From: Borislav Petkov <bp@alien8.de>
To: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Nathan Chancellor <natechancellor@gmail.com>,
Arnd Bergmann <arnd@kernel.org>, Ard Biesheuvel <ardb@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
x86@kernel.org, Nick Desaulniers <ndesaulniers@google.com>,
Arnd Bergmann <arnd@arndb.de>, Darren Hart <dvhart@infradead.org>,
Andy Shevchenko <andy@infradead.org>,
"H. Peter Anvin" <hpa@zytor.com>,
linux-efi@vger.kernel.org, platform-driver-x86@vger.kernel.org,
linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com
Subject: Re: [PATCH] x86: efi: avoid BUILD_BUG_ON() for non-constant p4d_index
Date: Fri, 15 Jan 2021 20:18:33 +0100 [thread overview]
Message-ID: <20210115191833.GF9138@zn.tnic> (raw)
In-Reply-To: <YAHo3ZEMu+6mESZA@rani.riverdale.lan>
On Fri, Jan 15, 2021 at 02:11:25PM -0500, Arvind Sankar wrote:
> That's how build-time assertions work: they are _supposed_ to be
> optimized away completely when the assertion is true. If they're
> _not_ optimized away, the build will fail.
Yah, that I know, thanks.
If gcc really inlines p4d_index() and does a lot more aggressive
optimization to determine that the condition is false and thus optimize
everything away (and clang doesn't), then that would explain the
observation.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2021-01-15 19:19 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-07 22:34 [PATCH] x86: efi: avoid BUILD_BUG_ON() for non-constant p4d_index Arnd Bergmann
2021-01-07 22:42 ` Nathan Chancellor
2021-01-13 17:51 ` Ard Biesheuvel
2021-01-15 18:23 ` Borislav Petkov
2021-01-15 18:32 ` Nathan Chancellor
2021-01-15 19:07 ` Borislav Petkov
2021-01-15 19:11 ` Arvind Sankar
2021-01-15 19:18 ` Borislav Petkov [this message]
2021-01-15 19:54 ` Arnd Bergmann
2021-01-15 20:12 ` Arvind Sankar
2021-01-15 20:32 ` Arvind Sankar
2021-01-15 19:07 ` Arvind Sankar
2021-01-15 20:27 ` Arvind Sankar
2021-01-16 16:34 ` Ard Biesheuvel
2021-01-18 20:24 ` Borislav Petkov
2021-01-18 21:42 ` Arvind Sankar
2021-01-20 9:33 ` Ard Biesheuvel
2021-01-20 11:44 ` Borislav Petkov
2021-02-03 18:51 ` Nathan Chancellor
2021-02-03 20:29 ` Ard Biesheuvel
2021-02-04 10:51 ` Borislav Petkov
2021-02-04 10:59 ` Ard Biesheuvel
2021-02-04 19:16 ` Nathan Chancellor
2021-02-04 21:43 ` Arvind Sankar
2021-02-04 22:13 ` Borislav Petkov
2021-02-05 0:08 ` Arvind Sankar
2021-02-05 11:39 ` [PATCH] x86/efi: Remove EFI PGD build time checks Borislav Petkov
2021-02-05 11:57 ` Ard Biesheuvel
2021-02-05 18:14 ` Nick Desaulniers
2021-02-05 18:56 ` Nathan Chancellor
2021-02-05 10:34 ` [PATCH] x86: efi: avoid BUILD_BUG_ON() for non-constant p4d_index Borislav Petkov
2021-02-05 18:27 ` Nick Desaulniers
2021-02-05 18:31 ` Nathan Chancellor
2021-01-20 11:26 ` Kirill A. Shutemov
2021-01-20 11:06 ` Kirill A. Shutemov
2021-02-06 12:56 ` [tip: x86/urgent] x86/efi: Remove EFI PGD build time checks tip-bot2 for Borislav Petkov
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