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 <[email protected]>
Signed-off-by: Vasily Gorbik <[email protected]>

Author: svens-s390

arch/s390/Kconfig

@@ -123,6 +123,7 @@ config S390
 	select GENERIC_ALLOCATOR
 	select GENERIC_CPU_AUTOPROBE
 	select GENERIC_CPU_VULNERABILITIES
+	select GENERIC_ENTRY
 	select GENERIC_FIND_FIRST_BIT
 	select GENERIC_GETTIMEOFDAY
 	select GENERIC_PTDUMP

arch/s390/Kconfig.debug

@@ -6,10 +6,12 @@ config TRACE_IRQFLAGS_SUPPORT
 config EARLY_PRINTK
 	def_bool y
 
-config DEBUG_USER_ASCE
-	bool "Debug User ASCE"
+config DEBUG_ENTRY
+	bool "Debug low-level entry code"
+	depends on DEBUG_KERNEL
 	help
-	  Check on exit to user space that address space control
-	  elements are setup correctly.
+	  This option enables sanity checks in s390 low-level entry code.
+	  Some of these sanity checks may slow down kernel entries and
+	  exits or otherwise impact performance.
 
 	  If unsure, say N.

arch/s390/configs/debug_defconfig

@@ -833,7 +833,6 @@ CONFIG_BPF_KPROBE_OVERRIDE=y
 CONFIG_HIST_TRIGGERS=y
 CONFIG_FTRACE_STARTUP_TEST=y
 # CONFIG_EVENT_TRACE_STARTUP_TEST is not set
-CONFIG_DEBUG_USER_ASCE=y
 CONFIG_NOTIFIER_ERROR_INJECTION=m
 CONFIG_NETDEV_NOTIFIER_ERROR_INJECT=m
 CONFIG_FAULT_INJECTION=y
@@ -857,3 +856,4 @@ CONFIG_PERCPU_TEST=m
 CONFIG_ATOMIC64_SELFTEST=y
 CONFIG_TEST_BITOPS=m
 CONFIG_TEST_BPF=m
+CONFIG_DEBUG_ENTRY=y

arch/s390/configs/defconfig

@@ -781,7 +781,6 @@ CONFIG_FTRACE_SYSCALLS=y
 CONFIG_BLK_DEV_IO_TRACE=y
 CONFIG_BPF_KPROBE_OVERRIDE=y
 CONFIG_HIST_TRIGGERS=y
-CONFIG_DEBUG_USER_ASCE=y
 CONFIG_LKDTM=m
 CONFIG_PERCPU_TEST=m
 CONFIG_ATOMIC64_SELFTEST=y

arch/s390/include/asm/cputime.h

@@ -35,4 +35,6 @@ u64 arch_cpu_idle_time(int cpu);
 
 #define arch_idle_time(cpu) arch_cpu_idle_time(cpu)
 
+void account_idle_time_irq(void);
+
 #endif /* _S390_CPUTIME_H */

arch/s390/include/asm/elf.h

@@ -233,8 +233,7 @@ extern char elf_platform[];
 do {								\
 	set_personality(PER_LINUX |				\
 		(current->personality & (~PER_MASK)));		\
-	current->thread.sys_call_table =			\
-		(unsigned long) &sys_call_table;		\
+	current->thread.sys_call_table = sys_call_table;	\
 } while (0)
 #else /* CONFIG_COMPAT */
 #define SET_PERSONALITY(ex)					\
@@ -245,11 +244,11 @@ do {								\
 	if ((ex).e_ident[EI_CLASS] == ELFCLASS32) {		\
 		set_thread_flag(TIF_31BIT);			\
 		current->thread.sys_call_table =		\
-			(unsigned long)	&sys_call_table_emu;	\
+			sys_call_table_emu;			\
 	} else {						\
 		clear_thread_flag(TIF_31BIT);			\
 		current->thread.sys_call_table =		\
-			(unsigned long) &sys_call_table;	\
+			sys_call_table;				\
 	}							\
 } while (0)
 #endif /* CONFIG_COMPAT */

