Messages in this thread | | | From | Arnd Bergmann <> | Date | Tue, 14 Nov 2017 14:03:08 +0100 | Subject | Re: [PATCH 4/9] posix-clocks: Enable compat syscalls always |
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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
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