xref: /openbmc/linux/arch/powerpc/kernel/signal_64.c (revision 732a675a)
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 {
79 	/* When CONFIG_ALTIVEC is set, we _always_ setup v_regs even if the
80 	 * process never used altivec yet (MSR_VEC is zero in pt_regs of
81 	 * the context). This is very important because we must ensure we
82 	 * don't lose the VRSAVE content that may have been set prior to
83 	 * the process doing its first vector operation
84 	 * Userland shall check AT_HWCAP to know wether it can rely on the
85 	 * v_regs pointer or not
86 	 */
87 #ifdef CONFIG_ALTIVEC
88 	elf_vrreg_t __user *v_regs = (elf_vrreg_t __user *)(((unsigned long)sc->vmx_reserve + 15) & ~0xful);
89 #endif
90 	unsigned long msr = regs->msr;
91 	long err = 0;
92 
93 	flush_fp_to_thread(current);
94 
95 #ifdef CONFIG_ALTIVEC
96 	err |= __put_user(v_regs, &sc->v_regs);
97 
98 	/* save altivec registers */
99 	if (current->thread.used_vr) {
100 		flush_altivec_to_thread(current);
101 		/* Copy 33 vec registers (vr0..31 and vscr) to the stack */
102 		err |= __copy_to_user(v_regs, current->thread.vr, 33 * sizeof(vector128));
103 		/* set MSR_VEC in the MSR value in the frame to indicate that sc->v_reg)
104 		 * contains valid data.
105 		 */
106 		msr |= MSR_VEC;
107 	}
108 	/* We always copy to/from vrsave, it's 0 if we don't have or don't
109 	 * use altivec.
110 	 */
111 	err |= __put_user(current->thread.vrsave, (u32 __user *)&v_regs[33]);
112 #else /* CONFIG_ALTIVEC */
113 	err |= __put_user(0, &sc->v_regs);
114 #endif /* CONFIG_ALTIVEC */
115 	err |= __put_user(&sc->gp_regs, &sc->regs);
116 	WARN_ON(!FULL_REGS(regs));
117 	err |= __copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE);
118 	err |= __put_user(msr, &sc->gp_regs[PT_MSR]);
119 	err |= __copy_to_user(&sc->fp_regs, &current->thread.fpr, FP_REGS_SIZE);
120 	err |= __put_user(signr, &sc->signal);
121 	err |= __put_user(handler, &sc->handler);
122 	if (set != NULL)
123 		err |=  __put_user(set->sig[0], &sc->oldmask);
124 
125 	return err;
126 }
127 
128 /*
129  * Restore the sigcontext from the signal frame.
130  */
131 
132 static long restore_sigcontext(struct pt_regs *regs, sigset_t *set, int sig,
133 			      struct sigcontext __user *sc)
134 {
135 #ifdef CONFIG_ALTIVEC
136 	elf_vrreg_t __user *v_regs;
137 #endif
138 	unsigned long err = 0;
139 	unsigned long save_r13 = 0;
140 	elf_greg_t *gregs = (elf_greg_t *)regs;
141 	unsigned long msr;
142 	int i;
143 
144 	/* If this is not a signal return, we preserve the TLS in r13 */
145 	if (!sig)
146 		save_r13 = regs->gpr[13];
147 
148 	/* copy everything before MSR */
149 	err |= __copy_from_user(regs, &sc->gp_regs,
150 				PT_MSR*sizeof(unsigned long));
151 
152 	/* get MSR separately, transfer the LE bit if doing signal return */
153 	err |= __get_user(msr, &sc->gp_regs[PT_MSR]);
154 	if (sig)
155 		regs->msr = (regs->msr & ~MSR_LE) | (msr & MSR_LE);
156 
157 	/* skip SOFTE */
158 	for (i = PT_MSR+1; i <= PT_RESULT; i++) {
159 		if (i == PT_SOFTE)
160 			continue;
161 		err |= __get_user(gregs[i], &sc->gp_regs[i]);
162 	}
163 
164 	if (!sig)
165 		regs->gpr[13] = save_r13;
166 	if (set != NULL)
167 		err |=  __get_user(set->sig[0], &sc->oldmask);
168 
169 	/*
170 	 * Do this before updating the thread state in
171 	 * current->thread.fpr/vr.  That way, if we get preempted
172 	 * and another task grabs the FPU/Altivec, it won't be
173 	 * tempted to save the current CPU state into the thread_struct
174 	 * and corrupt what we are writing there.
175 	 */
176 	discard_lazy_cpu_state();
177 
178 	/*
179 	 * Force reload of FP/VEC.
180 	 * This has to be done before copying stuff into current->thread.fpr/vr
181 	 * for the reasons explained in the previous comment.
