Re: [Xen-devel] [PATCH] x86/livepatch: Fail the build if duplicate symbols exist

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 05.04.19 at 23:02, <konrad.wilk@xxxxxxxxxx> wrote:
> On Fri, Apr 05, 2019 at 08:26:04PM +0100, Andrew Cooper wrote:
>> From: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
>> 
>> The binary diffing algorithm used by xen-livepatch depends on having unique
>> symbols.

Question: Is this an inherent requirement, or an effect of the
current implementation? It would seem to me that at least in the
common case (binary didn't changer overly heavily) it ought to
be possible to re-associate the duplicates with their correct
origins. And by making the build fail (including in cases like the
one we have right now), we're painting ourselves into the
corner of having to "fix" code which isn't actually buggy.

Was the option of altering (amending) the symbol name instead
of causing failure considered? Again, in the common case this
shouldn't have overly bad implications: Typically the order of
symbols wouldn't change between builds, so tagging the
duplicates with a sequence number might be good enough. And
even if the order changed, as long as both instances in fact
derive from the same inline function, all would still be fine afaict.
Granted there's some heuristic underlying this, in that we then
would hope for there not to be actually differing functions with
the same source file and symbol names.

>> Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
>> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

As for the time being this is hopefully going to do (once, as you
say, the currently present issue has been addressed):
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>

Jan



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