Hi,
Le 26/10/2019 à 09:23, Wangshaobo (bobo) a écrit :
Hi,
I encountered a problem about a loop nesting occurred in manufacturing
the alignment exception in machine check, trigger background is :
problem:
machine checkout or critical interrupt ->…->kbox_write[for recording
last words] -> memcpy(irremap_addr, src,size):_GLOBAL(memcpy)…
when we enter memcpy,a command ‘dcbz r11,r6’ will cause a alignment
exception, in this situation,r11 loads the ioremap address,which leads
to the alignment exception,
You can't use memcpy() on something else than memory.
For an ioremapped area, you have to use memcpy_toio()
Christophe
then the command can not be process successfully,as we still in machine
check.at the end ,it triggers a new irq machine check in irq handler
function,a loop nesting begins.
analysis:
We have analysed a lot,but it still can not come to a reasonable
description,in common,the alignment triggered in machine check context
can still be collected into the Kbox
after alignment exception be handled by handler function, but how does
the machine checkout can be triggered in the handler fucntion for any
causes? We print relevant registers
as follow when first enter machine check and alignment exception handler
function:
MSR:0x2 MSR:0x0
SRR1:0x2 SRR1:0x21002
But the manual says SRR1 should be set to MSR(0x2),why that
happened ?
Then a branch in handler function copy the SRR1 to MSR,this
enble MSR[ME] and MSR[CE],system collapses.
Conclusion:
1) why the alignment exception can not be handled in machine
check ?
2) besides memcpy,any other function can cause the alignment
exception ?
We still recurrent it, the line as follows:
Cpu dead lock->watch log->trigger
fiq->kbox_write->memcpy->alignment exception->print last words.
but for those problems as below,what the kbox printed is empty.
------------------kbox restart:[ 10.147594]----------------
kbox verify fs magic fail
kbox mem mabye destroyed, format it
kbox: load OK
lock-task: major[249] minor[0]
-----start show_destroyed_kbox_mem_head----
00000000: 00000000 00000000 00000000 00000000 ................
00000010: 00000000 00000000 00000000 00000000 ................
00000020: 00000000 00000000 00000000 00000000 ................
00000030: 00000000 00000000 00000000 00000000 ................
00000040: 00000000 00000000 00000000 00000000 ................
00000050: 00000000 00000000 00000000 00000000 ................
00000060: 00000000 00000000 00000000 00000000 ................
00000070: 00000000 00000000 00000000 00000000 ................
00000080: 00000000 00000000 00000000 00000000 ................
00000090: 00000000 00000000 00000000 00000000 ................