182 	 */
183 	regs->msr &= ~(MSR_FP | MSR_FE0 | MSR_FE1 | MSR_VEC);
184 
185 	err |= __copy_from_user(&current->thread.fpr, &sc->fp_regs, FP_REGS_SIZE);
186 
187 #ifdef CONFIG_ALTIVEC
188 	err |= __get_user(v_regs, &sc->v_regs);
189 	if (err)
190 		return err;
191 	if (v_regs && !access_ok(VERIFY_READ, v_regs, 34 * sizeof(vector128)))
192 		return -EFAULT;
193 	/* Copy 33 vec registers (vr0..31 and vscr) from the stack */
194 	if (v_regs != 0 && (msr & MSR_VEC) != 0)
195 		err |= __copy_from_user(current->thread.vr, v_regs,
196 					33 * sizeof(vector128));
197 	else if (current->thread.used_vr)
198 		memset(current->thread.vr, 0, 33 * sizeof(vector128));
199 	/* Always get VRSAVE back */
200 	if (v_regs != 0)
201 		err |= __get_user(current->thread.vrsave, (u32 __user *)&v_regs[33]);
202 	else
203 		current->thread.vrsave = 0;
204 #endif /* CONFIG_ALTIVEC */
205 
206 	return err;
207 }
208 
209 /*
210  * Setup the trampoline code on the stack
211  */
212 static long setup_trampoline(unsigned int syscall, unsigned int __user *tramp)
213 {
214 	int i;
215 	long err = 0;
216 
217 	/* addi r1, r1, __SIGNAL_FRAMESIZE  # Pop the dummy stackframe */
218 	err |= __put_user(0x38210000UL | (__SIGNAL_FRAMESIZE & 0xffff), &tramp[0]);
219 	/* li r0, __NR_[rt_]sigreturn| */
220 	err |= __put_user(0x38000000UL | (syscall & 0xffff), &tramp[1]);
221 	/* sc */
222 	err |= __put_user(0x44000002UL, &tramp[2]);
223 
224 	/* Minimal traceback info */
225 	for (i=TRAMP_TRACEBACK; i < TRAMP_SIZE ;i++)
226 		err |= __put_user(0, &tramp[i]);
227 
228 	if (!err)
229 		flush_icache_range((unsigned long) &tramp[0],
230 			   (unsigned long) &tramp[TRAMP_SIZE]);
231 
232 	return err;
233 }
234 
235 /*
236  * Handle {get,set,swap}_context operations
237  */
238 int sys_swapcontext(struct ucontext __user *old_ctx,
239 		    struct ucontext __user *new_ctx,
240 		    long ctx_size, long r6, long r7, long r8, struct pt_regs *regs)
241 {
242 	unsigned char tmp;
243 	sigset_t set;
244 
245 	/* Context size is for future use. Right now, we only make sure
246 	 * we are passed something we understand
247 	 */
248 	if (ctx_size < sizeof(struct ucontext))
249 		return -EINVAL;
250 
251 	if (old_ctx != NULL) {
252 		if (!access_ok(VERIFY_WRITE, old_ctx, sizeof(*old_ctx))
253 		    || setup_sigcontext(&old_ctx->uc_mcontext, regs, 0, NULL, 0)
254 		    || __copy_to_user(&old_ctx->uc_sigmask,
255 				      &current->blocked, sizeof(sigset_t)))
256 			return -EFAULT;
257 	}
258 	if (new_ctx == NULL)
259 		return 0;
260 	if (!access_ok(VERIFY_READ, new_ctx, sizeof(*new_ctx))
261 	    || __get_user(tmp, (u8 __user *) new_ctx)
262 	    || __get_user(tmp, (u8 __user *) (new_ctx + 1) - 1))
263 		return -EFAULT;
264 
265 	/*
266 	 * If we get a fault copying the context into the kernel's
267 	 * image of the user's registers, we can't just return -EFAULT
268 	 * because the user's registers will be corrupted.  For instance
269 	 * the NIP value may have been updated but not some of the
270 	 * other registers.  Given that we have done the access_ok
271 	 * and successfully read the first and last bytes of the region
272 	 * above, this should only happen in an out-of-memory situation
273 	 * or if another thread unmaps the region containing the context.
274 	 * We kill the task with a SIGSEGV in this situation.
275 	 */
276 
277 	if (__copy_from_user(&set, &new_ctx->uc_sigmask, sizeof(set)))
278 		do_exit(SIGSEGV);
279 	restore_sigmask(&set);
280 	if (restore_sigcontext(regs, NULL, 0, &new_ctx->uc_mcontext))
281 		do_exit(SIGSEGV);
282 
283 	/* This returns like rt_sigreturn */
284 	set_thread_flag(TIF_RESTOREALL);
285 	return 0;
286 }
287 
288 
289 /*
290  * Do a signal return; undo the signal stack.
