arm64: Signal handling support

/*

 * Copyright (C) 2012 ARM Ltd.

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program.  If not, see <http://www.gnu.org/licenses/>.

 */

#ifndef __ASM_SIGCONTEXT_H

#define __ASM_SIGCONTEXT_H

#include <linux/types.h>

/*

 * Signal context structure - contains all info to do with the state

 * before the signal handler was invoked.

 */

struct sigcontext {

	__u64 fault_address;

	/* AArch64 registers */

	__u64 regs[31];

	__u64 sp;

	__u64 pc;

	__u64 pstate;

	/* 4K reserved for FP/SIMD state and future expansion */

	__u8 __reserved[4096] __attribute__((__aligned__(16)));

};

/*

 * Header to be used at the beginning of structures extending the user

 * context. Such structures must be placed after the rt_sigframe on the stack

 * and be 16-byte aligned. The last structure must be a dummy one with the

 * magic and size set to 0.

 */

struct _aarch64_ctx {

	__u32 magic;

	__u32 size;

};

#define FPSIMD_MAGIC	0x46508001

struct fpsimd_context {

	struct _aarch64_ctx head;

	__u32 fpsr;

	__u32 fpcr;

	__uint128_t vregs[32];

};

#ifdef __KERNEL__

/*

 * Auxiliary context saved in the sigcontext.__reserved array. Not exported to

 * user space as it will change with the addition of new context. User space

 * should check the magic/size information.

 */

struct aux_context {

	struct fpsimd_context fpsimd;

	/* additional context to be added before "end" */

	struct _aarch64_ctx end;

};

#endif

#endif

/*

 * Copyright (C) 2012 ARM Ltd.

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program.  If not, see <http://www.gnu.org/licenses/>.

 */

#ifndef __ASM_SIGINFO_H

#define __ASM_SIGINFO_H

#define __ARCH_SI_PREAMBLE_SIZE	(4 * sizeof(int))

#include <asm-generic/siginfo.h>

#endif

/*

 * Copyright (C) 2012 ARM Ltd.

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program.  If not, see <http://www.gnu.org/licenses/>.

 */

#ifndef __ASM_SIGNAL_H

#define __ASM_SIGNAL_H

/* Required for AArch32 compatibility. */

#define SA_RESTORER	0x04000000

#include <asm-generic/signal.h>

#endif

/*

 * Copyright (C) 2012 ARM Ltd.

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program.  If not, see <http://www.gnu.org/licenses/>.

 */

#ifndef __ASM_UCONTEXT_H

#define __ASM_UCONTEXT_H

struct ucontext {

	unsigned long	  uc_flags;

	struct ucontext	 *uc_link;

	stack_t		  uc_stack;

	sigset_t	  uc_sigmask;

	/* glibc uses a 1024-bit sigset_t */

	__u8		  __unused[(1024 - sizeof(sigset_t)) / 8];

	/* last for future expansion */

	struct sigcontext uc_mcontext;

};

#endif /* __ASM_UCONTEXT_H */

/*

 * Based on arch/arm/kernel/signal.c

 *

 * Copyright (C) 1995-2009 Russell King

 * Copyright (C) 2012 ARM Ltd.

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program.  If not, see <http://www.gnu.org/licenses/>.

 */

#include <linux/errno.h>

#include <linux/signal.h>

#include <linux/personality.h>

#include <linux/freezer.h>

#include <linux/uaccess.h>

#include <linux/tracehook.h>

#include <linux/ratelimit.h>

#include <asm/compat.h>

#include <asm/debug-monitors.h>

#include <asm/elf.h>

#include <asm/cacheflush.h>

#include <asm/ucontext.h>

#include <asm/unistd.h>

#include <asm/fpsimd.h>

#include <asm/signal32.h>

#include <asm/vdso.h>

/*

 * Do a signal return; undo the signal stack. These are aligned to 128-bit.

