2 * Signal Handling for ARC
4 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
10 * vineetg: Jan 2010 (Restarting of timer related syscalls)
12 * vineetg: Nov 2009 (Everything needed for TIF_RESTORE_SIGMASK)
13 * -do_signal() supports TIF_RESTORE_SIGMASK
14 * -do_signal() no loner needs oldset, required by OLD sys_sigsuspend
15 * -sys_rt_sigsuspend() now comes from generic code, so discard arch implemen
16 * -sys_sigsuspend() no longer needs to fudge ptregs, hence that arg removed
17 * -sys_sigsuspend() no longer loops for do_signal(), sets TIF_xxx and leaves
18 * the job to do_signal()
21 * -Modified Code to support the uClibc provided userland sigreturn stub
22 * to avoid kernel synthesing it on user stack at runtime, costing TLB
23 * probes and Cache line flushes.
26 * -In stash_usr_regs( ) and restore_usr_regs( ), save/restore of user regs
27 * in done in block copy rather than one word at a time.
28 * This saves around 2K of code and improves LMBench lat_sig <catch>
30 * rajeshwarr: Feb 2009
31 * - Support for Realtime Signals
33 * vineetg: Aug 11th 2008: Bug #94183
34 * -ViXS were still seeing crashes when using insmod to load drivers.
35 * It turned out that the code to change Execute permssions for TLB entries
36 * of user was not guarded for interrupts (mod_tlb_permission)
37 * This was causing TLB entries to be overwritten on unrelated indexes
39 * Vineetg: July 15th 2008: Bug #94183
40 * -Exception happens in Delay slot of a JMP, and before user space resumes,
41 * Signal is delivered (Ctrl + C) = >SIGINT.
42 * setup_frame( ) sets up PC,SP,BLINK to enable user space signal handler
43 * to run, but doesn't clear the Delay slot bit from status32. As a result,
44 * on resuming user mode, signal handler branches off to BTA of orig JMP
45 * -FIX: clear the DE bit from status32 in setup_frame( )
47 * Rahul Trivedi, Kanika Nema: Codito Technologies 2004
50 #include <linux/signal.h>
51 #include <linux/ptrace.h>
52 #include <linux/personality.h>
53 #include <linux/uaccess.h>
54 #include <linux/syscalls.h>
55 #include <linux/tracehook.h>
56 #include <asm/ucontext.h>
61 #define MAGIC_SIGALTSTK 0x07302004
62 unsigned int sigret_magic
;
66 stash_usr_regs(struct rt_sigframe __user
*sf
, struct pt_regs
*regs
,
70 struct user_regs_struct uregs
;
72 uregs
.scratch
.bta
= regs
->bta
;
73 uregs
.scratch
.lp_start
= regs
->lp_start
;
74 uregs
.scratch
.lp_end
= regs
->lp_end
;
75 uregs
.scratch
.lp_count
= regs
->lp_count
;
76 uregs
.scratch
.status32
= regs
->status32
;
77 uregs
.scratch
.ret
= regs
->ret
;
78 uregs
.scratch
.blink
= regs
->blink
;
79 uregs
.scratch
.fp
= regs
->fp
;
80 uregs
.scratch
.gp
= regs
->r26
;
81 uregs
.scratch
.r12
= regs
->r12
;
82 uregs
.scratch
.r11
= regs
->r11
;
83 uregs
.scratch
.r10
= regs
->r10
;
84 uregs
.scratch
.r9
= regs
->r9
;
85 uregs
.scratch
.r8
= regs
->r8
;
86 uregs
.scratch
.r7
= regs
->r7
;
87 uregs
.scratch
.r6
= regs
->r6
;
88 uregs
.scratch
.r5
= regs
->r5
;
89 uregs
.scratch
.r4
= regs
->r4
;
90 uregs
.scratch
.r3
= regs
->r3
;
91 uregs
.scratch
.r2
= regs
->r2
;
92 uregs
.scratch
.r1
= regs
->r1
;
93 uregs
.scratch
.r0
= regs
->r0
;
94 uregs
.scratch
.sp
= regs
->sp
;
96 err
= __copy_to_user(&(sf
->uc
.uc_mcontext
.regs
.scratch
), &uregs
.scratch
,
97 sizeof(sf
->uc
.uc_mcontext
.regs
.scratch
));
98 err
|= __copy_to_user(&sf
->uc
.uc_sigmask
, set
, sizeof(sigset_t
));
103 static int restore_usr_regs(struct pt_regs
*regs
, struct rt_sigframe __user
*sf
)
107 struct user_regs_struct uregs
;
