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SubjectRe: [PATCH 1/5] bus: arm-cci: use asm unreachable
On Wed, Mar 21, 2018 at 12:02:02AM +0100, Stefan Agner wrote:
> Mixing asm and C code is not recommended in a naked function by
> gcc and leads to an error when using clang:
> drivers/bus/arm-cci.c:2107:2: error: non-ASM statement in naked
> function is not supported
> unreachable();
> ^
>
> Instead of using the unreachable() macro use the assember variant
> ASM_UNREACHABLE. This will no longer emit __builtin_unreachable(),
> but since the function is naked and its return type is void it seems
> not to have aversive effects.

I think that unreachable() there is rather silly - this function
*does* return, and the comments say as much. Just delete the silly
"unreachable()", there's no need to put an ASM_UNREACHABLE in there.

The function is not declared as not returning, and nothing in this
file uses it anyway - it's called from the mcpm code, which also
_does_ expect this function to return (if it doesn't, then we're
basically saying the CPU that called it is dead.)

>
> Signed-off-by: Stefan Agner <stefan@agner.ch>
> ---
> drivers/bus/arm-cci.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/bus/arm-cci.c b/drivers/bus/arm-cci.c
> index 5426c04fe24b..ee9da86fec47 100644
> --- a/drivers/bus/arm-cci.c
> +++ b/drivers/bus/arm-cci.c
> @@ -2084,6 +2084,7 @@ asmlinkage void __naked cci_enable_port_for_self(void)
>
> " mov r0, #0 \n"
> " bx lr \n"
> + ASM_UNREACHABLE
>
> " .align 2 \n"
> "5: .word cpu_port - . \n"
> @@ -2103,8 +2104,6 @@ asmlinkage void __naked cci_enable_port_for_self(void)
> [sizeof_struct_cpu_port] "i" (sizeof(struct cpu_port)),
> [sizeof_struct_ace_port] "i" (sizeof(struct cci_ace_port)),
> [offsetof_port_phys] "i" (offsetof(struct cci_ace_port, phys)) );
> -
> - unreachable();
> }
>
> /**
> --
> 2.16.2
>

--
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