Capstone supports an impressive breadth of architectures. However, if all you need is x86/AMD64 decoding and disassembly, there are much higher quality (in terms of accurate decoding) libraries out there.
I wrote a differential fuzzer for x86 decoders a few years ago, and XED and Zydis generally performed far better (in terms of accuracy) than Capstone[1]. And on the Rust side, yaxpeax and iced-x86 perform very admirably.
In my previous job, I've worked on a project that requires disassembling large amounts of x86/amd64 instructions (several billion instructions each running is very common). I've found also that Zydis is much faster than Capstone.
The spec is very large, not particularly well written, and is not “total” (in the sense that AMD64 and IA32e and other x86-64 flavors are all subtly different). There are a lot of ways to get it wrong; even XED (the reference decoder from Intel) has bugs.
If I remember correct, the Intel SDM alone is over 3000 pages long.
lol, no. For one Capstone has a lot of bugs (it uses some old version of LLVM as its base) but the whole question of how to decode things is complicated because there are a lot of pitfalls and inconsistencies that different disassemblers handle differently. And what the hardware does is a different question entirely: it may not match the spec, or even other processors with the same ISA.
I wrote a differential fuzzer for x86 decoders a few years ago, and XED and Zydis generally performed far better (in terms of accuracy) than Capstone[1]. And on the Rust side, yaxpeax and iced-x86 perform very admirably.
[1]: https://blog.trailofbits.com/2019/10/31/destroying-x86_64-in...