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 20:34:02 +0200 From: Borislav Petkov <bp@...en8.de> To: Yazen Ghannam <yazen.ghannam@....com> Cc: "Luck, Tony" <tony.luck@...el.com>, "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "x86@...nel.org" <x86@...nel.org>, "Smita.KoralahalliChannabasappa@....com" <Smita.KoralahalliChannabasappa@....com> Subject: Re: [PATCH] x86/mce: Increase maximum number of banks to 64 On Mon, Aug 24, 2020 at 10:11:05AM -0500, Yazen Ghannam wrote: > Thanks. Yeah, they're identical: > text data bss dec hex filename > 15710076 13519306 5398528 34627910 2106146 vmlinux-32banks > 15710076 13519306 5398528 34627910 2106146 vmlinux-64banks So I went crazy here and built allmodconfigs for hypothetical CPUs which support up to 4K MCA banks: text data bss dec hex filename 24618040 27211906 35409988 87239934 5332cfe vmlinux-32banks 24618040 27211906 35409988 87239934 5332cfe vmlinux-64banks 24618040 27211906 35409988 87239934 5332cfe vmlinux-128banks For the first three - up to 128 banks, the sizes don't change. 24618000 27216002 35401796 87235798 5331cd6 vmlinux-256banks Somewhere after 128 banks, it grows the data section but by exactly 4K, i.e., one more page: 27216002 - 27211906 = 4096 The last page is not full, of course. 27216002 % 4096 = 2178 27211906 % 4096 = 2178 24618000 27220098 35401796 87239894 5332cd6 vmlinux-512banks The same happens here. 27220098 - 27216002 = 4096 27220098 % 4096 = 2178 And so on: 24618000 27228290 35393604 87239894 5332cd6 vmlinux-1024banks 24618000 27244674 35377220 87239894 5332cd6 vmlinux-2048banks 24618000 27277442 35344452 87239894 5332cd6 vmlinux-4Kbanks So what I think happens is, the first 128 banks fit within the same .data section page thus vmlinux doesn't increase. I guess there might be a .config which could cause that data increase when the 32->64 banks move won't fit in the last .data page. It depends on where those ~2K you computed and I snipped, land. But since most kernels are allmodconfig builds, I guess we should be fine. So yeah, I guess we can take this one after you summarize the findings of this thread in v2's commit message. :-) Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette
Powered by blists - more mailing lists