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/resume_user_mode.h>
53 #include <linux/sched/task_stack.h>
55 #include <asm/ucontext.h>
56 #include <asm/entry.h>
61 #define MAGIC_SIGALTSTK 0x07302004
62 unsigned int sigret_magic;
65 static int save_arcv2_regs(struct sigcontext *mctx, struct pt_regs *regs)
68 #ifndef CONFIG_ISA_ARCOMPACT
69 struct user_regs_arcv2 v2abi;
71 v2abi.r30 = regs->r30;
72 #ifdef CONFIG_ARC_HAS_ACCL_REGS
73 v2abi.r58 = regs->r58;
74 v2abi.r59 = regs->r59;
76 v2abi.r58 = v2abi.r59 = 0;
78 err = __copy_to_user(&mctx->v2abi, &v2abi, sizeof(v2abi));
83 static int restore_arcv2_regs(struct sigcontext *mctx, struct pt_regs *regs)
86 #ifndef CONFIG_ISA_ARCOMPACT
87 struct user_regs_arcv2 v2abi;
89 err = __copy_from_user(&v2abi, &mctx->v2abi, sizeof(v2abi));
91 regs->r30 = v2abi.r30;
92 #ifdef CONFIG_ARC_HAS_ACCL_REGS
93 regs->r58 = v2abi.r58;
94 regs->r59 = v2abi.r59;
101 stash_usr_regs(struct rt_sigframe __user *sf, struct pt_regs *regs,
105 struct user_regs_struct uregs;
107 uregs.scratch.bta = regs->bta;
108 uregs.scratch.lp_start = regs->lp_start;
109 uregs.scratch.lp_end = regs->lp_end;
110 uregs.scratch.lp_count = regs->lp_count;
111 uregs.scratch.status32 = regs->status32;
112 uregs.scratch.ret = regs->ret;
113 uregs.scratch.blink = regs->blink;
114 uregs.scratch.fp = regs->fp;
115 uregs.scratch.gp = regs->r26;
116 uregs.scratch.r12 = regs->r12;
117 uregs.scratch.r11 = regs->r11;
118 uregs.scratch.r10 = regs->r10;
119 uregs.scratch.r9 = regs->r9;
120 uregs.scratch.r8 = regs->r8;
121 uregs.scratch.r7 = regs->r7;
122 uregs.scratch.r6 = regs->r6;
123 uregs.scratch.r5 = regs->r5;
124 uregs.scratch.r4 = regs->r4;
125 uregs.scratch.r3 = regs->r3;
126 uregs.scratch.r2 = regs->r2;
127 uregs.scratch.r1 = regs->r1;
128 uregs.scratch.r0 = regs->r0;
129 uregs.scratch.sp = regs->sp;
131 err = __copy_to_user(&(sf->uc.uc_mcontext.regs.scratch), &uregs.scratch,
132 sizeof(sf->uc.uc_mcontext.regs.scratch));
135 err |= save_arcv2_regs(&(sf->uc.uc_mcontext), regs);
137 err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(sigset_t));
139 return err ? -EFAULT : 0;
142 static int restore_usr_regs(struct pt_regs *regs, struct rt_sigframe __user *sf)
146 struct user_regs_struct uregs;
148 err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
149 err |= __copy_from_user(&uregs.scratch,
150 &(sf->uc.uc_mcontext.regs.scratch),
151 sizeof(sf->uc.uc_mcontext.regs.scratch));
154 err |= restore_arcv2_regs(&(sf->uc.uc_mcontext), regs);
159 set_current_blocked(&set);
160 regs->bta = uregs.scratch.bta;
161 regs->lp_start = uregs.scratch.lp_start;
162 regs->lp_end = uregs.scratch.lp_end;
163 regs->lp_count = uregs.scratch.lp_count;
164 regs->status32 = uregs.scratch.status32;
165 regs->ret = uregs.scratch.ret;
166 regs->blink = uregs.scratch.blink;
