xref: /openbmc/linux/arch/powerpc/kernel/signal_64.c (revision 4800cd83)
1 /*
2  *  PowerPC version
3  *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
4  *
5  *  Derived from "arch/i386/kernel/signal.c"
6  *    Copyright (C) 1991, 1992 Linus Torvalds
7  *    1997-11-28  Modified for POSIX.1b signals by Richard Henderson
8  *
9  *  This program is free software; you can redistribute it and/or
10  *  modify it under the terms of the GNU General Public License
11  *  as published by the Free Software Foundation; either version
12  *  2 of the License, or (at your option) any later version.
13  */
14 
15 #include <linux/sched.h>
16 #include <linux/mm.h>
17 #include <linux/smp.h>
18 #include <linux/kernel.h>
19 #include <linux/signal.h>
20 #include <linux/errno.h>
21 #include <linux/wait.h>
22 #include <linux/unistd.h>
23 #include <linux/stddef.h>
24 #include <linux/elf.h>
25 #include <linux/ptrace.h>
26 #include <linux/module.h>
27 
28 #include <asm/sigcontext.h>
29 #include <asm/ucontext.h>
30 #include <asm/uaccess.h>
31 #include <asm/pgtable.h>
32 #include <asm/unistd.h>
33 #include <asm/cacheflush.h>
34 #include <asm/syscalls.h>
35 #include <asm/vdso.h>
36 
37 #include "signal.h"
38 
39 #define DEBUG_SIG 0
40 
41 #define GP_REGS_SIZE	min(sizeof(elf_gregset_t), sizeof(struct pt_regs))
42 #define FP_REGS_SIZE	sizeof(elf_fpregset_t)
43 
44 #define TRAMP_TRACEBACK	3
45 #define TRAMP_SIZE	6
46 
47 /*
48  * When we have signals to deliver, we set up on the user stack,
49  * going down from the original stack pointer:
50  *	1) a rt_sigframe struct which contains the ucontext
51  *	2) a gap of __SIGNAL_FRAMESIZE bytes which acts as a dummy caller
52  *	   frame for the signal handler.
53  */
54 
55 struct rt_sigframe {
56 	/* sys_rt_sigreturn requires the ucontext be the first field */
57 	struct ucontext uc;
58 	unsigned long _unused[2];
59 	unsigned int tramp[TRAMP_SIZE];
60 	struct siginfo __user *pinfo;
61 	void __user *puc;
62 	struct siginfo info;
63 	/* 64 bit ABI allows for 288 bytes below sp before decrementing it. */
64 	char abigap[288];
65 } __attribute__ ((aligned (16)));
66 
67 static const char fmt32[] = KERN_INFO \
68 	"%s[%d]: bad frame in %s: %08lx nip %08lx lr %08lx\n";
69 static const char fmt64[] = KERN_INFO \
70 	"%s[%d]: bad frame in %s: %016lx nip %016lx lr %016lx\n";
71 
72 /*
73  * Set up the sigcontext for the signal frame.
74  */
75 
76 static long setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
77 		 int signr, sigset_t *set, unsigned long handler,
78 		 int ctx_has_vsx_region)
79 {
80 	/* When CONFIG_ALTIVEC is set, we _always_ setup v_regs even if the
81 	 * process never used altivec yet (MSR_VEC is zero in pt_regs of
82 	 * the context). This is very important because we must ensure we
83 	 * don't lose the VRSAVE content that may have been set prior to
84 	 * the process doing its first vector operation
85 	 * Userland shall check AT_HWCAP to know wether it can rely on the
86 	 * v_regs pointer or not
87 	 */
88 #ifdef CONFIG_ALTIVEC
89 	elf_vrreg_t __user *v_regs = (elf_vrreg_t __user *)(((unsigned long)sc->vmx_reserve + 15) & ~0xful);
90 #endif
91 	unsigned long msr = regs->msr;
92 	long err = 0;
93 
94 	flush_fp_to_thread(current);
95 
96 #ifdef CONFIG_ALTIVEC
97 	err |= __put_user(v_regs, &sc->v_regs);
98 
99 	/* save altivec registers */
100 	if (current->thread.used_vr) {
101 		flush_altivec_to_thread(current);
102 		/* Copy 33 vec registers (vr0..31 and vscr) to the stack */
103 		err |= __copy_to_user(v_regs, current->thread.vr, 33 * sizeof(vector128));
104 		/* set MSR_VEC in the MSR value in the frame to indicate that sc->v_reg)
105 		 * contains valid data.
