Messages in this thread | | | Date | Wed, 4 Mar 2015 12:40:34 +0100 | From | sanfilippo <> | Subject | Re: [RFC PATCH 0/1] Wrong structure alignment due to compiler attribute "section" |
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On 03.03.2015 15:41, Dave Martin wrote:
Dave,
thanks for your response.
> For the element _size_ issue, I'm confused. On 32-bit, that > structure is clearly 196 bytes in size, with the alignment requirement > of void * (4 bytes)... so there's no clear reason why the linker > shouldn't be inserting extra padding. > > I can't reproduce this with my current tools (upstream binutils-2.24, > gcc-4.9.2). > > > Can you try to track down where this discrepancy is coming from? > > i.e., > > * If you're juggling with multiple kernel trees, make sure there > are not differences between them that could be causing this, such > as changes to linker scripts or header files that are involved > in building these arrays.
I can reproduce this with a vanilla kernel (3.19) from kernel.org. What I do is:
- configure the kernel with mvebu_v5_defconfig - compile it
However this issue occurs (so far) only with this special toolchain: http://www.plugcomputer.org/405/us/gplugd/tool-chain/arm-marvell-linux-gnueabi.tar.bz2
If you like you can try this yourself. I am sure that you will get the same results.
I tried the same with three other toolchains but with those the problem did not occur. I also tried other kernel configurations with that "problematic" toolchain, but also the problem did not occur any more.
So I think its either a bug in that compiler/linker or the current solution in vmlinux.lds.h does not work correct under some special circumstances.
> > * See what the input to the assembler looks like, with regard to > .align directives. > > * See what the alignment of the affected sections is in each individual > .o file.
Not sure what exactly I should check here. Could you be a bit more precise?
> * See what __alignof__(struct of_device_id) evaluates to.
It evaluates to "4" even for the bad case.
Regards, Lino
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