[PATCH 5/9] y2038: introduce CONFIG_64BIT_TIME

[Deepa Dinamani <deepa.kernel@gmail.com>]

From: Arnd Bergmann <arnd@arndb.de>

There are a total of 53 system calls (aside from ioctl) that pass a time_t
or derived data structure as an argument, and in order to extend time_t
to 64-bit, we have to replace them with new system calls and keep providing
backwards compatibility.

To avoid adding completely new and untested code for this purpose, we
introduce a new CONFIG_64BIT_TIME symbol. Every architecture that supports
new 64 bit time_t syscalls enables this config via ARCH_HAS_64BIT_TIME.

After this is done for all architectures, the CONFIG_64BIT_TIME symbol
can be made a user-selected option, to enable users to build a kernel
that only provides y2038-safe system calls by making 32 time_t syscalls
conditionally included based on the above config.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
---
 arch/Kconfig | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/Kconfig b/arch/Kconfig
index 8911ff37335a..3266ac1a4ff7 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -875,6 +875,17 @@ config OLD_SIGACTION
 config COMPAT_OLD_SIGACTION
 	bool
 
+config ARCH_HAS_64BIT_TIME
+	def_bool n
+
+config 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 ARCH_NO_COHERENT_DMA_MMAP
 	bool
 
-- 
2.11.0