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 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM 204 BUG_ON(tsk != current); 205 206 if (MSR_TM_ACTIVE(tsk->thread.regs->msr)) { 207 tm_reclaim_current(TM_CAUSE_SIGNAL); 208 if (MSR_TM_TRANSACTIONAL(tsk->thread.regs->msr)) 209 return tsk->thread.ckpt_regs.gpr[1]; 210 } 211 #endif 212 return tsk->thread.regs->gpr[1]; 213 } 214