109 err
= __copy_from_user(&set
, &sf
->uc
.uc_sigmask
, sizeof(set
));
110 err
|= __copy_from_user(&uregs
.scratch
,
111 &(sf
->uc
.uc_mcontext
.regs
.scratch
),
112 sizeof(sf
->uc
.uc_mcontext
.regs
.scratch
));
116 set_current_blocked(&set
);
117 regs
->bta
= uregs
.scratch
.bta
;
118 regs
->lp_start
= uregs
.scratch
.lp_start
;
119 regs
->lp_end
= uregs
.scratch
.lp_end
;
120 regs
->lp_count
= uregs
.scratch
.lp_count
;
121 regs
->status32
= uregs
.scratch
.status32
;
122 regs
->ret
= uregs
.scratch
.ret
;
123 regs
->blink
= uregs
.scratch
.blink
;
124 regs
->fp
= uregs
.scratch
.fp
;
125 regs
->r26
= uregs
.scratch
.gp
;
126 regs
->r12
= uregs
.scratch
.r12
;
127 regs
->r11
= uregs
.scratch
.r11
;
128 regs
->r10
= uregs
.scratch
.r10
;
129 regs
->r9
= uregs
.scratch
.r9
;
130 regs
->r8
= uregs
.scratch
.r8
;
131 regs
->r7
= uregs
.scratch
.r7
;
132 regs
->r6
= uregs
.scratch
.r6
;
133 regs
->r5
= uregs
.scratch
.r5
;
134 regs
->r4
= uregs
.scratch
.r4
;
135 regs
->r3
= uregs
.scratch
.r3
;
136 regs
->r2
= uregs
.scratch
.r2
;
137 regs
->r1
= uregs
.scratch
.r1
;
138 regs
->r0
= uregs
.scratch
.r0
;
139 regs
->sp
= uregs
.scratch
.sp
;
144 static inline int is_do_ss_needed(unsigned int magic
)
146 if (MAGIC_SIGALTSTK
== magic
)
152 SYSCALL_DEFINE0(rt_sigreturn
)
154 struct rt_sigframe __user
*sf
;
156 struct pt_regs
*regs
= current_pt_regs();
158 /* Always make any pending restarted system calls return -EINTR */
159 current
->restart_block
.fn
= do_no_restart_syscall
;
161 /* Since we stacked the signal on a word boundary,
162 * then 'sp' should be word aligned here. If it's
163 * not, then the user is trying to mess with us.
168 sf
= (struct rt_sigframe __force __user
*)(regs
->sp
);
170 if (!access_ok(VERIFY_READ
, sf
, sizeof(*sf
)))
173 if (__get_user(magic
, &sf
->sigret_magic
))
176 if (unlikely(is_do_ss_needed(magic
)))
177 if (restore_altstack(&sf
->uc
.uc_stack
))
180 if (restore_usr_regs(regs
, sf
))
183 /* Don't restart from sigreturn */
184 syscall_wont_restart(regs
);
187 * Ensure that sigreturn always returns to user mode (in case the
188 * regs saved on user stack got fudged between save and sigreturn)
189 * Otherwise it is easy to panic the kernel with a custom
190 * signal handler and/or restorer which clobberes the status32/ret
191 * to return to a bogus location in kernel mode.
193 regs
->status32
|= STATUS_U_MASK
;
198 force_sig(SIGSEGV
, current
);
203 * Determine which stack to use..
205 static inline void __user
*get_sigframe(struct ksignal
*ksig
,
206 struct pt_regs
*regs
,
207 unsigned long framesize
)
209 unsigned long sp
= sigsp(regs
->sp
, ksig
);
212 /* No matter what happens, 'sp' must be word
213 * aligned otherwise nasty things could happen
216 /* ATPCS B01 mandates 8-byte alignment */
217 frame
= (void __user
*)((sp
- framesize
) & ~7);
219 /* Check that we can actually write to the signal frame */
220 if (!access_ok(VERIFY_WRITE
, frame
, framesize
))
227 setup_rt_frame(struct ksignal
*ksig
, sigset_t
*set
, struct pt_regs
*regs
)
229 struct rt_sigframe __user
*sf
;
230 unsigned int magic
= 0;
233 sf
= get_sigframe(ksig
, regs
, sizeof(struct rt_sigframe
));
238 * w/o SA_SIGINFO, struct ucontext is partially populated (only
239 * uc_mcontext/uc_sigmask) for kernel's normal user state preservation
240 * during signal handler execution. This works for SA_SIGINFO as well
241 * although the semantics are now overloaded (the same reg state can be
242 * inspected by userland: but are they allowed to fiddle with it ?
