1 // SPDX-License-Identifier: GPL-2.0-only
3 * Signal Handling for ARC
5 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
7 * vineetg: Jan 2010 (Restarting of timer related syscalls)
9 * vineetg: Nov 2009 (Everything needed for TIF_RESTORE_SIGMASK)
10 * -do_signal() supports TIF_RESTORE_SIGMASK
11 * -do_signal() no loner needs oldset, required by OLD sys_sigsuspend
12 * -sys_rt_sigsuspend() now comes from generic code, so discard arch implemen
13 * -sys_sigsuspend() no longer needs to fudge ptregs, hence that arg removed
14 * -sys_sigsuspend() no longer loops for do_signal(), sets TIF_xxx and leaves
15 * the job to do_signal()
18 * -Modified Code to support the uClibc provided userland sigreturn stub
19 * to avoid kernel synthesing it on user stack at runtime, costing TLB
20 * probes and Cache line flushes.
23 * -In stash_usr_regs( ) and restore_usr_regs( ), save/restore of user regs
24 * in done in block copy rather than one word at a time.
25 * This saves around 2K of code and improves LMBench lat_sig <catch>
27 * rajeshwarr: Feb 2009
28 * - Support for Realtime Signals
30 * vineetg: Aug 11th 2008: Bug #94183
31 * -ViXS were still seeing crashes when using insmod to load drivers.
32 * It turned out that the code to change Execute permssions for TLB entries
33 * of user was not guarded for interrupts (mod_tlb_permission)
34 * This was causing TLB entries to be overwritten on unrelated indexes
36 * Vineetg: July 15th 2008: Bug #94183
37 * -Exception happens in Delay slot of a JMP, and before user space resumes,
38 * Signal is delivered (Ctrl + C) = >SIGINT.
39 * setup_frame( ) sets up PC,SP,BLINK to enable user space signal handler
40 * to run, but doesn't clear the Delay slot bit from status32. As a result,
41 * on resuming user mode, signal handler branches off to BTA of orig JMP
42 * -FIX: clear the DE bit from status32 in setup_frame( )
44 * Rahul Trivedi, Kanika Nema: Codito Technologies 2004
47 #include <linux/signal.h>
48 #include <linux/ptrace.h>
49 #include <linux/personality.h>
50 #include <linux/uaccess.h>
51 #include <linux/syscalls.h>
52 #include <linux/tracehook.h>
53 #include <linux/sched/task_stack.h>
55 #include <asm/ucontext.h>
60 #define MAGIC_SIGALTSTK 0x07302004
61 unsigned int sigret_magic;
64 static int save_arcv2_regs(struct sigcontext __user *mctx, struct pt_regs *regs)
67 #ifndef CONFIG_ISA_ARCOMPACT
68 struct user_regs_arcv2 v2abi;
70 v2abi.r30 = regs->r30;
71 #ifdef CONFIG_ARC_HAS_ACCL_REGS
72 v2abi.r58 = regs->r58;
73 v2abi.r59 = regs->r59;
75 v2abi.r58 = v2abi.r59 = 0;
77 err = __copy_to_user(&mctx->v2abi, (void const *)&v2abi, sizeof(v2abi));
82 static int restore_arcv2_regs(struct sigcontext __user *mctx, struct pt_regs *regs)
85 #ifndef CONFIG_ISA_ARCOMPACT
86 struct user_regs_arcv2 v2abi;
88 err = __copy_from_user(&v2abi, &mctx->v2abi, sizeof(v2abi));
90 regs->r30 = v2abi.r30;
91 #ifdef CONFIG_ARC_HAS_ACCL_REGS
92 regs->r58 = v2abi.r58;
93 regs->r59 = v2abi.r59;
100 stash_usr_regs(struct rt_sigframe __user *sf, struct pt_regs *regs,
104 struct user_regs_struct uregs;
106 uregs.scratch.bta = regs->bta;
107 uregs.scratch.lp_start = regs->lp_start;
108 uregs.scratch.lp_end = regs->lp_end;
109 uregs.scratch.lp_count = regs->lp_count;
110 uregs.scratch.status32 = regs->status32;
111 uregs.scratch.ret = regs->ret;
112 uregs.scratch.blink = regs->blink;
113 uregs.scratch.fp = regs->fp;
114 uregs.scratch.gp = regs->r26;
115 uregs.scratch.r12 = regs->r12;
116 uregs.scratch.r11 = regs->r11;
117 uregs.scratch.r10 = regs->r10;
118 uregs.scratch.r9 = regs->r9;
119 uregs.scratch.r8 = regs->r8;
120 uregs.scratch.r7 = regs->r7;
121 uregs.scratch.r6 = regs->r6;
122 uregs.scratch.r5 = regs->r5;
123 uregs.scratch.r4 = regs->r4;
124 uregs.scratch.r3 = regs->r3;
125 uregs.scratch.r2 = regs->r2;
126 uregs.scratch.r1 = regs->r1;