106 		 */
107 		msr |= MSR_VEC;
108 	}
109 	/* We always copy to/from vrsave, it's 0 if we don't have or don't
110 	 * use altivec.
111 	 */
112 	err |= __put_user(current->thread.vrsave, (u32 __user *)&v_regs[33]);
113 #else /* CONFIG_ALTIVEC */
114 	err |= __put_user(0, &sc->v_regs);
115 #endif /* CONFIG_ALTIVEC */
116 	flush_fp_to_thread(current);
117 	/* copy fpr regs and fpscr */
118 	err |= copy_fpr_to_user(&sc->fp_regs, current);
119 #ifdef CONFIG_VSX
120 	/*
121 	 * Copy VSX low doubleword to local buffer for formatting,
122 	 * then out to userspace.  Update v_regs to point after the
123 	 * VMX data.
124 	 */
125 	if (current->thread.used_vsr && ctx_has_vsx_region) {
126 		__giveup_vsx(current);
127 		v_regs += ELF_NVRREG;
128 		err |= copy_vsx_to_user(v_regs, current);
129 		/* set MSR_VSX in the MSR value in the frame to
130 		 * indicate that sc->vs_reg) contains valid data.
131 		 */
132 		msr |= MSR_VSX;
133 	}
134 #endif /* CONFIG_VSX */
135 	err |= __put_user(&sc->gp_regs, &sc->regs);
136 	WARN_ON(!FULL_REGS(regs));
137 	err |= __copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE);
138 	err |= __put_user(msr, &sc->gp_regs[PT_MSR]);
139 	err |= __put_user(signr, &sc->signal);
140 	err |= __put_user(handler, &sc->handler);
141 	if (set != NULL)
142 		err |=  __put_user(set->sig[0], &sc->oldmask);
143 
144 	return err;
145 }
146 
147 /*
148  * Restore the sigcontext from the signal frame.
149  */
150 
151 static long restore_sigcontext(struct pt_regs *regs, sigset_t *set, int sig,
152 			      struct sigcontext __user *sc)
153 {
154 #ifdef CONFIG_ALTIVEC
155 	elf_vrreg_t __user *v_regs;
156 #endif
157 	unsigned long err = 0;
158 	unsigned long save_r13 = 0;
159 	unsigned long msr;
160 #ifdef CONFIG_VSX
161 	int i;
162 #endif
163 
164 	/* If this is not a signal return, we preserve the TLS in r13 */
165 	if (!sig)
166 		save_r13 = regs->gpr[13];
167 
168 	/* copy the GPRs */
169 	err |= __copy_from_user(regs->gpr, sc->gp_regs, sizeof(regs->gpr));
170 	err |= __get_user(regs->nip, &sc->gp_regs[PT_NIP]);
171 	/* get MSR separately, transfer the LE bit if doing signal return */
172 	err |= __get_user(msr, &sc->gp_regs[PT_MSR]);
173 	if (sig)
174 		regs->msr = (regs->msr & ~MSR_LE) | (msr & MSR_LE);
175 	err |= __get_user(regs->orig_gpr3, &sc->gp_regs[PT_ORIG_R3]);
176 	err |= __get_user(regs->ctr, &sc->gp_regs[PT_CTR]);
177 	err |= __get_user(regs->link, &sc->gp_regs[PT_LNK]);
178 	err |= __get_user(regs->xer, &sc->gp_regs[PT_XER]);
179 	err |= __get_user(regs->ccr, &sc->gp_regs[PT_CCR]);
180 	/* skip SOFTE */
181 	regs->trap = 0;
182 	err |= __get_user(regs->dar, &sc->gp_regs[PT_DAR]);
183 	err |= __get_user(regs->dsisr, &sc->gp_regs[PT_DSISR]);
184 	err |= __get_user(regs->result, &sc->gp_regs[PT_RESULT]);
185 
186 	if (!sig)
187 		regs->gpr[13] = save_r13;
188 	if (set != NULL)
189 		err |=  __get_user(set->sig[0], &sc->oldmask);
190 
191 	/*
192 	 * Do this before updating the thread state in
193 	 * current->thread.fpr/vr.  That way, if we get preempted
194 	 * and another task grabs the FPU/Altivec, it won't be
195 	 * tempted to save the current CPU state into the thread_struct
196 	 * and corrupt what we are writing there.
