From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D03F8C4727E for ; Thu, 1 Oct 2020 21:00:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 946A820759 for ; Thu, 1 Oct 2020 21:00:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387445AbgJAVAA (ORCPT ); Thu, 1 Oct 2020 17:00:00 -0400 Received: from bhuna.collabora.co.uk ([46.235.227.227]:41292 "EHLO bhuna.collabora.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726515AbgJAU74 (ORCPT ); Thu, 1 Oct 2020 16:59:56 -0400 Received: from [127.0.0.1] (localhost [127.0.0.1]) (Authenticated sender: krisman) with ESMTPSA id 63C9629D10B From: Gabriel Krisman Bertazi To: luto@kernel.org, tglx@linutronix.de Cc: hch@lst.de, hpa@zytor.com, bp@alien8.de, rric@kernel.org, peterz@infradead.org, mingo@redhat.com, x86@kernel.org, linux-kernel@vger.kernel.org, dave.hansen@linux.intel.com, Gabriel Krisman Bertazi , kernel@collabora.com Subject: [PATCH v2 8/9] x86: Convert mmu context ia32_compat into a proper flags field Date: Thu, 1 Oct 2020 16:58:18 -0400 Message-Id: <20201001205819.27879-9-krisman@collabora.com> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20201001205819.27879-1-krisman@collabora.com> References: <20201001205819.27879-1-krisman@collabora.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The ia32_compat attribute is a weird thing. It mirrors TIF_IA32 and TIF_X32 and is used only in two very unrelated places: (1) to decide if the vsyscall page is accessible (2) for uprobes to find whether the patched instruction is 32 or 64 bit. In preparation to remove the TI flags, we want new values for ia32_compat, but given its odd semantics, I'd rather make it a real flags field that configures these specific behaviours. So, set_personality_x64 can ask for the vsyscall page, which is not available in x32/ia32 and set_personality_ia32 can configure the uprobe code as needed. uprobe cannot rely on other methods like user_64bit_mode() to decide how to patch, so it needs some specific flag like this. Signed-off-by: Gabriel Krisman Bertazi --- arch/x86/entry/vsyscall/vsyscall_64.c | 2 +- arch/x86/include/asm/mmu.h | 6 ++++-- arch/x86/include/asm/mmu_context.h | 2 +- arch/x86/kernel/process_64.c | 17 +++++++++++------ 4 files changed, 17 insertions(+), 10 deletions(-) diff --git a/arch/x86/entry/vsyscall/vsyscall_64.c b/arch/x86/entry/vsyscall/vsyscall_64.c index 44c33103a955..20abc396dbe0 100644 --- a/arch/x86/entry/vsyscall/vsyscall_64.c +++ b/arch/x86/entry/vsyscall/vsyscall_64.c @@ -316,7 +316,7 @@ static struct vm_area_struct gate_vma __ro_after_init = { struct vm_area_struct *get_gate_vma(struct mm_struct *mm) { #ifdef CONFIG_COMPAT - if (!mm || mm->context.ia32_compat) + if (!mm || !(mm->context.flags & MM_CONTEXT_GATE_PAGE)) return NULL; #endif if (vsyscall_mode == NONE) diff --git a/arch/x86/include/asm/mmu.h b/arch/x86/include/asm/mmu.h index 9257667d13c5..76ab742a0e39 100644 --- a/arch/x86/include/asm/mmu.h +++ b/arch/x86/include/asm/mmu.h @@ -7,6 +7,9 @@ #include #include +#define MM_CONTEXT_UPROBE_IA32 1 /* Uprobes on this MM assume 32-bit code */ +#define MM_CONTEXT_GATE_PAGE 2 /* Whether MM has gate page */ + /* * x86 has arch-specific MMU state beyond what lives in mm_struct. */ @@ -33,8 +36,7 @@ typedef struct { #endif #ifdef CONFIG_X86_64 - /* True if mm supports a task running in 32 bit compatibility mode. */ - unsigned short ia32_compat; + unsigned short flags; #endif struct mutex lock; diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h index d98016b83755..054a79157323 100644 --- a/arch/x86/include/asm/mmu_context.h +++ b/arch/x86/include/asm/mmu_context.h @@ -177,7 +177,7 @@ static inline void arch_exit_mmap(struct mm_struct *mm) static inline bool is_64bit_mm(struct mm_struct *mm) { return !IS_ENABLED(CONFIG_IA32_EMULATION) || - !(mm->context.ia32_compat == TIF_IA32); + !(mm->context.flags & MM_CONTEXT_UPROBE_IA32); } #else static inline bool is_64bit_mm(struct mm_struct *mm) diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 56e882c339e6..3226ceed409c 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -650,10 +650,8 @@ void set_personality_64bit(void) /* Pretend that this comes from a 64bit execve */ task_pt_regs(current)->orig_ax = __NR_execve; current_thread_info()->status &= ~TS_COMPAT; - - /* Ensure the corresponding mm is not marked. */ if (current->mm) - current->mm->context.ia32_compat = 0; + current->mm->context.flags = MM_CONTEXT_GATE_PAGE; /* TBD: overwrites user setup. Should have two bits. But 64bit processes have always behaved this way, @@ -668,7 +666,8 @@ static void __set_personality_x32(void) clear_thread_flag(TIF_IA32); set_thread_flag(TIF_X32); if (current->mm) - current->mm->context.ia32_compat = TIF_X32; + current->mm->context.flags = 0; + current->personality &= ~READ_IMPLIES_EXEC; /* * in_32bit_syscall() uses the presence of the x32 syscall bit @@ -688,8 +687,14 @@ static void __set_personality_ia32(void) #ifdef CONFIG_IA32_EMULATION set_thread_flag(TIF_IA32); clear_thread_flag(TIF_X32); - if (current->mm) - current->mm->context.ia32_compat = TIF_IA32; + if (current->mm) { + /* + * uprobes applied to this MM need to know this and + * cannot use user_64bit_mode() at that time. + */ + current->mm->context.flags = MM_CONTEXT_UPROBE_IA32; + } + current->personality |= force_personality32; /* Prepare the first "return" to user space */ task_pt_regs(current)->orig_ax = __NR_ia32_execve; -- 2.28.0