• State Accepted Answer
  • +1 person also asked this people also asked this
  • Locked Locked
  • Replies 1 reply
  • Subscribers 350 subscribers
  • Views 5576 views
  • Users 0 members are here
Options
How was your experience today?
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

brk instrustion

hostia

Hi arm experts,

    I wrote some simple C functions to check if the result of memcpy is expected after enable MMU and data cache on Cortex-A53. The assembly (got by disassembling with aarch64-none-elf-objdump) of the one of these functions is very strange:

   C code:

void mem_copy_check(void)

{

    UINT32 *src = (UINT32 *)0x0, *dest = (UINT32 *)0x3101f300;

    UINT32 i, len = 0xc00;

    for (i = 0; i < (len/4); i++) {

        if (*(src + i) != *(dest + i)) {

            TRACE("mem_test(): check SCU_TCM failure, i: %d, src addr: 0x%x, src val: 0x%x, dest addr: 0x%x, dest val: 0x%x\n",

                   i, src, *(src + i), dest, *(dest + i));

            return;

        }

    }

}

After compile, assembly code:

0000000000000878 <mem_copy_check>:

     878:       d4200020        brk     #0x1

I found the variable "src" being "0" cause this "brk" instruction while there is no abnormal if the variable "src" is non 0. But, feel confusion since the code just "read" data from 0 but not write to.


I am using armclang v6.01.

0