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From: Andy Lutomirski <luto@kernel.org>
To: x86@kernel.org, linux-kernel@vger.kernel.org
Cc: "Frédéric Weisbecker" <fweisbec@gmail.com>,
	"Rik van Riel" <riel@redhat.com>,
	"Oleg Nesterov" <oleg@redhat.com>,
	"Denys Vlasenko" <vda.linux@googlemail.com>,
	"Borislav Petkov" <bp@alien8.de>,
	"Kees Cook" <keescook@chromium.org>,
	"Brian Gerst" <brgerst@gmail.com>,
	paulmck@linux.vnet.ibm.com, "Andy Lutomirski" <luto@kernel.org>
Subject: [PATCH v5 10/17] x86/entry/64: Really create an error-entry-from-usermode code path
Date: Fri,  3 Jul 2015 12:44:27 -0700
Message-ID: <91e17891e49fa3d61357eadc451529ad48143ee1.1435952415.git.luto@kernel.org> (raw)
In-Reply-To: <cover.1435952415.git.luto@kernel.org>

In 539f51136500 ("x86/asm/entry/64: Disentangle error_entry/exit
gsbase/ebx/usermode code"), I arranged the code slightly wrong --
IRET faults would skip the code path that was intended to execute on
all error entries from user mode.  Fix it up.

While we're at it, make all the labels in error_entry local.

This does not fix a bug, but we'll need it, and it slightly shrinks
the code.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/entry/entry_64.S | 28 ++++++++++++++++------------
 1 file changed, 16 insertions(+), 12 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 141a5d49dddc..ccfcba90de6e 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1143,12 +1143,17 @@ ENTRY(error_entry)
 	SAVE_EXTRA_REGS 8
 	xorl	%ebx, %ebx
 	testb	$3, CS+8(%rsp)
-	jz	error_kernelspace
+	jz	.Lerror_kernelspace
 
-	/* We entered from user mode */
+.Lerror_entry_from_usermode_swapgs:
+	/*
+	 * We entered from user mode or we're pretending to have entered
+	 * from user mode due to an IRET fault.
+	 */
 	SWAPGS
 
-error_entry_done:
+.Lerror_entry_from_usermode_after_swapgs:
+.Lerror_entry_done:
 	TRACE_IRQS_OFF
 	ret
 
@@ -1158,31 +1163,30 @@ error_entry_done:
 	 * truncated RIP for IRET exceptions returning to compat mode. Check
 	 * for these here too.
 	 */
-error_kernelspace:
+.Lerror_kernelspace:
 	incl	%ebx
 	leaq	native_irq_return_iret(%rip), %rcx
 	cmpq	%rcx, RIP+8(%rsp)
-	je	error_bad_iret
+	je	.Lerror_bad_iret
 	movl	%ecx, %eax			/* zero extend */
 	cmpq	%rax, RIP+8(%rsp)
-	je	bstep_iret
+	je	.Lbstep_iret
 	cmpq	$gs_change, RIP+8(%rsp)
-	jne	error_entry_done
+	jne	.Lerror_entry_done
 
 	/*
 	 * hack: gs_change can fail with user gsbase.  If this happens, fix up
 	 * gsbase and proceed.  We'll fix up the exception and land in
 	 * gs_change's error handler with kernel gsbase.
 	 */
-	SWAPGS
-	jmp	error_entry_done
+	jmp	.Lerror_entry_from_usermode_swapgs
 
-bstep_iret:
+.Lbstep_iret:
 	/* Fix truncated RIP */
 	movq	%rcx, RIP+8(%rsp)
 	/* fall through */
 
-error_bad_iret:
+.Lerror_bad_iret:
 	/*
 	 * We came from an IRET to user mode, so we have user gsbase.
 	 * Switch to kernel gsbase:
@@ -1198,7 +1202,7 @@ error_bad_iret:
 	call	fixup_bad_iret
 	mov	%rax, %rsp
 	decl	%ebx
-	jmp	error_entry_done
+	jmp	.Lerror_entry_from_usermode_after_swapgs
 END(error_entry)
 