 */

struct rt_sigframe {

	struct siginfo info;

	struct ucontext uc;

};

static int preserve_fpsimd_context(struct fpsimd_context __user *ctx)

{

	struct fpsimd_state *fpsimd = &current->thread.fpsimd_state;

	int err;

	/* dump the hardware registers to the fpsimd_state structure */

	fpsimd_save_state(fpsimd);

	/* copy the FP and status/control registers */

	err = __copy_to_user(ctx->vregs, fpsimd->vregs, sizeof(fpsimd->vregs));

	__put_user_error(fpsimd->fpsr, &ctx->fpsr, err);

	__put_user_error(fpsimd->fpcr, &ctx->fpcr, err);

	/* copy the magic/size information */

	__put_user_error(FPSIMD_MAGIC, &ctx->head.magic, err);

	__put_user_error(sizeof(struct fpsimd_context), &ctx->head.size, err);

	return err ? -EFAULT : 0;

}

static int restore_fpsimd_context(struct fpsimd_context __user *ctx)

{

	struct fpsimd_state fpsimd;

	__u32 magic, size;

	int err = 0;

	/* check the magic/size information */

	__get_user_error(magic, &ctx->head.magic, err);

	__get_user_error(size, &ctx->head.size, err);

	if (err)

		return -EFAULT;

	if (magic != FPSIMD_MAGIC || size != sizeof(struct fpsimd_context))

		return -EINVAL;

	/* copy the FP and status/control registers */

	err = __copy_from_user(fpsimd.vregs, ctx->vregs,

			       sizeof(fpsimd.vregs));

	__get_user_error(fpsimd.fpsr, &ctx->fpsr, err);

	__get_user_error(fpsimd.fpcr, &ctx->fpcr, err);

	/* load the hardware registers from the fpsimd_state structure */

	if (!err) {

		preempt_disable();

		fpsimd_load_state(&fpsimd);

		preempt_enable();

	}

	return err ? -EFAULT : 0;

}

static int restore_sigframe(struct pt_regs *regs,

			    struct rt_sigframe __user *sf)

{

	sigset_t set;

	int i, err;

	struct aux_context __user *aux =

		(struct aux_context __user *)sf->uc.uc_mcontext.__reserved;

	err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));

	if (err == 0)

		set_current_blocked(&set);

	for (i = 0; i < 31; i++)

		__get_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],

				 err);

	__get_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);

	__get_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);

	__get_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);

	/*

	 * Avoid sys_rt_sigreturn() restarting.

	 */

	regs->syscallno = ~0UL;

	err |= !valid_user_regs(&regs->user_regs);

	if (err == 0)

		err |= restore_fpsimd_context(&aux->fpsimd);

	return err;

}

asmlinkage long sys_rt_sigreturn(struct pt_regs *regs)

{

	struct rt_sigframe __user *frame;

	/* Always make any pending restarted system calls return -EINTR */

	current_thread_info()->restart_block.fn = do_no_restart_syscall;

	/*

	 * Since we stacked the signal on a 128-bit boundary, then 'sp' should

	 * be word aligned here.

	 */

	if (regs->sp & 15)

		goto badframe;

	frame = (struct rt_sigframe __user *)regs->sp;

	if (!access_ok(VERIFY_READ, frame, sizeof (*frame)))

		goto badframe;

	if (restore_sigframe(regs, frame))

		goto badframe;

	if (do_sigaltstack(&frame->uc.uc_stack,

			   NULL, regs->sp) == -EFAULT)

		goto badframe;

	return regs->regs[0];

badframe:

	if (show_unhandled_signals)

		pr_info_ratelimited("%s[%d]: bad frame in %s: pc=%08llx sp=%08llx\n",

				    current->comm, task_pid_nr(current), __func__,

				    regs->pc, regs->sp);

	force_sig(SIGSEGV, current);

	return 0;

}

asmlinkage long sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss,

				unsigned long sp)

{

	return do_sigaltstack(uss, uoss, sp);

}

static int setup_sigframe(struct rt_sigframe __user *sf,

			  struct pt_regs *regs, sigset_t *set)

