csky: Process management and Signal

This patch adds files related to task_switch, sigcontext, signal,
fpu context switch.

Signed-off-by: Guo Ren <ren_guo@c-sky.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Eric W. Biederman <ebiederm@xmission.com>

1 files changed, 347 insertions, 0 deletions

diff --git a/arch/csky/kernel/signal.c b/arch/csky/kernel/signal.c
new file mode 100644
index 000000000000..66e1b729b10b
--- /dev/null
+++ b/arch/csky/kernel/signal.c
@@ -0,0 +1,347 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
+
+#include <linux/sched.h>
+#include <linux/mm.h>
+#include <linux/kernel.h>
+#include <linux/signal.h>
+#include <linux/syscalls.h>
+#include <linux/errno.h>
+#include <linux/wait.h>
+#include <linux/ptrace.h>
+#include <linux/unistd.h>
+#include <linux/stddef.h>
+#include <linux/highuid.h>
+#include <linux/personality.h>
+#include <linux/tty.h>
+#include <linux/binfmts.h>
+#include <linux/tracehook.h>
+#include <linux/freezer.h>
+#include <linux/uaccess.h>
+
+#include <asm/setup.h>
+#include <asm/pgtable.h>
+#include <asm/traps.h>
+#include <asm/ucontext.h>
+#include <asm/vdso.h>
+
+#include <abi/regdef.h>
+
+#ifdef CONFIG_CPU_HAS_FPU
+#include <abi/fpu.h>
+
+static int restore_fpu_state(struct sigcontext *sc)
+{
+	int err = 0;
+	struct user_fp user_fp;
+
+	err = copy_from_user(&user_fp, &sc->sc_user_fp, sizeof(user_fp));
+
+	restore_from_user_fp(&user_fp);
+
+	return err;
+}
+
+static int save_fpu_state(struct sigcontext *sc)
+{
+	struct user_fp user_fp;
+
+	save_to_user_fp(&user_fp);
+
+	return copy_to_user(&sc->sc_user_fp, &user_fp, sizeof(user_fp));
+}
+#else
+static inline int restore_fpu_state(struct sigcontext *sc) { return 0; }
+static inline int save_fpu_state(struct sigcontext *sc) { return 0; }
+#endif
+
+struct rt_sigframe {
+	int sig;
+	struct siginfo *pinfo;
+	void *puc;
+	struct siginfo info;
+	struct ucontext uc;
+};
+
+static int
+restore_sigframe(struct pt_regs *regs,
+		 struct sigcontext *sc, int *pr2)
+{
+	int err = 0;
+
+	/* Always make any pending restarted system calls return -EINTR */
+	current_thread_info()->task->restart_block.fn = do_no_restart_syscall;
+
+	err |= copy_from_user(regs, &sc->sc_pt_regs, sizeof(struct pt_regs));
+
+	err |= restore_fpu_state(sc);
+
+	*pr2 = regs->a0;
+	return err;
+}
+
+asmlinkage int
+do_rt_sigreturn(void)
+{
+	sigset_t set;
+	int a0;
+	struct pt_regs *regs = current_pt_regs();
+	struct rt_sigframe *frame = (struct rt_sigframe *)(regs->usp);
+
+	if (verify_area(VERIFY_READ, frame, sizeof(*frame)))
+		goto badframe;
+	if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
+		goto badframe;
+
+	sigdelsetmask(&set, (sigmask(SIGKILL) | sigmask(SIGSTOP)));
+	spin_lock_irq(&current->sighand->siglock);
+	current->blocked = set;
+	recalc_sigpending();
+	spin_unlock_irq(&current->sighand->siglock);
+
+	if (restore_sigframe(regs, &frame->uc.uc_mcontext, &a0))
+		goto badframe;
+
+	return a0;
+
+badframe:
+	force_sig(SIGSEGV, current);
+	return 0;
+}
+
+static int setup_sigframe(struct sigcontext *sc, struct pt_regs *regs)
+{
+	int err = 0;
+
+	err |= copy_to_user(&sc->sc_pt_regs, regs, sizeof(struct pt_regs));
+	err |= save_fpu_state(sc);
+
+	return err;
+}
+
+static inline void *
+get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size)
+{
+	unsigned long usp;
+
+	/* Default to using normal stack.  */
+	usp = regs->usp;
+
+	/* This is the X/Open sanctioned signal stack switching.  */
+	if ((ka->sa.sa_flags & SA_ONSTACK) && !sas_ss_flags(usp)) {
+		if (!on_sig_stack(usp))
+			usp = current->sas_ss_sp + current->sas_ss_size;
+	}
+	return (void *)((usp - frame_size) & -8UL);
+}
+
+static int
+setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
+{
+	struct rt_sigframe *frame;
+	int err = 0;
+
+	struct csky_vdso *vdso = current->mm->context.vdso;
+
+	frame = get_sigframe(&ksig->ka, regs, sizeof(*frame));
+	if (!frame)
+		return 1;
+
+	err |= __put_user(ksig->sig, &frame->sig);
+	err |= __put_user(&frame->info, &frame->pinfo);
+	err |= __put_user(&frame->uc, &frame->puc);
+	err |= copy_siginfo_to_user(&frame->info, &ksig->info);
+
+	/* Create the ucontext.  */
+	err |= __put_user(0, &frame->uc.uc_flags);
+	err |= __put_user(0, &frame->uc.uc_link);
+	err |= __put_user((void *)current->sas_ss_sp,
+			&frame->uc.uc_stack.ss_sp);