167 regs->fp = uregs.scratch.fp;
168 regs->r26 = uregs.scratch.gp;
169 regs->r12 = uregs.scratch.r12;
170 regs->r11 = uregs.scratch.r11;
171 regs->r10 = uregs.scratch.r10;
172 regs->r9 = uregs.scratch.r9;
173 regs->r8 = uregs.scratch.r8;
174 regs->r7 = uregs.scratch.r7;
175 regs->r6 = uregs.scratch.r6;
176 regs->r5 = uregs.scratch.r5;
177 regs->r4 = uregs.scratch.r4;
178 regs->r3 = uregs.scratch.r3;
179 regs->r2 = uregs.scratch.r2;
180 regs->r1 = uregs.scratch.r1;
181 regs->r0 = uregs.scratch.r0;
182 regs->sp = uregs.scratch.sp;
187 static inline int is_do_ss_needed(unsigned int magic)
189 if (MAGIC_SIGALTSTK == magic)
195 SYSCALL_DEFINE0(rt_sigreturn)
197 struct rt_sigframe __user *sf;
199 struct pt_regs *regs = current_pt_regs();
201 /* Always make any pending restarted system calls return -EINTR */
202 current->restart_block.fn = do_no_restart_syscall;
204 /* Since we stacked the signal on a word boundary,
205 * then 'sp' should be word aligned here. If it's
206 * not, then the user is trying to mess with us.
211 sf = (struct rt_sigframe __force __user *)(regs->sp);
213 if (!access_ok(sf, sizeof(*sf)))
216 if (__get_user(magic, &sf->sigret_magic))
219 if (unlikely(is_do_ss_needed(magic)))
220 if (restore_altstack(&sf->uc.uc_stack))
223 if (restore_usr_regs(regs, sf))
226 /* Don't restart from sigreturn */
227 syscall_wont_restart(regs);
230 * Ensure that sigreturn always returns to user mode (in case the
231 * regs saved on user stack got fudged between save and sigreturn)
232 * Otherwise it is easy to panic the kernel with a custom
233 * signal handler and/or restorer which clobberes the status32/ret
234 * to return to a bogus location in kernel mode.
236 regs->status32 |= STATUS_U_MASK;
246 * Determine which stack to use..
248 static inline void __user *get_sigframe(struct ksignal *ksig,
249 struct pt_regs *regs,
250 unsigned long framesize)
252 unsigned long sp = sigsp(regs->sp, ksig);
255 /* No matter what happens, 'sp' must be word
256 * aligned otherwise nasty things could happen
259 /* ATPCS B01 mandates 8-byte alignment */
260 frame = (void __user *)((sp - framesize) & ~7);
262 /* Check that we can actually write to the signal frame */
263 if (!access_ok(frame, framesize))
270 setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
272 struct rt_sigframe __user *sf;
273 unsigned int magic = 0;
276 sf = get_sigframe(ksig, regs, sizeof(struct rt_sigframe));
281 * w/o SA_SIGINFO, struct ucontext is partially populated (only
282 * uc_mcontext/uc_sigmask) for kernel's normal user state preservation
283 * during signal handler execution. This works for SA_SIGINFO as well
284 * although the semantics are now overloaded (the same reg state can be
285 * inspected by userland: but are they allowed to fiddle with it ?
