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From: tip-bot for Joerg Roedel <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: dvlasenk@redhat.com, mingo@kernel.org, will.deacon@arm.com,
	jgross@suse.com, tglx@linutronix.de, eduval@amazon.com,
	torvalds@linux-foundation.org, dhgutteridge@sympatico.ca,
	dave.hansen@intel.com, peterz@infradead.org, hpa@zytor.com,
	brgerst@gmail.com, jpoimboe@redhat.com, luto@kernel.org,
	boris.ostrovsky@oracle.com, David.Laight@aculab.com,
	bp@alien8.de, aarcange@redhat.com, llong@redhat.com,
	linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org,
	jroedel@suse.de, jkosina@suse.cz, pavel@ucw.cz
Subject: [tip:x86/pti] x86/entry/32: Leave the kernel via trampoline stack
Date: Thu, 19 Jul 2018 16:22:32 -0700	[thread overview]
Message-ID: <tip-e5862d0515ad970ccec6208ecf5bb0cffe291ea3@git.kernel.org> (raw)
In-Reply-To: <1531906876-13451-9-git-send-email-joro@8bytes.org>

Commit-ID:  e5862d0515ad970ccec6208ecf5bb0cffe291ea3
Gitweb:     https://git.kernel.org/tip/e5862d0515ad970ccec6208ecf5bb0cffe291ea3
Author:     Joerg Roedel <jroedel@suse.de>
AuthorDate: Wed, 18 Jul 2018 11:40:45 +0200
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Fri, 20 Jul 2018 01:11:37 +0200

x86/entry/32: Leave the kernel via trampoline stack

Switch back to the trampoline stack before returning to userspace.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Pavel Machek <pavel@ucw.cz>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: linux-mm@kvack.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: David Laight <David.Laight@aculab.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Eduardo Valentin <eduval@amazon.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: aliguori@amazon.com
Cc: daniel.gruss@iaik.tugraz.at
Cc: hughd@google.com
Cc: keescook@google.com
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Waiman Long <llong@redhat.com>
Cc: "David H . Gutteridge" <dhgutteridge@sympatico.ca>
Cc: joro@8bytes.org
Link: https://lkml.kernel.org/r/1531906876-13451-9-git-send-email-joro@8bytes.org

---
 arch/x86/entry/entry_32.S | 79 +++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 77 insertions(+), 2 deletions(-)

diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index fea49ec345ba..a905e6215ea9 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -342,6 +342,60 @@
 .Lend_\@:
 .endm
 
+/*
+ * Switch back from the kernel stack to the entry stack.
+ *
+ * The %esp register must point to pt_regs on the task stack. It will
+ * first calculate the size of the stack-frame to copy, depending on
+ * whether we return to VM86 mode or not. With that it uses 'rep movsl'
+ * to copy the contents of the stack over to the entry stack.
+ *
+ * We must be very careful here, as we can't trust the contents of the
+ * task-stack once we switched to the entry-stack. When an NMI happens
+ * while on the entry-stack, the NMI handler will switch back to the top
+ * of the task stack, overwriting our stack-frame we are about to copy.
+ * Therefore we switch the stack only after everything is copied over.
+ */
+.macro SWITCH_TO_ENTRY_STACK
+
+	ALTERNATIVE     "", "jmp .Lend_\@", X86_FEATURE_XENPV
+
+	/* Bytes to copy */
+	movl	$PTREGS_SIZE, %ecx
+
+#ifdef CONFIG_VM86
+	testl	$(X86_EFLAGS_VM), PT_EFLAGS(%esp)
+	jz	.Lcopy_pt_regs_\@
+
+	/* Additional 4 registers to copy when returning to VM86 mode */
+	addl    $(4 * 4), %ecx
+
+.Lcopy_pt_regs_\@:
+#endif
+
+	/* Initialize source and destination for movsl */
+	movl	PER_CPU_VAR(cpu_tss_rw + TSS_sp0), %edi
+	subl	%ecx, %edi
+	movl	%esp, %esi
+
+	/* Save future stack pointer in %ebx */
+	movl	%edi, %ebx
+
+	/* Copy over the stack-frame */
+	shrl	$2, %ecx
+	cld
+	rep movsl
+
+	/*
+	 * Switch to entry-stack - needs to happen after everything is
+	 * copied because the NMI handler will overwrite the task-stack
+	 * when on entry-stack
+	 */
+	movl	%ebx, %esp
+
+.Lend_\@:
+.endm
+
 /*
  * %eax: prev task
  * %edx: next task
@@ -581,25 +635,45 @@ ENTRY(entry_SYSENTER_32)
 
