On 09/11/2018 16:13, Arnd Bergmann wrote:

quoted

+
+extern struct vdso_data _vdso_data;
+
+static __always_inline notrace int gettimeofday_fallback(struct timeval *_tv,
+                                                        struct timezone *_tz)

I'm trying to get rid of the last users of 'struct timeval' in the kernel so
we can remove the definition (it will clash with future glibc implementations
in the uapi headers). Could you change this to use __kernel_old_timeval
instead?

Ok, will update all the data types in v2.

... 

quoted

diff --git a/arch/arm64/kernel/vdso/vdso.lds.S b/arch/arm64/kernel/vdso/vdso.lds.S
index beca249bc2f3..9de0ffc369c5 100644
--- a/arch/arm64/kernel/vdso/vdso.lds.S
+++ b/arch/arm64/kernel/vdso/vdso.lds.S

@@ -88,6 +88,7 @@ VERSION
                __kernel_gettimeofday;
                __kernel_clock_gettime;
                __kernel_clock_getres;
+               __kernel_time;
        local: *;
        };
 }

I would  prefer to not add any deprecated interfaces in the VDSO. If we
have the 64-bit version of clock_gettime, we don't need the 32-bit version
of it, and we don't need gettimeofday() or time() either. The C library
can easily implement those by calling into clock_gettime.

I like the idea, this would make the vdso lib code more simple and more maintainable.

In this patchset I tried to cover the widest possible scenario making things configurable: each architecture can select and enable exactly what it needs from the vdso common code. 

Based on what you are proposing, once the C library will implement things in this way, it will be easy to deprecate and remove the unused code.

I am not familiar with the development plans of the various C libraries, but looking at bionic libc currently seems using all the vdso exposed functions [1].

[1] https://github.com/aosp-mirror/platform_bionic/blob/master/libc/bionic/vdso.cpp

...

        Arnd

-- 
Regards,
Vincenzo