On Tue, Feb 4, 2014 at 2:15 AM, <[email protected]> wrote:
> From: Stefani Seibold <[email protected]>
>
> This patch add the VDSO time support for the IA32 Emulation Layer.
>
> Due the nature of the kernel headers and the LP64 compiler where the
> size of a long and a pointer differs against a 32 bit compiler, there
> is a lot of type hacking necessary.
>
> The vsyscall_gtod_data struture must be a little bit rearranged, to
> serve for 32- and 64-bit code access.
>
> Signed-off-by: Stefani Seibold <[email protected]>
> ---
> arch/x86/include/asm/vgtod.h | 23 +++++----
> arch/x86/kernel/vsyscall_gtod.c | 10 ++--
> arch/x86/vdso/vclock_gettime.c | 93
> +++++++++++++++++++++++------------
> arch/x86/vdso/vdso32/vclock_gettime.c | 11 +++++
> include/uapi/linux/time.h | 2 +-
> 5 files changed, 92 insertions(+), 47 deletions(-)
>
> diff --git a/arch/x86/include/asm/vgtod.h b/arch/x86/include/asm/vgtod.h
> index 46e24d3..3032eb8 100644
> --- a/arch/x86/include/asm/vgtod.h
> +++ b/arch/x86/include/asm/vgtod.h
> @@ -4,16 +4,16 @@
> #include <asm/vsyscall.h>
> #include <linux/clocksource.h>
>
> -struct vsyscall_gtod_data {
> - seqcount_t seq;
> -
> - struct { /* extract of a clocksource struct */
> - int vclock_mode;
> - cycle_t cycle_last;
> - cycle_t mask;
> - u32 mult;
> - u32 shift;
> - } clock;
> +/*
> + * vsyscall_gtod_data will be accessed by 32 and 64 bit code at the same time
> + * so the structure must be packed
> + */
> +struct __attribute__((packed)) vsyscall_gtod_data {
> + int vclock_mode;
> + cycle_t cycle_last;
> + cycle_t mask;
> + u32 mult;
> + u32 shift;
>
> /* open coded 'struct timespec' */
> time_t wall_time_sec;
> @@ -24,6 +24,9 @@ struct vsyscall_gtod_data {
> struct timezone sys_tz;
> struct timespec wall_time_coarse;
> struct timespec monotonic_time_coarse;
> +
> + /* must be at the end, because the size depends on the kernel config
> */
> + seqcount_t seq;
Please don't move this. You are probably increasing the number of
cachelines needed to do vclock_gettime if lockdep is off.
(vclock_gettime with CLOCK_REALTIME or CLOCK_MONOTONIC is probably the
most important case.) I'd much rather this be just 'unsigned seq' or
'u32 seq' and stay at the beginning.
> @@ -57,6 +70,18 @@ notrace static long vdso_fallback_gtod(struct timeval *tv,
> struct timezone *tz)
> u8 hpet_page
> __attribute__((visibility("hidden")));
>
> +struct api_timeval {
> + s32 tv_sec; /* seconds */
> + s32 tv_usec; /* microseconds */
> +};
> +
> +struct api_timespec {
> + s32 tv_sec; /* seconds */
> + s32 tv_nsec; /* microseconds */
> +};
These ought to be unifiable between 32-bit and 64-bit. Isn't 'long
tv_sec; long tv_nsec;' correct in all cases?
--Andy
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
