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, 24 Apr 2017 12:17:03 +0200 From: Geert Uytterhoeven <geert@...ux-m68k.org> To: Arnd Bergmann <arnd@...db.de> Cc: "Maciej W. Rozycki" <macro@...ux-mips.org>, Kees Cook <keescook@...omium.org>, linux-arch <linux-arch@...r.kernel.org>, linux-kbuild <linux-kbuild@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, Russell King <rmk+kernel@...linux.org.uk>, Andrew Morton <akpm@...ux-foundation.org>, kernel-build-reports@...ts.linaro.org, kvmarm@...ts.cs.columbia.edu Subject: Re: [RFC] minimum gcc version for kernel: raise to gcc-4.3 or 4.6? Hi Arnd, On Mon, Apr 24, 2017 at 11:44 AM, Arnd Bergmann <arnd@...db.de> wrote: > On Sun, Apr 23, 2017 at 10:13 PM, Geert Uytterhoeven > <geert@...ux-m68k.org> wrote: >> On Sat, Apr 22, 2017 at 5:30 PM, Arnd Bergmann <arnd@...db.de> wrote: >>> Based on what I found so far, gcc-4 can be pretty much ruled out from >>> being the minimum version based on the number of failures I got. >>> It's much better than 3.4 but much worse than 4.1 or 4.2 which seem >>> fixable on MIPS and x86 at least, and may or may not work depending >>> on configuration. So the best two possible (but conflicting) answers I >>> have are >>> >>> a) There are known users on gcc-4.1, and we never break things that >>> work for users, so gcc-4.1 (or possibly 4.0 if a user shows up) would >>> be the minimum version. >>> b) gcc-4.1 and 4.2 have too many problems, so users are better off >>> when we tell them to upgrade to something newer, and a minimum >>> version of gcc-4.3 has fewer surprises. We should remove all >>> workarounds for pre-gcc-4.3 compilers and just force a build error >>> message. >> >> If there's no real good reason (brokenness) to deprecate gcc-4.1, I would not >> do it.I guess most people using old compilers know what they're doing. > > What I'm trying to find out first is whether "people regularly using 10+ > year old compilers for the latest kernels" is a strict subset of "people in > Geert's household". Fair enough. >> My main motivation for keep on using gcc-4.1 is that it gives many warnings >> that were disabled in later gcc versions. I do look at all new warnings, and >> send patches when they are real bugs, or are trivial to silence. > > What kind of warnings do you see that disappeared with later versions? > Do you know what caused them to disappear in later versions (different > optimization decisions, warning getting disabled by default but still available > for turning on manually, ...)? Do you know if the disabled warnings are > still there in gcc-4.3 (I can try it out if you give me examples)? Mostly the "may be used uninitialized" warnings. I believe they were disabled in gcc-4.3 (4.2?) and later due to too many false positives, which is not an issue for me, as I look at differences. They were re-enabled lately (with much less false-positives), that's why you see them, and fix them. For example, do you see the warning fixed by commit 1b8c1012142d8322 ("drivers: net: xgene: Simplify xgene_enet_setup_mss() to kill warning") with gcc-4.3? Yes, that was a false positive. Or see commit cc4a7ffe02c95f53 ("spi: fsl-lpspi: Pre-initialize ret in fsl_lpspi_transfer_one_msg()"). That one was a real bug. I don't see that in any of the kisskb build logs, and they use gcc-4.2.4 for avr32. So having gcc-4.2 or gcc-4.3 in a farm won't help. And as long as I find real bugs this way, I'd like to continue doing it. >> BTW, below is the diff I use to avoid an ICE. >> After that, it builds and (test)boots fine on ARAnyM ;-) > > I guess this means that even your builds require extra patches and you > can't strictly build a defconfig and expect that to work ;-) No sane people enable GFS in defconfig, so it's not affected. Oh wait, some mips, powerpc, s390, and tile do ;-) Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
Powered by blists - more mailing lists