Re: [Xen-devel] [PATCH v8 04/13] x86: properly calculate xen ELF end of image address

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 29.09.16 at 00:51, <daniel.kiper@xxxxxxxxxx> wrote:
> Currently xen ELF end of image address is calculated using first line from
> "nm -nr xen/xen-syms" output. However, potentially it may contain symbol
> address not related to the end of image in any way. It can happen if a symbol
> is introduced with address larger than _end symbol address. Such situation
> encountered when I linked xen ELF binary with xen/arch/x86/efi/relocs-dummy.S.
> Then first line from "nm -nr xen/xen-syms" contained "ffff82d0c0000000 A 
> ALT_START"
> and xen ELF image memory size was silently set to 1023 MiB. This issue 
> happened
> because there is no check which symbol address is used to calculate end of
> image address. So, let's fix it and take ELF end of image address by reading
> _end symbol address from nm output. This way xen ELF image build process is
> not prone to changes in order of nm output.
> 
> This patch is prereq for "efi: build xen.gz with EFI code" patch which adds,
> among others, xen/arch/x86/efi/relocs-dummy.S to xen.gz output.

I still dislike how you put this. It would make a lot more sense if this
extra paragraph came much earlier (perhaps right after the first
sentence), and the rest of the description would then be slightly
re-worded to fit this aspect.

> --- a/xen/arch/x86/Makefile
> +++ b/xen/arch/x86/Makefile
> @@ -91,7 +91,7 @@ endif
>  
>  $(TARGET): $(TARGET)-syms $(efi-y) boot/mkelf32
>       ./boot/mkelf32 $(notes_phdrs) $(TARGET)-syms $(TARGET) 0x100000 \
> -     `$(NM) -nr $(TARGET)-syms | head -n 1 | sed -e 's/^\([^ ]*\).*/0x\1/'`
> +             `$(NM) $(TARGET)-syms | sed -ne 's/^\([^ ]*\) . _end$$/0x\1/p'`

I thought we had agreed to use __2M_rwdata_end here.

And also note that I had said "such that the command line argument
here aligns with the first one on the previous line" in my reply to v7
regarding the indentation change.

Jan


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