197 	 */
198 	discard_lazy_cpu_state();
199 
200 	/*
201 	 * Force reload of FP/VEC.
202 	 * This has to be done before copying stuff into current->thread.fpr/vr
203 	 * for the reasons explained in the previous comment.
204 	 */
205 	regs->msr &= ~(MSR_FP | MSR_FE0 | MSR_FE1 | MSR_VEC | MSR_VSX);
206 
207 #ifdef CONFIG_ALTIVEC
208 	err |= __get_user(v_regs, &sc->v_regs);
209 	if (err)
210 		return err;
211 	if (v_regs && !access_ok(VERIFY_READ, v_regs, 34 * sizeof(vector128)))
212 		return -EFAULT;
213 	/* Copy 33 vec registers (vr0..31 and vscr) from the stack */
214 	if (v_regs != 0 && (msr & MSR_VEC) != 0)
215 		err |= __copy_from_user(current->thread.vr, v_regs,
216 					33 * sizeof(vector128));
217 	else if (current->thread.used_vr)
218 		memset(current->thread.vr, 0, 33 * sizeof(vector128));
219 	/* Always get VRSAVE back */
220 	if (v_regs != 0)
221 		err |= __get_user(current->thread.vrsave, (u32 __user *)&v_regs[33]);
222 	else
223 		current->thread.vrsave = 0;
224 #endif /* CONFIG_ALTIVEC */
225 	/* restore floating point */
226 	err |= copy_fpr_from_user(current, &sc->fp_regs);
227 #ifdef CONFIG_VSX
228 	/*
229 	 * Get additional VSX data. Update v_regs to point after the
230 	 * VMX data.  Copy VSX low doubleword from userspace to local
231 	 * buffer for formatting, then into the taskstruct.
232 	 */
233 	v_regs += ELF_NVRREG;
234 	if ((msr & MSR_VSX) != 0)
235 		err |= copy_vsx_from_user(current, v_regs);
236 	else
237 		for (i = 0; i < 32 ; i++)
238 			current->thread.fpr[i][TS_VSRLOWOFFSET] = 0;
239 #endif
240 	return err;
241 }
242 
243 /*
244  * Setup the trampoline code on the stack
245  */
246 static long setup_trampoline(unsigned int syscall, unsigned int __user *tramp)
247 {
248 	int i;
249 	long err = 0;
250 
251 	/* addi r1, r1, __SIGNAL_FRAMESIZE  # Pop the dummy stackframe */
252 	err |= __put_user(0x38210000UL | (__SIGNAL_FRAMESIZE & 0xffff), &tramp[0]);
253 	/* li r0, __NR_[rt_]sigreturn| */
254 	err |= __put_user(0x38000000UL | (syscall & 0xffff), &tramp[1]);
255 	/* sc */
256 	err |= __put_user(0x44000002UL, &tramp[2]);
257 
258 	/* Minimal traceback info */
259 	for (i=TRAMP_TRACEBACK; i < TRAMP_SIZE ;i++)
260 		err |= __put_user(0, &tramp[i]);
261 
262 	if (!err)
263 		flush_icache_range((unsigned long) &tramp[0],
264 			   (unsigned long) &tramp[TRAMP_SIZE]);
265 
266 	return err;
267 }
268 
269 /*
270  * Userspace code may pass a ucontext which doesn't include VSX added
271  * at the end.  We need to check for this case.
272  */
273 #define UCONTEXTSIZEWITHOUTVSX \
274 		(sizeof(struct ucontext) - 32*sizeof(long))
275 
276 /*
277  * Handle {get,set,swap}_context operations
278  */
279 int sys_swapcontext(struct ucontext __user *old_ctx,
280 		    struct ucontext __user *new_ctx,
281 		    long ctx_size, long r6, long r7, long r8, struct pt_regs *regs)
282 {
283 	unsigned char tmp;
284 	sigset_t set;
285 	unsigned long new_msr = 0;
286 	int ctx_has_vsx_region = 0;
287 
288 	if (new_ctx &&
289 	    get_user(new_msr, &new_ctx->uc_mcontext.gp_regs[PT_MSR]))
290 		return -EFAULT;
291 	/*
292 	 * Check that the context is not smaller than the original
293 	 * size (with VMX but without VSX)
294 	 */
295 	if (ctx_size < UCONTEXTSIZEWITHOUTVSX)
296 		return -EINVAL;
297 	/*
298 	 * If the new context state sets the MSR VSX bits but
299 	 * it doesn't provide VSX state.
