From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 5B1CCDDE21 for ; Mon, 7 Jul 2008 15:48:22 +1000 (EST) Subject: Re: [PATCH 1/2] elf loader support for auxvec base platform string From: Benjamin Herrenschmidt To: Roland McGrath In-Reply-To: <20080704021929.5E9EF1541F5@magilla.localdomain> References: <20080703234140.GC9594@localdomain> <20080704021929.5E9EF1541F5@magilla.localdomain> Content-Type: text/plain Date: Mon, 07 Jul 2008 15:48:13 +1000 Message-Id: <1215409693.8970.79.camel@pasglop> Mime-Version: 1.0 Cc: linuxppc-dev@ozlabs.org, Nathan Lynch , linux-kernel@vger.kernel.org, Paul Mackerras Reply-To: benh@kernel.crashing.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, 2008-07-03 at 19:19 -0700, Roland McGrath wrote: > Why not just use ELF_HWCAP for this? It looks like powerpc only has 3 bits > left there (keeping it to 32), but 3 is not 0. If not that, why not use > dsocaps? That is, some magic in the vDSO, which glibc already supports on > all machines where it uses the vDSO. (For how it works, see the use in > arch/x86/vdso/vdso32/note.S for CONFIG_XEN.) Well, we use strings to represent the platforms already (ie, the actual CPU microarchitecture). Fitting those into bits would be annoying, it makes sense to have AT_BASE_PLATFORM to be the "base" variant of AT_PLATFORM. _However_ there is a bug in that this patch adds an entry without bumping the number of entries in the cached array (ie. AT_VECTOR_SIZE_BASE needs to be updated). Ben.