Re: [PATCH] Make alignment cflags configurable.

From: H. Peter Anvin
Date: Wed Aug 12 2015 - 18:37:56 EST

NAK. This is crazy.

On August 12, 2015 3:30:19 PM PDT, Jan-Simon Moeller <dl9pf@xxxxxx> wrote:
>Hi all!
>> You could mention that this is to fix the clang build. But why is it
>> needed? It isn't that clang just doesn't accept the option, is it?
>> Otherwise we could just use $(call cc-option, -falign-jumps=1) etc.
>Yes it is to fix the build with clang.
>I tried cc-option, but it does not improve the situation (more below).
>This is why I chose the config option approach in the patch.
>> Did you get to the bottom of the clang failure here? Just turning
>> off without a coherent explanation doesn't seem like the right thing
>> do.
>I know it is not the final solution which is why I turned it into a
>option. We can still debate if default should be "y" or "n". This way
>we all
>can proceed.
>@Ingo: would it be fine if we wrap it into a config option defaulting
>to "y" ?
>What I can say so far is that although clang warns about the unknown
>and ignores it, the resulting kernel still fails to boot somewhere
>early in
>start_kernel(). I'm still investigating.
>My current trace ends like this:
>page_address_init ~ setup_arch ~ then arch/x86/kernel/setup.c:898
>setup.c:898 is a printk actually ...
>early_idt_handler_array[i] ~> early_idt_handler_common
>The mail thread is here:
><wild guess>
>We still build with -no-integrated-as which means we use gas. Maybe the
>is passed-on there and things get confused.
></wile guess>

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