metag: Signal handling

Add signal handling code for metag.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>

arch/metag/include/uapi/asm/sigcontext.h

+#ifndef _ASM_METAG_SIGCONTEXT_H
+#define _ASM_METAG_SIGCONTEXT_H
+
+#include <asm/ptrace.h>
+
+/*
+ * In a sigcontext structure we need to store the active state of the
+ * user process so that it does not get trashed when we call the signal
+ * handler. That not really the same as a user context that we are
+ * going to store on syscall etc.
+ */
+struct sigcontext {
+	struct user_gp_regs regs;	/* needs to be first */
+
+	/*
+	 * Catch registers describing a memory fault.
+	 * If USER_GP_REGS_STATUS_CATCH_BIT is set in regs.status then catch
+	 * buffers have been saved and will be replayed on sigreturn.
+	 * Clear that bit to discard the catch state instead of replaying it.
+	 */
+	struct user_cb_regs cb;
+
+	/*
+	 * Read pipeline state. This will get restored on sigreturn.
+	 */
+	struct user_rp_state rp;
+
+	unsigned long oldmask;
+};
+
+#endif

arch/metag/include/uapi/asm/siginfo.h

+#ifndef _METAG_SIGINFO_H
+#define _METAG_SIGINFO_H
+
+#define __ARCH_SI_TRAPNO
+
+#include <asm-generic/siginfo.h>
+
+#endif