{

	int i, err = 0;

	struct aux_context __user *aux =

		(struct aux_context __user *)sf->uc.uc_mcontext.__reserved;

	for (i = 0; i < 31; i++)

		__put_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],

				 err);

	__put_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);

	__put_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);

	__put_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);

	__put_user_error(current->thread.fault_address, &sf->uc.uc_mcontext.fault_address, err);

	err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set));

	if (err == 0)

		err |= preserve_fpsimd_context(&aux->fpsimd);

	/* set the "end" magic */

	__put_user_error(0, &aux->end.magic, err);

	__put_user_error(0, &aux->end.size, err);

	return err;

}

static void __user *get_sigframe(struct k_sigaction *ka, struct pt_regs *regs,

				 int framesize)

{

	unsigned long sp, sp_top;

	void __user *frame;

	sp = sp_top = regs->sp;

	/*

	 * This is the X/Open sanctioned signal stack switching.

	 */

	if ((ka->sa.sa_flags & SA_ONSTACK) && !sas_ss_flags(sp))

		sp = sp_top = current->sas_ss_sp + current->sas_ss_size;

	/* room for stack frame (FP, LR) */

	sp -= 16;

	sp = (sp - framesize) & ~15;

	frame = (void __user *)sp;

	/*

	 * Check that we can actually write to the signal frame.

	 */

	if (!access_ok(VERIFY_WRITE, frame, sp_top - sp))

		frame = NULL;

	return frame;

}

static int setup_return(struct pt_regs *regs, struct k_sigaction *ka,

			void __user *frame, int usig)

{

	int err = 0;

	__sigrestore_t sigtramp;

	unsigned long __user *sp = (unsigned long __user *)regs->sp;

	/* set up the stack frame */

	__put_user_error(regs->regs[29], sp - 2, err);

	__put_user_error(regs->regs[30], sp - 1, err);

	regs->regs[0] = usig;

	regs->regs[29] = regs->sp - 16;

	regs->sp = (unsigned long)frame;

	regs->pc = (unsigned long)ka->sa.sa_handler;

	if (ka->sa.sa_flags & SA_RESTORER)

		sigtramp = ka->sa.sa_restorer;

	else

		sigtramp = VDSO_SYMBOL(current->mm->context.vdso, sigtramp);

	regs->regs[30] = (unsigned long)sigtramp;

	return err;

}

static int setup_rt_frame(int usig, struct k_sigaction *ka, siginfo_t *info,

			  sigset_t *set, struct pt_regs *regs)

{

	struct rt_sigframe __user *frame;

	stack_t stack;

	int err = 0;

	frame = get_sigframe(ka, regs, sizeof(*frame));

	if (!frame)

		return 1;

	__put_user_error(0, &frame->uc.uc_flags, err);

	__put_user_error(NULL, &frame->uc.uc_link, err);

	memset(&stack, 0, sizeof(stack));

	stack.ss_sp = (void __user *)current->sas_ss_sp;

	stack.ss_flags = sas_ss_flags(regs->sp);

	stack.ss_size = current->sas_ss_size;

	err |= __copy_to_user(&frame->uc.uc_stack, &stack, sizeof(stack));

	err |= setup_sigframe(frame, regs, set);

	if (err == 0)

		err = setup_return(regs, ka, frame, usig);

	if (err == 0 && ka->sa.sa_flags & SA_SIGINFO) {

		err |= copy_siginfo_to_user(&frame->info, info);

		regs->regs[1] = (unsigned long)&frame->info;

		regs->regs[2] = (unsigned long)&frame->uc;

	}

	return err;

}

static void setup_restart_syscall(struct pt_regs *regs)

{

	if (is_compat_task())

		compat_setup_restart_syscall(regs);

	else

		regs->regs[8] = __NR_restart_syscall;

}

/*

 * OK, we're invoking a handler

 */

static void handle_signal(unsigned long sig, struct k_sigaction *ka,

			  siginfo_t *info, struct pt_regs *regs)

{

	struct thread_info *thread = current_thread_info();

	struct task_struct *tsk = current;

	sigset_t *oldset = sigmask_to_save();

	int usig = sig;

	int ret;

