| Greg Reid | e5bf5b2 | 2012-10-22 16:05:45 -0400 | [diff] [blame] | 1 | /* Copyright (c) 2012, The Linux Foundation. All rights reserved. |
| 2 | * |
| 3 | * Redistribution and use in source and binary forms, with or without |
| 4 | * modification, are permitted provided that the following conditions are |
| 5 | * met: |
| 6 | * * Redistributions of source code must retain the above copyright |
| 7 | * notice, this list of conditions and the following disclaimer. |
| 8 | * * Redistributions in binary form must reproduce the above |
| 9 | * copyright notice, this list of conditions and the following |
| 10 | * disclaimer in the documentation and/or other materials provided |
| 11 | * with the distribution. |
| 12 | * * Neither the name of The Linux Foundation nor the names of its |
| 13 | * contributors may be used to endorse or promote products derived |
| 14 | * from this software without specific prior written permission. |
| 15 | * |
| 16 | * THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESS OR IMPLIED |
| 17 | * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF |
| 18 | * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT |
| 19 | * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS |
| 20 | * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
| 21 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
| 22 | * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR |
| 23 | * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, |
| 24 | * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE |
| 25 | * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN |
| 26 | * IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 27 | * |
| 28 | */ |
| 29 | |
| 30 | #include <string.h> |
| 31 | #include <stdint.h> |
| 32 | #include <time.h> |
| 33 | #include <sys/time.h> |
| 34 | #include <machine/cpu-features.h> |
| 35 | #include <machine/kernel_user_helper.h> |
| 36 | |
| 37 | int clock_gettime(int clk_id, struct timespec *tp) |
| 38 | { |
| 39 | unsigned prelock, postlock; |
| 40 | |
| 41 | /* |
| 42 | * Check if the offset in the kernel user helper page has |
| 43 | * the flag set appropriately to show that this feature is |
| 44 | * enabled in the kernel. If not, default to the original |
| 45 | * clock_gettime system call. |
| 46 | * |
| 47 | * Also, if this is anything other than CLOCK_MONOTONIC, route |
| 48 | * to the original system call as well. |
| 49 | */ |
| 50 | if ((__kuser_gtod_feature != __kuser_gtod_feature_flag) || |
| 51 | (clk_id != CLOCK_MONOTONIC)) |
| 52 | return clock_gettime_syscall(clk_id, tp); |
| 53 | |
| 54 | if (tp) { |
| 55 | struct gtod_t dgtod; |
| 56 | uint32_t nscount, cycleoffset; |
| 57 | uint32_t mono_sec, mono_nsec; |
| 58 | uint64_t cycle_delta; |
| 59 | |
| 60 | do { |
| 61 | prelock = __kuser_gtod_seqnum; |
| 62 | |
| 63 | dgtod.cycle_last = __kuser_gtod_cycle_last; |
| 64 | dgtod.mask = __kuser_gtod_mask; |
| 65 | dgtod.mult = __kuser_gtod_mult; |
| 66 | dgtod.shift = __kuser_gtod_shift; |
| 67 | dgtod.tv_sec = __kuser_gtod_tv_sec; |
| 68 | dgtod.tv_nsec = __kuser_gtod_tv_nsec; |
| 69 | |
| 70 | mono_sec = __kuser_gtod_wtm_tv_sec; |
| 71 | mono_nsec = __kuser_gtod_wtm_tv_nsec; |
| 72 | |
| 73 | cycleoffset = __kuser_gtod_offset; |
| 74 | cycleoffset += __kuser_gtod_cycle_base; |
| 75 | nscount = *(uint32_t *)cycleoffset; |
| 76 | |
| 77 | postlock = __kuser_gtod_seqnum; |
| 78 | } while (prelock != postlock); |
| 79 | |
| 80 | cycle_delta = (nscount - dgtod.cycle_last) & dgtod.mask; |
| 81 | dgtod.tv_nsec += (cycle_delta * dgtod.mult) >> dgtod.shift; |
| 82 | dgtod.tv_sec += mono_sec; |
| 83 | dgtod.tv_nsec += mono_nsec; |
| 84 | while (dgtod.tv_nsec >= NSEC_PER_SEC) { |
| 85 | dgtod.tv_sec += 1; |
| 86 | dgtod.tv_nsec -= NSEC_PER_SEC; |
| 87 | } |
| 88 | |
| 89 | tp->tv_sec = dgtod.tv_sec; |
| 90 | tp->tv_nsec = dgtod.tv_nsec; |
| 91 | } |
| 92 | |
| 93 | return 0; |
| 94 | } |