Hi,
I am writing some code and found that system crashed. I found it was
unaligned access which causes `data abort` exception. I write a piece of code
and objdump
it. I am not sure this is right or not.
command:
arm-poky-linux-gnueabi-gcc -marm -mno-thumb-interwork -mabi=aapcs-linux
-mword-relocations -march=armv7-a -mno-unaligned-access -ffunction-sections
-fdata-sections -fno-common -ffixed-r9 -msoft-float -pipe -O2 -c 2.c -o 2.o
arch is armv7-a and used '-mno-unaligned access'
c code:
typedef unsigned char u8;
int func(u8 *data)
{
return *(unsigned int *)data;
}
The objdumped asm code is:
Disassembly of section .text.func:
00000000 <func>:
0: e5900000 ldr r0, [r0]
4: e12fff1e bx lr
from the asm code, we can see that 'ldr r0, [r0]' corresponding to '*(unsigned
int*)data'. is this correct?
we can not guarantee that pointer data is 4bytes aligned. If pointer data is
not 4bytes aligned, and aligned
access check is enabled by setting a hardware bit in arm coprocessor, then
`data abort` may occur.
Regards,
Peng.
