From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AIpwx4/Yvz2GjPn9zptH+d7oxKDkBuVHtawgk+fkB9HSBJnDzkv4XYh0+VqlSwMiKrwhoxQBC6g1 ARC-Seal: i=1; a=rsa-sha256; t=1524498473; cv=none; d=google.com; s=arc-20160816; b=pCKO8xVHviXHWnLle6XpAadOtpj77KrXRHUNqWcsxIGYNLOgQjUmrxh3mjsiyrs77E BrMcTsQ9L6HU4k+p9BXII0xFVlxQPC6ZujgvM4tOyd77AHYJGgt17gmOFZmXbSQAm0ME /dbXz+sPu/NeQWbOC2uVZXyea3Z3VU3DYaqdST4rVNU9hQgkqQS2lp8T+DpyMXU8mokg dli0J2ChVT9yyByHwbr2LKXOyTe7O+Lv2Lg5YEQzmN+FK7V13Cg2otBknqmP7nmyKvSX D5iAA+VTn/bhTLguwE0UUebDXfJ5T3H7aeA8Gf53VL0okwSdkokt6X28ykj2zgpTaiUu fizA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=references:in-reply-to:message-id:date:subject:cc:to:from :dkim-signature:arc-authentication-results; bh=OcvQhocRGo8adLG5spe7U+na6Cqu9Y9MpjcgHIpoCVg=; b=UHeS4/rZEKRLj7BOu7P+AxIZd4p/+9p7+7s/MM63EAmENr3vtEQJUbCmCUQiLo0uGy /gPwaKtJ4kFbdFvwyIWf9hp2dMlWz4oO6i9qiyBuQrsCMXr1wR93pm2eaUJQRkA3H0xN bP0mCLXr/eVqvZwrpdTIZ6UNy6ew8qPbug4MlwQozJ7yE+VnPO9YcZnlelbevYEZXPo7 yrdDJtdSI6k9GbaZnh5srU52E/iE0TtMWIAEHYAMoF/YB8B8dsr3WZ7NXQvlPAhus0VT huqb3F5f8SJ5tRwvMyE+e9YrZZc8dRf/KV/+KIu5e9/y01/BETJnod+aOtn8Gml3M30n 6Uvg== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass (test mode) header.i=@8bytes.org header.s=mail-1 header.b=FAJuawDA; spf=pass (google.com: domain of joro@8bytes.org designates 2a01:238:4383:600:38bc:a715:4b6d:a889 as permitted sender) smtp.mailfrom=joro@8bytes.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=8bytes.org Authentication-Results: mx.google.com; dkim=pass (test mode) header.i=@8bytes.org header.s=mail-1 header.b=FAJuawDA; spf=pass (google.com: domain of joro@8bytes.org designates 2a01:238:4383:600:38bc:a715:4b6d:a889 as permitted sender) smtp.mailfrom=joro@8bytes.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=8bytes.org From: Joerg Roedel To: Thomas Gleixner , Ingo Molnar , "H . Peter Anvin" Cc: x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Linus Torvalds , Andy Lutomirski , Dave Hansen , Josh Poimboeuf , Juergen Gross , Peter Zijlstra , Borislav Petkov , Jiri Kosina , Boris Ostrovsky , Brian Gerst , David Laight , Denys Vlasenko , Eduardo Valentin , Greg KH , Will Deacon , aliguori@amazon.com, daniel.gruss@iaik.tugraz.at, hughd@google.com, keescook@google.com, Andrea Arcangeli , Waiman Long , Pavel Machek , "David H . Gutteridge" , jroedel@suse.de, joro@8bytes.org Subject: [PATCH 14/37] x86/entry/32: Add PTI cr3 switches to NMI handler code Date: Mon, 23 Apr 2018 17:47:17 +0200 Message-Id: <1524498460-25530-15-git-send-email-joro@8bytes.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1524498460-25530-1-git-send-email-joro@8bytes.org> References: <1524498460-25530-1-git-send-email-joro@8bytes.org> X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1598552510843022690?= X-GMAIL-MSGID: =?utf-8?q?1598552510843022690?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: From: Joerg Roedel The NMI handler is special, as it needs to leave with the same cr3 as it was entered with. We need to do this because we could enter the NMI handler from kernel code with user-cr3 already loaded. Signed-off-by: Joerg Roedel --- arch/x86/entry/entry_32.S | 41 +++++++++++++++++++++++++++++++++++------ 1 file changed, 35 insertions(+), 6 deletions(-) diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index b2b0ecb..f47e535 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -77,6 +77,8 @@ #endif .endm +#define PTI_SWITCH_MASK (1 << PAGE_SHIFT) + /* * User gs save/restore * @@ -213,8 +215,19 @@ .endm -.macro SAVE_ALL_NMI +.macro SAVE_ALL_NMI cr3_reg:req SAVE_ALL + + /* + * Now switch the CR3 when PTI is enabled. + * + * We can enter with either user or kernel cr3, the code will + * store the old cr3 in \cr3_reg and switches to the kernel cr3 + * if necessary. + */ + SWITCH_TO_KERNEL_CR3 scratch_reg=\cr3_reg + +.Lend_\@: .endm /* * This is a sneaky trick to help the unwinder find pt_regs on the stack. The @@ -262,7 +275,23 @@ POP_GS_EX .endm -.macro RESTORE_ALL_NMI pop=0 +.macro RESTORE_ALL_NMI cr3_reg:req pop=0 + /* + * Now switch the CR3 when PTI is enabled. + * + * We enter with kernel cr3 and switch the cr3 to the value + * stored on \cr3_reg, which is either a user or a kernel cr3. + */ + ALTERNATIVE "jmp .Lswitched_\@", "", X86_FEATURE_PTI + + testl $PTI_SWITCH_MASK, \cr3_reg + jz .Lswitched_\@ + + /* User cr3 in \cr3_reg - write it to hardware cr3 */ + movl \cr3_reg, %cr3 + +.Lswitched_\@: + RESTORE_REGS pop=\pop .endm @@ -1333,7 +1362,7 @@ ENTRY(nmi) #endif pushl %eax # pt_regs->orig_ax - SAVE_ALL_NMI + SAVE_ALL_NMI cr3_reg=%edi ENCODE_FRAME_POINTER xorl %edx, %edx # zero error code movl %esp, %eax # pt_regs pointer @@ -1361,7 +1390,7 @@ ENTRY(nmi) .Lnmi_return: CHECK_AND_APPLY_ESPFIX - RESTORE_ALL_NMI pop=4 + RESTORE_ALL_NMI cr3_reg=%edi pop=4 jmp .Lirq_return #ifdef CONFIG_X86_ESPFIX32 @@ -1377,12 +1406,12 @@ ENTRY(nmi) pushl 16(%esp) .endr pushl %eax - SAVE_ALL_NMI + SAVE_ALL_NMI cr3_reg=%edi ENCODE_FRAME_POINTER FIXUP_ESPFIX_STACK # %eax == %esp xorl %edx, %edx # zero error code call do_nmi - RESTORE_ALL_NMI + RESTORE_ALL_NMI cr3_reg=%edi lss 12+4(%esp), %esp # back to espfix stack jmp .Lirq_return #endif -- 2.7.4