 /* Opportunistic SYSEXIT */
 	TRACE_IRQS_ON			/* User mode traces as IRQs on. */
+
+	/*
+	 * Setup entry stack - we keep the pointer in %eax and do the
+	 * switch after almost all user-state is restored.
+	 */
+
+	/* Load entry stack pointer and allocate frame for eflags/eax */
+	movl	PER_CPU_VAR(cpu_tss_rw + TSS_sp0), %eax
+	subl	$(2*4), %eax
+
+	/* Copy eflags and eax to entry stack */
+	movl	PT_EFLAGS(%esp), %edi
+	movl	PT_EAX(%esp), %esi
+	movl	%edi, (%eax)
+	movl	%esi, 4(%eax)
+
+	/* Restore user registers and segments */
 	movl	PT_EIP(%esp), %edx	/* pt_regs->ip */
 	movl	PT_OLDESP(%esp), %ecx	/* pt_regs->sp */
 1:	mov	PT_FS(%esp), %fs
 	PTGS_TO_GS
+
 	popl	%ebx			/* pt_regs->bx */
 	addl	$2*4, %esp		/* skip pt_regs->cx and pt_regs->dx */
 	popl	%esi			/* pt_regs->si */
 	popl	%edi			/* pt_regs->di */
 	popl	%ebp			/* pt_regs->bp */
-	popl	%eax			/* pt_regs->ax */
+
+	/* Switch to entry stack */
+	movl	%eax, %esp
 
 	/*
 	 * Restore all flags except IF. (We restore IF separately because
 	 * STI gives a one-instruction window in which we won't be interrupted,
 	 * whereas POPF does not.)
 	 */
-	addl	$PT_EFLAGS-PT_DS, %esp	/* point esp at pt_regs->flags */
 	btrl	$X86_EFLAGS_IF_BIT, (%esp)
 	popfl
+	popl	%eax
 
 	/*
 	 * Return back to the vDSO, which will pop ecx and edx.
@@ -668,6 +742,7 @@ ENTRY(entry_INT80_32)
 
 restore_all:
 	TRACE_IRQS_IRET
+	SWITCH_TO_ENTRY_STACK
 .Lrestore_all_notrace:
 	CHECK_AND_APPLY_ESPFIX
 .Lrestore_nocheck:

  reply	other threads:[~2018-07-19 23:23 UTC|newest]