291  */
292 
293 int sys_rt_sigreturn(unsigned long r3, unsigned long r4, unsigned long r5,
294 		     unsigned long r6, unsigned long r7, unsigned long r8,
295 		     struct pt_regs *regs)
296 {
297 	struct ucontext __user *uc = (struct ucontext __user *)regs->gpr[1];
298 	sigset_t set;
299 
300 	/* Always make any pending restarted system calls return -EINTR */
301 	current_thread_info()->restart_block.fn = do_no_restart_syscall;
302 
303 	if (!access_ok(VERIFY_READ, uc, sizeof(*uc)))
304 		goto badframe;
305 
306 	if (__copy_from_user(&set, &uc->uc_sigmask, sizeof(set)))
307 		goto badframe;
308 	restore_sigmask(&set);
309 	if (restore_sigcontext(regs, NULL, 1, &uc->uc_mcontext))
310 		goto badframe;
311 
312 	/* do_sigaltstack expects a __user pointer and won't modify
313 	 * what's in there anyway
314 	 */
315 	do_sigaltstack(&uc->uc_stack, NULL, regs->gpr[1]);
316 
317 	set_thread_flag(TIF_RESTOREALL);
318 	return 0;
319 
320 badframe:
321 #if DEBUG_SIG
322 	printk("badframe in sys_rt_sigreturn, regs=%p uc=%p &uc->uc_mcontext=%p\n",
323 	       regs, uc, &uc->uc_mcontext);
324 #endif
325 	if (show_unhandled_signals && printk_ratelimit())
326 		printk(regs->msr & MSR_SF ? fmt64 : fmt32,
327 			current->comm, current->pid, "rt_sigreturn",
328 			(long)uc, regs->nip, regs->link);
329 
330 	force_sig(SIGSEGV, current);
331 	return 0;
332 }
333 
334 int handle_rt_signal64(int signr, struct k_sigaction *ka, siginfo_t *info,
335 		sigset_t *set, struct pt_regs *regs)
336 {
337 	/* Handler is *really* a pointer to the function descriptor for
338 	 * the signal routine.  The first entry in the function
339 	 * descriptor is the entry address of signal and the second
340 	 * entry is the TOC value we need to use.
341 	 */
342 	func_descr_t __user *funct_desc_ptr;
343 	struct rt_sigframe __user *frame;
344 	unsigned long newsp = 0;
345 	long err = 0;
346 
347 	frame = get_sigframe(ka, regs, sizeof(*frame));
348 	if (unlikely(frame == NULL))
349 		goto badframe;
350 
351 	err |= __put_user(&frame->info, &frame->pinfo);
352 	err |= __put_user(&frame->uc, &frame->puc);
353 	err |= copy_siginfo_to_user(&frame->info, info);
354 	if (err)
355 		goto badframe;
356 
357 	/* Create the ucontext.  */
358 	err |= __put_user(0, &frame->uc.uc_flags);
359 	err |= __put_user(0, &frame->uc.uc_link);
360 	err |= __put_user(current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
361 	err |= __put_user(sas_ss_flags(regs->gpr[1]),
362 			  &frame->uc.uc_stack.ss_flags);
363 	err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
364 	err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, signr, NULL,
365 				(unsigned long)ka->sa.sa_handler);
366 	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
367 	if (err)
368 		goto badframe;
369 
370 	/* Make sure signal handler doesn't get spurious FP exceptions */
371 	current->thread.fpscr.val = 0;
372 
373 	/* Set up to return from userspace. */
374 	if (vdso64_rt_sigtramp && current->mm->context.vdso_base) {
375 		regs->link = current->mm->context.vdso_base + vdso64_rt_sigtramp;
376 	} else {
377 		err |= setup_trampoline(__NR_rt_sigreturn, &frame->tramp[0]);
378 		if (err)
379 			goto badframe;
380 		regs->link = (unsigned long) &frame->tramp[0];
381 	}
382 	funct_desc_ptr = (func_descr_t __user *) ka->sa.sa_handler;
383 
384 	/* Allocate a dummy caller frame for the signal handler. */
385 	newsp = ((unsigned long)frame) - __SIGNAL_FRAMESIZE;
386 	err |= put_user(regs->gpr[1], (unsigned long __user *)newsp);
387 
388 	/* Set up "regs" so we "return" to the signal handler. */
389 	err |= get_user(regs->nip, &funct_desc_ptr->entry);
390 	/* enter the signal handler in big-endian mode */
391 	regs->msr &= ~MSR_LE;
392 	regs->gpr[1] = newsp;
393 	err |= get_user(regs->gpr[2], &funct_desc_ptr->toc);
394 	regs->gpr[3] = signr;
395 	regs->result = 0;
396 	if (ka->sa.sa_flags & SA_SIGINFO) {
397 		err |= get_user(regs->gpr[4], (unsigned long __user *)&frame->pinfo);
398 		err |= get_user(regs->gpr[5], (unsigned long __user *)&frame->puc);
399 		regs->gpr[6] = (unsigned long) frame;
400 	} else {
401 		regs->gpr[4] = (unsigned long)&frame->uc.uc_mcontext;
402 	}
403 	if (err)
404 		goto badframe;
405 
406 	return 1;
407 
408 badframe:
409 #if DEBUG_SIG
410 	printk("badframe in setup_rt_frame, regs=%p frame=%p newsp=%lx\n",
411 	       regs, frame, newsp);
412 #endif
413 	if (show_unhandled_signals && printk_ratelimit())
414 		printk(regs->msr & MSR_SF ? fmt64 : fmt32,
415 			current->comm, current->pid, "setup_rt_frame",
416 			(long)frame, regs->nip, regs->link);
417 
418 	force_sigsegv(signr, current);
419 	return 0;
420 }
421