[PATCH v2 19/44] metag: Signal handling

[James Hogan <james.hogan@imgtec.com>]

Add signal handling code for metag.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
---
 arch/metag/include/uapi/asm/sigcontext.h |   31 +++
 arch/metag/include/uapi/asm/siginfo.h    |    8 +
 arch/metag/kernel/signal.c               |  345 ++++++++++++++++++++++++++++++
 3 files changed, 384 insertions(+), 0 deletions(-)
 create mode 100644 arch/metag/include/uapi/asm/sigcontext.h
 create mode 100644 arch/metag/include/uapi/asm/siginfo.h
 create mode 100644 arch/metag/kernel/signal.c

diff --git a/arch/metag/include/uapi/asm/sigcontext.h b/arch/metag/include/uapi/asm/sigcontext.h
new file mode 100644
index 0000000..ef79a91
--- /dev/null
+++ b/arch/metag/include/uapi/asm/sigcontext.h
@@ -0,0 +1,31 @@
+#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
diff --git a/arch/metag/include/uapi/asm/siginfo.h b/arch/metag/include/uapi/asm/siginfo.h
new file mode 100644
index 0000000..b2e0c8b
--- /dev/null
+++ b/arch/metag/include/uapi/asm/siginfo.h
@@ -0,0 +1,8 @@
+#ifndef _METAG_SIGINFO_H
+#define _METAG_SIGINFO_H
+
+#define __ARCH_SI_TRAPNO
+
+#include <asm-generic/siginfo.h>
+
+#endif
diff --git a/arch/metag/kernel/signal.c b/arch/metag/kernel/signal.c
new file mode 100644
index 0000000..9d7065a
--- /dev/null
+++ b/arch/metag/kernel/signal.c
@@ -0,0 +1,345 @@
+/*
+ *  Copyright (C) 1991,1992  Linus Torvalds
+ *  Copyright (C) 2005,2006,2007,2008,2009  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
+
+int sys_sigaltstack(const stack_t __user *uss,
+		    stack_t __user *uoss,
+		    unsigned long arg3,
+		    unsigned long arg4,
+		    unsigned long arg5,
+		    unsigned long arg6,
+		    struct pt_regs *regs)
+{
+	return do_sigaltstack(uss, uoss, regs->REG_SP);
+}
+
+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;
+}
+
+int sys_rt_sigreturn(unsigned long arg1,
+		     unsigned long arg2,
+		     unsigned long arg3,
+		     unsigned long arg4,
+		     unsigned long arg5,
+		     unsigned long arg6,
+		     struct pt_regs *regs)    /* regs always arg7 on Meta */
+{
+	/* NOTE - Meta stack goes UPWARDS - so we wind the stack back */
+	struct rt_sigframe __user *frame;
+	sigset_t set;
+	stack_t st;
+
+	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 (__copy_from_user(&st, &frame->uc.uc_stack, sizeof(st)))
+		goto badframe;
+	/* It is more difficult to avoid calling this function than to
+	   call it and ignore errors.  */
+	do_sigaltstack((__force const stack_t __user *)&st, NULL, regs->REG_SP);
+
+	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 |= __put_user(current->sas_ss_sp,
+			  (unsigned long __user *)&frame->uc.uc_stack.ss_sp);
+	err |= __put_user(sas_ss_flags(regs->REG_SP),
+			  &frame->uc.uc_stack.ss_flags);
+	err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
+	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,
+			  int from_syscall, unsigned int orig_syscall)
+{
+	sigset_t *oldset = sigmask_to_save();
+
+	/* Are we from a system call? */
+	if (from_syscall) {
+		/* If so, check system call restarting.. */
+		switch (syscall_get_error(current, regs)) {
+		case -ERESTART_RESTARTBLOCK:
+		case -ERESTARTNOHAND:
+			regs->REG_RETVAL = -EINTR;
+			break;
+
+		case -ERESTARTSYS:
+			if (!(ka->sa.sa_flags & SA_RESTART)) {
+				regs->REG_RETVAL = -EINTR;
+				break;
+			}
+		/* fallthrough */
+		case -ERESTARTNOINTR:
+			regs->REG_SYSCALL = orig_syscall;
+			regs->REG_PC -= 4;
+			break;
+		}
+	}
+
+	/* 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 and orig_syscall on the stack.
+  * This is for two reasons:
+  * 1) having syscall_nr in our context does not fit with TBI, and corrupted
+  *    the stack.
+  * 2) We need to have orig_syscall and from_syscall to implement syscall
+  *    restarting.
+  */
+static void do_signal(struct pt_regs *regs, int from_syscall,
+		      unsigned int orig_syscall)
+{
+	struct k_sigaction ka;
+	siginfo_t info;
+	int signr;
+
+	/*
+	 * We want the common case to go fast, which
+	 * is why we may in certain cases get here from
+	 * kernel mode. Just return without doing anything
+	 * if so.
+	 */
+	if (!user_mode(regs))
+		return;
+
+	signr = get_signal_to_deliver(&info, &ka, regs, NULL);
+	if (signr > 0) {
+		/* Whee! Actually deliver the signal.  */
+		handle_signal(signr, &info, &ka, regs, from_syscall,
+			      orig_syscall);
+		return;
+	}
+
+	/* Did we come from a system call? */
+	if (from_syscall) {
+		/* Restart the system call - no handlers present */
+		switch (syscall_get_error(current, regs)) {
+		case -ERESTARTNOHAND:
+		case -ERESTARTSYS:
+		case -ERESTARTNOINTR:
+			regs->REG_SYSCALL = orig_syscall;
+			regs->REG_PC -= 4;
+			break;
+
+		case -ERESTART_RESTARTBLOCK:
+			regs->REG_SYSCALL = __NR_restart_syscall;
+			regs->REG_PC -= 4;
+			break;
+		}
+	}
+
+	/*
+	 * If there's no signal to deliver, we just put the saved sigmask
+	 * back.
+	 */
+	restore_saved_sigmask();
+}
+
+void do_notify_resume(struct pt_regs *regs, int from_syscall,
+		      unsigned int orig_syscall,
+		      unsigned long thread_info_flags)
+{
+	/* deal with pending signal delivery */
+	if (thread_info_flags & _TIF_SIGPENDING)
+		do_signal(regs, from_syscall, orig_syscall);
+
+	if (thread_info_flags & _TIF_NOTIFY_RESUME) {
+		clear_thread_flag(TIF_NOTIFY_RESUME);
+		tracehook_notify_resume(regs);
+	}
+}
-- 
1.7.7.6