Re: [PATCH] riscv: VMAP_STACK overflow detection thread-safe

Deepak Gupta
2022-11-24T08:26:32Z

On Thu, Nov 24, 2022 at 09:32:19AM +0800, Guo Ren wrote:
>> +.macro asm_per_cpu dst sym tmp
>> + REG_L \tmp, TASK_TI_CPU_NUM(tp)
>> + slli \tmp, \tmp, 0x3
>> + la \dst, __per_cpu_offset
>> + add \dst, \dst, \tmp
>> + REG_L \tmp, 0(\dst)
>> + la \dst, \sym
>> + add \dst, \dst, \tmp
>Another tricky asm code of using percpu, I don't know how the percpu
>maintenance guy thinks.

On this, if you can point me to someone, I would like to get their feedback.
While discussing this, one issue that comes in my mind is if the shift of 0x3
is correct or not on 32bit systems. I don't know what's the size of each entry
in `__per_cpu_offset`. On 64bit it's 8 bytes and thus 3 bit shift.