Lab1: Get Time & Reboot

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Get Time

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float getTime() {
  register unsigned long f, t;
  // Get the current counter frequency
  asm volatile("mrs %0, cntfrq_el0" : "=r"(f));
  // Read the current counter
  asm volatile("mrs %0, cntpct_el0" : "=r"(t));
  return (float)t / f;
}

Reboot

經測試，可於 QEMU 6.1 raspb3 運作

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#define PM_PASSWORD 0x5a000000
#define PM_RSTC ((volatile unsigned int *)(0x3F10001c))
#define PM_WDOG ((volatile unsigned int *)(0x3F100024))

void reset(int tick) {
  // reboot after watchdog timer expire
  *PM_RSTC = PM_PASSWORD | 0x20; // full reset
  *PM_WDOG = PM_PASSWORD | tick; // number of watchdog tick
}

void cancel_reset() {
  *PM_RSTC = PM_PASSWORD | 0; // full reset
  *PM_WDOG = PM_PASSWORD | 0; // number of watchdog tick
}

Testing script

套用在pwntools ，一開始擔心不停頓一直傳送指令會有問題，但rpi3的FIFO深度(4096)顯然是足夠的。serialtube很多餘的將換行符號轉換，必須停用convert_newlines。

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if self.convert_newlines:
    data = data.replace(b'\n', b'\r\n')
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from pwn import *
import sys

try:
    filename = sys.argv[1]
    port = sys.argv[2]
except(IndexError):
    exit(1)

try:
    with open(filename) as f:
        io = serialtube(port, baudrate=115200, convert_newlines=False)
        for line in f:
            io.send(str.encode(line))

except(FileNotFoundError):
    print("File Not Found!")
    exit(1)