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From: Joerg Roedel <joro@8bytes.org>
To: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@kernel.org>, "H . Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andy Lutomirski <luto@kernel.org>,
	Dave Hansen <dave.hansen@intel.com>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Juergen Gross <jgross@suse.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Borislav Petkov <bp@alien8.de>, Jiri Kosina <jkosina@suse.cz>,
	Boris Ostrovsky <boris.ostrovsky@oracle.com>,
	Brian Gerst <brgerst@gmail.com>,
	David Laight <David.Laight@aculab.com>,
	Denys Vlasenko <dvlasenk@redhat.com>,
	Eduardo Valentin <eduval@amazon.com>,
	Greg KH <gregkh@linuxfoundation.org>,
	Will Deacon <will.deacon@arm.com>,
	aliguori@amazon.com, daniel.gruss@iaik.tugraz.at,
	hughd@google.com, keescook@google.com,
	Andrea Arcangeli <aarcange@redhat.com>,
	Waiman Long <llong@redhat.com>, Pavel Machek <pavel@ucw.cz>,
	"David H . Gutteridge" <dhgutteridge@sympatico.ca>,
	jroedel@suse.de, joro@8bytes.org
Subject: [PATCH 13/39] x86/entry/32: Add PTI cr3 switch to non-NMI entry/exit points
Date: Wed, 11 Jul 2018 13:29:20 +0200
Message-ID: <1531308586-29340-14-git-send-email-joro@8bytes.org> (raw)
In-Reply-To: <1531308586-29340-1-git-send-email-joro@8bytes.org>

From: Joerg Roedel <jroedel@suse.de>

Add unconditional cr3 switches between user and kernel cr3
to all non-NMI entry and exit points.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
 arch/x86/entry/entry_32.S | 83 ++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 79 insertions(+), 4 deletions(-)

diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index 9e06431..311aefa 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -154,6 +154,33 @@
 
 #endif /* CONFIG_X86_32_LAZY_GS */
 
+/* Unconditionally switch to user cr3 */
+.macro SWITCH_TO_USER_CR3 scratch_reg:req
+	ALTERNATIVE "jmp .Lend_\@", "", X86_FEATURE_PTI
+
+	movl	%cr3, \scratch_reg
+	orl	$PTI_SWITCH_MASK, \scratch_reg
+	movl	\scratch_reg, %cr3
+.Lend_\@:
+.endm
+
+/*
+ * Switch to kernel cr3 if not already loaded and return current cr3 in
+ * \scratch_reg
+ */
+.macro SWITCH_TO_KERNEL_CR3 scratch_reg:req
+	ALTERNATIVE "jmp .Lend_\@", "", X86_FEATURE_PTI
+	movl	%cr3, \scratch_reg
+	/* Test if we are already on kernel CR3 */
+	testl	$PTI_SWITCH_MASK, \scratch_reg
+	jz	.Lend_\@
+	andl	$(~PTI_SWITCH_MASK), \scratch_reg
+	movl	\scratch_reg, %cr3
+	/* Return original CR3 in \scratch_reg */
+	orl	$PTI_SWITCH_MASK, \scratch_reg
+.Lend_\@:
+.endm
+
 .macro SAVE_ALL pt_regs_ax=%eax switch_stacks=0
 	cld
 	/* Push segment registers and %eax */
@@ -288,7 +315,6 @@
 #endif /* CONFIG_X86_ESPFIX32 */
 .endm
 
-
 /*
  * Called with pt_regs fully populated and kernel segments loaded,
  * so we can access PER_CPU and use the integer registers.
@@ -301,11 +327,19 @@
  */
 
 #define CS_FROM_ENTRY_STACK	(1 << 31)
+#define CS_FROM_USER_CR3	(1 << 30)
 
