On Tue, Nov 14, 2017 at 12:26 AM, Deepa Dinamani deepa.kernel@gmail.com wrote:
On Mon, Nov 13, 2017 at 1:03 PM, Thomas Gleixner tglx@linutronix.de wrote:
On Fri, 10 Nov 2017, Deepa Dinamani wrote:
-#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE2(nanosleep, struct compat_timespec __user *, rqtp, struct compat_timespec __user *, rmtp) { @@ -1574,7 +1572,6 @@ COMPAT_SYSCALL_DEFINE2(nanosleep, struct compat_timespec __user *, rqtp, current->restart_block.nanosleep.compat_rmtp = rmtp; return hrtimer_nanosleep(&tu, HRTIMER_MODE_REL, CLOCK_MONOTONIC); } -#endif
So if I'm not missing something important this will make the compat syscall define available even for
CONFIG_X86_64=y CONFIG_IA32_EMULATION=n CONFIG_X86_X32=n
which is wrong because in that configuration we don't have any 32bit executable support. So why would we need a compat syscall in that case?
I was thinking that we would switch the meaning of CONFIG_64BIT_TIME after all architectures have enabled support for 64 bit time_t syscalls.
I think at that point the CONFIG_64BIT_TIME symbol can just go away, the name would not express any useful meaning any more once all architectures use 64-bit time types.
After that, I was going to use the config to mean enable only 64 bit time_t support and so all compat syscalls would have #ifndef CONFIG_64BIT_TIME around them. Compat syscalls do not mean compat anymore for these time syscalls as the data structure is defined in a way that they are the same on 64 bit and 32 bit architectures.
But, you are right. It will leave in compat syscalls when it is not required now. I could add a dependency on CONFIG_COMPAT and __BITS_PER_LONG for now if you prefer. I could introduce additional dependencies later on.
In kernel uapi headers, checking for __BITS_PER_LONG is appropriate, but we can't check for CONFIG_COMPAT there, since user space does not see the CONFIG_ namespace.
In the kernel, checking for 64-bit architectures is better done using the CONFIG_64BIT symbol.
So we could do
-#ifdef CONFIG_COMPAT +#if defined(CONFIG_COMPAT) || !defined(CONFIG_64BIT) - COMPAT_SYSCALL_DEFINE2(nanosleep, struct compat_timespec __user *, rqtp, struct compat_timespec __user *, rmtp)
The trick with renaming the Kconfig symbol worked better with the old CONFIG_COMPAT_TIME name that I had in an earlier draft of the series, it would also enable us to leave out the 32-bit time compat syscall implementation for future architectures that never had the old uapi.
Arnd