signal.c

/*
 * Signal handling
 *
 * Copyright (C) 2008-2009 Michal Simek <[email protected]>
 * Copyright (C) 2008-2009 PetaLogix
 * Copyright (C) 2003,2004 John Williams <[email protected]>
 * Copyright (C) 2001 NEC Corporation
 * Copyright (C) 2001 Miles Bader <[email protected]>
 * Copyright (C) 1999,2000 Niibe Yutaka & Kaz Kojima
 * Copyright (C) 1991,1992 Linus Torvalds
 *
 * 1997-11-28 Modified for POSIX.1b signals by Richard Henderson
 *
 * This file was derived from the sh version, arch/sh/kernel/signal.c
 *
 * This file is subject to the terms and conditions of the GNU General
 * Public License. See the file COPYING in the main directory of this
 * archive for more details.
 */

#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/errno.h>
#include <linux/wait.h>
#include <linux/ptrace.h>
#include <linux/unistd.h>
#include <linux/stddef.h>
#include <linux/personality.h>
#include <linux/percpu.h>
#include <linux/linkage.h>
#include <linux/resume_user_mode.h>
#include <asm/entry.h>
#include <asm/ucontext.h>
#include <linux/uaccess.h>
#include <linux/syscalls.h>
#include <asm/cacheflush.h>
#include <asm/syscalls.h>

/*
 * Do a signal return; undo the signal stack.
 */
struct sigframe {
	struct sigcontext sc;
	unsigned long extramask[_NSIG_WORDS-1];
	unsigned long tramp[2];	/* signal trampoline */
};

struct rt_sigframe {
	struct siginfo info;
	struct ucontext uc;
	unsigned long tramp[2];	/* signal trampoline */
};

static int restore_sigcontext(struct pt_regs *regs,
				struct sigcontext __user *sc, int *rval_p)
{
	unsigned int err = 0;

#define COPY(x)		{err |= __get_user(regs->x, &sc->regs.x); }
	COPY(r0);
	COPY(r1);
	COPY(r2);	COPY(r3);	COPY(r4);	COPY(r5);
	COPY(r6);	COPY(r7);	COPY(r8);	COPY(r9);
	COPY(r10);	COPY(r11);	COPY(r12);	COPY(r13);
	COPY(r14);	COPY(r15);	COPY(r16);	COPY(r17);
	COPY(r18);	COPY(r19);	COPY(r20);	COPY(r21);
	COPY(r22);	COPY(r23);	COPY(r24);	COPY(r25);
	COPY(r26);	COPY(r27);	COPY(r28);	COPY(r29);
	COPY(r30);	COPY(r31);
	COPY(pc);	COPY(ear);	COPY(esr);	COPY(fsr);
#undef COPY

	*rval_p = regs->r3;

	return err;
}

asmlinkage long sys_rt_sigreturn(struct pt_regs *regs)
{
	struct rt_sigframe __user *frame =
		(struct rt_sigframe __user *)(regs->r1);

	sigset_t set;
	int rval;

	/* Always make any pending restarted system calls return -EINTR */
	current->restart_block.fn = do_no_restart_syscall;

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

	if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
		goto badframe;

	set_current_blocked(&set);

	if (restore_sigcontext(regs, &frame->uc.uc_mcontext, &rval))
		goto badframe;

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

	return rval;

badframe:
	force_sig(SIGSEGV);
	return 0;
}

/*
 * Set up a signal frame.
 */

static int
setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
		unsigned long mask)
{
	int err = 0;

#define COPY(x)		{err |= __put_user(regs->x, &sc->regs.x); }
	COPY(r0);
	COPY(r1);
	COPY(r2);	COPY(r3);	COPY(r4);	COPY(r5);
	COPY(r6);	COPY(r7);	COPY(r8);	COPY(r9);
	COPY(r10);	COPY(r11);	COPY(r12);	COPY(r13);
	COPY(r14);	COPY(r15);	COPY(r16);	COPY(r17);
	COPY(r18);	COPY(r19);	COPY(r20);	COPY(r21);
	COPY(r22);	COPY(r23);	COPY(r24);	COPY(r25);
	COPY(r26);	COPY(r27);	COPY(r28);	COPY(r29);
	COPY(r30);	COPY(r31);
	COPY(pc);	COPY(ear);	COPY(esr);	COPY(fsr);
#undef COPY

	err |= __put_user(mask, &sc->oldmask);

	return err;
}

/*
 * Determine which stack to use..
 */
static inline void __user *
get_sigframe(struct ksignal *ksig, struct pt_regs *regs, size_t frame_size)
{
	/* Default to using normal stack */
	unsigned long sp = sigsp(regs->r1, ksig);

	return (void __user *)((sp - frame_size) & -8UL);
}

static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
			  struct pt_regs *regs)
{
	struct rt_sigframe __user *frame;
	int err = 0, sig = ksig->sig;
	unsigned long address = 0;
	pmd_t *pmdp;
	pte_t *ptep;

