signal.c

// SPDX-License-Identifier: GPL-2.0
// Copyright (C) 2005-2017 Andes Technology Corporation

#include <linux/errno.h>
#include <linux/signal.h>
#include <linux/ptrace.h>
#include <linux/personality.h>
#include <linux/freezer.h>
#include <linux/resume_user_mode.h>
#include <linux/uaccess.h>

#include <asm/cacheflush.h>
#include <asm/ucontext.h>
#include <asm/unistd.h>
#include <asm/fpu.h>

#include <asm/ptrace.h>
#include <asm/vdso.h>

struct rt_sigframe {
	struct siginfo info;
	struct ucontext uc;
};
#if IS_ENABLED(CONFIG_FPU)
static inline int restore_sigcontext_fpu(struct pt_regs *regs,
					 struct sigcontext __user *sc)
{
	struct task_struct *tsk = current;
	unsigned long used_math_flag;
	int ret = 0;

	clear_used_math();
	__get_user_error(used_math_flag, &sc->used_math_flag, ret);

	if (!used_math_flag)
		return 0;
	set_used_math();

#if IS_ENABLED(CONFIG_LAZY_FPU)
	preempt_disable();
	if (current == last_task_used_math) {
		last_task_used_math = NULL;
		disable_ptreg_fpu(regs);
	}
	preempt_enable();
#else
	clear_fpu(regs);
#endif

	return __copy_from_user(&tsk->thread.fpu, &sc->fpu,
				sizeof(struct fpu_struct));
}

static inline int setup_sigcontext_fpu(struct pt_regs *regs,
				       struct sigcontext __user *sc)
{
	struct task_struct *tsk = current;
	int ret = 0;

	__put_user_error(used_math(), &sc->used_math_flag, ret);

	if (!used_math())
		return ret;

	preempt_disable();
#if IS_ENABLED(CONFIG_LAZY_FPU)
	if (last_task_used_math == tsk)
		save_fpu(last_task_used_math);
#else
	unlazy_fpu(tsk);
#endif
	ret = __copy_to_user(&sc->fpu, &tsk->thread.fpu,
			     sizeof(struct fpu_struct));
	preempt_enable();
	return ret;
}
#endif

static int restore_sigframe(struct pt_regs *regs,
			    struct rt_sigframe __user * sf)
{
	sigset_t set;
	int err;

	err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
	if (err == 0) {
		set_current_blocked(&set);
	}

	__get_user_error(regs->uregs[0], &sf->uc.uc_mcontext.nds32_r0, err);
	__get_user_error(regs->uregs[1], &sf->uc.uc_mcontext.nds32_r1, err);
	__get_user_error(regs->uregs[2], &sf->uc.uc_mcontext.nds32_r2, err);
	__get_user_error(regs->uregs[3], &sf->uc.uc_mcontext.nds32_r3, err);
	__get_user_error(regs->uregs[4], &sf->uc.uc_mcontext.nds32_r4, err);
	__get_user_error(regs->uregs[5], &sf->uc.uc_mcontext.nds32_r5, err);
	__get_user_error(regs->uregs[6], &sf->uc.uc_mcontext.nds32_r6, err);
	__get_user_error(regs->uregs[7], &sf->uc.uc_mcontext.nds32_r7, err);
	__get_user_error(regs->uregs[8], &sf->uc.uc_mcontext.nds32_r8, err);
	__get_user_error(regs->uregs[9], &sf->uc.uc_mcontext.nds32_r9, err);
	__get_user_error(regs->uregs[10], &sf->uc.uc_mcontext.nds32_r10, err);
	__get_user_error(regs->uregs[11], &sf->uc.uc_mcontext.nds32_r11, err);
	__get_user_error(regs->uregs[12], &sf->uc.uc_mcontext.nds32_r12, err);
	__get_user_error(regs->uregs[13], &sf->uc.uc_mcontext.nds32_r13, err);
	__get_user_error(regs->uregs[14], &sf->uc.uc_mcontext.nds32_r14, err);
	__get_user_error(regs->uregs[15], &sf->uc.uc_mcontext.nds32_r15, err);
	__get_user_error(regs->uregs[16], &sf->uc.uc_mcontext.nds32_r16, err);
	__get_user_error(regs->uregs[17], &sf->uc.uc_mcontext.nds32_r17, err);
	__get_user_error(regs->uregs[18], &sf->uc.uc_mcontext.nds32_r18, err);
	__get_user_error(regs->uregs[19], &sf->uc.uc_mcontext.nds32_r19, err);
	__get_user_error(regs->uregs[20], &sf->uc.uc_mcontext.nds32_r20, err);
	__get_user_error(regs->uregs[21], &sf->uc.uc_mcontext.nds32_r21, err);
	__get_user_error(regs->uregs[22], &sf->uc.uc_mcontext.nds32_r22, err);
	__get_user_error(regs->uregs[23], &sf->uc.uc_mcontext.nds32_r23, err);
	__get_user_error(regs->uregs[24], &sf->uc.uc_mcontext.nds32_r24, err);
	__get_user_error(regs->uregs[25], &sf->uc.uc_mcontext.nds32_r25, err);

