diff options
Diffstat (limited to 'lib/libc/i386/sys/__vdso_gettc.c')
| -rw-r--r-- | lib/libc/i386/sys/__vdso_gettc.c | 58 |
1 files changed, 56 insertions, 2 deletions
diff --git a/lib/libc/i386/sys/__vdso_gettc.c b/lib/libc/i386/sys/__vdso_gettc.c index c6f2dfb3556a..1454f16699d2 100644 --- a/lib/libc/i386/sys/__vdso_gettc.c +++ b/lib/libc/i386/sys/__vdso_gettc.c @@ -31,24 +31,78 @@ __FBSDID("$FreeBSD$"); #include <sys/time.h> #include <sys/vdso.h> #include <machine/cpufunc.h> +#include <machine/specialreg.h> #include "libc_private.h" +static int lfence_works = -1; + +static int +get_lfence_usage(void) +{ + u_int cpuid_supported, p[4]; + + if (lfence_works == -1) { + __asm __volatile( + " pushfl\n" + " popl %%eax\n" + " movl %%eax,%%ecx\n" + " xorl $0x200000,%%eax\n" + " pushl %%eax\n" + " popfl\n" + " pushfl\n" + " popl %%eax\n" + " xorl %%eax,%%ecx\n" + " je 1f\n" + " movl $1,%0\n" + " jmp 2f\n" + "1: movl $0,%0\n" + "2:\n" + : "=r" (cpuid_supported) : : "eax", "ecx"); + if (cpuid_supported) { + __asm __volatile( + " pushl %%ebx\n" + " cpuid\n" + " movl %%ebx,%1\n" + " popl %%ebx\n" + : "=a" (p[0]), "=r" (p[1]), "=c" (p[2]), "=d" (p[3]) + : "0" (0x1)); + lfence_works = (p[3] & CPUID_SSE2) != 0; + } else + lfence_works = 0; + } + return (lfence_works); +} + static u_int __vdso_gettc_low(const struct vdso_timehands *th) { - uint32_t rv; + u_int rv; + if (get_lfence_usage() == 1) + lfence(); __asm __volatile("rdtsc; shrd %%cl, %%edx, %0" : "=a" (rv) : "c" (th->th_x86_shift) : "edx"); return (rv); } +static u_int +__vdso_rdtsc32(void) +{ + u_int rv; + + if (get_lfence_usage() == 1) + lfence(); + rv = rdtsc32(); + return (rv); +} + #pragma weak __vdso_gettc u_int __vdso_gettc(const struct vdso_timehands *th) { - return (th->th_x86_shift > 0 ? __vdso_gettc_low(th) : rdtsc32()); + return (th->th_x86_shift > 0 ? __vdso_gettc_low(th) : + __vdso_rdtsc32()); } #pragma weak __vdso_gettimekeep |