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

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

	if (ksig->ka.sa.sa_flags & SA_SIGINFO)
		err |= copy_siginfo_to_user(&frame->info, &ksig->info);

	/* Create the ucontext. */
	err |= __put_user(0, &frame->uc.uc_flags);
	err |= __put_user(NULL, &frame->uc.uc_link);
	err |= __save_altstack(&frame->uc.uc_stack, regs->r1);
	err |= setup_sigcontext(&frame->uc.uc_mcontext,
			regs, set->sig[0]);
	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));

	/* Set up to return from userspace. If provided, use a stub
	 already in userspace. */
	/* minus 8 is offset to cater for "rtsd r15,8" */
	/* addi r12, r0, __NR_sigreturn */
	err |= __put_user(0x31800000 | __NR_rt_sigreturn ,
			frame->tramp + 0);
	/* brki r14, 0x8 */
	err |= __put_user(0xb9cc0008, frame->tramp + 1);

	/* Return from sighandler will jump to the tramp.
	 Negative 8 offset because return is rtsd r15, 8 */
	regs->r15 = ((unsigned long)frame->tramp)-8;

	address = ((unsigned long)frame->tramp);
	pmdp = pmd_off(current->mm, address);

	preempt_disable();
	ptep = pte_offset_map(pmdp, address);
	if (ptep && pte_present(*ptep)) {
		address = (unsigned long) page_address(pte_page(*ptep));
		/* MS: I need add offset in page */
		address += ((unsigned long)frame->tramp) & ~PAGE_MASK;
		/* MS address is virtual */
		address = __virt_to_phys(address);
		invalidate_icache_range(address, address + 8);
		flush_dcache_range(address, address + 8);
	}
	if (ptep)
		pte_unmap(ptep);
	preempt_enable();
	if (err)
		return -EFAULT;

	/* Set up registers for signal handler */
	regs->r1 = (unsigned long) frame;

	/* Signal handler args: */
	regs->r5 = sig; /* arg 0: signum */
	regs->r6 = (unsigned long) &frame->info; /* arg 1: siginfo */
	regs->r7 = (unsigned long) &frame->uc; /* arg2: ucontext */
	/* Offset to handle microblaze rtid r14, 0 */
	regs->pc = (unsigned long)ksig->ka.sa.sa_handler;

#ifdef DEBUG_SIG
	pr_info("SIG deliver (%s:%d): sp=%p pc=%08lx\n",
		current->comm, current->pid, frame, regs->pc);
#endif

	return 0;
}

/* Handle restarting system calls */
static inline void
handle_restart(struct pt_regs *regs, struct k_sigaction *ka, int has_handler)
{
	switch (regs->r3) {
	case -ERESTART_RESTARTBLOCK:
	case -ERESTARTNOHAND:
		if (!has_handler)
			goto do_restart;
		regs->r3 = -EINTR;
		break;
	case -ERESTARTSYS:
		if (has_handler && !(ka->sa.sa_flags & SA_RESTART)) {
			regs->r3 = -EINTR;
			break;
	}
		fallthrough;
	case -ERESTARTNOINTR:
do_restart:
		/* offset of 4 bytes to re-execute trap (brki) instruction */
		regs->pc -= 4;
		break;
	}
}

/*
 * OK, we're invoking a handler
 */

static void
handle_signal(struct ksignal *ksig, struct pt_regs *regs)
{
	sigset_t *oldset = sigmask_to_save();
	int ret;

	/* Set up the stack frame */
	ret = setup_rt_frame(ksig, oldset, regs);

	signal_setup_done(ret, ksig, test_thread_flag(TIF_SINGLESTEP));
}

/*
 * 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, int in_syscall)
{
	struct ksignal ksig;

#ifdef DEBUG_SIG
	pr_info("do signal: %p %d\n", regs, in_syscall);
	pr_info("do signal2: %lx %lx %ld [%lx]\n", regs->pc, regs->r1,
			regs->r12, read_thread_flags());
#endif

	if (get_signal(&ksig)) {
		/* Whee! Actually deliver the signal. */
		if (in_syscall)
			handle_restart(regs, &ksig.ka, 1);
		handle_signal(&ksig, regs);
		return;
	}

	if (in_syscall)
		handle_restart(regs, NULL, 0);

	/*
	 * If there's no signal to deliver, we just put the saved sigmask
	 * back.
	 */
	restore_saved_sigmask();
}

asmlinkage void do_notify_resume(struct pt_regs *regs, int in_syscall)
{
	if (test_thread_flag(TIF_SIGPENDING) ||
	    test_thread_flag(TIF_NOTIFY_SIGNAL))
		do_signal(regs, in_syscall);

	if (test_thread_flag(TIF_NOTIFY_RESUME))
		resume_user_mode_work(regs);
}