	__get_user_error(regs->fp, &sf->uc.uc_mcontext.nds32_fp, err);
	__get_user_error(regs->gp, &sf->uc.uc_mcontext.nds32_gp, err);
	__get_user_error(regs->lp, &sf->uc.uc_mcontext.nds32_lp, err);
	__get_user_error(regs->sp, &sf->uc.uc_mcontext.nds32_sp, err);
	__get_user_error(regs->ipc, &sf->uc.uc_mcontext.nds32_ipc, err);
#if defined(CONFIG_HWZOL)
	__get_user_error(regs->lc, &sf->uc.uc_mcontext.zol.nds32_lc, err);
	__get_user_error(regs->le, &sf->uc.uc_mcontext.zol.nds32_le, err);
	__get_user_error(regs->lb, &sf->uc.uc_mcontext.zol.nds32_lb, err);
#endif
#if IS_ENABLED(CONFIG_FPU)
	err |= restore_sigcontext_fpu(regs, &sf->uc.uc_mcontext);
#endif
	/*
	 * Avoid sys_rt_sigreturn() restarting.
	 */
	forget_syscall(regs);
	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->restart_block.fn = do_no_restart_syscall;

	/*
	 * Since we stacked the signal on a 64-bit boundary,
	 * then 'sp' should be two-word aligned here.  If it's
	 * not, then the user is trying to mess with us.
	 */
	if (regs->sp & 7)
		goto badframe;

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

	if (!access_ok(frame, sizeof(*frame)))
		goto badframe;

	if (restore_sigframe(regs, frame))
		goto badframe;

	if (restore_altstack(&frame->uc.uc_stack))
		goto badframe;

	return regs->uregs[0];

badframe:
	force_sig(SIGSEGV);
	return 0;
}

static int
setup_sigframe(struct rt_sigframe __user * sf, struct pt_regs *regs,
	       sigset_t * set)
{
	int err = 0;

	__put_user_error(regs->uregs[0], &sf->uc.uc_mcontext.nds32_r0, err);
	__put_user_error(regs->uregs[1], &sf->uc.uc_mcontext.nds32_r1, err);
	__put_user_error(regs->uregs[2], &sf->uc.uc_mcontext.nds32_r2, err);
	__put_user_error(regs->uregs[3], &sf->uc.uc_mcontext.nds32_r3, err);
	__put_user_error(regs->uregs[4], &sf->uc.uc_mcontext.nds32_r4, err);
	__put_user_error(regs->uregs[5], &sf->uc.uc_mcontext.nds32_r5, err);
	__put_user_error(regs->uregs[6], &sf->uc.uc_mcontext.nds32_r6, err);
	__put_user_error(regs->uregs[7], &sf->uc.uc_mcontext.nds32_r7, err);
	__put_user_error(regs->uregs[8], &sf->uc.uc_mcontext.nds32_r8, err);
	__put_user_error(regs->uregs[9], &sf->uc.uc_mcontext.nds32_r9, err);
	__put_user_error(regs->uregs[10], &sf->uc.uc_mcontext.nds32_r10, err);
	__put_user_error(regs->uregs[11], &sf->uc.uc_mcontext.nds32_r11, err);
	__put_user_error(regs->uregs[12], &sf->uc.uc_mcontext.nds32_r12, err);
	__put_user_error(regs->uregs[13], &sf->uc.uc_mcontext.nds32_r13, err);
	__put_user_error(regs->uregs[14], &sf->uc.uc_mcontext.nds32_r14, err);
	__put_user_error(regs->uregs[15], &sf->uc.uc_mcontext.nds32_r15, err);
	__put_user_error(regs->uregs[16], &sf->uc.uc_mcontext.nds32_r16, err);
	__put_user_error(regs->uregs[17], &sf->uc.uc_mcontext.nds32_r17, err);
	__put_user_error(regs->uregs[18], &sf->uc.uc_mcontext.nds32_r18, err);
	__put_user_error(regs->uregs[19], &sf->uc.uc_mcontext.nds32_r19, err);
	__put_user_error(regs->uregs[20], &sf->uc.uc_mcontext.nds32_r20, err);

	__put_user_error(regs->uregs[21], &sf->uc.uc_mcontext.nds32_r21, err);
	__put_user_error(regs->uregs[22], &sf->uc.uc_mcontext.nds32_r22, err);
	__put_user_error(regs->uregs[23], &sf->uc.uc_mcontext.nds32_r23, err);
	__put_user_error(regs->uregs[24], &sf->uc.uc_mcontext.nds32_r24, err);
	__put_user_error(regs->uregs[25], &sf->uc.uc_mcontext.nds32_r25, err);
	__put_user_error(regs->fp, &sf->uc.uc_mcontext.nds32_fp, err);
	__put_user_error(regs->gp, &sf->uc.uc_mcontext.nds32_gp, err);
	__put_user_error(regs->lp, &sf->uc.uc_mcontext.nds32_lp, err);
	__put_user_error(regs->sp, &sf->uc.uc_mcontext.nds32_sp, err);
	__put_user_error(regs->ipc, &sf->uc.uc_mcontext.nds32_ipc, err);
#if defined(CONFIG_HWZOL)
	__put_user_error(regs->lc, &sf->uc.uc_mcontext.zol.nds32_lc, err);
	__put_user_error(regs->le, &sf->uc.uc_mcontext.zol.nds32_le, err);
	__put_user_error(regs->lb, &sf->uc.uc_mcontext.zol.nds32_lb, err);
#endif
#if IS_ENABLED(CONFIG_FPU)
	err |= setup_sigcontext_fpu(regs, &sf->uc.uc_mcontext);
#endif