300 	 */
301 	if ((ctx_size < sizeof(struct ucontext)) &&
302 	    (new_msr & MSR_VSX))
303 		return -EINVAL;
304 	/* Does the context have enough room to store VSX data? */
305 	if (ctx_size >= sizeof(struct ucontext))
306 		ctx_has_vsx_region = 1;
307 
308 	if (old_ctx != NULL) {
309 		if (!access_ok(VERIFY_WRITE, old_ctx, ctx_size)
310 		    || setup_sigcontext(&old_ctx->uc_mcontext, regs, 0, NULL, 0,
311 					ctx_has_vsx_region)
312 		    || __copy_to_user(&old_ctx->uc_sigmask,
313 				      &current->blocked, sizeof(sigset_t)))
314 			return -EFAULT;
315 	}
316 	if (new_ctx == NULL)
317 		return 0;
318 	if (!access_ok(VERIFY_READ, new_ctx, ctx_size)
319 	    || __get_user(tmp, (u8 __user *) new_ctx)
320 	    || __get_user(tmp, (u8 __user *) new_ctx + ctx_size - 1))
321 		return -EFAULT;
322 
323 	/*
324 	 * If we get a fault copying the context into the kernel's
325 	 * image of the user's registers, we can't just return -EFAULT
326 	 * because the user's registers will be corrupted.  For instance
327 	 * the NIP value may have been updated but not some of the
328 	 * other registers.  Given that we have done the access_ok
329 	 * and successfully read the first and last bytes of the region
330 	 * above, this should only happen in an out-of-memory situation
331 	 * or if another thread unmaps the region containing the context.
332 	 * We kill the task with a SIGSEGV in this situation.
333 	 */
334 
335 	if (__copy_from_user(&set, &new_ctx->uc_sigmask, sizeof(set)))
336 		do_exit(SIGSEGV);
337 	restore_sigmask(&set);
338 	if (restore_sigcontext(regs, NULL, 0, &new_ctx->uc_mcontext))
339 		do_exit(SIGSEGV);
340 
341 	/* This returns like rt_sigreturn */
342 	set_thread_flag(TIF_RESTOREALL);
343 	return 0;
344 }
345 
346 
347 /*
348  * Do a signal return; undo the signal stack.
349  */
350 
351 int sys_rt_sigreturn(unsigned long r3, unsigned long r4, unsigned long r5,
352 		     unsigned long r6, unsigned long r7, unsigned long r8,
353 		     struct pt_regs *regs)
354 {
355 	struct ucontext __user *uc = (struct ucontext __user *)regs->gpr[1];
356 	sigset_t set;
357 
358 	/* Always make any pending restarted system calls return -EINTR */
359 	current_thread_info()->restart_block.fn = do_no_restart_syscall;
360 
361 	if (!access_ok(VERIFY_READ, uc, sizeof(*uc)))
362 		goto badframe;
363 
364 	if (__copy_from_user(&set, &uc->uc_sigmask, sizeof(set)))
365 		goto badframe;
366 	restore_sigmask(&set);
367 	if (restore_sigcontext(regs, NULL, 1, &uc->uc_mcontext))
368 		goto badframe;
369 
370 	/* do_sigaltstack expects a __user pointer and won't modify
371 	 * what's in there anyway
372 	 */
373 	do_sigaltstack(&uc->uc_stack, NULL, regs->gpr[1]);
374 
375 	set_thread_flag(TIF_RESTOREALL);
376 	return 0;
377 
378 badframe:
379 #if DEBUG_SIG
380 	printk("badframe in sys_rt_sigreturn, regs=%p uc=%p &uc->uc_mcontext=%p\n",
381 	       regs, uc, &uc->uc_mcontext);
382 #endif
383 	if (show_unhandled_signals && printk_ratelimit())
384 		printk(regs->msr & MSR_SF ? fmt64 : fmt32,
385 			current->comm, current->pid, "rt_sigreturn",
386 			(long)uc, regs->nip, regs->link);
387 
388 	force_sig(SIGSEGV, current);
389 	return 0;
390 }
391 
392 int handle_rt_signal64(int signr, struct k_sigaction *ka, siginfo_t *info,
393 		sigset_t *set, struct pt_regs *regs)
394 {
395 	/* Handler is *really* a pointer to the function descriptor for
396 	 * the signal routine.  The first entry in the function
397 	 * descriptor is the entry address of signal and the second
398 	 * entry is the TOC value we need to use.