Thread overview: 96+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-18  9:40 [PATCH 00/39 v8] PTI support for x86-32 Joerg Roedel
2018-07-18  9:40 ` [PATCH 01/39] x86/asm-offsets: Move TSS_sp0 and TSS_sp1 to asm-offsets.c Joerg Roedel
2018-07-19 23:18   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:40 ` [PATCH 02/39] x86/entry/32: Rename TSS_sysenter_sp0 to TSS_entry2task_stack Joerg Roedel
2018-07-19 23:19   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:40 ` [PATCH 03/39] x86/entry/32: Load task stack from x86_tss.sp1 in SYSENTER handler Joerg Roedel
2018-07-19 23:19   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:40 ` [PATCH 04/39] x86/entry/32: Put ESPFIX code into a macro Joerg Roedel
2018-07-19 23:20   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:40 ` [PATCH 05/39] x86/entry/32: Unshare NMI return path Joerg Roedel
2018-07-19 23:21   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:40 ` [PATCH 06/39] x86/entry/32: Split off return-to-kernel path Joerg Roedel
2018-07-19 23:21   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:40 ` [PATCH 07/39] x86/entry/32: Enter the kernel via trampoline stack Joerg Roedel
2018-07-18 18:09   ` Brian Gerst
2018-07-19 20:52     ` Thomas Gleixner
2018-07-19 23:22   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:40 ` [PATCH 08/39] x86/entry/32: Leave " Joerg Roedel
2018-07-19 23:22   ` tip-bot for Joerg Roedel [this message]
2018-07-18  9:40 ` [PATCH 09/39] x86/entry/32: Introduce SAVE_ALL_NMI and RESTORE_ALL_NMI Joerg Roedel
2018-07-19 23:23   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:40 ` [PATCH 10/39] x86/entry/32: Handle Entry from Kernel-Mode on Entry-Stack Joerg Roedel
2018-07-19 23:23   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-10-12 18:29   ` [PATCH 10/39] " Jan Kiszka
2018-10-13  9:54     ` [PATCH] x86/entry/32: Fix setup of CS high bits Jan Kiszka
2018-10-13 15:12       ` Andy Lutomirski
2018-10-15 13:08         ` Jan Kiszka
2018-10-15 13:14           ` David Laight
2018-10-15 13:18             ` Jan Kiszka
2018-10-15 13:29               ` David Laight
2018-10-15  9:10       ` Joerg Roedel
2018-10-15 14:09       ` [PATCH v2] " Jan Kiszka
2018-10-15 15:09         ` [tip:x86/urgent] x86/entry/32: Clear the " tip-bot for Jan Kiszka
2018-10-18  6:21         ` tip-bot for Jan Kiszka
2018-07-18  9:40 ` [PATCH 11/39] x86/entry/32: Simplify debug entry point Joerg Roedel
2018-07-19 23:24   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:40 ` [PATCH 12/39] x86/entry/32: Add PTI cr3 switch to non-NMI entry/exit points Joerg Roedel
2018-07-19 23:24   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:40 ` [PATCH 13/39] x86/entry/32: Add PTI cr3 switches to NMI handler code Joerg Roedel
2018-07-19 23:25   ` [tip:x86/pti] x86/entry/32: Add PTI CR3 " tip-bot for Joerg Roedel
2018-07-18  9:40 ` [PATCH 14/39] x86/entry: Rename update_sp0 to update_task_stack Joerg Roedel
2018-07-19 23:25   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:40 ` [PATCH 15/39] x86/pgtable: Rename pti_set_user_pgd to pti_set_user_pgtbl Joerg Roedel
2018-07-19 23:26   ` [tip:x86/pti] x86/pgtable: Rename pti_set_user_pgd() to pti_set_user_pgtbl() tip-bot for Joerg Roedel
2018-07-18  9:40 ` [PATCH 16/39] x86/pgtable/pae: Unshare kernel PMDs when PTI is enabled Joerg Roedel
2018-07-19 23:26   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:40 ` [PATCH 17/39] x86/pgtable/32: Allocate 8k page-tables " Joerg Roedel
2018-07-19 23:27   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:40 ` [PATCH 18/39] x86/pgtable: Move pgdp kernel/user conversion functions to pgtable.h Joerg Roedel
2018-07-19 23:27   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:40 ` [PATCH 19/39] x86/pgtable: Move pti_set_user_pgtbl() " Joerg Roedel
2018-07-19 23:28   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:40 ` [PATCH 20/39] x86/pgtable: Move two more functions from pgtable_64.h " Joerg Roedel
2018-07-19 23:28   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:40 ` [PATCH 21/39] x86/mm/pae: Populate valid user PGD entries Joerg Roedel
2018-07-19 23:29   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:40 ` [PATCH 22/39] x86/mm/pae: Populate the user page-table with user pgd's Joerg Roedel
2018-07-19 23:30   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:41 ` [PATCH 23/39] x86/mm/legacy: " Joerg Roedel
2018-07-19 23:30   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:41 ` [PATCH 24/39] x86/mm/pti: Add an overflow check to pti_clone_pmds() Joerg Roedel
2018-07-19 23:31   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:41 ` [PATCH 25/39] x86/mm/pti: Define X86_CR3_PTI_PCID_USER_BIT on x86_32 Joerg Roedel
2018-07-19 23:31   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:41 ` [PATCH 26/39] x86/mm/pti: Clone CPU_ENTRY_AREA on PMD level " Joerg Roedel
2018-07-19 23:32   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:41 ` [PATCH 27/39] x86/mm/pti: Make pti_clone_kernel_text() compile on 32 bit Joerg Roedel
2018-07-19 23:32   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:41 ` [PATCH 28/39] x86/mm/pti: Keep permissions when cloning kernel text in pti_clone_kernel_text() Joerg Roedel
2018-07-19 23:33   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:41 ` [PATCH 29/39] x86/mm/pti: Introduce pti_finalize() Joerg Roedel
2018-07-19 23:33   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:41 ` [PATCH 30/39] x86/mm/pti: Clone entry-text again in pti_finalize() Joerg Roedel
2018-07-19 23:34   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:41 ` [PATCH 31/39] x86/mm/dump_pagetables: Define INIT_PGD Joerg Roedel
2018-07-19 23:34   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:41 ` [PATCH 32/39] x86/pgtable/pae: Use separate kernel PMDs for user page-table Joerg Roedel
2018-07-19 23:35   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-10-05 14:06   ` [PATCH 32/39] " Arnd Bergmann
2018-07-18  9:41 ` [PATCH 33/39] x86/ldt: Reserve address-space range on 32 bit for the LDT Joerg Roedel
2018-07-19 23:35   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:41 ` [PATCH 34/39] x86/ldt: Define LDT_END_ADDR Joerg Roedel
2018-07-19 23:36   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:41 ` [PATCH 35/39] x86/ldt: Split out sanity check in map_ldt_struct() Joerg Roedel
2018-07-19 23:36   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:41 ` [PATCH 36/39] x86/ldt: Enable LDT user-mapping for PAE Joerg Roedel
2018-07-19 23:37   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:41 ` [PATCH 37/39] x86/pti: Allow CONFIG_PAGE_TABLE_ISOLATION for x86_32 Joerg Roedel
2018-07-19 23:37   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:41 ` [PATCH 38/39] x86/mm/pti: Add Warning when booting on a PCID capable CPU Joerg Roedel
2018-07-19 23:38   ` [tip:x86/pti] " tip-bot for Joerg Roedel
2018-07-18  9:41 ` [PATCH 39/39] x86/entry/32: Add debug code to check entry/exit cr3 Joerg Roedel
2018-07-19 23:38   ` [tip:x86/pti] x86/entry/32: Add debug code to check entry/exit CR3 tip-bot for Joerg Roedel
2018-07-18 11:59 ` [PATCH 00/39 v8] PTI support for x86-32 Pavel Machek
2018-07-19 23:21 ` Thomas Gleixner
2018-07-20  7:59   ` Joerg Roedel

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