Re: [PATCH v10 02/15] livepatch: avoid position-based search if `-z unique-symbol` is available

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On Mon, Feb 14, 2022 at 10:10:00AM -0800, Josh Poimboeuf wrote:
> On Mon, Feb 14, 2022 at 01:24:33PM +0100, Alexander Lobakin wrote:
> > > One idea I mentioned before, it may be worth exploring changing the "F"
> > > in FGKASLR to "File" instead of "Function".  In other words, only
> > > shuffle at an object-file granularity.  Then, even with duplicates, the
> > > <file+function> symbol pair doesn't change in the symbol table.  And as
> > > a bonus, it should help FGKASLR i-cache performance, significantly.
> > 
> > Yeah, I keep that in mind. However, this wouldn't solve the
> > duplicate static function names problem, right?
> > Let's say you have a static function f() in file1 and f() in file2,
> > then the layout each boot can be
> > 
> > .text.file1  or  .text.file2
> > f()              f()
> > .text.file2      .text.file1
> > f()              f()
> > 
> > and position-based search won't work anyway, right?
> 
> Right, so we'd have to abandon position-based search in favor of
> file+func based search.
> 
> It's not perfect because there are still a few file+func duplicates.
> But it might be good enough.  We would presumably just refuse to patch a
> duplicate.  Or we could remove them (and enforce their continued removal
> with tooling-based warnings).
> 

You're talking about duplicate file+func combinations as stored in the
symbol table?


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