From: Mark Brown <broonie@kernel.org>
To: Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>
Cc: Mark Brown <broonie@kernel.org>, linux-arm-kernel@lists.infradead.org
Subject: [PATCH v3 1/3] arm64: insn: Don't assume unrecognized HINTs are NOPs
Date: Fri, 1 May 2020 13:37:07 +0100 [thread overview]
Message-ID: <20200501123709.6640-2-broonie@kernel.org> (raw)
In-Reply-To: <20200501123709.6640-1-broonie@kernel.org>
Currently the kernel assumes that any HINT which it does not explicitly
recognise is a NOP. This is not robust as new instructions may be added
which need special handling, including recent extensions like PAC, 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>
---
arch/arm64/kernel/insn.c | 12 ++++--------
1 file changed, 4 insertions(+), 8 deletions(-)
diff --git a/arch/arm64/kernel/insn.c b/arch/arm64/kernel/insn.c
index 4a9e773a177f..595c0fddeeb2 100644
--- a/arch/arm64/kernel/insn.c
+++ b/arch/arm64/kernel/insn.c
@@ -51,21 +51,17 @@ enum aarch64_insn_encoding_class __kprobes aarch64_get_insn_class(u32 insn)
return aarch64_insn_encoding_class[(insn >> 25) & 0xf];
}
-/* NOP is an alias of HINT */
+/* NOP is a specific HINT */
bool __kprobes aarch64_insn_is_nop(u32 insn)
{
if (!aarch64_insn_is_hint(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;
}
}
--
2.20.1
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next prev parent reply other threads:[~2020-05-01 12:37 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-01 12:37 [PATCH v3 0/3] arm64: Make NOP handling a whitelist Mark Brown
2020-05-01 12:37 ` Mark Brown [this message]
2020-05-01 12:37 ` [PATCH v3 2/3] arm64: insn: Add constants for new HINT instruction decode Mark Brown
2020-05-01 12:37 ` [PATCH v3 3/3] arm64: insn: Report PAC and BTI instructions as NOPs Mark Brown
2020-05-01 12:57 ` Mark Rutland
2020-05-01 16:12 ` Mark Brown
2020-05-04 12:14 ` Will Deacon
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