Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966001AbXEKTLy (ORCPT ); Fri, 11 May 2007 15:11:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758914AbXEKTKF (ORCPT ); Fri, 11 May 2007 15:10:05 -0400 Received: from 161.sub-75-209-96.myvzw.com ([75.209.96.161]:60104 "EHLO mail.goop.org" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S965426AbXEKTKC (ORCPT ); Fri, 11 May 2007 15:10:02 -0400 Message-Id: <20070511001156.003375000@goop.org> References: <20070511000643.025196000@goop.org> User-Agent: quilt/0.46-1 Date: Thu, 10 May 2007 17:06:45 -0700 From: Jeremy Fitzhardinge To: Andi Kleen Cc: Andrew Morton , virtualization@lists.osdl.org, lkml , Chris Wright , Xen-devel , Ian Pratt , Christian Limpach , Zachary Amsden , Roland McGrath , Ulrich Drepper Subject: [patch 02/28]xen: Add nosegneg capability to the vsyscall page notes Content-Disposition: inline; filename=xen-vsyscall-note.patch Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3306 Lines: 96 Add the "nosegneg" fake capabilty to the vsyscall page notes. This is used by the runtime linker to select a glibc version which then disables negative-offset accesses to the thread-local segment via %gs. These accesses require emulation in Xen (because segments are truncated to protect the hypervisor address space) and avoiding them provides a measurable performance boost. Signed-off-by: Ian Pratt Signed-off-by: Christian Limpach Signed-off-by: Chris Wright Signed-off-by: Jeremy Fitzhardinge Acked-by: Zachary Amsden Cc: Roland McGrath Cc: Ulrich Drepper --- arch/i386/kernel/vsyscall-note.S | 23 +++++++++++++++++++++++ include/asm-i386/elf.h | 14 ++++++++++---- 2 files changed, 33 insertions(+), 4 deletions(-) =================================================================== --- a/arch/i386/kernel/vsyscall-note.S +++ b/arch/i386/kernel/vsyscall-note.S @@ -12,3 +12,26 @@ ELFNOTE_START(Linux, 0, "a") ELFNOTE_START(Linux, 0, "a") .long LINUX_VERSION_CODE ELFNOTE_END + +#ifdef CONFIG_XEN +#include + +/* + * Add a special note telling glibc's dynamic linker a fake hardware + * flavor that it will use to choose the search path for libraries in the + * same way it uses real hardware capabilities like "mmx". + * We supply "nosegneg" as the fake capability, to indicate that we + * do not like negative offsets in instructions using segment overrides, + * since we implement those inefficiently. This makes it possible to + * install libraries optimized to avoid those access patterns in someplace + * like /lib/i686/tls/nosegneg. Note that an /etc/ld.so.conf.d/file + * corresponding to the bits here is needed to make ldconfig work right. + * It should contain: + * hwcap 0 nosegneg + * to match the mapping of bit to name that we give here. + */ +ELFNOTE_START(GNU, 2, "a") + .long 1, 1< #include #include @@ -24,6 +26,9 @@ #define R_386_GOTPC 10 #define R_386_NUM 11 +/* + * ELF register definitions.. + */ typedef unsigned long elf_greg_t; #define ELF_NGREG (sizeof (struct user_regs_struct) / sizeof(elf_greg_t)) @@ -160,6 +165,7 @@ do if (vdso_enabled) { \ NEW_AUX_ENT(AT_SYSINFO_EHDR, VDSO_CURRENT_BASE); \ } while (0) -#endif +#endif /* ARCH_DLINFO */ +#endif /* __ASSEMBLY__ */ #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/