Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755548AbYGQGhr (ORCPT ); Thu, 17 Jul 2008 02:37:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751685AbYGQGhj (ORCPT ); Thu, 17 Jul 2008 02:37:39 -0400 Received: from gate.crashing.org ([63.228.1.57]:37350 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751296AbYGQGhi (ORCPT ); Thu, 17 Jul 2008 02:37:38 -0400 Subject: Re: [PATCH] elf loader support for auxvec base platform string From: Benjamin Herrenschmidt Reply-To: benh@kernel.crashing.org To: Linus Torvalds , Andrew Morton Cc: linuxppc-dev@ozlabs.org, linux-kernel@vger.kernel.org, roland@redhat.com, Nathan Lynch In-Reply-To: <1216166331-14810-2-git-send-email-ntl@pobox.com> References: <1216166331-14810-1-git-send-email-ntl@pobox.com> <1216166331-14810-2-git-send-email-ntl@pobox.com> Content-Type: text/plain Date: Thu, 17 Jul 2008 16:35:39 +1000 Message-Id: <1216276539.7740.309.camel@pasglop> Mime-Version: 1.0 X-Mailer: Evolution 2.22.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4480 Lines: 118 Hi Linus, Andrew ! Should I seek somebody's ack before merging a patch like the one below ? I'm a bit reluctant to merge via the powerpc.git tree some changes to generic files without at least an ack from somebody else :-) There have been some debate on whether this AT_BASE_PLATFORM is the right approach, though I haven't seen them reach any useful conclusion and our toolchain people internally are screaming for it... Cheers, Ben. On Tue, 2008-07-15 at 18:58 -0500, Nathan Lynch wrote: > Some IBM POWER-based platforms have the ability to run in a > mode which mostly appears to the OS as a different processor from the > actual hardware. For example, a Power6 system may appear to be a > Power5+, which makes the AT_PLATFORM value "power5+". This means that > programs are restricted to the ISA supported by Power5+; > Power6-specific instructions are treated as illegal. > > However, some applications (virtual machines, optimized libraries) can > benefit from knowledge of the underlying CPU model. A new aux vector > entry, AT_BASE_PLATFORM, will denote the actual hardware. For > example, on a Power6 system in Power5+ compatibility mode, AT_PLATFORM > will be "power5+" and AT_BASE_PLATFORM will be "power6". The idea is > that AT_PLATFORM indicates the instruction set supported, while > AT_BASE_PLATFORM indicates the underlying microarchitecture. > > If the architecture has defined ELF_BASE_PLATFORM, copy that value to > the user stack in the same manner as ELF_PLATFORM. > > Signed-off-by: Nathan Lynch > --- > fs/binfmt_elf.c | 23 +++++++++++++++++++++++ > include/linux/auxvec.h | 5 ++++- > 2 files changed, 27 insertions(+), 1 deletions(-) > > diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c > index d48ff5f..834c2c4 100644 > --- a/fs/binfmt_elf.c > +++ b/fs/binfmt_elf.c > @@ -131,6 +131,10 @@ static int padzero(unsigned long elf_bss) > #define STACK_ALLOC(sp, len) ({ sp -= len ; sp; }) > #endif > > +#ifndef ELF_BASE_PLATFORM > +#define ELF_BASE_PLATFORM NULL > +#endif > + > static int > create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec, > unsigned long load_addr, unsigned long interp_load_addr) > @@ -142,7 +146,9 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec, > elf_addr_t __user *envp; > elf_addr_t __user *sp; > elf_addr_t __user *u_platform; > + elf_addr_t __user *u_base_platform; > const char *k_platform = ELF_PLATFORM; > + const char *k_base_platform = ELF_BASE_PLATFORM; > int items; > elf_addr_t *elf_info; > int ei_index = 0; > @@ -172,6 +178,19 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec, > return -EFAULT; > } > > + /* > + * If this architecture has a "base" platform capability > + * string, copy it to userspace. > + */ > + u_base_platform = NULL; > + if (k_base_platform) { > + size_t len = strlen(k_base_platform) + 1; > + > + u_base_platform = (elf_addr_t __user *)STACK_ALLOC(p, len); > + if (__copy_to_user(u_base_platform, k_base_platform, len)) > + return -EFAULT; > + } > + > /* Create the ELF interpreter info */ > elf_info = (elf_addr_t *)current->mm->saved_auxv; > /* update AT_VECTOR_SIZE_BASE if the number of NEW_AUX_ENT() changes */ > @@ -208,6 +227,10 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec, > NEW_AUX_ENT(AT_PLATFORM, > (elf_addr_t)(unsigned long)u_platform); > } > + if (k_base_platform) { > + NEW_AUX_ENT(AT_BASE_PLATFORM, > + (elf_addr_t)(unsigned long)u_base_platform); > + } > if (bprm->interp_flags & BINPRM_FLAGS_EXECFD) { > NEW_AUX_ENT(AT_EXECFD, bprm->interp_data); > } > diff --git a/include/linux/auxvec.h b/include/linux/auxvec.h > index ad89545..1adc61d 100644 > --- a/include/linux/auxvec.h > +++ b/include/linux/auxvec.h > @@ -26,8 +26,11 @@ > > #define AT_SECURE 23 /* secure mode boolean */ > > +#define AT_BASE_PLATFORM 38 /* string identifying real platform, may > + * differ from AT_PLATFORM. */ > + > #ifdef __KERNEL__ > -#define AT_VECTOR_SIZE_BASE (14 + 2) /* NEW_AUX_ENT entries in auxiliary table */ > +#define AT_VECTOR_SIZE_BASE (14 + 3) /* NEW_AUX_ENT entries in auxiliary table */ > #endif > > #endif /* _LINUX_AUXVEC_H */ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/