287 err |= stash_usr_regs(sf, regs, set);
290 * SA_SIGINFO requires 3 args to signal handler:
291 * #1: sig-no (common to any handler)
293 * #3: struct ucontext (completely populated)
295 if (unlikely(ksig->ka.sa.sa_flags & SA_SIGINFO)) {
296 err |= copy_siginfo_to_user(&sf->info, &ksig->info);
297 err |= __put_user(0, &sf->uc.uc_flags);
298 err |= __put_user(NULL, &sf->uc.uc_link);
299 err |= __save_altstack(&sf->uc.uc_stack, regs->sp);
301 /* setup args 2 and 3 for user mode handler */
302 regs->r1 = (unsigned long)&sf->info;
303 regs->r2 = (unsigned long)&sf->uc;
306 * small optim to avoid unconditionally calling do_sigaltstack
307 * in sigreturn path, now that we only have rt_sigreturn
309 magic = MAGIC_SIGALTSTK;
312 err |= __put_user(magic, &sf->sigret_magic);
316 /* #1 arg to the user Signal handler */
317 regs->r0 = ksig->sig;
319 /* setup PC of user space signal handler */
320 regs->ret = (unsigned long)ksig->ka.sa.sa_handler;
323 * handler returns using sigreturn stub provided already by userspace
324 * If not, nuke the process right away
326 if(!(ksig->ka.sa.sa_flags & SA_RESTORER))
329 regs->blink = (unsigned long)ksig->ka.sa.sa_restorer;
331 /* User Stack for signal handler will be above the frame just carved */
332 regs->sp = (unsigned long)sf;
335 * Bug 94183, Clear the DE bit, so that when signal handler
336 * starts to run, it doesn't use BTA
338 regs->status32 &= ~STATUS_DE_MASK;
339 regs->status32 |= STATUS_L_MASK;
344 static void arc_restart_syscall(struct k_sigaction *ka, struct pt_regs *regs)
347 case -ERESTART_RESTARTBLOCK:
348 case -ERESTARTNOHAND:
350 * ERESTARTNOHAND means that the syscall should
351 * only be restarted if there was no handler for
352 * the signal, and since we only get here if there
353 * is a handler, we don't restart
355 regs->r0 = -EINTR; /* ERESTART_xxx is internal */
360 * ERESTARTSYS means to restart the syscall if
361 * there is no handler or the handler was
362 * registered with SA_RESTART
364 if (!(ka->sa.sa_flags & SA_RESTART)) {
370 case -ERESTARTNOINTR:
372 * ERESTARTNOINTR means that the syscall should
373 * be called again after the signal handler returns.
374 * Setup reg state just as it was before doing the trap
375 * r0 has been clobbered with sys call ret code thus it
376 * needs to be reloaded with orig first arg to syscall
377 * in orig_r0. Rest of relevant reg-file:
378 * r8 (syscall num) and (r1 - r7) will be reset to
379 * their orig user space value when we ret from kernel
381 regs->r0 = regs->orig_r0;
382 regs->ret -= is_isa_arcv2() ? 2 : 4;
388 * OK, we're invoking a handler
391 handle_signal(struct ksignal *ksig, struct pt_regs *regs)
393 sigset_t *oldset = sigmask_to_save();
396 /* Set up the stack frame */
397 failed = setup_rt_frame(ksig, oldset, regs);
399 signal_setup_done(failed, ksig, 0);
402 void do_signal(struct pt_regs *regs)
407 restart_scall = in_syscall(regs) && syscall_restartable(regs);
409 if (test_thread_flag(TIF_SIGPENDING) && get_signal(&ksig)) {
411 arc_restart_syscall(&ksig.ka, regs);
412 syscall_wont_restart(regs); /* No more restarts */
414 handle_signal(&ksig, regs);
419 /* No handler for syscall: restart it */
420 if (regs->r0 == -ERESTARTNOHAND ||
421 regs->r0 == -ERESTARTSYS || regs->r0 == -ERESTARTNOINTR) {
422 regs->r0 = regs->orig_r0;
423 regs->ret -= is_isa_arcv2() ? 2 : 4;
424 } else if (regs->r0 == -ERESTART_RESTARTBLOCK) {
425 regs->r8 = __NR_restart_syscall;
426 regs->ret -= is_isa_arcv2() ? 2 : 4;
428 syscall_wont_restart(regs); /* No more restarts */
431 /* If there's no signal to deliver, restore the saved sigmask back */
432 restore_saved_sigmask();
435 void do_notify_resume(struct pt_regs *regs)
438 * ASM glue guarantees that this is only called when returning to
441 if (test_thread_flag(TIF_NOTIFY_RESUME))
442 resume_user_mode_work(regs);