127 uregs.scratch.r0 = regs->r0;
128 uregs.scratch.sp = regs->sp;
130 err = __copy_to_user(&(sf->uc.uc_mcontext.regs.scratch), &uregs.scratch,
131 sizeof(sf->uc.uc_mcontext.regs.scratch));
134 err |= save_arcv2_regs(&(sf->uc.uc_mcontext), regs);
136 err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(sigset_t));
138 return err ? -EFAULT : 0;
141 static int restore_usr_regs(struct pt_regs *regs, struct rt_sigframe __user *sf)
145 struct user_regs_struct uregs;
147 err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
148 err |= __copy_from_user(&uregs.scratch,
149 &(sf->uc.uc_mcontext.regs.scratch),
150 sizeof(sf->uc.uc_mcontext.regs.scratch));
153 err |= restore_arcv2_regs(&(sf->uc.uc_mcontext), regs);
158 set_current_blocked(&set);
159 regs->bta = uregs.scratch.bta;
160 regs->lp_start = uregs.scratch.lp_start;
161 regs->lp_end = uregs.scratch.lp_end;
162 regs->lp_count = uregs.scratch.lp_count;
163 regs->status32 = uregs.scratch.status32;
164 regs->ret = uregs.scratch.ret;
165 regs->blink = uregs.scratch.blink;
166 regs->fp = uregs.scratch.fp;
167 regs->r26 = uregs.scratch.gp;
168 regs->r12 = uregs.scratch.r12;
169 regs->r11 = uregs.scratch.r11;
170 regs->r10 = uregs.scratch.r10;
171 regs->r9 = uregs.scratch.r9;
172 regs->r8 = uregs.scratch.r8;
173 regs->r7 = uregs.scratch.r7;
174 regs->r6 = uregs.scratch.r6;
175 regs->r5 = uregs.scratch.r5;
176 regs->r4 = uregs.scratch.r4;
177 regs->r3 = uregs.scratch.r3;
178 regs->r2 = uregs.scratch.r2;
179 regs->r1 = uregs.scratch.r1;
180 regs->r0 = uregs.scratch.r0;
181 regs->sp = uregs.scratch.sp;
186 static inline int is_do_ss_needed(unsigned int magic)
188 if (MAGIC_SIGALTSTK == magic)
194 SYSCALL_DEFINE0(rt_sigreturn)
196 struct rt_sigframe __user *sf;
198 struct pt_regs *regs = current_pt_regs();
200 /* Always make any pending restarted system calls return -EINTR */
201 current->restart_block.fn = do_no_restart_syscall;
203 /* Since we stacked the signal on a word boundary,
204 * then 'sp' should be word aligned here. If it's
205 * not, then the user is trying to mess with us.
210 sf = (struct rt_sigframe __force __user *)(regs->sp);
212 if (!access_ok(sf, sizeof(*sf)))
215 if (__get_user(magic, &sf->sigret_magic))
218 if (unlikely(is_do_ss_needed(magic)))
219 if (restore_altstack(&sf->uc.uc_stack))
222 if (restore_usr_regs(regs, sf))
225 /* Don't restart from sigreturn */
226 syscall_wont_restart(regs);
229 * Ensure that sigreturn always returns to user mode (in case the
230 * regs saved on user stack got fudged between save and sigreturn)
231 * Otherwise it is easy to panic the kernel with a custom
232 * signal handler and/or restorer which clobberes the status32/ret
233 * to return to a bogus location in kernel mode.
235 regs->status32 |= STATUS_U_MASK;
245 * Determine which stack to use..
247 static inline void __user *get_sigframe(struct ksignal *ksig,
248 struct pt_regs *regs,
249 unsigned long framesize)
251 unsigned long sp = sigsp(regs->sp, ksig);
254 /* No matter what happens, 'sp' must be word
255 * aligned otherwise nasty things could happen
258 /* ATPCS B01 mandates 8-byte alignment */
259 frame = (void __user *)((sp - framesize) & ~7);
261 /* Check that we can actually write to the signal frame */
262 if (!access_ok(frame, framesize))
269 setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
271 struct rt_sigframe __user *sf;
272 unsigned int magic = 0;
275 sf = get_sigframe(ksig, regs, sizeof(struct rt_sigframe));
280 * w/o SA_SIGINFO, struct ucontext is partially populated (only
281 * uc_mcontext/uc_sigmask) for kernel's normal user state preservation
282 * during signal handler execution. This works for SA_SIGINFO as well
283 * although the semantics are now overloaded (the same reg state can be
284 * inspected by userland: but are they allowed to fiddle with it ?
