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SubjectRe: [PATCH v6 32/33] arm64: irq-gic: Replace unreachable() with -EINVAL
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 <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(-)

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 <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;

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...

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