Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756042AbYGVCDx (ORCPT ); Mon, 21 Jul 2008 22:03:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754119AbYGVCDp (ORCPT ); Mon, 21 Jul 2008 22:03:45 -0400 Received: from gate.crashing.org ([63.228.1.57]:42852 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750991AbYGVCDo (ORCPT ); Mon, 21 Jul 2008 22:03:44 -0400 Subject: Re: [PATCH v4] elf loader support for auxvec base platform string From: Benjamin Herrenschmidt Reply-To: benh@kernel.crashing.org To: Nathan Lynch Cc: Andrew Morton , torvalds@linux-foundation.org, linuxppc-dev@ozlabs.org, linux-kernel@vger.kernel.org, roland@redhat.com, John Reiser In-Reply-To: <20080721184846.GU9594@localdomain> References: <1216166331-14810-1-git-send-email-ntl@pobox.com> <1216166331-14810-2-git-send-email-ntl@pobox.com> <1216276539.7740.309.camel@pasglop> <20080717000951.5f8cab37.akpm@linux-foundation.org> <20080717221932.GL9594@localdomain> <20080717154218.8981035c.akpm@linux-foundation.org> <20080721184846.GU9594@localdomain> Content-Type: text/plain Date: Tue, 22 Jul 2008 12:03:11 +1000 Message-Id: <1216692191.11027.177.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: 4902 Lines: 133 On Mon, 2008-07-21 at 13:48 -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 Andrew, I'll merge that after John patch shows up if you give me your Ack :-) Cheers, Ben. > --- > > Andrew Morton wrote: > > OK. > > > > But it conflicts directly with the already-queued > > execve-filename-document-and-export-via-auxiliary-vector.patch (which > > various potential reviewers blithely deleted - don't come complaining > > to me!): > > > > Rebased to -mm to resolve conflicts with > execve-filename-document-and-export-via-auxiliary-vector.patch, and > changed AT_BASE_PLATFORM to lowest unclaimed value (24). > > > fs/binfmt_elf.c | 28 ++++++++++++++++++++++++++++ > include/linux/auxvec.h | 6 +++++- > 2 files changed, 33 insertions(+), 1 deletions(-) > > diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c > index bad7d87..180f92b 100644 > --- a/fs/binfmt_elf.c > +++ b/fs/binfmt_elf.c > @@ -131,6 +131,15 @@ static int padzero(unsigned long elf_bss) > #define STACK_ALLOC(sp, len) ({ sp -= len ; sp; }) > #endif > > +#ifndef ELF_BASE_PLATFORM > +/* > + * AT_BASE_PLATFORM indicates the "real" hardware/microarchitecture. > + * If the arch defines ELF_BASE_PLATFORM (in asm/elf.h), the value > + * will be copied to the user stack in the same manner as AT_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 +151,9 @@ 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 +183,19 @@ 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 */ > @@ -209,6 +233,10 @@ 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 0da17d1..d7afa9d 100644 > --- a/include/linux/auxvec.h > +++ b/include/linux/auxvec.h > @@ -26,9 +26,13 @@ > > #define AT_SECURE 23 /* secure mode boolean */ > > +#define AT_BASE_PLATFORM 24 /* string identifying real platform, may > + * differ from AT_PLATFORM. */ > + > #define AT_EXECFN 31 /* filename of program */ > + > #ifdef __KERNEL__ > -#define AT_VECTOR_SIZE_BASE 17 /* NEW_AUX_ENT entries in auxiliary table */ > +#define AT_VECTOR_SIZE_BASE 18 /* NEW_AUX_ENT entries in auxiliary table */ > /* number of "#define AT_.*" above, minus {AT_NULL, AT_IGNORE, AT_NOTELF} */ > #endif > -- 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/