arch/metag/kernel/signal.c

+/*
+ *  Copyright (C) 1991,1992  Linus Torvalds
+ *  Copyright (C) 2005-2012  Imagination Technologies Ltd.
+ *
+ *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
+ *
+ */
+
+#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/uaccess.h>
+#include <linux/tracehook.h>
+
+#include <asm/ucontext.h>
+#include <asm/cacheflush.h>
+#include <asm/switch.h>
+#include <asm/syscall.h>
+#include <asm/syscalls.h>
+
+#define REG_FLAGS	ctx.SaveMask
+#define REG_RETVAL	ctx.DX[0].U0
+#define REG_SYSCALL	ctx.DX[0].U1
+#define REG_SP		ctx.AX[0].U0
+#define REG_ARG1	ctx.DX[3].U1
+#define REG_ARG2	ctx.DX[3].U0
+#define REG_ARG3	ctx.DX[2].U1
+#define REG_PC		ctx.CurrPC
+#define REG_RTP		ctx.DX[4].U1
+
+struct rt_sigframe {
+	struct siginfo info;
+	struct ucontext uc;
+	unsigned long retcode[2];
+};
+
+static int restore_sigcontext(struct pt_regs *regs,
+			      struct sigcontext __user *sc)
+{
+	int err;
+
+	/* Always make any pending restarted system calls return -EINTR */
+	current_thread_info()->restart_block.fn = do_no_restart_syscall;
+
+	err = metag_gp_regs_copyin(regs, 0, sizeof(struct user_gp_regs), NULL,
+				   &sc->regs);
+	if (!err)
+		err = metag_cb_regs_copyin(regs, 0,
+					   sizeof(struct user_cb_regs), NULL,
+					   &sc->cb);
+	if (!err)
+		err = metag_rp_state_copyin(regs, 0,
+					    sizeof(struct user_rp_state), NULL,
+					    &sc->rp);
+
+	/* This is a user-mode context. */
+	regs->REG_FLAGS |= TBICTX_PRIV_BIT;
+
+	return err;
+}
+
+long sys_rt_sigreturn(void)
+{
+	/* NOTE - Meta stack goes UPWARDS - so we wind the stack back */
+	struct pt_regs *regs = current_pt_regs();
+	struct rt_sigframe __user *frame;
+	sigset_t set;
+
+	frame = (__force struct rt_sigframe __user *)(regs->REG_SP -
+						      sizeof(*frame));
+
+	if (!access_ok(VERIFY_READ, 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))
+		goto badframe;
+
+	if (restore_altstack(&frame->uc.uc_stack))
+		goto badframe;
+
+	return regs->REG_RETVAL;
+
+badframe:
+	force_sig(SIGSEGV, current);
+
+	return 0;
+}
+
+static int setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
+			    unsigned long mask)
+{
+	int err;
+
+	err = metag_gp_regs_copyout(regs, 0, sizeof(struct user_gp_regs), NULL,
+				    &sc->regs);
+
+	if (!err)
+		err = metag_cb_regs_copyout(regs, 0,
+					    sizeof(struct user_cb_regs), NULL,
+					    &sc->cb);
+	if (!err)
+		err = metag_rp_state_copyout(regs, 0,
+					     sizeof(struct user_rp_state), NULL,
+					     &sc->rp);
+
+	/* OK, clear that cbuf flag in the old context, or our stored
+	 * catch buffer will be restored when we go to call the signal
+	 * handler. Also clear out the CBRP RA/RD pipe bit incase
+	 * that is pending as well!
+	 * Note that as we have already stored this context, these
+	 * flags will get restored on sigreturn to their original
+	 * state.
+	 */
+	regs->REG_FLAGS &= ~(TBICTX_XCBF_BIT | TBICTX_CBUF_BIT |
+			     TBICTX_CBRP_BIT);
+
+	/* Clear out the LSM_STEP bits in case we are in the middle of
+	 * and MSET/MGET.
+	 */
+	regs->ctx.Flags &= ~TXSTATUS_LSM_STEP_BITS;
+
+	err |= __put_user(mask, &sc->oldmask);
+
+	return err;
+}
+
+/*
+ * Determine which stack to use..
+ */
+static void __user *get_sigframe(struct k_sigaction *ka, unsigned long sp,
+				 size_t frame_size)
+{
+	/* Meta stacks grows upwards */
+	if ((ka->sa.sa_flags & SA_ONSTACK) && (sas_ss_flags(sp) == 0))
+		sp = current->sas_ss_sp;
+
+	sp = (sp + 7) & ~7;			/* 8byte align stack */
+
+	return (void __user *)sp;
+}
+
+static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
+			  sigset_t *set, struct pt_regs *regs)
+{
+	struct rt_sigframe __user *frame;
+	int err = -EFAULT;
+	unsigned long code;
+
+	frame = get_sigframe(ka, regs->REG_SP, sizeof(*frame));
+	if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
+		goto out;
+
+	err = copy_siginfo_to_user(&frame->info, info);
+
+	/* Create the ucontext.  */
+	err |= __put_user(0, &frame->uc.uc_flags);
+	err |= __put_user(0, (unsigned long __user *)&frame->uc.uc_link);
+	err |= __save_altstack(&frame->uc.uc_stack, regs->REG_SP);
+	err |= setup_sigcontext(&frame->uc.uc_mcontext,
+				regs, set->sig[0]);
+	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
+
+	if (err)
+		goto out;
+
+	/* Set up to return from userspace.  */
+
+	/* MOV D1Re0 (D1.0), #__NR_rt_sigreturn */
+	code = 0x03000004 | (__NR_rt_sigreturn << 3);
