Fix Infinite Loop in arm_dcache.c

[PwnVerse]

Infinite Loop can happen since ways is assigned to an int32_t tmpways. This can cause infinite loop if ways gets a sufficiently large integer.

void up_enable_dcache(void)
{
  uint32_t ways;
  ccr = getreg32(NVIC_CFGCON);
  ways   = CCSIDR_WAYS(ccsidr);          /* (Number of ways) - 1 */

  ARM_DSB();
  do
    {
      int32_t tmpways = ways;

      do
        {
          sw = ((tmpways << wshift) | (sets << sshift));
          putreg32(sw, NVIC_DCISW);
        }
      while (tmpways--);
    }
  while (sets--);
}

[xiaoxiang781216]

but no real difference I think?

[PwnVerse]

Atleast it wont be a negetive number anymore right? However I agree that it will still take a very long time to finish

[xiaoxiang781216]

do you really get a negative number from real device? This register is read only and officially defined by arm:
https://developer.arm.com/documentation/ddi0595/2021-03/AArch32-Registers/CCSIDR--Current-Cache-Size-ID-Register.
CCSIDR_WAYS(ccsidr) expends to (ccsider >> 3) & 0x3ff, it is impossible to become a negative number.