1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
4  */
5 
6 #include <linux/module.h>
7 #include <linux/ptrace.h>
8 #include <linux/sched.h>
9 #include <linux/ftrace.h>
10 #include <asm/siginfo.h>
11 #include <asm/signal.h>
12 #include <asm/unistd.h>
13 #include <frame_kern.h>
14 #include <kern_util.h>
15 #include <os.h>
16 
17 EXPORT_SYMBOL(block_signals);
18 EXPORT_SYMBOL(unblock_signals);
19 
block_signals_trace(void)20 void block_signals_trace(void)
21 {
22 	block_signals();
23 	if (current_thread_info())
24 		trace_hardirqs_off();
25 }
26 
unblock_signals_trace(void)27 void unblock_signals_trace(void)
28 {
29 	if (current_thread_info())
30 		trace_hardirqs_on();
31 	unblock_signals();
32 }
33 
um_trace_signals_on(void)34 void um_trace_signals_on(void)
35 {
36 	if (current_thread_info())
37 		trace_hardirqs_on();
38 }
39 
um_trace_signals_off(void)40 void um_trace_signals_off(void)
41 {
42 	if (current_thread_info())
43 		trace_hardirqs_off();
44 }
45 
46 /*
47  * OK, we're invoking a handler
48  */
handle_signal(struct ksignal * ksig,struct pt_regs * regs)49 static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
50 {
51 	sigset_t *oldset = sigmask_to_save();
52 	int singlestep = 0;
53 	unsigned long sp;
54 	int err;
55 
56 	if (test_thread_flag(TIF_SINGLESTEP) && (current->ptrace & PT_PTRACED))
57 		singlestep = 1;
58 
59 	/* Did we come from a system call? */
60 	if (PT_REGS_SYSCALL_NR(regs) >= 0) {
61 		/* If so, check system call restarting.. */
62 		switch (PT_REGS_SYSCALL_RET(regs)) {
63 		case -ERESTART_RESTARTBLOCK:
64 		case -ERESTARTNOHAND:
65 			PT_REGS_SYSCALL_RET(regs) = -EINTR;
66 			break;
67 
68 		case -ERESTARTSYS:
69 			if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
70 				PT_REGS_SYSCALL_RET(regs) = -EINTR;
71 				break;
72 			}
73 			fallthrough;
74 		case -ERESTARTNOINTR:
75 			PT_REGS_RESTART_SYSCALL(regs);
76 			PT_REGS_ORIG_SYSCALL(regs) = PT_REGS_SYSCALL_NR(regs);
77 			break;
78 		}
79 	}
80 
81 	sp = PT_REGS_SP(regs);
82 	if ((ksig->ka.sa.sa_flags & SA_ONSTACK) && (sas_ss_flags(sp) == 0))
83 		sp = current->sas_ss_sp + current->sas_ss_size;
84 
85 #ifdef CONFIG_ARCH_HAS_SC_SIGNALS
86 	if (!(ksig->ka.sa.sa_flags & SA_SIGINFO))
87 		err = setup_signal_stack_sc(sp, ksig, regs, oldset);
88 	else
89 #endif
90 		err = setup_signal_stack_si(sp, ksig, regs, oldset);
91 
92 	signal_setup_done(err, ksig, singlestep);
93 }
94 
do_signal(struct pt_regs * regs)95 void do_signal(struct pt_regs *regs)
96 {
97 	struct ksignal ksig;
98 	int handled_sig = 0;
99 
100 	while (get_signal(&ksig)) {
101 		handled_sig = 1;
102 		/* Whee!  Actually deliver the signal.  */
103 		handle_signal(&ksig, regs);
104 	}
105 
106 	/* Did we come from a system call? */
107 	if (!handled_sig && (PT_REGS_SYSCALL_NR(regs) >= 0)) {
108 		/* Restart the system call - no handlers present */
109 		switch (PT_REGS_SYSCALL_RET(regs)) {
110 		case -ERESTARTNOHAND:
111 		case -ERESTARTSYS:
112 		case -ERESTARTNOINTR:
113 			PT_REGS_ORIG_SYSCALL(regs) = PT_REGS_SYSCALL_NR(regs);
114 			PT_REGS_RESTART_SYSCALL(regs);
115 			break;
116 		case -ERESTART_RESTARTBLOCK:
117 			PT_REGS_ORIG_SYSCALL(regs) = __NR_restart_syscall;
118 			PT_REGS_RESTART_SYSCALL(regs);
119 			break;
120 		}
121 	}
122 
123 	/*
124 	 * This closes a way to execute a system call on the host.  If
125 	 * you set a breakpoint on a system call instruction and singlestep
126 	 * from it, the tracing thread used to PTRACE_SINGLESTEP the process
127 	 * rather than PTRACE_SYSCALL it, allowing the system call to execute
128 	 * on the host.  The tracing thread will check this flag and
129 	 * PTRACE_SYSCALL if necessary.
130 	 */
131 	if (test_thread_flag(TIF_SINGLESTEP))
132 		current->thread.singlestep_syscall =
133 			is_syscall(PT_REGS_IP(&current->thread.regs));
134 
135 	/*
136 	 * if there's no signal to deliver, we just put the saved sigmask
137 	 * back
138 	 */
139 	if (!handled_sig)
140 		restore_saved_sigmask();
141 }
142