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XINST_CREATE_add with 2 registers produces an unencodable instruction on x86 #4861

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derekbruening opened this issue Apr 20, 2021 · 0 comments · Fixed by #4862
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XINST_CREATE_add with 2 registers produces an unencodable instruction on x86 #4861

derekbruening opened this issue Apr 20, 2021 · 0 comments · Fixed by #4862
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@derekbruening
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This code:

        XINST_CREATE_add(drcontext, opnd_create_reg(reg_val), opnd_create_reg(reg_ptr));

Produces an encoding error. It's because it tries to create a LEA base-disp with an index register but a 0 scale which is not allowed.

The same bug exists in XINST_CREATE_add_2src on x86.
@derekbruening derekbruening self-assigned this Apr 20, 2021
derekbruening added a commit that referenced this issue Apr 20, 2021
@derekbruening
i#4861: Fix x86 encode bug in 2-reg XINST_CREATE_add
ff18fd1 
XINST_CREATE_add leaves the scale as 0 even when an index register is
present, which does not encode.  We fix that here, along with fixing
the same bug in XINST_CREATE_add_2src.

A test case is added.

Fixes #4861
@derekbruening derekbruening mentioned this issue Apr 20, 2021
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derekbruening added a commit that referenced this issue Apr 20, 2021
@derekbruening
i#4861: Fix x86 encode bug in 2-reg XINST_CREATE_add (#4862)
d29440e 
XINST_CREATE_add leaves the scale as 0 even when an index register is
present, which does not encode.  We fix that here, along with fixing
the same bug in XINST_CREATE_add_2src.

A test case is added.

Fixes #4861
@derekbruening derekbruening mentioned this issue Apr 21, 2021
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i#4861: Fix x86 encode bug in 2-reg XINST_CREATE_add DynamoRIO/dynamorio
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@derekbruening