 .macro SWITCH_TO_KERNEL_STACK
 
 	ALTERNATIVE     "", "jmp .Lend_\@", X86_FEATURE_XENPV
 
+	SWITCH_TO_KERNEL_CR3 scratch_reg=%eax
+
+	/*
+	 * %eax now contains the entry cr3 and we carry it forward in
+	 * that register for the time this macro runs
+	 */
+
 	/* Are we on the entry stack? Bail out if not! */
 	movl	PER_CPU_VAR(cpu_entry_area), %edi
 	addl	$CPU_ENTRY_AREA_entry_stack, %edi
@@ -374,7 +408,8 @@
 	 * but switch back to the entry-stack again when we approach
 	 * iret and return to the interrupted code-path. This usually
 	 * happens when we hit an exception while restoring user-space
-	 * segment registers on the way back to user-space.
+	 * segment registers on the way back to user-space or when the
+	 * sysenter handler runs with eflags.tf set.
 	 *
 	 * When we switch to the task-stack here, we can't trust the
 	 * contents of the entry-stack anymore, as the exception handler
@@ -391,6 +426,7 @@
 	 *
 	 * %esi: Entry-Stack pointer (same as %esp)
 	 * %edi: Top of the task stack
+	 * %eax: CR3 on kernel entry
 	 */
 
 	/* Calculate number of bytes on the entry stack in %ecx */
@@ -407,6 +443,14 @@
 	orl	$CS_FROM_ENTRY_STACK, PT_CS(%esp)
 
 	/*
+	 * Test the cr3 used to enter the kernel and add a marker
+	 * so that we can switch back to it before iret.
+	 */
+	testl	$PTI_SWITCH_MASK, %eax
+	jz	.Lcopy_pt_regs_\@
+	orl	$CS_FROM_USER_CR3, PT_CS(%esp)
+
+	/*
 	 * %esi and %edi are unchanged, %ecx contains the number of
 	 * bytes to copy. The code at .Lcopy_pt_regs_\@ will allocate
 	 * the stack-frame on task-stack and copy everything over
@@ -472,7 +516,7 @@
 
 /*
  * This macro handles the case when we return to kernel-mode on the iret
- * path and have to switch back to the entry stack.
+ * path and have to switch back to the entry stack and/or user-cr3
  *
  * See the comments below the .Lentry_from_kernel_\@ label in the
  * SWITCH_TO_KERNEL_STACK macro for more details.
@@ -518,6 +562,18 @@
 	/* Safe to switch to entry-stack now */
 	movl	%ebx, %esp
 
+	/*
+	 * We came from entry-stack and need to check if we also need to
+	 * switch back to user cr3.
+	 */
+	testl	$CS_FROM_USER_CR3, PT_CS(%esp)
+	jz	.Lend_\@
+
+	/* Clear marker from stack-frame */
+	andl	$(~CS_FROM_USER_CR3), PT_CS(%esp)
+
+	SWITCH_TO_USER_CR3 scratch_reg=%eax
+
 .Lend_\@:
 .endm
 /*
@@ -711,6 +767,18 @@ ENTRY(xen_sysenter_target)
  * 0(%ebp) arg6
  */
 ENTRY(entry_SYSENTER_32)
+	/*
+	 * On entry-stack with all userspace-regs live - save and
+	 * restore eflags and %eax to use it as scratch-reg for the cr3
+	 * switch.
+	 */
+	pushfl
+	pushl	%eax
+	SWITCH_TO_KERNEL_CR3 scratch_reg=%eax
+	popl	%eax
+	popfl
+
+	/* Stack empty again, switch to task stack */
 	movl	TSS_entry_stack(%esp), %esp
 
 .Lsysenter_past_esp:
@@ -791,6 +859,9 @@ ENTRY(entry_SYSENTER_32)
 	/* Switch to entry stack */
 	movl	%eax, %esp
 
+	/* Now ready to switch the cr3 */
+	SWITCH_TO_USER_CR3 scratch_reg=%eax
+
 	/*
 	 * Restore all flags except IF. (We restore IF separately because
 	 * STI gives a one-instruction window in which we won't be interrupted,
@@ -871,7 +942,11 @@ restore_all:
 .Lrestore_all_notrace:
 	CHECK_AND_APPLY_ESPFIX
 .Lrestore_nocheck:
-	RESTORE_REGS 4				# skip orig_eax/error_code
+	/* Switch back to user CR3 */
+	SWITCH_TO_USER_CR3 scratch_reg=%eax
+
+	/* Restore user state */
+	RESTORE_REGS pop=4			# skip orig_eax/error_code
 .Lirq_return:
 	/*
 	 * ARCH_HAS_MEMBARRIER_SYNC_CORE rely on IRET core serialization
-- 
2.7.4