arch/s390/include/asm/entry-common.h

@@ -0,0 +1,60 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef ARCH_S390_ENTRY_COMMON_H
+#define ARCH_S390_ENTRY_COMMON_H
+
+#include <linux/sched.h>
+#include <linux/audit.h>
+#include <linux/tracehook.h>
+#include <linux/processor.h>
+#include <linux/uaccess.h>
+#include <asm/fpu/api.h>
+
+#define ARCH_EXIT_TO_USER_MODE_WORK (_TIF_GUARDED_STORAGE | _TIF_PER_TRAP)
+
+void do_per_trap(struct pt_regs *regs);
+void do_syscall(struct pt_regs *regs);
+
+typedef void (*pgm_check_func)(struct pt_regs *regs);
+
+extern pgm_check_func pgm_check_table[128];
+
+#ifdef CONFIG_DEBUG_ENTRY
+static __always_inline void arch_check_user_regs(struct pt_regs *regs)
+{
+	debug_user_asce(0);
+}
+
+#define arch_check_user_regs arch_check_user_regs
+#endif /* CONFIG_DEBUG_ENTRY */
+
+static __always_inline void arch_exit_to_user_mode_work(struct pt_regs *regs,
+							unsigned long ti_work)
+{
+	if (ti_work & _TIF_PER_TRAP) {
+		clear_thread_flag(TIF_PER_TRAP);
+		do_per_trap(regs);
+	}
+
+	if (ti_work & _TIF_GUARDED_STORAGE)
+		gs_load_bc_cb(regs);
+}
+
+#define arch_exit_to_user_mode_work arch_exit_to_user_mode_work
+
+static __always_inline void arch_exit_to_user_mode(void)
+{
+	if (test_cpu_flag(CIF_FPU))
+		__load_fpu_regs();
+
+	if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
+		debug_user_asce(1);
+}
+
+#define arch_exit_to_user_mode arch_exit_to_user_mode
+
+static inline bool on_thread_stack(void)
+{
+	return !(((unsigned long)(current->stack) ^ current_stack_pointer()) & ~(THREAD_SIZE - 1));
+}
+
+#endif

arch/s390/include/asm/fpu/api.h

@@ -47,6 +47,8 @@
 #include <linux/preempt.h>
 
 void save_fpu_regs(void);
+void load_fpu_regs(void);
+void __load_fpu_regs(void);
 
 static inline int test_fp_ctl(u32 fpc)
 {

arch/s390/include/asm/idle.h

@@ -20,11 +20,13 @@ struct s390_idle_data {
 	unsigned long long clock_idle_exit;
 	unsigned long long timer_idle_enter;
 	unsigned long long timer_idle_exit;
+	unsigned long mt_cycles_enter[8];
 };
 
 extern struct device_attribute dev_attr_idle_count;
 extern struct device_attribute dev_attr_idle_time_us;
 
-void psw_idle(struct s390_idle_data *, unsigned long);
+void psw_idle(struct s390_idle_data *data, unsigned long psw_mask);
+void psw_idle_exit(void);
 
 #endif /* _S390_IDLE_H */

arch/s390/include/asm/lowcore.h

@@ -81,8 +81,8 @@ struct lowcore {
 	psw_t	return_mcck_psw;		/* 0x02a0 */
 
 	/* CPU accounting and timing values. */
-	__u64	sync_enter_timer;		/* 0x02b0 */
-	__u64	async_enter_timer;		/* 0x02b8 */
+	__u64	sys_enter_timer;		/* 0x02b0 */
+	__u8	pad_0x02b8[0x02c0-0x02b8];	/* 0x02b8 */
 	__u64	mcck_enter_timer;		/* 0x02c0 */
 	__u64	exit_timer;			/* 0x02c8 */
 	__u64	user_timer;			/* 0x02d0 */