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From:   Chen Zhongjin <chenzhongjin@huawei.com>
To:     <linux-kernel@vger.kernel.org>, <linux-arch@vger.kernel.org>,
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CC:     <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>,
        <chenzhongjin@huawei.com>, <rmk+kernel@armlinux.org.uk>,
        <madvenka@linux.microsoft.com>, <christophe.leroy@csgroup.eu>,
        <daniel.thompson@linaro.org>
Subject: [PATCH v6 32/33] arm64: irq-gic: Replace unreachable() with -EINVAL
Date:   Thu, 23 Jun 2022 09:49:16 +0800
Message-ID: <20220623014917.199563-33-chenzhongjin@huawei.com>
In-Reply-To: <20220623014917.199563-1-chenzhongjin@huawei.com>
References: <20220623014917.199563-1-chenzhongjin@huawei.com>
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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 <chenzhongjin@huawei.com>
---
 arch/arm64/kvm/hyp/vgic-v3-sr.c | 7 +++----
 drivers/irqchip/irq-gic-v3.c    | 2 +-
 2 files changed, 4 insertions(+), 5 deletions(-)

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 <hyp/adjust_pc.h>
 
-#include <linux/compiler.h>
 #include <linux/irqchip/arm-gic-v3.h>
 #include <linux/kvm_host.h>
 
@@ -55,7 +54,7 @@ static u64 __gic_v3_get_lr(unsigned int lr)
 		return read_gicreg(ICH_LR15_EL2);
 	}
 
-	unreachable();
+	return -EINVAL;
 }
 
 static void __gic_v3_set_lr(u64 val, int lr)
@@ -166,7 +165,7 @@ static u32 __vgic_v3_read_ap0rn(int n)
 		val = read_gicreg(ICH_AP0R3_EL2);
 		break;
 	default:
-		unreachable();
+		val = -EINVAL;
 	}
 
 	return val;
@@ -190,7 +189,7 @@ static u32 __vgic_v3_read_ap1rn(int n)
 		val = read_gicreg(ICH_AP1R3_EL2);
 		break;
 	default:
-		unreachable();
+		val = -EINVAL;
 	}
 
 	return val;
diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
index b252d5534547..2ef98e32d257 100644
--- a/drivers/irqchip/irq-gic-v3.c
+++ b/drivers/irqchip/irq-gic-v3.c
@@ -475,7 +475,7 @@ static u32 __gic_get_ppi_index(irq_hw_number_t hwirq)
 	case EPPI_RANGE:
 		return hwirq - EPPI_BASE_INTID + 16;
 	default:
-		unreachable();
+		return -EINVAL;
 	}
 }
 
-- 
2.17.1