Merge tag 'y2038-timekeeping' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/playground into timers/core

Pull y2038 timekeeping syscall changes from Arnd Bergmann:

This is the first set of system call entry point changes to enable 32-bit
architectures to have variants on both 32-bit and 64-bit time_t. Typically
these system calls take a 'struct timespec' argument, but that structure
is defined in user space by the C library and its layout will change.

The kernel already supports handling the 32-bit time_t on 64-bit
architectures through the CONFIG_COMPAT mechanism. As there are a total
of 51 system calls suffering from this problem, reusing that mechanism
on 32-bit architectures.

We already have patches for most of the remaining system calls, but this
set contains most of the complexity and is best tested.  There was one
last-minute regression that prevented it from going into 4.17, but that
is fixed now.

More details from Deepa's patch series description:

   Big picture is as per the lwn article:
   https://lwn.net/Articles/643234/ [2]

   The series is directed at converting posix clock syscalls:
   clock_gettime, clock_settime, clock_getres and clock_nanosleep
   to use a new data structure __kernel_timespec at syscall boundaries.
   __kernel_timespec maintains 64 bit time_t across all execution modes.

   vdso will be handled as part of each architecture when they enable
   support for 64 bit time_t.

   The compat syscalls are repurposed to provide backward compatibility
   by using them as native syscalls as well for 32 bit architectures.
   They will continue to use timespec at syscall boundaries.

   CONFIG_64_BIT_TIME controls whether the syscalls use __kernel_timespec
   or timespec at syscall boundaries.

   The series does the following:
   1. Enable compat syscalls on 32 bit architectures.
   2. Add a new __kernel_timespec type to be used as the data structure
      for all the new syscalls.
   3. Add new config CONFIG_64BIT_TIME(intead of the CONFIG_COMPAT_TIME in
      [1] and [2] to switch to new definition of __kernel_timespec. It is
      the same as struct timespec otherwise.
   4. Add new CONFIG_32BIT_TIME to conditionally compile compat syscalls.

Author: KAGA-KOKO

arch/Kconfig

@@ -870,6 +870,21 @@ config OLD_SIGACTION
 config COMPAT_OLD_SIGACTION
 	bool
 
+config 64BIT_TIME
+	def_bool ARCH_HAS_64BIT_TIME
+	help
+	  This should be selected by all architectures that need to support
+	  new system calls with a 64-bit time_t. This is relevant on all 32-bit
+	  architectures, and 64-bit architectures as part of compat syscall
+	  handling.
+
+config COMPAT_32BIT_TIME
+	def_bool (!64BIT && 64BIT_TIME) || COMPAT
+	help
+	  This enables 32 bit time_t support in addition to 64 bit time_t support.
+	  This is relevant on all 32-bit architectures, and 64-bit architectures
+	  as part of compat syscall handling.
+
 config ARCH_NO_COHERENT_DMA_MMAP
 	bool
 

arch/alpha/include/asm/Kbuild

@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 
 
+generic-y += compat.h
 generic-y += exec.h
 generic-y += export.h
 generic-y += fb.h

arch/arc/include/asm/Kbuild

@@ -1,5 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
 generic-y += bugs.h
+generic-y += compat.h
 generic-y += device.h
 generic-y += div64.h
 generic-y += emergency-restart.h

arch/arm/include/asm/Kbuild

@@ -1,3 +1,4 @@
+generic-y += compat.h
 generic-y += current.h
 generic-y += early_ioremap.h
 generic-y += emergency-restart.h

arch/arm64/include/asm/compat.h

@@ -34,7 +34,6 @@
 
 typedef u32		compat_size_t;
 typedef s32		compat_ssize_t;
-typedef s32		compat_time_t;
 typedef s32		compat_clock_t;
 typedef s32		compat_pid_t;
 typedef u16		__compat_uid_t;
@@ -66,16 +65,6 @@ typedef u32		compat_ulong_t;
 typedef u64		compat_u64;
 typedef u32		compat_uptr_t;
 
-struct compat_timespec {
-	compat_time_t	tv_sec;
-	s32		tv_nsec;
-};
-
-struct compat_timeval {
-	compat_time_t	tv_sec;
-	s32		tv_usec;
-};
-
 struct compat_stat {
 #ifdef __AARCH64EB__
 	short		st_dev;

arch/arm64/include/asm/stat.h

@@ -20,6 +20,7 @@
 
 #ifdef CONFIG_COMPAT
 
+#include <linux/compat_time.h>
 #include <asm/compat.h>
 
 /*

arch/arm64/kernel/hw_breakpoint.c

@@ -30,7 +30,6 @@
 #include <linux/smp.h>
 #include <linux/uaccess.h>
 
-#include <asm/compat.h>
 #include <asm/current.h>
 #include <asm/debug-monitors.h>
 #include <asm/hw_breakpoint.h>

arch/arm64/kernel/perf_regs.c

@@ -1,11 +1,11 @@
 // SPDX-License-Identifier: GPL-2.0
+#include <linux/compat.h>
 #include <linux/errno.h>
 #include <linux/kernel.h>
 #include <linux/perf_event.h>
 #include <linux/bug.h>
 #include <linux/sched/task_stack.h>
 
-#include <asm/compat.h>
 #include <asm/perf_regs.h>
 #include <asm/ptrace.h>
 

arch/c6x/include/asm/Kbuild

@@ -1,6 +1,7 @@
 generic-y += atomic.h
 generic-y += barrier.h
 generic-y += bugs.h
+generic-y += compat.h
 generic-y += current.h
 generic-y += device.h
 generic-y += div64.h

arch/h8300/include/asm/Kbuild

@@ -3,6 +3,7 @@ generic-y += barrier.h
 generic-y += bugs.h
 generic-y += cacheflush.h
 generic-y += checksum.h
+generic-y += compat.h
 generic-y += current.h
 generic-y += delay.h
 generic-y += device.h