From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1946236AbdEYW20 (ORCPT ); Thu, 25 May 2017 18:28:26 -0400 Received: from mail-qt0-f196.google.com ([209.85.216.196]:34648 "EHLO mail-qt0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1946116AbdEYW2W (ORCPT ); Thu, 25 May 2017 18:28:22 -0400 Subject: Re: [PATCH v2] um: Allow building and running on older hosts To: Thomas Meyer Cc: linux-kernel@vger.kernel.org, elicooper@gmx.com, Jeff Dike , Richard Weinberger , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , "open list:USER-MODE LINUX (UML)" , "open list:USER-MODE LINUX (UML)" References: <20170525183627.9375-1-f.fainelli@gmail.com> From: Florian Fainelli Message-ID: <82371937-3efc-06e7-8394-2acbb8d38d3a@gmail.com> Date: Thu, 25 May 2017 15:28:18 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/25/2017 12:51 PM, Thomas Meyer wrote: > >> Am 25.05.2017 um 20:36 schrieb Florian Fainelli : >> >> Commit a78ff1112263 ("um: add extended processor state save/restore >> support") and b6024b21fec8 ("um: extend fpstate to _xstate to support >> YMM registers") forced the use of the x86 FP _xstate and >> PTRACE_GETREGSET/SETREGSET. On older hosts, we would neither be able to >> build UML nor run it anymore with these two commits applied because we >> don't have definitions for struct _xstate nor these two ptrace requests. > > Btw. what soy you mean with older host? I need to revert two commits to make an UML kernel work again on a Fedora 25 installation. This is centos 6.9, so kernel 2.6.32 and glibc 2.12, this neither has xstate nor PTRACE_GETREGSET/SETREGSET, hence this patch. > >> >> We can determine at build time which fp context structure to check >> against, just like we can keep using the old i387 fp save/restore if >> PTRACE_GETRESET/SETREGSET are not defined. >> >> Fixes: a78ff1112263 ("um: add extended processor state save/restore support") >> Fixes: b6024b21fec8 ("um: extend fpstate to _xstate to support YMM registers") >> Signed-off-by: Florian Fainelli >> --- >> Changes in v2: >> >> - re-arrange the #ifdef/curly braces to not take the branch >> >> arch/x86/um/os-Linux/registers.c | 12 ++++++++---- >> arch/x86/um/user-offsets.c | 4 ++++ >> 2 files changed, 12 insertions(+), 4 deletions(-) >> >> diff --git a/arch/x86/um/os-Linux/registers.c b/arch/x86/um/os-Linux/registers.c >> index 00f54a91bb4b..28775f55bde2 100644 >> --- a/arch/x86/um/os-Linux/registers.c >> +++ b/arch/x86/um/os-Linux/registers.c >> @@ -26,6 +26,7 @@ int save_i387_registers(int pid, unsigned long *fp_regs) >> >> int save_fp_registers(int pid, unsigned long *fp_regs) >> { >> +#ifdef PTRACE_GETREGSET >> struct iovec iov; >> >> if (have_xstate_support) { >> @@ -34,9 +35,9 @@ int save_fp_registers(int pid, unsigned long *fp_regs) >> if (ptrace(PTRACE_GETREGSET, pid, NT_X86_XSTATE, &iov) < 0) >> return -errno; >> return 0; >> - } else { >> + } else >> +#endif >> return save_i387_registers(pid, fp_regs); >> - } >> } >> >> int restore_i387_registers(int pid, unsigned long *fp_regs) >> @@ -48,6 +49,7 @@ int restore_i387_registers(int pid, unsigned long *fp_regs) >> >> int restore_fp_registers(int pid, unsigned long *fp_regs) >> { >> +#ifdef PTRACE_SETREGSET >> struct iovec iov; >> >> if (have_xstate_support) { >> @@ -56,9 +58,9 @@ int restore_fp_registers(int pid, unsigned long *fp_regs) >> if (ptrace(PTRACE_SETREGSET, pid, NT_X86_XSTATE, &iov) < 0) >> return -errno; >> return 0; >> - } else { >> + } else >> +#endif >> return restore_i387_registers(pid, fp_regs); >> - } >> } >> >> #ifdef __i386__ >> @@ -122,6 +124,7 @@ int put_fp_registers(int pid, unsigned long *regs) >> >> void arch_init_registers(int pid) >> { >> +#ifdef PTRACE_GETREGSET >> struct _xstate fp_regs; >> struct iovec iov; >> >> @@ -129,6 +132,7 @@ void arch_init_registers(int pid) >> iov.iov_len = sizeof(struct _xstate); >> if (ptrace(PTRACE_GETREGSET, pid, NT_X86_XSTATE, &iov) == 0) >> have_xstate_support = 1; > > In my setup above call works correctly and so have_xstate_support will be set, but save_fp_registers fails with errno 4 or so... > >> +#endif >> } >> #endif >> >> diff --git a/arch/x86/um/user-offsets.c b/arch/x86/um/user-offsets.c >> index cb3c22370cf5..8af0fb5d2780 100644 >> --- a/arch/x86/um/user-offsets.c >> +++ b/arch/x86/um/user-offsets.c >> @@ -50,7 +50,11 @@ void foo(void) >> DEFINE(HOST_GS, GS); >> DEFINE(HOST_ORIG_AX, ORIG_EAX); >> #else >> +#if defined(PTRACE_GETREGSET) && defined(PTRACE_SETREGSET) >> DEFINE(HOST_FP_SIZE, sizeof(struct _xstate) / sizeof(unsigned long)); >> +#else >> + DEFINE(HOST_FP_SIZE, sizeof(struct _fpstate) / sizeof(unsigned long)); >> +#endif >> DEFINE_LONGS(HOST_BX, RBX); >> DEFINE_LONGS(HOST_CX, RCX); >> DEFINE_LONGS(HOST_DI, RDI); >> -- >> 2.12.2 >> -- Florian