Re: [PATCH v6 01/19] kernel: Standardize vdso_datapage

On Tue, Jun 04, 2019 at 01:05:40PM +0100, Vincenzo Frascino wrote:

On 31/05/2019 09:16, Arnd Bergmann wrote:

...

On Thu, May 30, 2019 at 4:15 PM Vincenzo Frascino vincenzo.frascino@arm.com wrote:

...

• • vdso_data will be accessed by 64 bit and compat code at the same time
• • so we should be careful before modifying this structure.
• */

+struct vdso_data {

•   u32                     seq;
  

•   s32                     clock_mode;
  

•   u64                     cycle_last;
  

•   u64                     mask;
  

•   u32                     mult;
  

•   u32                     shift;
  

•   struct vdso_timestamp   basetime[VDSO_BASES];
  

•   s32                     tz_minuteswest;
  

•   s32                     tz_dsttime;
  

•   u32                     hrtimer_res;
  

+};

The structure contains four padding bytes at the end, which is something we try to avoid, at least if this ends up being used as an ABI. Maybe add "u32 __unused" at the end?

Agreed, I will fix this in v7.

Note that this is also necessary to ensure that CLOCK_MONOTONIC_RAW works in the 32-bit vDSO on x86_64 kernels.

Huw.