On Thu, Jan 30, 2014 at 2:49 AM, <[email protected]> wrote: > From: Stefani Seibold <[email protected]> > > This patch add the support for the IA32 Emulation Layer to run 32 bit > applications on a 64 bit kernel. > > 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. > > This kind of type hacking could be prevent in the future by doing a call to > the > 64 bit code by the following sequence: > > - Compile the arch/x86/vdso/vclock_gettime.c as 64 bit, but only generate > the assemble output. > - Next compile a 32 bit object by including the 64 bit vclock_gettime.s > prefixed with .code64 > - At least we need a trampolin code which invokes the 64 bit code and do > the API conversation (64 bit longs to 32 bit longs), like the > followig snipped: > > ENTRY(call64) > push %ebp > movl %esp, %ebp > ljmp $__USER_CS, $1f > .code64
I bet that this trampoline takes at least as long as a syscall / sysenter instruction. I'd be surprised if designers of modern cpus care at all about ljmp latency. > > Signed-off-by: Stefani Seibold <[email protected]> > --- > arch/x86/vdso/vclock_gettime.c | 112 > ++++++++++++++++++++++++++-------- > arch/x86/vdso/vdso32/vclock_gettime.c | 7 +++ > 2 files changed, 95 insertions(+), 24 deletions(-) > > diff --git a/arch/x86/vdso/vclock_gettime.c b/arch/x86/vdso/vclock_gettime.c > index 19b2a49..a2417e2 100644 > --- a/arch/x86/vdso/vclock_gettime.c > +++ b/arch/x86/vdso/vclock_gettime.c > @@ -31,12 +31,24 @@ > > #define gtod (&VVAR(vsyscall_gtod_data)) > > +struct api_timeval { > + long tv_sec; /* seconds */ > + long tv_usec; /* microseconds */ > +}; > + > +struct api_timespec { > + long tv_sec; /* seconds */ > + long tv_nsec; /* microseconds */ > +}; > + > +typedef long api_time_t; > + > static notrace cycle_t vread_hpet(void) > { > return readl((const void __iomem *)fix_to_virt(VSYSCALL_HPET) + > HPET_COUNTER); > } > > -notrace static long vdso_fallback_gettime(long clock, struct timespec *ts) > +notrace static long vdso_fallback_gettime(long clock, struct api_timespec > *ts) > { > long ret; > asm("syscall" : "=a" (ret) : > @@ -44,7 +56,8 @@ notrace static long vdso_fallback_gettime(long clock, > struct timespec *ts) > return ret; > } > > -notrace static long vdso_fallback_gtod(struct timeval *tv, struct timezone > *tz) > +notrace static long vdso_fallback_gtod(struct api_timeval *tv, > + struct timezone *tz) > { > long ret; > > @@ -54,20 +67,68 @@ notrace static long vdso_fallback_gtod(struct timeval > *tv, struct timezone *tz) > } > #else > > +#ifdef CONFIG_IA32_EMULATION > +typedef s64 arch_time_t; > + > +struct arch_timespec { > + s64 tv_sec; > + s64 tv_nsec; > +}; > + > +#define ALIGN8 __attribute__ ((aligned (8))) > + > +struct arch_vsyscall_gtod_data { > + seqcount_t seq ALIGN8; > + > + struct { /* extract of a clocksource struct */ > + int vclock_mode ALIGN8; > + cycle_t cycle_last ALIGN8; > + cycle_t mask ALIGN8; > + u32 mult; > + u32 shift; > + } clock; > + > + /* open coded 'struct timespec' */ > + arch_time_t wall_time_sec; > + u64 wall_time_snsec; > + u64 monotonic_time_snsec; > + arch_time_t monotonic_time_sec; > + > + struct timezone sys_tz; > + struct arch_timespec wall_time_coarse; > + struct arch_timespec monotonic_time_coarse; > +}; Yuck! Can you see how hard it would be to just make the real gtod data have the same layout for 32-bit and 64-bit code? --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/
