lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Mon, 03 Aug 2020 21:09:36 +1000 From: Michael Ellerman <mpe@...erman.id.au> To: Geert Uytterhoeven <geert@...ux-m68k.org>, Segher Boessenkool <segher@...nel.crashing.org> Cc: Nathan Chancellor <natechancellor@...il.com>, Arnd Bergmann <arnd@...db.de>, Geoff Levand <geoff@...radead.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, clang-built-linux <clang-built-linux@...glegroups.com>, Paul Mackerras <paulus@...ba.org>, Joel Stanley <joel@....id.au>, linuxppc-dev <linuxppc-dev@...ts.ozlabs.org> Subject: Re: [PATCH] powerpc/boot: Use address-of operator on section symbols Geert Uytterhoeven <geert@...ux-m68k.org> writes: > On Mon, Jul 20, 2020 at 11:03 PM Segher Boessenkool > <segher@...nel.crashing.org> wrote: >> On Sat, Jul 18, 2020 at 09:50:50AM +0200, Geert Uytterhoeven wrote: >> > On Wed, Jun 24, 2020 at 6:02 AM Nathan Chancellor >> > <natechancellor@...il.com> wrote: >> > > /* If we have an image attached to us, it overrides anything >> > > * supplied by the loader. */ >> > > - if (_initrd_end > _initrd_start) { >> > > + if (&_initrd_end > &_initrd_start) { >> > >> > Are you sure that fix is correct? >> > >> > extern char _initrd_start[]; >> > extern char _initrd_end[]; >> > extern char _esm_blob_start[]; >> > extern char _esm_blob_end[]; >> > >> > Of course the result of their comparison is a constant, as the addresses >> > are constant. If clangs warns about it, perhaps that warning should be moved >> > to W=1? >> > >> > But adding "&" is not correct, according to C. >> >> Why not? >> >> 6.5.3.2/3 >> The unary & operator yields the address of its operand. [...] >> Otherwise, the result is a pointer to the object or function designated >> by its operand. >> >> This is the same as using the name of an array without anything else, >> yes. It is a bit clearer if it would not be declared as array, perhaps, >> but it is correct just fine like this. > > Thanks, I stand corrected. > > Regardless, the comparison is still a comparison between two constant > addresses, so my fear is that the compiler will start generating > warnings for that in the near or distant future, making this change > futile. They're not constant at compile time though. So I don't think the compiler could (sensibly) warn about that? (surely!) cheers
Powered by blists - more mailing lists