  parent reply index

Thread overview: 80+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-11 11:29 [PATCH 00/39 v7] PTI support for x86-32 Joerg Roedel
2018-07-11 11:29 ` [PATCH 01/39] x86/asm-offsets: Move TSS_sp0 and TSS_sp1 to asm-offsets.c Joerg Roedel
2018-07-12 20:44   ` Andy Lutomirski
2018-07-11 11:29 ` [PATCH 02/39] x86/entry/32: Rename TSS_sysenter_sp0 to TSS_entry_stack Joerg Roedel
2018-07-12 20:44   ` Andy Lutomirski
2018-07-11 11:29 ` [PATCH 03/39] x86/entry/32: Load task stack from x86_tss.sp1 in SYSENTER handler Joerg Roedel
2018-07-12 20:49   ` Andy Lutomirski
2018-07-13  9:48     ` Joerg Roedel
2018-07-13 17:19       ` Andy Lutomirski
2018-07-13 23:17         ` Andy Lutomirski
2018-07-17  7:05           ` Joerg Roedel
2018-07-17 20:04             ` Andy Lutomirski
2018-07-11 11:29 ` [PATCH 04/39] x86/entry/32: Put ESPFIX code into a macro Joerg Roedel
2018-07-11 11:29 ` [PATCH 05/39] x86/entry/32: Unshare NMI return path Joerg Roedel
2018-07-12 20:53   ` Andy Lutomirski
2018-07-13 10:05     ` Joerg Roedel
2018-07-13 17:26       ` Andy Lutomirski
2018-07-11 11:29 ` [PATCH 06/39] x86/entry/32: Split off return-to-kernel path Joerg Roedel
2018-07-11 11:29 ` [PATCH 07/39] x86/entry/32: Enter the kernel via trampoline stack Joerg Roedel
2018-07-12 21:09   ` Andy Lutomirski
2018-07-13 10:56     ` Joerg Roedel
2018-07-13 17:21       ` Andy Lutomirski
2018-07-17  7:07         ` Joerg Roedel
2018-07-11 11:29 ` [PATCH 08/39] x86/entry/32: Leave " Joerg Roedel
2018-07-11 11:29 ` [PATCH 09/39] x86/entry/32: Introduce SAVE_ALL_NMI and RESTORE_ALL_NMI Joerg Roedel
2018-07-11 11:29 ` [PATCH 10/39] x86/entry/32: Handle Entry from Kernel-Mode on Entry-Stack Joerg Roedel
2018-07-13 23:31   ` Andy Lutomirski
2018-07-14  5:21     ` Joerg Roedel
2018-07-14  6:26       ` Andy Lutomirski
2018-07-14  8:01         ` Joerg Roedel
2018-07-14 14:36           ` Andy Lutomirski
2018-07-17  7:15             ` Joerg Roedel
2018-07-17 20:06               ` Andy Lutomirski
2018-07-18 11:59                 ` Joerg Roedel
2018-07-11 11:29 ` [PATCH 11/39] x86/entry/32: Simplify debug entry point Joerg Roedel
2018-07-11 11:29 ` [PATCH 12/39] x86/32: Use tss.sp1 as cpu_current_top_of_stack Joerg Roedel
2018-07-11 11:29 ` Joerg Roedel [this message]
2018-07-11 11:29 ` [PATCH 14/39] x86/entry/32: Add PTI cr3 switches to NMI handler code Joerg Roedel
2018-07-11 11:29 ` [PATCH 15/39] x86/pgtable: Rename pti_set_user_pgd to pti_set_user_pgtbl Joerg Roedel
2018-07-11 11:29 ` [PATCH 16/39] x86/pgtable/pae: Unshare kernel PMDs when PTI is enabled Joerg Roedel
2018-07-11 11:29 ` [PATCH 17/39] x86/pgtable/32: Allocate 8k page-tables " Joerg Roedel
2018-07-11 11:29 ` [PATCH 18/39] x86/pgtable: Move pgdp kernel/user conversion functions to pgtable.h Joerg Roedel
