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, 1 Aug 2022 12:31:42 +0800 From: Youling Tang <tangyouling@...ngson.cn> To: Huacai Chen <chenhuacai@...nel.org>, Xi Ruoyao <xry111@...111.site> Cc: loongarch@...ts.linux.dev, LKML <linux-kernel@...r.kernel.org>, WANG Xuerui <kernel@...0n.name>, Jinyang He <hejinyang@...ngson.cn>, Lulu Cheng <chenglulu@...ngson.cn> Subject: Re: [PATCH v4 0/4] LoongArch: Support new relocation types Hi, all On 08/01/2022 10:34 AM, Huacai Chen wrote: > Hi, all, > > On Mon, Aug 1, 2022 at 10:16 AM Youling Tang <tangyouling@...ngson.cn> wrote: >> >> Hi, Ruoyao >> >> On 07/30/2022 10:52 AM, Xi Ruoyao wrote: >>> On Sat, 2022-07-30 at 10:24 +0800, Xi Ruoyao wrote: >>>> On Sat, 2022-07-30 at 01:55 +0800, Xi Ruoyao wrote: >>>>> On Fri, 2022-07-29 at 20:19 +0800, Youling Tang wrote: >>>>> >>>>>> On 07/29/2022 07:45 PM, Xi Ruoyao wrote: >>>>>>> Hmm... The problem is the "addresses" of per-cpu symbols are >>>>>>> faked: they >>>>>>> are actually offsets from $r21. So we can't just load such an >>>>>>> offset >>>>>>> with PCALA addressing. >>>>>>> >>>>>>> It looks like we'll need to introduce an attribute for GCC to >>>>>>> make >>>>>>> an >>>>>>> variable "must be addressed via GOT", and add the attribute into >>>>>>> PER_CPU_ATTRIBUTES. >>>>> >>>>>> Yes, we need a GCC attribute to specify the per-cpu variable. >>>>> >>>>> GCC patch adding "addr_global" attribute for LoongArch: >>>>> https://gcc.gnu.org/pipermail/gcc-patches/2022-July/599064.html >>>>> >>>>> An experiment to use it: >>>>> https://github.com/xry111/linux/commit/c1d5d70 >>>> >>>> Correction: https://github.com/xry111/linux/commit/c1d5d708 Using the new toolchain (with the "addr_global" attribute) to build the kernel can successfully load the nf_tables.ko module after applying the "c1d5d708" commit. Thanks, Youling >>>> >>>> It seems 7-bit SHA is not enough for kernel repo. >>> >>> If addr_global is rejected or not implemented (for example, building the >>> kernel with GCC 12), *I expect* the following hack to work (I've not >>> tested it because I'm AFK now). Using visibility in kernel seems >>> strange, but I think it may make some sense because the modules are some >>> sort of similar to an ELF shared object being dlopen()'ed, and our way >>> to inject per-CPU symbols is analog to ELF interposition. >>> >>> arch/loongarch/include/asm/percpu.h: >>> >>> #if !__has_attribute(__addr_global__) && defined(MODULE) >>> /* Magically remove "static" for per-CPU variables. */ >>> # define ARCH_NEEDS_WEAK_PER_CPU >>> /* Force GOT-relocation for per-CPU variables. */ >>> # define PER_CPU_ATTRIBUTES __attribute__((__visibility__("default"))) >>> #endif >>> >>> arch/loongarch/Makefile: >>> >>> # Hack for per-CPU variables, see PER_CPU_ATTRIBUTES in >>> # include/asm/percpu.h >>> if (call gcc-does-not-support-addr-global) >>> KBUILD_CFLAGS_MODULE += -fPIC -fvisibility=hidden >>> endif >>> >> Using the old toolchain (GCC 12) can successfully load the nf_tables.ko >> module after applying the above patch. > I don't like such a hack..., can we consider using old relocation > types when building by old toolchains? > > Huacai >> >> Thanks, >> Youling >>
Powered by blists - more mailing lists