Re: [Qemu-devel] [PATCH 3/5] exec: fix code tlb entry misused as iotlb in get_page_addr_code()

[Max Filippov]

>>> get_page_addr_code() reads a code tlb entry, but interprets it as an
>>> iotlb entry.  This works by accident since the low bits of a RAM code
>>> tlb entry are clear, and match a RAM iotlb entry.  This accident is
>>> about to unhappen, so fix the code to use an iotlb entry (using the
>>> code entry with TLB_MMIO may fail if the page is a watchpoint).
>>>
>>> Signed-off-by: Avi Kivity<address@hidden>
>>> ---
>>>   exec.c |    2 +-
>>>   1 files changed, 1 insertions(+), 1 deletions(-)
>>>
>>> diff --git a/exec.c b/exec.c
>>> index a35eb4f..f26d1b0 100644
>>> --- a/exec.c
>>> +++ b/exec.c
>>> @@ -4685,7 +4685,7 @@ tb_page_addr_t get_page_addr_code(CPUState
>>> *env1, target_ulong addr)
>>>                    (addr&  TARGET_PAGE_MASK))) {
>>>           ldub_code(addr);
>>>       }
>>> -    pd = env1->tlb_table[mmu_idx][page_index].addr_code&
>>> ~TARGET_PAGE_MASK;
>>> +    pd = env1->iotlb[mmu_idx][page_index]&  ~TARGET_PAGE_MASK;
>>>       if (pd != io_mem_ram.ram_addr&&  pd != io_mem_rom.ram_addr
>>>           &&  !io_mem_region[pd]->rom_device) {
>>>   #if defined(TARGET_ALPHA) || defined(TARGET_MIPS) ||
>>> defined(TARGET_SPARC)
>>
>> With this patch xtensa debug option unit test causes qemu abort with
>> the message
>>
>>  qemu: fatal: Trying to execute code outside RAM or ROM at 0xd000088c
>>
>> This happens immediately after a watchpoint setup for a data
>> breakpoint at the same memory page where the currently
>> executed code is located. Any idea on how to fix it?
>
> Can you provide details on how to reproduce this?

It may be reproduced by running test_break.tst unit test:

qemu-system-xtensa -M sim -cpu dc232b -nographic -semihosting  -kernel
./test_break.tst

Compiled test binary is here:
http://jcmvbkbc.spb.ru/~dumb/ws/osll/qemu-xtensa/20120318/test_break.tst

-- 
Thanks.
-- Max