s390: convert to generic entry

This patch converts s390 to use the generic entry infrastructure from
kernel/entry/*.

There are a few special things on s390:

- PIF_PER_TRAP is moved to TIF_PER_TRAP as the generic code doesn't
  know about our PIF flags in exit_to_user_mode_loop().

- The old code had several ways to restart syscalls:

  a) PIF_SYSCALL_RESTART, which was only set during execve to force a
     restart after upgrading a process (usually qemu-kvm) to pgste page
     table extensions.

  b) PIF_SYSCALL, which is set by do_signal() to indicate that the
     current syscall should be restarted. This is changed so that
     do_signal() now also uses PIF_SYSCALL_RESTART. Continuing to use
     PIF_SYSCALL doesn't work with the generic code, and changing it
     to PIF_SYSCALL_RESTART makes PIF_SYSCALL and PIF_SYSCALL_RESTART
     more unique.

- On s390 calling sys_sigreturn or sys_rt_sigreturn is implemented by
executing a svc instruction on the process stack which causes a fault.
While handling that fault the fault code sets PIF_SYSCALL to hand over
processing to the syscall code on exit to usermode.

The patch introduces PIF_SYSCALL_RET_SET, which is set if ptrace sets
a return value for a syscall. The s390x ptrace ABI uses r2 both for the
syscall number and return value, so ptrace cannot set the syscall number +
return value at the same time. The flag makes handling that a bit easier.
do_syscall() will just skip executing the syscall if PIF_SYSCALL_RET_SET
is set.

CONFIG_DEBUG_ASCE was removd in favour of the generic CONFIG_DEBUG_ENTRY.
CR1/7/13 will be checked both on kernel entry and exit to contain the
correct asces.

Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

1 files changed, 172 insertions, 0 deletions

diff --git a/arch/s390/kernel/syscall.c b/arch/s390/kernel/syscall.c
new file mode 100644
index 000000000000..25c0fb19b0a5
--- /dev/null
+++ b/arch/s390/kernel/syscall.c
@@ -0,0 +1,172 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  S390 version
+ *    Copyright IBM Corp. 1999, 2000
+ *    Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com),
+ *               Thomas Spatzier (tspat@de.ibm.com)
+ *
+ *  Derived from "arch/i386/kernel/sys_i386.c"
+ *
+ *  This file contains various random system calls that
+ *  have a non-standard calling sequence on the Linux/s390
+ *  platform.
+ */
+
+#include <linux/errno.h>
+#include <linux/sched.h>
+#include <linux/mm.h>
+#include <linux/fs.h>
+#include <linux/smp.h>
+#include <linux/sem.h>
+#include <linux/msg.h>
+#include <linux/shm.h>
+#include <linux/stat.h>
+#include <linux/syscalls.h>
+#include <linux/mman.h>
+#include <linux/file.h>
+#include <linux/utsname.h>
+#include <linux/personality.h>
+#include <linux/unistd.h>
+#include <linux/ipc.h>
+#include <linux/uaccess.h>
+#include <linux/string.h>
+#include <linux/thread_info.h>
+#include <linux/entry-common.h>
+
+#include <asm/ptrace.h>
+#include <asm/vtime.h>
+
+#include "entry.h"
+
+/*
+ * Perform the mmap() system call. Linux for S/390 isn't able to handle more
+ * than 5 system call parameters, so this system call uses a memory block
+ * for parameter passing.
+ */
+
+struct s390_mmap_arg_struct {
+	unsigned long addr;
+	unsigned long len;
+	unsigned long prot;
+	unsigned long flags;
+	unsigned long fd;
+	unsigned long offset;
+};
+
+SYSCALL_DEFINE1(mmap2, struct s390_mmap_arg_struct __user *, arg)
+{
+	struct s390_mmap_arg_struct a;
+	int error = -EFAULT;
+
+	if (copy_from_user(&a, arg, sizeof(a)))
+		goto out;
+	error = ksys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd, a.offset);
+out:
+	return error;
+}
+
+#ifdef CONFIG_SYSVIPC
+/*
+ * sys_ipc() is the de-multiplexer for the SysV IPC calls.
+ */
+SYSCALL_DEFINE5(s390_ipc, uint, call, int, first, unsigned long, second,
+		unsigned long, third, void __user *, ptr)
+{
+	if (call >> 16)
+		return -EINVAL;
+	/* The s390 sys_ipc variant has only five parameters instead of six
+	 * like the generic variant. The only difference is the handling of
+	 * the SEMTIMEDOP subcall where on s390 the third parameter is used
+	 * as a pointer to a struct timespec where the generic variant uses
+	 * the fifth parameter.
+	 * Therefore we can call the generic variant by simply passing the
+	 * third parameter also as fifth parameter.
+	 */
+	return ksys_ipc(call, first, second, third, ptr, third);
+}
+#endif /* CONFIG_SYSVIPC */
+
+SYSCALL_DEFINE1(s390_personality, unsigned int, personality)
+{
+	unsigned int ret = current->personality;
+
+	if (personality(current->personality) == PER_LINUX32 &&
+	    personality(personality) == PER_LINUX)
+		personality |= PER_LINUX32;
+
+	if (personality != 0xffffffff)
+		set_personality(personality);
+
+	if (personality(ret) == PER_LINUX32)
+		ret &= ~PER_LINUX32;
+
+	return ret;
+}
+
+SYSCALL_DEFINE0(ni_syscall)
+{
+	return -ENOSYS;
+}
+
+void do_syscall(struct pt_regs *regs)
+{
+	unsigned long nr;
+
+	nr = regs->int_code & 0xffff;
+	if (!nr) {
+		nr = regs->gprs[1] & 0xffff;
+		regs->int_code &= ~0xffffUL;
+		regs->int_code |= nr;
+	}
+
+	regs->gprs[2] = nr;
+
+	nr = syscall_enter_from_user_mode_work(regs, nr);
+
+	/*
+	 * In the s390 ptrace ABI, both the syscall number and the return value
+	 * use gpr2. However, userspace puts the syscall number either in the
+	 * svc instruction itself, or uses gpr1. To make at least skipping syscalls
+	 * work, the ptrace code sets PIF_SYSCALL_RET_SET, which is checked here
+	 * and if set, the syscall will be skipped.
+	 */
+	if (!test_pt_regs_flag(regs, PIF_SYSCALL_RET_SET)) {
+		regs->gprs[2] = -ENOSYS;
+		if (likely(nr < NR_syscalls)) {
+			regs->gprs[2] = current->thread.sys_call_table[nr](
+					regs->orig_gpr2, regs->gprs[3],
+					regs->gprs[4], regs->gprs[5],
+					regs->gprs[6], regs->gprs[7]);
+		}
+	} else {
+		clear_pt_regs_flag(regs, PIF_SYSCALL_RET_SET);
+	}
+	syscall_exit_to_user_mode_work(regs);
+}
+
+void noinstr __do_syscall(struct pt_regs *regs, int per_trap)
+{
+	enter_from_user_mode(regs);
+
+	memcpy(&regs->gprs[8], S390_lowcore.save_area_sync, 8 * sizeof(unsigned long));
+	memcpy(&regs->int_code, &S390_lowcore.svc_ilc, sizeof(regs->int_code));
+	regs->psw = S390_lowcore.svc_old_psw;
+
+	update_timer_sys();
+
+	local_irq_enable();
+	regs->orig_gpr2 = regs->gprs[2];
+
+	if (per_trap)
+		set_thread_flag(TIF_PER_TRAP);
+
+	for (;;) {
+		regs->flags = 0;
+		set_pt_regs_flag(regs, PIF_SYSCALL);
+		do_syscall(regs);
+		if (!test_pt_regs_flag(regs, PIF_SYSCALL_RESTART))
+			break;
+		local_irq_enable();
+	}
+	exit_to_user_mode();
+}