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: Tue, 25 Aug 2020 00:31:18 -0700 From: Nick Desaulniers <ndesaulniers@...gle.com> To: Masahiro Yamada <masahiroy@...nel.org> Cc: Dávid Bolvanský <david.bolvansky@...il.com>, Eli Friedman <efriedma@...cinc.com>, Linus Torvalds <torvalds@...ux-foundation.org>, "H. Peter Anvin" <hpa@...or.com>, Andrew Morton <akpm@...ux-foundation.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Michal Marek <michal.lkml@...kovi.net>, Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, Kees Cook <keescook@...omium.org>, Tony Luck <tony.luck@...el.com>, Dmitry Vyukov <dvyukov@...gle.com>, Michael Ellerman <mpe@...erman.id.au>, Joe Perches <joe@...ches.com>, Joel Fernandes <joel@...lfernandes.org>, Daniel Axtens <dja@...ens.net>, Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, Alexandru Ardelean <alexandru.ardelean@...log.com>, Yury Norov <yury.norov@...il.com>, "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>, Ard Biesheuvel <ardb@...nel.org>, "Paul E . McKenney" <paulmck@...nel.org>, Daniel Kiper <daniel.kiper@...cle.com>, Bruce Ashfield <bruce.ashfield@...il.com>, Marco Elver <elver@...gle.com>, Vamshi K Sthambamkadi <vamshi.k.sthambamkadi@...il.com>, Arvind Sankar <nivedita@...m.mit.edu> Subject: Re: [PATCH 0/4] -ffreestanding/-fno-builtin-* patches On Tue, Aug 25, 2020 at 12:10 AM Nick Desaulniers <ndesaulniers@...gle.com> wrote: > > On Mon, Aug 24, 2020 at 10:34 AM Arvind Sankar <nivedita@...m.mit.edu> wrote: > > > > On Tue, Aug 25, 2020 at 12:57:22AM +0900, Masahiro Yamada wrote: > > > > > > > > > To prevent transformation from foo() into bar(), > > > there are two ways in Clang to do that; > > > -fno-builtin-foo, and -fno-builtin-bar. > > > There is only one in GCC; -fno-buitin-foo. > > > > > > Is this correct? > > > > > > > It looked that way from previous experimentation, but... > > > > > > > > > > > I just played the optimization > > > from printf("helloworld\n") to puts("helloworld"). > > > > > > https://godbolt.org/z/5s4ded > > > > > > > > > -fno-builtin-puts cannot prevent clang > > > from emitting puts. > > > Is it because clang does not support > > > -fno-builtin-puts? > > > > Ugh. clang doesn't have __builtin_puts() but it optimizes printf() into > > puts(). It doesn't have __builtin_putchar() but will optimize > > printf("c") into putchar('c'). > > Bah, merely a <strikethrough>flesh > wound</strikethrough><strikethrough>compiler bug</strikethrough>rather > long TODO in the compiler. > https://github.com/llvm/llvm-project/blob/be2bc7d4cef2edd66c7fb74b70adf62fc68754db/clang/include/clang/Basic/Builtins.def#L943 > > Anyways, give me a week and I'll hack through the rest of them > https://reviews.llvm.org/D86508. Certainly made HPA's point hit home, > that's a lot of functionality to implement or disable in an > environment. > > Masahiro, are you implying that we shouldn't take the > -fno-builtin-stpcpy patch, because Clang is inconsistent? (That can be > fixed.) Even though -fno-builtin-stpcpy works here as intended? > https://lore.kernel.org/lkml/20200817220212.338670-2-ndesaulniers@google.com/ Sorry, the above link ^ should be this hunk (beyond tired, getting up in 4.5hrs for plumbers): diff --git a/Makefile b/Makefile index c4470a4e131f..6a08cdfa58ae 100644 --- a/Makefile +++ b/Makefile @@ -577,6 +577,7 @@ ifneq ($(LLVM_IAS),1) CLANG_FLAGS += -no-integrated-as endif CLANG_FLAGS += -Werror=unknown-warning-option +CLANG_FLAGS += -fno-builtin-stpcpy KBUILD_CFLAGS += $(CLANG_FLAGS) KBUILD_AFLAGS += $(CLANG_FLAGS) export CLANG_FLAGS > > Otherwise we need to provide an implementation of this symbol in the kernel. > https://lore.kernel.org/lkml/20200815020946.1538085-1-ndesaulniers@google.com/ > > Please, pick your poison. > -- > Thanks, > ~Nick Desaulniers -- Thanks, ~Nick Desaulniers
Powered by blists - more mailing lists