1 // Copyright 2017 The Chromium OS Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 use libc::{gmtime_r, time, time_t, tm}; 6 use std::cmp::min; 7 use std::mem; 8 9 use crate::{BusAccessInfo, BusDevice}; 10 11 const INDEX_MASK: u8 = 0x7f; 12 const INDEX_OFFSET: u64 = 0x0; 13 const DATA_OFFSET: u64 = 0x1; 14 const DATA_LEN: usize = 128; 15 16 /// A CMOS/RTC device commonly seen on x86 I/O port 0x70/0x71. 17 pub struct Cmos { 18 index: u8, 19 data: [u8; DATA_LEN], 20 } 21 22 impl Cmos { 23 /// Constructs a CMOS/RTC device with initial data. 24 /// `mem_below_4g` is the size of memory in bytes below the 32-bit gap. 25 /// `mem_above_4g` is the size of memory in bytes above the 32-bit gap. new(mem_below_4g: u64, mem_above_4g: u64) -> Cmos26 pub fn new(mem_below_4g: u64, mem_above_4g: u64) -> Cmos { 27 let mut data = [0u8; DATA_LEN]; 28 29 data[0x0B] = 0x02; // Status Register B: 24-hour mode 30 31 // Extended memory from 16 MB to 4 GB in units of 64 KB 32 let ext_mem = min( 33 0xFFFF, 34 mem_below_4g.saturating_sub(16 * 1024 * 1024) / (64 * 1024), 35 ); 36 data[0x34] = ext_mem as u8; 37 data[0x35] = (ext_mem >> 8) as u8; 38 39 // High memory (> 4GB) in units of 64 KB 40 let high_mem = min(0xFFFFFF, mem_above_4g / (64 * 1024)); 41 data[0x5b] = high_mem as u8; 42 data[0x5c] = (high_mem >> 8) as u8; 43 data[0x5d] = (high_mem >> 16) as u8; 44 45 Cmos { index: 0, data } 46 } 47 } 48 49 impl BusDevice for Cmos { debug_label(&self) -> String50 fn debug_label(&self) -> String { 51 "cmos".to_owned() 52 } 53 write(&mut self, info: BusAccessInfo, data: &[u8])54 fn write(&mut self, info: BusAccessInfo, data: &[u8]) { 55 if data.len() != 1 { 56 return; 57 } 58 59 match info.offset { 60 INDEX_OFFSET => self.index = data[0] & INDEX_MASK, 61 DATA_OFFSET => self.data[self.index as usize] = data[0], 62 o => panic!("bad write offset on CMOS device: {}", o), 63 } 64 } 65 read(&mut self, info: BusAccessInfo, data: &mut [u8])66 fn read(&mut self, info: BusAccessInfo, data: &mut [u8]) { 67 fn to_bcd(v: u8) -> u8 { 68 assert!(v < 100); 69 ((v / 10) << 4) | (v % 10) 70 } 71 72 if data.len() != 1 { 73 return; 74 } 75 76 data[0] = match info.offset { 77 INDEX_OFFSET => self.index, 78 DATA_OFFSET => { 79 let seconds; 80 let minutes; 81 let hours; 82 let week_day; 83 let day; 84 let month; 85 let year; 86 // The time and gmtime_r calls are safe as long as the structs they are given are 87 // large enough, and neither of them fail. It is safe to zero initialize the tm 88 // struct because it contains only plain data. 89 unsafe { 90 let mut tm: tm = mem::zeroed(); 91 let mut now: time_t = 0; 92 time(&mut now as *mut _); 93 gmtime_r(&now, &mut tm as *mut _); 94 // The following lines of code are safe but depend on tm being in scope. 95 seconds = tm.tm_sec; 96 minutes = tm.tm_min; 97 hours = tm.tm_hour; 98 week_day = tm.tm_wday + 1; 99 day = tm.tm_mday; 100 month = tm.tm_mon + 1; 101 year = tm.tm_year; 102 }; 103 match self.index { 104 0x00 => to_bcd(seconds as u8), 105 0x02 => to_bcd(minutes as u8), 106 0x04 => to_bcd(hours as u8), 107 0x06 => to_bcd(week_day as u8), 108 0x07 => to_bcd(day as u8), 109 0x08 => to_bcd(month as u8), 110 0x09 => to_bcd((year % 100) as u8), 111 0x32 => to_bcd(((year + 1900) / 100) as u8), 112 _ => { 113 // self.index is always guaranteed to be in range via INDEX_MASK. 114 self.data[(self.index & INDEX_MASK) as usize] 115 } 116 } 117 } 118 o => panic!("bad read offset on CMOS device: {}", o), 119 } 120 } 121 } 122