Commit c71052cc authored May 04, 2020 by Mark Brown Committed by Will Deacon May 04, 2020

arm64: insn: Don't assume unrecognized HINTs are skippable



Currently the kernel assumes that any HINT which it does not explicitly
recognise is skippable.  This is not robust as new instructions may be
added which need special handling, and in any case software should only
be using explicit NOP instructions for deliberate NOPs.

This has the effect of rendering PAC and BTI instructions unprobeable
which means that probes can't be inserted on the first instruction of
functions built with those features.

Signed-off-by: Mark Brown <broonie@kernel.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20200504131326.18290-4-broonie@kernel.org


Signed-off-by: Will Deacon <will@kernel.org>

parent 07dcd967

arch/arm64/kernel/insn.c

+3 −7

Original line number	Diff line number	Diff line
		@@ -57,14 +57,10 @@ bool __kprobes aarch64_insn_is_steppable_hint(u32 insn)
		return false;

		switch (insn & 0xFE0) {
		case AARCH64_INSN_HINT_YIELD:
		case AARCH64_INSN_HINT_WFE:
		case AARCH64_INSN_HINT_WFI:
		case AARCH64_INSN_HINT_SEV:
		case AARCH64_INSN_HINT_SEVL:
		return false;
		default:
		case AARCH64_INSN_HINT_NOP:
		return true;
		default:
		return false;
		}
		}

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