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What is a relatively quick and easy method of looking up what an arbitrary opcode means (say, 0xC8) in x86?
The Intel Software Developer's manual isn't very fun to search through...
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The x86 opcode bytes are 8-bit equivalents of iii field that we discussed in simplified encoding. This provides for up to 512 different instruction classes, although the x86 does not yet use them all.
al. states that the current x86-64 design “contains 981 unique mnemonics and a total of 3,684 instruction variants” [2]. However they do not specify which features are included in their count.
The x86 instruction set refers to the set of instructions that x86-compatible microprocessors support. The instructions are usually part of an executable program, often stored as a computer file and executed on the processor.
Check this very complete table of x86 opcodes on x86asm.net.
Just CTRL+F and you're done! Be sure to read the correct line tho, as C8 for example may appear in several locations.
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Here is a pretty nice visual. Doesn't go into much detail, but if you just need to look up a hex value really quick, this should do it-
Source: http://pnx.tf/files/x86_opcode_structure_and_instruction_overview.pdf
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