2018-07-11 11:29 ` [PATCH 19/39] x86/pgtable: Move pti_set_user_pgtbl() " Joerg Roedel
2018-07-11 11:29 ` [PATCH 20/39] x86/pgtable: Move two more functions from pgtable_64.h " Joerg Roedel
2018-07-11 11:29 ` [PATCH 21/39] x86/mm/pae: Populate valid user PGD entries Joerg Roedel
2018-07-11 11:29 ` [PATCH 22/39] x86/mm/pae: Populate the user page-table with user pgd's Joerg Roedel
2018-07-11 11:29 ` [PATCH 23/39] x86/mm/legacy: " Joerg Roedel
2018-07-11 11:29 ` [PATCH 24/39] x86/mm/pti: Add an overflow check to pti_clone_pmds() Joerg Roedel
2018-07-11 11:29 ` [PATCH 25/39] x86/mm/pti: Define X86_CR3_PTI_PCID_USER_BIT on x86_32 Joerg Roedel
2018-07-11 11:29 ` [PATCH 26/39] x86/mm/pti: Clone CPU_ENTRY_AREA on PMD level " Joerg Roedel
2018-07-11 11:29 ` [PATCH 27/39] x86/mm/pti: Make pti_clone_kernel_text() compile on 32 bit Joerg Roedel
2018-07-11 11:29 ` [PATCH 28/39] x86/mm/pti: Keep permissions when cloning kernel text in pti_clone_kernel_text() Joerg Roedel
2018-07-13 23:25   ` Andy Lutomirski
2018-07-11 11:29 ` [PATCH 29/39] x86/mm/pti: Introduce pti_finalize() Joerg Roedel
2018-07-11 11:29 ` [PATCH 30/39] x86/mm/pti: Clone entry-text again in pti_finalize() Joerg Roedel
2018-07-13 23:21   ` Andy Lutomirski
2018-07-14  5:04     ` Joerg Roedel
2018-07-11 11:29 ` [PATCH 31/39] x86/mm/dump_pagetables: Define INIT_PGD Joerg Roedel
2018-07-11 11:29 ` [PATCH 32/39] x86/pgtable/pae: Use separate kernel PMDs for user page-table Joerg Roedel
2018-07-11 11:29 ` [PATCH 33/39] x86/ldt: Reserve address-space range on 32 bit for the LDT Joerg Roedel
2018-07-11 11:29 ` [PATCH 34/39] x86/ldt: Define LDT_END_ADDR Joerg Roedel
2018-07-13 17:29   ` Andy Lutomirski
2018-07-11 11:29 ` [PATCH 35/39] x86/ldt: Split out sanity check in map_ldt_struct() Joerg Roedel
2018-07-13 23:18   ` Andy Lutomirski
2018-07-11 11:29 ` [PATCH 36/39] x86/ldt: Enable LDT user-mapping for PAE Joerg Roedel
2018-07-11 11:29 ` [PATCH 37/39] x86/pti: Allow CONFIG_PAGE_TABLE_ISOLATION for x86_32 Joerg Roedel
2018-07-11 11:29 ` [PATCH 38/39] x86/mm/pti: Add Warning when booting on a PCID capable CPU Joerg Roedel
2018-07-13 18:59   ` Andy Lutomirski
2018-07-14  5:08     ` Joerg Roedel
2018-07-11 11:29 ` [PATCH 39/39] x86/entry/32: Add debug code to check entry/exit cr3 Joerg Roedel
2018-07-13 17:28   ` Andy Lutomirski
2018-07-14  5:09     ` Joerg Roedel
2018-07-11 16:28 ` [PATCH 00/39 v7] PTI support for x86-32 Linus Torvalds
2018-07-11 17:28   ` Jiri Kosina
2018-07-11 19:57     ` Thomas Backlund
2018-07-12 13:59       ` Boris Ostrovsky
2018-07-11 21:07   ` Pavel Machek
2018-07-16  7:51 ` Pavel Machek
2018-07-17  2:07 ` David H. Gutteridge
2018-07-17  6:16   ` Joerg Roedel

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