+	err |= __put_user(sas_ss_flags(regs->usp),
+			&frame->uc.uc_stack.ss_flags);
+	err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
+	err |= setup_sigframe(&frame->uc.uc_mcontext, regs);
+	err |= copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
+
+	if (err)
+		goto give_sigsegv;
+
+	/* Set up registers for signal handler */
+	regs->usp = (unsigned long)frame;
+	regs->pc = (unsigned long)ksig->ka.sa.sa_handler;
+	regs->lr = (unsigned long)vdso->rt_signal_retcode;
+
+adjust_stack:
+	regs->a0 = ksig->sig; /* first arg is signo */
+	regs->a1 = (unsigned long)(&(frame->info));
+	regs->a2 = (unsigned long)(&(frame->uc));
+	return err;
+
+give_sigsegv:
+	if (ksig->sig == SIGSEGV)
+		ksig->ka.sa.sa_handler = SIG_DFL;
+	force_sig(SIGSEGV, current);
+	goto adjust_stack;
+}
+
+/*
+ * OK, we're invoking a handler
+ */
+static int
+handle_signal(struct ksignal *ksig, struct pt_regs *regs)
+{
+	int ret;
+	sigset_t *oldset = sigmask_to_save();
+
+	/*
+	 * set up the stack frame, regardless of SA_SIGINFO,
+	 * and pass info anyway.
+	 */
+	ret = setup_rt_frame(ksig, oldset, regs);
+
+	if (ret != 0) {
+		force_sigsegv(ksig->sig, current);
+		return ret;
+	}
+
+	/* Block the signal if we were successful. */
+	spin_lock_irq(&current->sighand->siglock);
+	sigorsets(&current->blocked, &current->blocked, &ksig->ka.sa.sa_mask);
+	if (!(ksig->ka.sa.sa_flags & SA_NODEFER))
+		sigaddset(&current->blocked, ksig->sig);
+	recalc_sigpending();
+	spin_unlock_irq(&current->sighand->siglock);
+
+	return 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, int syscall)
+{
+	unsigned int retval = 0, continue_addr = 0, restart_addr = 0;
+	struct ksignal ksig;
+
+	/*
+	 * 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;
+
+	current->thread.esp0 = (unsigned long)regs;
+
+	/*
+	 * If we were from a system call, check for system call restarting...
+	 */
+	if (syscall) {
+		continue_addr = regs->pc;
+#if defined(__CSKYABIV2__)
+		restart_addr = continue_addr - 4;
+#else
+		restart_addr = continue_addr - 2;
+#endif
+		retval = regs->a0;
+
+		/*
+		 * Prepare for system call restart.  We do this here so that a
+		 * debugger will see the already changed.
+		 */
+		switch (retval) {
+		case -ERESTARTNOHAND:
+		case -ERESTARTSYS:
+		case -ERESTARTNOINTR:
+			regs->a0 = regs->orig_a0;
+			regs->pc = restart_addr;
+			break;
+		case -ERESTART_RESTARTBLOCK:
+			regs->a0 = -EINTR;
+			break;
+		}
+	}
+
+	if (try_to_freeze())
+		goto no_signal;
+
+	/*
+	 * Get the signal to deliver.  When running under ptrace, at this
+	 * point the debugger may change all our registers ...
+	 */
+	if (get_signal(&ksig)) {
+		/*
+		 * 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) {
+			if (retval == -ERESTARTNOHAND ||
+			    (retval == -ERESTARTSYS &&
+			     !(ksig.ka.sa.sa_flags & SA_RESTART))) {
+				regs->a0 = -EINTR;
+				regs->pc = continue_addr;
+			}
+		}
+
+		/* Whee!  Actually deliver the signal.  */
+		if (handle_signal(&ksig, regs) == 0) {
+			/*
+			 * A signal was successfully delivered; the saved
+			 * sigmask will have been stored in the signal frame,
+			 * and will be restored by sigreturn, so we can simply
+			 * clear the TIF_RESTORE_SIGMASK flag.
+			 */
+			if (test_thread_flag(TIF_RESTORE_SIGMASK))
+				clear_thread_flag(TIF_RESTORE_SIGMASK);
+		}
+		return;
+	}
+
+no_signal:
+	if (syscall) {
+		/*
+		 * Handle restarting a different system call.  As above,
+		 * if a debugger has chosen to restart at a different PC,
+		 * ignore the restart.
+		 */
+		if (retval == -ERESTART_RESTARTBLOCK
+				&& regs->pc == continue_addr) {
+#if defined(__CSKYABIV2__)
+			regs->regs[3] = __NR_restart_syscall;
+			regs->pc -= 4;
+#else
+			regs->regs[9] = __NR_restart_syscall;
+			regs->pc -= 2;
+#endif
+		}
+
+		/*
+		 * If there's no signal to deliver, we just put the saved
+		 * sigmask back.
+		 */
+		if (test_thread_flag(TIF_RESTORE_SIGMASK)) {
+			clear_thread_flag(TIF_RESTORE_SIGMASK);
+			sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
+		}
+	}
+}
+
+asmlinkage void
+do_notify_resume(unsigned int thread_flags, struct pt_regs *regs, int syscall)
+{
+	if (thread_flags & _TIF_SIGPENDING)
+		do_signal(regs, syscall);
+
+	if (thread_flags & _TIF_NOTIFY_RESUME) {
+		clear_thread_flag(TIF_NOTIFY_RESUME);
+		tracehook_notify_resume(regs);
+	}
+}