static 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
102static 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	if (is32) {
135        	if (ksig.ka.sa.sa_flags & SA_SIGINFO)
136			ret = handle_rt_signal32(&ksig, oldset, regs);
137		else
138			ret = handle_signal32(&ksig, oldset, regs);
139	} else {
140		ret = handle_rt_signal64(&ksig, oldset, regs);
141	}
142
143	regs->trap = 0;
144	signal_setup_done(ret, &ksig, test_thread_flag(TIF_SINGLESTEP));
145}
146
147void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags)
148{
149	user_exit();
150
151	if (thread_info_flags & _TIF_UPROBE)
152		uprobe_notify_resume(regs);
153
154	if (thread_info_flags & _TIF_SIGPENDING)
155		do_signal(regs);
156
157	if (thread_info_flags & _TIF_NOTIFY_RESUME) {
158		clear_thread_flag(TIF_NOTIFY_RESUME);
159		tracehook_notify_resume(regs);
160	}
161
162	user_enter();
163}
164
165unsigned long get_tm_stackpointer(struct pt_regs *regs)
166{
167	/* When in an active transaction that takes a signal, we need to be
168	 * careful with the stack.  It's possible that the stack has moved back
169	 * up after the tbegin.  The obvious case here is when the tbegin is
170	 * called inside a function that returns before a tend.  In this case,
171	 * the stack is part of the checkpointed transactional memory state.
172	 * If we write over this non transactionally or in suspend, we are in
173	 * trouble because if we get a tm abort, the program counter and stack
174	 * pointer will be back at the tbegin but our in memory stack won't be
175	 * valid anymore.
176	 *
177	 * To avoid this, when taking a signal in an active transaction, we
178	 * need to use the stack pointer from the checkpointed state, rather
179	 * than the speculated state.  This ensures that the signal context
180	 * (written tm suspended) will be written below the stack required for
181	 * the rollback.  The transaction is aborted becuase of the treclaim,
182	 * so any memory written between the tbegin and the signal will be
183	 * rolled back anyway.
184	 *
185	 * For signals taken in non-TM or suspended mode, we use the
186	 * normal/non-checkpointed stack pointer.
187	 */
188
189#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
190	if (MSR_TM_ACTIVE(regs->msr)) {
191		tm_reclaim_current(TM_CAUSE_SIGNAL);
192		if (MSR_TM_TRANSACTIONAL(regs->msr))
193			return current->thread.ckpt_regs.gpr[1];
194	}
195#endif
196	return regs->gpr[1];
197}
198