286 err |= stash_usr_regs(sf, regs, set);
289 * SA_SIGINFO requires 3 args to signal handler:
290 * #1: sig-no (common to any handler)
292 * #3: struct ucontext (completely populated)
294 if (unlikely(ksig->ka.sa.sa_flags & SA_SIGINFO)) {
295 err |= copy_siginfo_to_user(&sf->info, &ksig->info);
296 err |= __put_user(0, &sf->uc.uc_flags);
297 err |= __put_user(NULL, &sf->uc.uc_link);
298 err |= __save_altstack(&sf->uc.uc_stack, regs->sp);
300 /* setup args 2 and 3 for user mode handler */
301 regs->r1 = (unsigned long)&sf->info;
302 regs->r2 = (unsigned long)&sf->uc;
305 * small optim to avoid unconditonally calling do_sigaltstack
306 * in sigreturn path, now that we only have rt_sigreturn
308 magic = MAGIC_SIGALTSTK;
311 err |= __put_user(magic, &sf->sigret_magic);
315 /* #1 arg to the user Signal handler */
316 regs->r0 = ksig->sig;
318 /* setup PC of user space signal handler */
319 regs->ret = (unsigned long)ksig->ka.sa.sa_handler;
322 * handler returns using sigreturn stub provided already by userpsace
323 * If not, nuke the process right away
325 if(!(ksig->ka.sa.sa_flags & SA_RESTORER))
328 regs->blink = (unsigned long)ksig->ka.sa.sa_restorer;
330 /* User Stack for signal handler will be above the frame just carved */
331 regs->sp = (unsigned long)sf;
334 * Bug 94183, Clear the DE bit, so that when signal handler
335 * starts to run, it doesn't use BTA
337 regs->status32 &= ~STATUS_DE_MASK;
338 regs->status32 |= STATUS_L_MASK;
343 static void arc_restart_syscall(struct k_sigaction *ka, struct pt_regs *regs)
346 case -ERESTART_RESTARTBLOCK:
347 case -ERESTARTNOHAND:
349 * ERESTARTNOHAND means that the syscall should
350 * only be restarted if there was no handler for
351 * the signal, and since we only get here if there
352 * is a handler, we don't restart
354 regs->r0 = -EINTR; /* ERESTART_xxx is internal */
359 * ERESTARTSYS means to restart the syscall if
360 * there is no handler or the handler was
361 * registered with SA_RESTART
363 if (!(ka->sa.sa_flags & SA_RESTART)) {
369 case -ERESTARTNOINTR:
371 * ERESTARTNOINTR means that the syscall should
372 * be called again after the signal handler returns.
373 * Setup reg state just as it was before doing the trap
374 * r0 has been clobbered with sys call ret code thus it
375 * needs to be reloaded with orig first arg to syscall
376 * in orig_r0. Rest of relevant reg-file:
377 * r8 (syscall num) and (r1 - r7) will be reset to
378 * their orig user space value when we ret from kernel
380 regs->r0 = regs->orig_r0;
381 regs->ret -= is_isa_arcv2() ? 2 : 4;
387 * OK, we're invoking a handler
390 handle_signal(struct ksignal *ksig, struct pt_regs *regs)
392 sigset_t *oldset = sigmask_to_save();
395 /* Set up the stack frame */
396 failed = setup_rt_frame(ksig, oldset, regs);
398 signal_setup_done(failed, ksig, 0);
401 void do_signal(struct pt_regs *regs)
406 restart_scall = in_syscall(regs) && syscall_restartable(regs);
408 if (test_thread_flag(TIF_SIGPENDING) && get_signal(&ksig)) {
410 arc_restart_syscall(&ksig.ka, regs);
411 syscall_wont_restart(regs); /* No more restarts */
413 handle_signal(&ksig, regs);
418 /* No handler for syscall: restart it */
419 if (regs->r0 == -ERESTARTNOHAND ||
420 regs->r0 == -ERESTARTSYS || regs->r0 == -ERESTARTNOINTR) {
421 regs->r0 = regs->orig_r0;
422 regs->ret -= is_isa_arcv2() ? 2 : 4;
423 } else if (regs->r0 == -ERESTART_RESTARTBLOCK) {
424 regs->r8 = __NR_restart_syscall;
425 regs->ret -= is_isa_arcv2() ? 2 : 4;
427 syscall_wont_restart(regs); /* No more restarts */
430 /* If there's no signal to deliver, restore the saved sigmask back */
431 restore_saved_sigmask();
434 void do_notify_resume(struct pt_regs *regs)
437 * ASM glue gaurantees that this is only called when returning to
440 if (test_thread_flag(TIF_NOTIFY_RESUME))
441 tracehook_notify_resume(regs);