Re: [Xen-devel] [PATCH v4 12/16] bug/x86/arm: Align bug_frames sections.

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 16.09.16 at 18:38, <konrad.wilk@xxxxxxxxxx> wrote:
> Most of the WARN_ON or BUG_ON sections are properly aligned on
> x86. However on ARM and on x86 assembler the macros don't include
> any aligment information - hence they end up being the default
> byte granularity.
> 
> On ARM32 it is paramount that the aligment is word-size (4)
> otherwise if one tries to use (uint32_t*) access (such
> as livepatch ELF relocations) we get a Data Abort.
> 
> Enforcing bug_frames to have the proper aligment across all
> architectures and in both C and x86 makes them all the same.
> 
> Furthermore on x86 the bloat-o-meter detects that with this
> change:
> 
> add/remove: 0/0 grow/shrink: 0/0 up/down: 0/0 (0)
> function                                     old     new   delta
> 
> On ARM32:
> add/remove: 1/0 grow/shrink: 0/1 up/down: 384/-288 (96)
> function                                     old     new   delta
> gnttab_unpopulate_status_frames                -     384    +384
> do_grant_table_op                          10808   10520    -288
> 
> And ARM64:
> add/remove: 1/2 grow/shrink: 0/1 up/down: 4164/-4236 (-72)
> function                                     old     new   delta
> gnttab_map_grant_ref                           -    4164   +4164
> do_grant_table_op                           9892    9836     -56
> grant_map_exists                             300       -    -300
> __gnttab_map_grant_ref                      3880       -   -3880
> 
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

x86 parts:
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>


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