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SubjectRe: [PATCH] pinctrl: ingenic: Make unreachable path more robust
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On 2/14/20 8:37 AM, Josh Poimboeuf wrote:
> In the second loop of ingenic_pinconf_set(), it annotates the switch
> default case as unreachable(). The annotation is technically correct,
> because that same case would have resulted in an early return in the
> previous loop.
>
> However, if a bug were to get introduced later, for example if an
> additional case were added to the first loop without adjusting the
> second loop, it would result in nasty undefined behavior: most likely
> the function's generated code would fall through to the next function.
>
> Another issue is that, while objtool normally understands unreachable()
> annotations, there's one special case where it doesn't: when the
> annotation occurs immediately after a 'ret' instruction. That happens
> to be the case here because unreachable() is immediately before the
> return.
>
> So change the unreachable() to BUG() so that the unreachable code, if
> ever executed, would panic instead of introducing undefined behavior.
> This also makes objtool happy.
>
> This fixes the following objtool warning:
>
> drivers/pinctrl/pinctrl-ingenic.o: warning: objtool: ingenic_pinconf_set() falls through to next function ingenic_pinconf_group_set()
>
> Reported-by: Randy Dunlap <rdunlap@infradead.org>
> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>

Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested

Thanks.

> ---
> drivers/pinctrl/pinctrl-ingenic.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/pinctrl/pinctrl-ingenic.c b/drivers/pinctrl/pinctrl-ingenic.c
> index 96f04d121ebd..6b61ac6cd4d2 100644
> --- a/drivers/pinctrl/pinctrl-ingenic.c
> +++ b/drivers/pinctrl/pinctrl-ingenic.c
> @@ -2158,7 +2158,7 @@ static int ingenic_pinconf_set(struct pinctrl_dev *pctldev, unsigned int pin,
> break;
>
> default:
> - unreachable();
> + BUG();
> }
> }
>
>

--
~Randy

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