244 err
|= stash_usr_regs(sf
, regs
, set
);
247 * SA_SIGINFO requires 3 args to signal handler:
248 * #1: sig-no (common to any handler)
250 * #3: struct ucontext (completely populated)
252 if (unlikely(ksig
->ka
.sa
.sa_flags
& SA_SIGINFO
)) {
253 err
|= copy_siginfo_to_user(&sf
->info
, &ksig
->info
);
254 err
|= __put_user(0, &sf
->uc
.uc_flags
);
255 err
|= __put_user(NULL
, &sf
->uc
.uc_link
);
256 err
|= __save_altstack(&sf
->uc
.uc_stack
, regs
->sp
);
258 /* setup args 2 and 3 for user mode handler */
259 regs
->r1
= (unsigned long)&sf
->info
;
260 regs
->r2
= (unsigned long)&sf
->uc
;
263 * small optim to avoid unconditonally calling do_sigaltstack
264 * in sigreturn path, now that we only have rt_sigreturn
266 magic
= MAGIC_SIGALTSTK
;
269 err
|= __put_user(magic
, &sf
->sigret_magic
);
273 /* #1 arg to the user Signal handler */
274 regs
->r0
= ksig
->sig
;
276 /* setup PC of user space signal handler */
277 regs
->ret
= (unsigned long)ksig
->ka
.sa
.sa_handler
;
280 * handler returns using sigreturn stub provided already by userpsace
281 * If not, nuke the process right away
283 if(!(ksig
->ka
.sa
.sa_flags
& SA_RESTORER
))
286 regs
->blink
= (unsigned long)ksig
->ka
.sa
.sa_restorer
;
288 /* User Stack for signal handler will be above the frame just carved */
289 regs
->sp
= (unsigned long)sf
;
292 * Bug 94183, Clear the DE bit, so that when signal handler
293 * starts to run, it doesn't use BTA
295 regs
->status32
&= ~STATUS_DE_MASK
;
296 regs
->status32
|= STATUS_L_MASK
;
301 static void arc_restart_syscall(struct k_sigaction
*ka
, struct pt_regs
*regs
)
304 case -ERESTART_RESTARTBLOCK
:
305 case -ERESTARTNOHAND
:
307 * ERESTARTNOHAND means that the syscall should
308 * only be restarted if there was no handler for
309 * the signal, and since we only get here if there
310 * is a handler, we don't restart
312 regs
->r0
= -EINTR
; /* ERESTART_xxx is internal */
317 * ERESTARTSYS means to restart the syscall if
318 * there is no handler or the handler was
319 * registered with SA_RESTART
321 if (!(ka
->sa
.sa_flags
& SA_RESTART
)) {
327 case -ERESTARTNOINTR
:
329 * ERESTARTNOINTR means that the syscall should
330 * be called again after the signal handler returns.
331 * Setup reg state just as it was before doing the trap
332 * r0 has been clobbered with sys call ret code thus it
333 * needs to be reloaded with orig first arg to syscall
334 * in orig_r0. Rest of relevant reg-file:
335 * r8 (syscall num) and (r1 - r7) will be reset to
336 * their orig user space value when we ret from kernel
338 regs
->r0
= regs
->orig_r0
;
339 regs
->ret
-= is_isa_arcv2() ? 2 : 4;
345 * OK, we're invoking a handler
348 handle_signal(struct ksignal
*ksig
, struct pt_regs
*regs
)
350 sigset_t
*oldset
= sigmask_to_save();
353 /* Set up the stack frame */
354 failed
= setup_rt_frame(ksig
, oldset
, regs
);
356 signal_setup_done(failed
, ksig
, 0);
359 void do_signal(struct pt_regs
*regs
)
364 restart_scall
= in_syscall(regs
) && syscall_restartable(regs
);
366 if (get_signal(&ksig
)) {
368 arc_restart_syscall(&ksig
.ka
, regs
);
369 syscall_wont_restart(regs
); /* No more restarts */
371 handle_signal(&ksig
, regs
);
376 /* No handler for syscall: restart it */
377 if (regs
->r0
== -ERESTARTNOHAND
||
378 regs
->r0
== -ERESTARTSYS
|| regs
->r0
== -ERESTARTNOINTR
) {
379 regs
->r0
= regs
->orig_r0
;
380 regs
->ret
-= is_isa_arcv2() ? 2 : 4;
381 } else if (regs
->r0
== -ERESTART_RESTARTBLOCK
) {
382 regs
->r8
= __NR_restart_syscall
;
383 regs
->ret
-= is_isa_arcv2() ? 2 : 4;
385 syscall_wont_restart(regs
); /* No more restarts */
388 /* If there's no signal to deliver, restore the saved sigmask back */
389 restore_saved_sigmask();
392 void do_notify_resume(struct pt_regs
*regs
)
395 * ASM glue gaurantees that this is only called when returning to
398 if (test_and_clear_thread_flag(TIF_NOTIFY_RESUME
))
399 tracehook_notify_resume(regs
);