+	err |= __put_user(code, (unsigned long __user *)(&frame->retcode[0]));
+
+	/* SWITCH #__METAG_SW_SYS */
+	code = __METAG_SW_ENCODING(SYS);
+	err |= __put_user(code, (unsigned long __user *)(&frame->retcode[1]));
+
+	if (err)
+		goto out;
+
+	/* Set up registers for signal handler */
+	regs->REG_RTP = (unsigned long) frame->retcode;
+	regs->REG_SP = (unsigned long) frame + sizeof(*frame);
+	regs->REG_ARG1 = sig;
+	regs->REG_ARG2 = (unsigned long) &frame->info;
+	regs->REG_ARG3 = (unsigned long) &frame->uc;
+	regs->REG_PC = (unsigned long) ka->sa.sa_handler;
+
+	pr_debug("SIG deliver (%s:%d): sp=%p pc=%08x pr=%08x\n",
+		 current->comm, current->pid, frame, regs->REG_PC,
+		 regs->REG_RTP);
+
+	/* Now pass size of 'new code' into sigtramp so we can do a more
+	 * effective cache flush - directed rather than 'full flush'.
+	 */
+	flush_cache_sigtramp(regs->REG_RTP, sizeof(frame->retcode));
+out:
+	if (err) {
+		force_sigsegv(sig, current);
+		return -EFAULT;
+	}
+	return 0;
+}
+
+static void handle_signal(unsigned long sig, siginfo_t *info,
+			  struct k_sigaction *ka, struct pt_regs *regs)
+{
+	sigset_t *oldset = sigmask_to_save();
+
+	/* Set up the stack frame */
+	if (setup_rt_frame(sig, ka, info, oldset, regs))
+		return;
+
+	signal_delivered(sig, info, ka, regs, test_thread_flag(TIF_SINGLESTEP));
+}
+
+ /*
+  * Notes for Meta.
+  * We have moved from the old 2.4.9 SH way of using syscall_nr (in the stored
+  * context) to passing in the syscall flag on the stack.
+  * This is because having syscall_nr in our context does not fit with TBX, and
+  * corrupted the stack.
+  */
+static int do_signal(struct pt_regs *regs, int syscall)
+{
+	unsigned int retval = 0, continue_addr = 0, restart_addr = 0;
+	struct k_sigaction ka;
+	siginfo_t info;
+	int signr;
+	int restart = 0;
+
+	/*
+	 * By the end of rt_sigreturn the context describes the point that the
+	 * signal was taken (which may happen to be just before a syscall if
+	 * it's already been restarted). This should *never* be mistaken for a
+	 * system call in need of restarting.
+	 */
+	if (syscall == __NR_rt_sigreturn)
+		syscall = -1;
+
+	/* Did we come from a system call? */
+	if (syscall >= 0) {
+		continue_addr = regs->REG_PC;
+		restart_addr = continue_addr - 4;
+		retval = regs->REG_RETVAL;
+
+		/*
+		 * Prepare for system call restart. We do this here so that a
+		 * debugger will see the already changed PC.
+		 */
+		switch (retval) {
+		case -ERESTART_RESTARTBLOCK:
+			restart = -2;
+		case -ERESTARTNOHAND:
+		case -ERESTARTSYS:
+		case -ERESTARTNOINTR:
+			++restart;
+			regs->REG_PC = restart_addr;
+			break;
+		}
+	}
+
+	/*
+	 * Get the signal to deliver. When running under ptrace, at this point
+	 * the debugger may change all our registers ...
+	 */
+	signr = get_signal_to_deliver(&info, &ka, regs, NULL);
+	/*
+	 * 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->REG_PC != restart_addr)
+		restart = 0;
+	if (signr > 0) {
+		if (unlikely(restart)) {
+			if (retval == -ERESTARTNOHAND
+			    || retval == -ERESTART_RESTARTBLOCK
+			    || (retval == -ERESTARTSYS
+				&& !(ka.sa.sa_flags & SA_RESTART))) {
+				regs->REG_RETVAL = -EINTR;
+				regs->REG_PC = continue_addr;
+			}
+		}
+
+		/* Whee! Actually deliver the signal.  */
+		handle_signal(signr, &info, &ka, regs);
+		return 0;
+	}
+
+	/* Handlerless -ERESTART_RESTARTBLOCK re-enters via restart_syscall */
+	if (unlikely(restart < 0))
+		regs->REG_SYSCALL = __NR_restart_syscall;
+
+	/*
+	 * If there's no signal to deliver, we just put the saved sigmask back.
+	 */
+	restore_saved_sigmask();
+
+	return restart;
+}
+
+int do_work_pending(struct pt_regs *regs, unsigned int thread_flags,
+		    int syscall)
+{
+	do {
+		if (likely(thread_flags & _TIF_NEED_RESCHED)) {
+			schedule();
+		} else {
+			if (unlikely(!user_mode(regs)))
+				return 0;
+			local_irq_enable();
+			if (thread_flags & _TIF_SIGPENDING) {
+				int restart = do_signal(regs, syscall);
+				if (unlikely(restart)) {
+					/*
+					 * Restart without handlers.
+					 * Deal with it without leaving
+					 * the kernel space.
+					 */
+					return restart;
+				}
+				syscall = -1;
+			} else {
+				clear_thread_flag(TIF_NOTIFY_RESUME);
+				tracehook_notify_resume(regs);
+			}
+		}
+		local_irq_disable();
+		thread_flags = current_thread_info()->flags;
+	} while (thread_flags & _TIF_WORK_MASK);
+	return 0;
+}