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Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jUVEc-0008CI-7Z; Fri, 01 May 2020 12:57:42 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jUVEZ-0008BX-FI for linux-arm-kernel@lists.infradead.org; Fri, 01 May 2020 12:57:40 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id C947E1FB; Fri, 1 May 2020 05:57:38 -0700 (PDT) Received: from C02TD0UTHF1T.local (unknown [10.57.7.8]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 870F93F305; Fri, 1 May 2020 05:57:37 -0700 (PDT) Date: Fri, 1 May 2020 13:57:34 +0100 From: Mark Rutland To: Mark Brown Subject: Re: [PATCH v3 3/3] arm64: insn: Report PAC and BTI instructions as NOPs Message-ID: <20200501125734.GD53528@C02TD0UTHF1T.local> References: <20200501123709.6640-1-broonie@kernel.org> <20200501123709.6640-4-broonie@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200501123709.6640-4-broonie@kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200501_055739_551526_BABC6FAB X-CRM114-Status: GOOD ( 17.31 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, May 01, 2020 at 01:37:09PM +0100, Mark Brown wrote: > In order to allow probing of PAC and BTI instructions without more > specialized support recognize them as NOPs. > > Signed-off-by: Mark Brown > Acked-by: Catalin Marinas > --- > arch/arm64/kernel/insn.c | 23 +++++++++++++++++++++++ > 1 file changed, 23 insertions(+) > > diff --git a/arch/arm64/kernel/insn.c b/arch/arm64/kernel/insn.c > index d458604a96a3..aa525975bf94 100644 > --- a/arch/arm64/kernel/insn.c > +++ b/arch/arm64/kernel/insn.c > @@ -57,7 +57,30 @@ bool __kprobes aarch64_insn_is_nop(u32 insn) > if (!aarch64_insn_is_hint(insn)) > return false; > > + /* > + * The PAC and BTI instructons are not strictly NOPs but until > + * better support is added we can treat them as such and they > + * are commonly placed in locations where it is useful to be > + * able to probe. > + */ > switch (insn & 0xFE0) { > + case AARCH64_INSN_HINT_XPACLRI: > + case AARCH64_INSN_HINT_PACIA_1716: > + case AARCH64_INSN_HINT_PACIB_1716: > + case AARCH64_INSN_HINT_AUTIA_1716: > + case AARCH64_INSN_HINT_AUTIB_1716: > + case AARCH64_INSN_HINT_PACIAZ: > + case AARCH64_INSN_HINT_PACIASP: > + case AARCH64_INSN_HINT_PACIBZ: > + case AARCH64_INSN_HINT_PACIBSP: > + case AARCH64_INSN_HINT_AUTIAZ: > + case AARCH64_INSN_HINT_AUTIASP: > + case AARCH64_INSN_HINT_AUTIBZ: > + case AARCH64_INSN_HINT_AUTIBSP: > + case AARCH64_INSN_HINT_BTI: > + case AARCH64_INSN_HINT_BTIC: > + case AARCH64_INSN_HINT_BTIJ: > + case AARCH64_INSN_HINT_BTIJC: > case AARCH64_INSN_HINT_NOP: > return true; > default: I appreciate the desire to not change this code too much, but could we please rename this to aarch64_insn_is_steppable_hint() to avoid the misleading name? This is only ever used in the stepping code today, so the impact is just the prototype/declaration/callside, but it avoids confusion in future and renders the comment redundant. If we really need to identify true nops in future we can add a new aarch64_insn_is_nop() implementation just for that. Thanks, Mark. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel