Re: [RFC PATCH v2 20/21] x86: Add support for CONFIG_CFI_CLANG
From: Peter Zijlstra <peterz@infradead.org>
Date: 2022-05-16 21:02:14
Also in:
linux-hardening, lkml, llvm
On Mon, May 16, 2022 at 12:39:19PM -0700, Sami Tolvanen wrote:
quoted
quoted
With the current compiler patch, LLVM sets up function arguments after the CFI check. if it's a problem, we can look into changing that.Yes, please fix that. Again see that same patch for why this is a problem. Objtool can trivially find retpoline calls, but finding this kCFI gadget is going to be hard work. If you ensure they're unconditionally stuck together, then the problem goes away find one, finds the other.You can use .kcfi_traps to locate the check right now, but I agree, it's not quite ideal.
Oohh, indeed. Looking at that, I think .kcfi_traps would be better as
relative offsets; eg. 'addr = (void*)s + *s' like. Halfs the amount of
storage needed for it.
Also, that code can use a few {} extra.
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