Re: [Qemu-devel] qemu log function to print out the registers of the guest

[Max Filippov <jcmvbkbc@gmail.com>]

On Fri, Aug 17, 2012 at 3:14 PM, 陳韋任 (Wei-Ren Chen)
<chenwj@iis.sinica.edu.tw> wrote:
>> > On Thu, Aug 16, 2012 at 7:49 PM, Steven <wangwangkang@gmail.com> wrote:
>> > [...]
>> >> I want to get the guest memory address in the instruction mov
>> >> 0x4(%ebx)  %eax, whic is 0x4(%ebx).
>> >> Since %ebx is not resolved until the execution time, the code in
>> >> softmmu_header.h does not generate any hit or miss information.
>> >> Do you know any place that I could resolve the memory access address? Thanks.
>> >
>> > You'll have to generate code.  Look at how helpers work.
>> Hi, Laurent,
>> do you mean the target-i386/op_helper.c/helper.c or the tcg helper? Thanks.
>
>   What do you mean by "resolve the memory access address"? Do you want
> to get guest virtual address for each guest memory access, right? As Max
> mentioned before (you can also read [1]), there are fast and slow path
> in QEMU softmmu, tlb hit and tlb miss respectively. Max provided patch
> for slow path. As for fast path, take a look on tcg_out_tlb_load (tcg
> /i386/tcg-target.c). tcg_out_tlb_load will generate native code in the
> code cache to do tlb lookup, I think you cannot use the trick Max used
> since tcg_out_tlb_load will not be called when the fast path executed,

That's why I've posted the following hunk that should have made all
accesses go via slow path:

diff --git a/tcg/i386/tcg-target.c b/tcg/i386/tcg-target.c
index da17bba..ec68c19 100644
--- a/tcg/i386/tcg-target.c
+++ b/tcg/i386/tcg-target.c
@@ -1062,7 +1062,7 @@ static inline void tcg_out_tlb_load(TCGContext
*s, int addrlo_idx,
     tcg_out_mov(s, type, r0, addrlo);

     /* jne label1 */
-    tcg_out8(s, OPC_JCC_short + JCC_JNE);
+    tcg_out8(s, OPC_JMP_short);
     label_ptr[0] = s->code_ptr;
     s->code_ptr++;


> it "generates" code instead. Therefore, you might have to insert your
> instrument code in the code cache, perhaps modifying tcg_out_tlb_load
> to log value of "addrlo" (see comments above tcg_out_tlb_load).

-- 
Thanks.
-- Max