399 	 */
400 	func_descr_t __user *funct_desc_ptr;
401 	struct rt_sigframe __user *frame;
402 	unsigned long newsp = 0;
403 	long err = 0;
404 
405 	frame = get_sigframe(ka, regs, sizeof(*frame), 0);
406 	if (unlikely(frame == NULL))
407 		goto badframe;
408 
409 	err |= __put_user(&frame->info, &frame->pinfo);
410 	err |= __put_user(&frame->uc, &frame->puc);
411 	err |= copy_siginfo_to_user(&frame->info, info);
412 	if (err)
413 		goto badframe;
414 
415 	/* Create the ucontext.  */
416 	err |= __put_user(0, &frame->uc.uc_flags);
417 	err |= __put_user(0, &frame->uc.uc_link);
418 	err |= __put_user(current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
419 	err |= __put_user(sas_ss_flags(regs->gpr[1]),
420 			  &frame->uc.uc_stack.ss_flags);
421 	err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
422 	err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, signr, NULL,
423 				(unsigned long)ka->sa.sa_handler, 1);
424 	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
425 	if (err)
426 		goto badframe;
427 
428 	/* Make sure signal handler doesn't get spurious FP exceptions */
429 	current->thread.fpscr.val = 0;
430 
431 	/* Set up to return from userspace. */
432 	if (vdso64_rt_sigtramp && current->mm->context.vdso_base) {
433 		regs->link = current->mm->context.vdso_base + vdso64_rt_sigtramp;
434 	} else {
435 		err |= setup_trampoline(__NR_rt_sigreturn, &frame->tramp[0]);
436 		if (err)
437 			goto badframe;
438 		regs->link = (unsigned long) &frame->tramp[0];
439 	}
440 	funct_desc_ptr = (func_descr_t __user *) ka->sa.sa_handler;
441 
442 	/* Allocate a dummy caller frame for the signal handler. */
443 	newsp = ((unsigned long)frame) - __SIGNAL_FRAMESIZE;
444 	err |= put_user(regs->gpr[1], (unsigned long __user *)newsp);
445 
446 	/* Set up "regs" so we "return" to the signal handler. */
447 	err |= get_user(regs->nip, &funct_desc_ptr->entry);
448 	/* enter the signal handler in big-endian mode */
449 	regs->msr &= ~MSR_LE;
450 	regs->gpr[1] = newsp;
451 	err |= get_user(regs->gpr[2], &funct_desc_ptr->toc);
452 	regs->gpr[3] = signr;
453 	regs->result = 0;
454 	if (ka->sa.sa_flags & SA_SIGINFO) {
455 		err |= get_user(regs->gpr[4], (unsigned long __user *)&frame->pinfo);
456 		err |= get_user(regs->gpr[5], (unsigned long __user *)&frame->puc);
457 		regs->gpr[6] = (unsigned long) frame;
458 	} else {
459 		regs->gpr[4] = (unsigned long)&frame->uc.uc_mcontext;
460 	}
461 	if (err)
462 		goto badframe;
463 
464 	return 1;
465 
466 badframe:
467 #if DEBUG_SIG
468 	printk("badframe in setup_rt_frame, regs=%p frame=%p newsp=%lx\n",
469 	       regs, frame, newsp);
470 #endif
471 	if (show_unhandled_signals && printk_ratelimit())
472 		printk(regs->msr & MSR_SF ? fmt64 : fmt32,
473 			current->comm, current->pid, "setup_rt_frame",
474 			(long)frame, regs->nip, regs->link);
475 
476 	force_sigsegv(signr, current);
477 	return 0;
478 }
479