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
| ||
|
Message-ID: <20220717195448.GB25951@gate.crashing.org> Date: Sun, 17 Jul 2022 14:54:48 -0500 From: Segher Boessenkool <segher@...nel.crashing.org> To: Linus Torvalds <torvalds@...ux-foundation.org> Cc: Sudip Mukherjee <sudipm.mukherjee@...il.com>, Kees Cook <keescook@...omium.org>, linux-kernel <linux-kernel@...r.kernel.org>, Paul Mackerras <paulus@...ba.org>, linux-hardening@...r.kernel.org, linuxppc-dev <linuxppc-dev@...ts.ozlabs.org> Subject: Re: mainline build failure of powerpc allmodconfig for prom_init_check On Sun, Jul 17, 2022 at 07:44:22AM -0700, Linus Torvalds wrote: > On Sun, Jul 17, 2022 at 2:13 AM Sudip Mukherjee > <sudipm.mukherjee@...il.com> wrote: > > I was trying to check it. With gcc-11 the assembly code generated is > > not using memset, but using __memset. > > But with gcc-12, I can see the assembly code is using memset. One > > example from the assembly: > > You could try making the 'args' array in 'struct prom_args' be marked > 'volatile'. > > Ie something like this: > > --- a/arch/powerpc/kernel/prom_init.c > +++ b/arch/powerpc/kernel/prom_init.c > @@ -115,6 +115,6 @@ struct prom_args { > __be32 service; > __be32 nargs; > __be32 nret; > - __be32 args[10]; > + volatile __be32 args[10]; > }; > > because I think it's just the compilers turning the small loop over > those fields into a "memset()". Yes. See <https://gcc.gnu.org/onlinedocs/gcc/Standards.html#C-Language> near the end: Most of the compiler support routines used by GCC are present in libgcc, but there are a few exceptions. GCC requires the freestanding environment provide memcpy, memmove, memset and memcmp. Finally, if __builtin_trap is used, and the target does not implement the trap pattern, then GCC emits a call to abort. Can't we simply have a small simple implementation of these functions in arch/powerpc/boot/? This stuff is not performance-critical, and this is not the first time we hit these problems. Segher
Powered by blists - more mailing lists