qemu-devel
[Top][All Lists]
Advanced

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Qemu-devel] [RFC][PATCH 07/16 v6] target-i386: Add API to add extra


From: Wen Congyang
Subject: Re: [Qemu-devel] [RFC][PATCH 07/16 v6] target-i386: Add API to add extra memory mapping
Date: Fri, 17 Feb 2012 17:32:56 +0800
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100413 Fedora/3.0.4-2.fc13 Thunderbird/3.0.4

At 02/15/2012 06:21 PM, Jan Kiszka Wrote:
> On 2012-02-15 10:44, Wen Congyang wrote:
>> At 02/15/2012 05:21 PM, Jan Kiszka Wrote:
>>> On 2012-02-15 06:19, Wen Congyang wrote:
>>>> At 02/15/2012 01:35 AM, Jan Kiszka Wrote:
>>>>> On 2012-02-09 04:24, Wen Congyang wrote:
>>>>>> Crash needs extra memory mapping to determine phys_base.
>>>>>>
>>>>>> Signed-off-by: Wen Congyang <address@hidden>
>>>>>> ---
>>>>>>  cpu-all.h               |    2 ++
>>>>>>  target-i386/arch-dump.c |   43 
>>>>>> +++++++++++++++++++++++++++++++++++++++++++
>>>>>>  2 files changed, 45 insertions(+), 0 deletions(-)
>>>>>>
>>>>>> diff --git a/cpu-all.h b/cpu-all.h
>>>>>> index efb5ba3..290c43a 100644
>>>>>> --- a/cpu-all.h
>>>>>> +++ b/cpu-all.h
>>>>>> @@ -530,10 +530,12 @@ int cpu_write_elf64_note(int fd, CPUState *env, 
>>>>>> int cpuid,
>>>>>>                           target_phys_addr_t *offset);
>>>>>>  int cpu_write_elf32_note(int fd, CPUState *env, int cpuid,
>>>>>>                           target_phys_addr_t *offset);
>>>>>> +int cpu_add_extra_memory_mapping(MemoryMappingList *list);
>>>>>>  #else
>>>>>>  #define cpu_get_memory_mapping(list, env)
>>>>>>  #define cpu_write_elf64_note(fd, env, cpuid, offset) ({ -1; })
>>>>>>  #define cpu_write_elf32_note(fd, env, cpuid, offset) ({ -1; })
>>>>>> +#define cpu_add_extra_memory_mapping(list) ({ 0; })
>>>>>>  #endif
>>>>>>  
>>>>>>  #endif /* CPU_ALL_H */
>>>>>> diff --git a/target-i386/arch-dump.c b/target-i386/arch-dump.c
>>>>>> index 4c0ff77..d96f6ae 100644
>>>>>> --- a/target-i386/arch-dump.c
>>>>>> +++ b/target-i386/arch-dump.c
>>>>>> @@ -495,3 +495,46 @@ int cpu_write_elf32_note(int fd, CPUState *env, int 
>>>>>> cpuid,
>>>>>>  {
>>>>>>      return x86_write_elf32_note(fd, env, cpuid, offset);
>>>>>>  }
>>>>>> +
>>>>>> +/* This function is copied from crash */
>>>>>
>>>>> And what does it do there and here? I suppose it is Linux-specific - any
>>>>> version? This should be documented and encoded in the function name.
>>>>>
>>>>>> +static target_ulong get_phys_base_addr(CPUState *env, target_ulong 
>>>>>> *base_vaddr)
>>>>>> +{
>>>>>> +    int i;
>>>>>> +    target_ulong kernel_base = -1;
>>>>>> +    target_ulong last, mask;
>>>>>> +
>>>>>> +    for (i = 30, last = -1; (kernel_base == -1) && (i >= 20); i--) {
>>>>>> +        mask = ~((1LL << i) - 1);
>>>>>> +        *base_vaddr = env->idt.base & mask;
>>>>>> +        if (*base_vaddr == last) {
>>>>>> +            continue;
>>>>>> +        }
>>>>>> +
>>>>>> +        kernel_base = cpu_get_phys_page_debug(env, *base_vaddr);
>>>>>> +        last = *base_vaddr;
>>>>>> +    }
>>>>>> +
>>>>>> +    return kernel_base;
>>>>>> +}
>>>>>> +
>>>>>> +int cpu_add_extra_memory_mapping(MemoryMappingList *list)
>>>>>
>>>>> Again, what does "extra" mean? Probably guest-specific, no?
>>>>
>>>> crash will calculate the phys_base according to the virtual address and 
>>>> physical
>>>> address stored in the PT_LOAD.
>>>
>>> Crash is a Linux-only tool, dump must not be restricted to that guest -
>>> but could contain transparent extensions of the file format if needed.
>>>
>>>>
>>>> If the vmcore is generated by 'virsh dump'(use migration to implement 
>>>> dumping),
>>>> crash calculates the phys_base according to idt.base. The function 
>>>> get_phys_base_addr()
>>>> uses the same way to calculates the phys_base.
>>>
>>> Hmm, where are those special registers (idt, gdt, tr etc.) stored in the
>>> vmcore file, BTW?
>>
>> 'virsh dump' uses mirgation to implement dumping now. So the vmcore has all
>> registers.
> 
> This is about the new format. And there we are lacking those special

Yes, this file can be processed with crash. gdb cannot process such file.

> registers. At some point, gdb will understand and need them to do proper
> system-level debugging. I don't know the format structure here: can we
> add sections to the core file in a way that consumers that don't know
> them simply ignore them?

I donot find such section now. If there is such section, I think it is
better to store all cpu's register in the core file.

I try to let the core file can be processed with crash and gdb. But crash
still does not work well sometimes.

I think we can add some option to let user choose whether to store memory
mapping in the core file. Because crash does not need such mapping. If
the p_vaddr in all PT_LOAD segments is 0, crash know the file is generated
by qemu dump, and use another way to calculate phys_base.

If you agree with it, please ignore this patch.

Thanks
Wen Congyang

> 
> Jan
> 




reply via email to

[Prev in Thread] Current Thread [Next in Thread]