Messages in this thread | | | Date | Thu, 23 Jan 2020 14:35:03 +0000 | From | Will Deacon <> | Subject | Re: [RFC v5 00/57] objtool: Add support for arm64 |
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On Thu, Jan 23, 2020 at 01:52:17PM +0000, Julien Thierry wrote: > > > On 1/21/20 10:30 AM, Will Deacon wrote: > > On Thu, Jan 09, 2020 at 04:02:03PM +0000, Julien Thierry wrote: > > > This patch series is the continuation of Raphael's work [1]. All the > > > patches can be retrieved from: > > > git clone -b arm64-objtool-v5 https://github.com/julien-thierry/linux.git > > > > [...] > > > > > objtool: arm64: Decode unknown instructions > > > objtool: arm64: Decode simple data processing instructions > > > objtool: arm64: Decode add/sub immediate instructions > > > objtool: arm64: Decode logical data processing instructions > > > objtool: arm64: Decode system instructions not affecting the flow > > > objtool: arm64: Decode calls to higher EL > > > objtool: arm64: Decode brk instruction > > > objtool: arm64: Decode instruction triggering context switch > > > objtool: arm64: Decode branch instructions with PC relative immediates > > > objtool: arm64: Decode branch to register instruction > > > objtool: arm64: Decode basic load/stores > > > objtool: arm64: Decode load/store with register offset > > > objtool: arm64: Decode load/store register pair instructions > > > objtool: arm64: Decode FP/SIMD load/store instructions > > > objtool: arm64: Decode load/store exclusive > > > objtool: arm64: Decode atomic load/store > > > objtool: arm64: Decode pointer auth load instructions > > > objtool: arm64: Decode load acquire/store release > > > objtool: arm64: Decode load/store with memory tag > > > objtool: arm64: Decode load literal > > > objtool: arm64: Decode register data processing instructions > > > objtool: arm64: Decode FP/SIMD data processing instructions > > > objtool: arm64: Decode SVE instructions > > > > That's a lot of decoding logic which we already have in > > arch/arm64/{kernel/insn.c,include/asm/insn.h}. I'd prefer to see this stuff > > reused or generated from a single source, since it's really easy to get it > > wrong, has a tendency to bitrot and is nasty to debug. > > > > The thing is that the code in those files is mostly encoding logic > (motivated by BPF) rather than decoding (except for the instruction that > might be trapped, but these rarely overlap with instructions that objtools > cares about). I agree that ideally the decoding/encoding should be under > arch/arm64/lib, I was just a bit weary introducing a lot of decoding code > under arch/arm64 that wouldn't even be used in kernel code.
Hmm, but kprobes decodes instructions somehow :p
Not saying you have to refactor everything, but I'd hope you could reuse some of the aarch64_insn_is* and aarch64_insn_extract* functions at least.
Will
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