	__put_user_error(current->thread.trap_no, &sf->uc.uc_mcontext.trap_no,
			 err);
	__put_user_error(current->thread.error_code,
			 &sf->uc.uc_mcontext.error_code, err);
	__put_user_error(current->thread.address,
			 &sf->uc.uc_mcontext.fault_address, err);
	__put_user_error(set->sig[0], &sf->uc.uc_mcontext.oldmask, err);

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

	return err;
}

static inline void __user *get_sigframe(struct ksignal *ksig,
					struct pt_regs *regs, int framesize)
{
	unsigned long sp;

	/* Default to using normal stack */
	sp = regs->sp;

	/*
	 * If we are on the alternate signal stack and would overflow it, don't.
	 * Return an always-bogus address instead so we will die with SIGSEGV.
	 */
	if (on_sig_stack(sp) && !likely(on_sig_stack(sp - framesize)))
		return (void __user __force *)(-1UL);

	/* This is the X/Open sanctioned signal stack switching. */
	sp = (sigsp(sp, ksig) - framesize);

	/*
	 * nds32 mandates 8-byte alignment
	 */
	sp &= ~0x7UL;

	return (void __user *)sp;
}

static int
setup_return(struct pt_regs *regs, struct ksignal *ksig, void __user * frame)
{
	unsigned long handler = (unsigned long)ksig->ka.sa.sa_handler;
	unsigned long retcode;

	retcode = VDSO_SYMBOL(current->mm->context.vdso, rt_sigtramp);
	regs->uregs[0] = ksig->sig;
	regs->sp = (unsigned long)frame;
	regs->lp = retcode;
	regs->ipc = handler;

	return 0;
}

static int
setup_rt_frame(struct ksignal *ksig, sigset_t * set, struct pt_regs *regs)
{
	struct rt_sigframe __user *frame =
	    get_sigframe(ksig, regs, sizeof(*frame));
	int err = 0;

	if (!access_ok(frame, sizeof(*frame)))
		return -EFAULT;

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

	err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
	err |= setup_sigframe(frame, regs, set);
	if (err == 0) {
		setup_return(regs, ksig, frame);
		if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
			err |= copy_siginfo_to_user(&frame->info, &ksig->info);
			regs->uregs[1] = (unsigned long)&frame->info;
			regs->uregs[2] = (unsigned long)&frame->uc;
		}
	}
	return err;
}

/*
 * OK, we're invoking a handler
 */
static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
{
	int ret;
	sigset_t *oldset = sigmask_to_save();

	if (in_syscall(regs)) {
		/* Avoid additional syscall restarting via ret_slow_syscall. */
		forget_syscall(regs);

		switch (regs->uregs[0]) {
		case -ERESTART_RESTARTBLOCK:
		case -ERESTARTNOHAND:
			regs->uregs[0] = -EINTR;
			break;
		case -ERESTARTSYS:
			if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
				regs->uregs[0] = -EINTR;
				break;
			}
			fallthrough;
		case -ERESTARTNOINTR:
			regs->uregs[0] = regs->orig_r0;
			regs->ipc -= 4;
			break;
		}
	}
	/*
	 * Set up the stack frame
	 */
	ret = setup_rt_frame(ksig, oldset, regs);

	signal_setup_done(ret, ksig, 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)
{
	struct ksignal ksig;

	if (get_signal(&ksig)) {
		handle_signal(&ksig, regs);
		return;
	}

	/*
	 * If we were from a system call, check for system call restarting...
	 */
	if (in_syscall(regs)) {
		/* Restart the system call - no handlers present */

		/* Avoid additional syscall restarting via ret_slow_syscall. */
		forget_syscall(regs);

		switch (regs->uregs[0]) {
		case -ERESTART_RESTARTBLOCK:
			regs->uregs[15] = __NR_restart_syscall;
			fallthrough;
		case -ERESTARTNOHAND:
		case -ERESTARTSYS:
		case -ERESTARTNOINTR:
			regs->uregs[0] = regs->orig_r0;
			regs->ipc -= 0x4;
			break;
		}
	}
	restore_saved_sigmask();
}

asmlinkage void
do_notify_resume(struct pt_regs *regs, unsigned int thread_flags)
{
	if (thread_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
		do_signal(regs);

	if (thread_flags & _TIF_NOTIFY_RESUME)
		resume_user_mode_work(regs);
}