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SubjectRe: [GIT PULL] compiler-attributes for v5.3-rc8
On Thu, Sep 5, 2019 at 9:20 AM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> On Wed, Sep 4, 2019 at 11:18 AM Miguel Ojeda
> <miguel.ojeda.sandonis@gmail.com> wrote:
> >
> > I was going to send this for 5.4 since it is not that trivial, but since
> > you are doing an -rc8, and it fixes an oops, please consider pulling it.
>
> I looked at this, and while it seems safe, I end up worrying.
>
> Macro stringification isn't entirely obvious, and an unquoted string
> could become corrupted if the stringification ends up not happening
> immediately.
>
> It does seem safe just because we do
>
> #define __section(S) __attribute__((__section__(#S)))
>
> but I had to go _check_ that we do, because it wouldn't have been safe
> if there had been another level of macro expansion, because then the
> argument in turn could have been expanded before it was stringified.
>
> So sometimes you actually _want_ to pass in a string to be
> stringified, because it's safer. I realize it then gets string-quoted,
> but this has worked for gcc. Even if I suspect nobody really _thought_
> about it.
>
> So I'm not unhappy about the patch, but it's the kind of thing I'd
> really prefer not to do at this stage.
>
> Particularly since it seems to do other things too than just fix
> double quoting. As far as I can tell, it doesn't just fix double
> string quoting, it changes a lot of singly-quoted strings to use the
> macro and unquotes them, ie
>
> - __attribute__((__section__(".arch.info.init"))) = { \
> + __section(.arch.info.init) = { \
>
> doesn't actually "fix" anything that I can see, it just uses the simpler form.

Please consider picking up just:
https://github.com/ojeda/linux/commit/c97e82b97f4bba00304905fe7965f923abd2d755
That lone patch is the one that fixes the particularly observed Oops.
The rest are just cleanup; if I made that change in the more important
patch, why not clean up the rest of the instances in the kernel?
--
Thanks,
~Nick Desaulniers

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