150 lines
3.3 KiB
C
150 lines
3.3 KiB
C
/**
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* \file vsyscall.c
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* License details are found in the file LICENSE.
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* \brief
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* implements x86's vsyscall
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* \author Gou Nakamura <go.nakamura.yw@hitachi-solutions.com> \par
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* Copyright (C) 2014 Hitachi, Ltd.
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* \author Gou Nakamura <go.nakamura.yw@hitachi-solutions.com> \par
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* Copyright (C) 2015 RIKEN AICS
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*/
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/*
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* HISTORY:
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*/
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/*
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* .vsyscall.* section's LMAs are different from their VMA.
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* make sure that these are position-independent codes.
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*/
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#include <syscall.h>
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#include <ihk/atomic.h>
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#include <arch/cpu.h>
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extern int vsyscall_gettimeofday(struct timeval *tv, void *tz)
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__attribute__ ((section (".vsyscall.gettimeofday")));
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struct tod_data_s tod_data
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__attribute__ ((section(".vsyscall.gettimeofday.data"))) = {
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.do_local = 0,
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.version = IHK_ATOMIC64_INIT(0),
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};
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static inline void cpu_pause_for_vsyscall(void)
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{
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asm volatile ("pause" ::: "memory");
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return;
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} /* cpu_pause_for_vsyscall() */
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static inline void calculate_time_from_tsc(struct timespec *ts)
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{
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long ver;
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unsigned long current_tsc;
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__time_t sec_delta;
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long ns_delta;
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for (;;) {
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while ((ver = ihk_atomic64_read(&tod_data.version)) & 1) {
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/* settimeofday() is in progress */
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cpu_pause_for_vsyscall();
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}
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rmb();
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*ts = tod_data.origin;
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rmb();
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if (ver == ihk_atomic64_read(&tod_data.version)) {
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break;
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}
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/* settimeofday() has intervened */
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cpu_pause_for_vsyscall();
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}
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current_tsc = rdtsc();
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sec_delta = current_tsc / tod_data.clocks_per_sec;
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ns_delta = NS_PER_SEC * (current_tsc % tod_data.clocks_per_sec)
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/ tod_data.clocks_per_sec;
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/* calc. of ns_delta overflows if clocks_per_sec exceeds 18.44 GHz */
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ts->tv_sec += sec_delta;
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ts->tv_nsec += ns_delta;
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if (ts->tv_nsec >= NS_PER_SEC) {
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ts->tv_nsec -= NS_PER_SEC;
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++ts->tv_sec;
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}
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return;
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} /* calculate_time_from_tsc() */
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int vsyscall_gettimeofday(struct timeval *tv, void *tz)
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{
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int error;
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struct timespec ats;
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if (!tv && !tz) {
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/* nothing to do */
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return 0;
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}
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/* Do it locally if supported */
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if (!tz && tod_data.do_local) {
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calculate_time_from_tsc(&ats);
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tv->tv_sec = ats.tv_sec;
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tv->tv_usec = ats.tv_nsec / 1000;
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return 0;
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}
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/* Otherwise syscall */
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asm ("syscall" : "=a" (error)
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: "a" (__NR_gettimeofday), "D" (tv), "S" (tz)
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: "%rcx", "%r11", "memory");
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if (error) {
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*(int *)0 = 0; /* i.e. raise(SIGSEGV) */
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}
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return error;
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} /* vsyscall_gettimeofday() */
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extern long vsyscall_time(void *tp)
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__attribute__ ((section (".vsyscall.time")));
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long vsyscall_time(void *tp)
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{
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long t;
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asm ( "syscall ;"
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/*
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* This vsyscall_time() cannot fail, because glibc's
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* vsyscall_time() does not set the errno.
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*
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* Because a possible error is only a memory access error,
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* in order that this function generates SIGSEGV
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* rather than returns error when a memory access error occurs,
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* this function accesses memory in user mode.
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*/
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"test %%rdx,%%rdx;"
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"jz 1f;"
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"mov %%rax,(%%rdx);"
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"1:"
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: "=a" (t)
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: "a" (__NR_time), "d" (tp), "D" (0)
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: "%rcx", "%r11", "memory");
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return t;
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}
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extern int vsyscall_getcpu(unsigned *cpup, unsigned *nodep, void *tcachep)
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__attribute__ ((section (".vsyscall.getcpu")));
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int vsyscall_getcpu(unsigned *cpup, unsigned *nodep, void *tcachep)
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{
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int error;
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asm ("syscall" : "=a" (error)
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: "a" (__NR_getcpu), "D" (cpup), "S" (nodep), "d" (tcachep)
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: "%rcx", "%r11", "memory");
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return error;
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}
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