Dereferencing memory

[carlo cannarsa]

Hi, I need an inline assembly instruction to dereference some memory location using square brackets, like

mov eax, [ebx]

I searched into the documentation and I tried drutil_insert_get_mem_addr but in the logs it just adds a lea and not what I want. Is there a DR macro that can solve my problem?

Thanks in advance,

Carlo

[sharma...@google.com]

Hi Carlo,

There are various XINST_create_load macros available at https://dynamorio.org/dr__ir__macros__x86_8h.html#aad24f4f2a447e6556931d254afb87e06. Do they help?

Abhinav

[carlo cannarsa]

Hi Abhinav ,

thank you for your reply. I tried also the macros you proposed, but I didn't manage to create a dereference correctly. Can you suggest me an example for my case?

Carlo

[sharma...@google.com]

Hi Carlo,

Can you provide more details of your use-case, what you tried and the result of your attempts?

Also, see example usages of XINST_create_load in our codebase (https://github.com/DynamoRIO/dynamorio/blob/ceacb6d957c234947a9ea8ca0eae15e35f48eaec/clients/drcachesim/tracer/tracer.cpp#L656). 

Abhinav

[carlo cannarsa]

Hi Abhinav,

I wanted to load the content of memory at addr 0xA, so [0xA]. I think I solved the problem using OPND_CREATE_MEM32. Thank you anyway for your help.

Carlo