lkml.org 
[lkml]   [2014]   [Feb]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH v11 9/9] Add 32 bit VDSO time support for 64 bit kernel
On Tue, Feb 4, 2014 at 2:15 AM,  <stefani@seibold.net> wrote:
> From: Stefani Seibold <stefani@seibold.net>
>
> 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 <stefani@seibold.net>
> ---
> 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


\
 
 \ /
  Last update: 2014-02-04 20:01    [W:0.098 / U:0.288 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site