	/*

	 * translate the signal

	 */

	if (usig < 32 && thread->exec_domain && thread->exec_domain->signal_invmap)

		usig = thread->exec_domain->signal_invmap[usig];

	/*

	 * Set up the stack frame

	 */

	if (is_compat_task()) {

		if (ka->sa.sa_flags & SA_SIGINFO)

			ret = compat_setup_rt_frame(usig, ka, info, oldset,

						    regs);

		else

			ret = compat_setup_frame(usig, ka, oldset, regs);

	} else {

		ret = setup_rt_frame(usig, ka, info, oldset, regs);

	}

	/*

	 * Check that the resulting registers are actually sane.

	 */

	ret |= !valid_user_regs(&regs->user_regs);

	if (ret != 0) {

		force_sigsegv(sig, tsk);

		return;

	}

	/*

	 * Fast forward the stepping logic so we step into the signal

	 * handler.

	 */

	user_fastforward_single_step(tsk);

	signal_delivered(sig, info, ka, regs, 0);

}

/*

 * Note that 'init' is a special process: it doesn't get signals it doesn't

 * want to handle. Thus you cannot kill init even with a SIGKILL even by

 * mistake.

 *

 * Note that we go through the signals twice: once to check the signals that

 * the kernel can handle, and then we build all the user-level signal handling

 * stack-frames in one go after that.

 */

static void do_signal(struct pt_regs *regs)

{

	unsigned long continue_addr = 0, restart_addr = 0;

	struct k_sigaction ka;

	siginfo_t info;

	int signr, retval = 0;

	int syscall = (int)regs->syscallno;

	/*

	 * If we were from a system call, check for system call restarting...

	 */

	if (syscall >= 0) {

		continue_addr = regs->pc;

		restart_addr = continue_addr - (compat_thumb_mode(regs) ? 2 : 4);

		retval = regs->regs[0];

		/*

		 * Avoid additional syscall restarting via ret_to_user.

		 */

		regs->syscallno = ~0UL;

		/*

		 * Prepare for system call restart. We do this here so that a

		 * debugger will see the already changed PC.

		 */

		switch (retval) {

		case -ERESTARTNOHAND:

		case -ERESTARTSYS:

		case -ERESTARTNOINTR:

		case -ERESTART_RESTARTBLOCK:

			regs->regs[0] = regs->orig_x0;

			regs->pc = restart_addr;

			break;

		}

	}

	/*

	 * Get the signal to deliver. When running under ptrace, at this point

	 * the debugger may change all of our registers.

	 */

	signr = get_signal_to_deliver(&info, &ka, regs, NULL);

	if (signr > 0) {

		/*

		 * Depending on the signal settings, we may need to revert the

		 * decision to restart the system call, but skip this if a

		 * debugger has chosen to restart at a different PC.

		 */

		if (regs->pc == restart_addr &&

		    (retval == -ERESTARTNOHAND ||

		     retval == -ERESTART_RESTARTBLOCK ||

		     (retval == -ERESTARTSYS &&

		      !(ka.sa.sa_flags & SA_RESTART)))) {

			regs->regs[0] = -EINTR;

			regs->pc = continue_addr;

		}

		handle_signal(signr, &ka, &info, regs);

		return;

	}

	/*

	 * Handle restarting a different system call. As above, if a debugger

	 * has chosen to restart at a different PC, ignore the restart.

	 */

	if (syscall >= 0 && regs->pc == restart_addr) {

		if (retval == -ERESTART_RESTARTBLOCK)

			setup_restart_syscall(regs);

		user_rewind_single_step(current);

	}

	restore_saved_sigmask();

}

asmlinkage void do_notify_resume(struct pt_regs *regs,

				 unsigned int thread_flags)

{

	if (thread_flags & _TIF_SIGPENDING)

		do_signal(regs);

	if (thread_flags & _TIF_NOTIFY_RESUME) {

		clear_thread_flag(TIF_NOTIFY_RESUME);

		tracehook_notify_resume(regs);

	}

}