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Thu, 23 Jun 2022 09:13:09 +0100 MIME-Version: 1.0 Date: Thu, 23 Jun 2022 09:13:08 +0100 From: Marc Zyngier To: Chen Zhongjin Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org, linux-kbuild@vger.kernel.org, live-patching@vger.kernel.org, jpoimboe@kernel.org, peterz@infradead.org, catalin.marinas@arm.com, will@kernel.org, masahiroy@kernel.org, michal.lkml@markovi.net, ndesaulniers@google.com, mark.rutland@arm.com, pasha.tatashin@soleen.com, broonie@kernel.org, rmk+kernel@armlinux.org.uk, madvenka@linux.microsoft.com, christophe.leroy@csgroup.eu, daniel.thompson@linaro.org Subject: Re: [PATCH v6 32/33] arm64: irq-gic: Replace unreachable() with -EINVAL In-Reply-To: <20220623014917.199563-33-chenzhongjin@huawei.com> References: <20220623014917.199563-1-chenzhongjin@huawei.com> <20220623014917.199563-33-chenzhongjin@huawei.com> User-Agent: Roundcube Webmail/1.4.13 Message-ID: <7d26e36686495866e0752e12c38f170e@kernel.org> X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: chenzhongjin@huawei.com, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org, linux-kbuild@vger.kernel.org, live-patching@vger.kernel.org, jpoimboe@kernel.org, peterz@infradead.org, catalin.marinas@arm.com, will@kernel.org, masahiroy@kernel.org, michal.lkml@markovi.net, ndesaulniers@google.com, mark.rutland@arm.com, pasha.tatashin@soleen.com, broonie@kernel.org, rmk+kernel@armlinux.org.uk, madvenka@linux.microsoft.com, christophe.leroy@csgroup.eu, daniel.thompson@linaro.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220623_011314_390974_C2EA2425 X-CRM114-Status: GOOD ( 18.13 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2022-06-23 02:49, Chen Zhongjin wrote: > Using unreachable() at default of switch generates an extra branch at > end of the function, and compiler won't generate a ret to close this > branch because it knows it's unreachable. > > If there's no instruction in this branch, compiler will generate a NOP, > And it will confuse objtool to warn this NOP as a fall through branch. > > In fact these branches are actually unreachable, so we can replace > unreachable() with returning a -EINVAL value. > > Signed-off-by: Chen Zhongjin > --- > arch/arm64/kvm/hyp/vgic-v3-sr.c | 7 +++---- > drivers/irqchip/irq-gic-v3.c | 2 +- > 2 files changed, 4 insertions(+), 5 deletions(-) Basic courtesy would have been to Cc the maintainers of this code. > > diff --git a/arch/arm64/kvm/hyp/vgic-v3-sr.c > b/arch/arm64/kvm/hyp/vgic-v3-sr.c > index 4fb419f7b8b6..f3cee92c3038 100644 > --- a/arch/arm64/kvm/hyp/vgic-v3-sr.c > +++ b/arch/arm64/kvm/hyp/vgic-v3-sr.c > @@ -6,7 +6,6 @@ > > #include > > -#include > #include > #include > > @@ -55,7 +54,7 @@ static u64 __gic_v3_get_lr(unsigned int lr) > return read_gicreg(ICH_LR15_EL2); > } > > - unreachable(); > + return -EINVAL; NAK. That's absolutely *wrong*, and will hide future bugs. Nothing checks for -EINVAL, and we *never* expect to reach this, hence the perfectly valid annotation. If something needs fixing, it probably is your tooling. M. -- Jazz is not dead. It just smells funny... _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel