Re: [PATCH v6 32/33] arm64: irq-gic: Replace unreachable() with -EINVAL
From: Marc Zyngier <maz@kernel.org>
Date: 2022-06-23 08:13:18
Also in:
linux-arch, linux-arm-kernel, linux-kbuild, live-patching, lkml
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 <redacted> --- 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.
quoted hunk ↗ jump to hunk
diff --git a/arch/arm64/kvm/hyp/vgic-v3-sr.cb/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...