Re: [Xen-devel] [PATCH] x86/boot: fix build with certain older gcc versions

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 16.12.16 at 11:33, <daniel.kiper@xxxxxxxxxx> wrote:
> On Thu, Dec 15, 2016 at 07:04:51AM -0700, Jan Beulich wrote:
>> Despite all attempts so far (ending in commit fecf584294 ["Config.mk:
>> fix comment for debug option"] adjusting the respective comment),
>> Config.mk's debug= setting still affects the hypervisor build: CFLAGS
>> gets -g added there.
>>
>> xen/arch/x86/boot/build32.mk includes that file, and hence inherits the
>> setting too. Some gcc versions take -g to create an .eh_frame section
>> despite -fno-asynchronous-unwind-tables (which instead one would expect
>> to produce .debug_frame).
> 
> Hmmm... Smells like a bug...

Possibly - I have no idea what the formal spec of linker behavior
here is (assuming there is one anywhere, which I doubt).

>> In turn, commit 93c0c0287a ("x86/boot: create *.lnk files with linker
>> script") was - in my understanding - supposed to make sure .text is
>> first, but apparently it did also not really achieve that effect: Both
> 
> The main goal was to have text and data sections merged into one text 
> section.
> 
>> reloc.lnk and reloc.bin in the case here ended up with .eh_frame first,
>> which obviously rendered the whole final binary unusable.
> 
> Should not we discard unneeded sections in build32.lds? It looks a bit
> more complicated but maybe we should consider such option too.

Hmm - would you mean a wholesale *(*) pattern to be used here?
I think this whole keep-some-discard-some approach is rather
fragile, not matter how much we customize it.

Jan


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