 
-- 
2.4.3


  parent reply index

Thread overview: 70+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-07-03 19:44 [PATCH v5 00/17] x86: Rewrite exit-to-userspace code Andy Lutomirski
2015-07-03 19:44 ` [PATCH v5 01/17] selftests/x86: Add a test for 32-bit fast syscall arg faults Andy Lutomirski
2015-07-07 10:49   ` [tip:x86/asm] x86/entry, " tip-bot for Andy Lutomirski
2015-07-03 19:44 ` [PATCH v5 02/17] x86/entry/64/compat: Fix bad fast syscall arg failure path Andy Lutomirski
2015-07-07 10:49   ` [tip:x86/asm] " tip-bot for Andy Lutomirski
2015-07-03 19:44 ` [PATCH v5 03/17] uml: Fix do_signal() prototype Andy Lutomirski
2015-07-07 10:49   ` [tip:x86/asm] um: " tip-bot for Ingo Molnar
2015-07-03 19:44 ` [PATCH v5 04/17] context_tracking: Add ct_state and CT_WARN_ON Andy Lutomirski
2015-07-07 10:50   ` [tip:x86/asm] context_tracking: Add ct_state() and CT_WARN_ON() tip-bot for Andy Lutomirski
2015-07-03 19:44 ` [PATCH v5 05/17] notifiers: Assert that RCU is watching in notify_die Andy Lutomirski
2015-07-07 10:50   ` [tip:x86/asm] notifiers, RCU: Assert that RCU is watching in notify_die() tip-bot for Andy Lutomirski
2015-07-03 19:44 ` [PATCH v5 06/17] x86: Move C entry and exit code to arch/x86/entry/common.c Andy Lutomirski
2015-07-07 10:50   ` [tip:x86/asm] x86/entry: Move C entry and exit code to arch/x86/ entry/common.c tip-bot for Andy Lutomirski
2015-07-03 19:44 ` [PATCH v5 07/17] x86/traps: Assert that we're in CONTEXT_KERNEL in exception entries Andy Lutomirski
2015-07-07 10:51   ` [tip:x86/asm] x86/traps, context_tracking: Assert that we' re " tip-bot for Andy Lutomirski
2015-07-03 19:44 ` [PATCH v5 08/17] x86/entry: Add enter_from_user_mode and use it in syscalls Andy Lutomirski
2015-07-07 10:51   ` [tip:x86/asm] x86/entry: Add enter_from_user_mode() " tip-bot for Andy Lutomirski
2015-07-14 23:00     ` Frederic Weisbecker
2015-07-14 23:04       ` Andy Lutomirski
2015-07-14 23:28         ` Frederic Weisbecker
2015-12-21 20:50   ` [PATCH v5 08/17] x86/entry: Add enter_from_user_mode " Sasha Levin
2015-12-21 22:44     ` Andy Lutomirski
2015-07-03 19:44 ` [PATCH v5 09/17] x86/entry: Add new, comprehensible entry and exit hooks Andy Lutomirski
2015-07-07 10:51   ` [tip:x86/asm] x86/entry: Add new, comprehensible entry and exit handlers written in C tip-bot for Andy Lutomirski
2015-07-14 23:07     ` Frederic Weisbecker
2015-07-15 19:56       ` Linus Torvalds
2015-07-15 20:46         ` Andy Lutomirski
2015-07-15 21:25           ` [PATCH] x86/entry: Fix _TIF_USER_RETURN_NOTIFY check in prepare_exit_to_usermode Andy Lutomirski
2015-07-18  3:25             ` [tip:x86/asm] " tip-bot for Andy Lutomirski
2015-07-03 19:44 ` Andy Lutomirski [this message]
2015-07-07 10:52   ` [tip:x86/asm] x86/entry/64: Really create an error-entry-from-usermode code path tip-bot for Andy Lutomirski
2015-07-03 19:44 ` [PATCH v5 11/17] x86/entry/64: Migrate 64-bit and compat syscalls to new exit hooks Andy Lutomirski
2015-07-07 10:52   ` [tip:x86/asm] x86/entry/64: Migrate 64-bit and compat syscalls to the new exit handlers and remove old assembly code tip-bot for Andy Lutomirski
2015-07-03 19:44 ` [PATCH v5 12/17] x86/asm/entry/64: Save all regs on interrupt entry Andy Lutomirski
2015-07-07 10:52   ` [tip:x86/asm] " tip-bot for Andy Lutomirski
2015-07-03 19:44 ` [PATCH v5 13/17] x86/asm/entry/64: Simplify irq stack pt_regs handling Andy Lutomirski
2015-07-07 10:53   ` [tip:x86/asm] x86/asm/entry/64: Simplify IRQ " tip-bot for Andy Lutomirski
2015-07-03 19:44 ` [PATCH v5 14/17] x86/asm/entry/64: Migrate error and interrupt exit work to C Andy Lutomirski
2015-07-07 10:53   ` [tip:x86/asm] x86/asm/entry/64: Migrate error and IRQ exit work to C and remove old assembly code tip-bot for Andy Lutomirski
2015-08-11 22:18     ` Frederic Weisbecker
2015-08-11 22:25       ` Andy Lutomirski
2015-08-11 22:49         ` Frederic Weisbecker
2015-08-11 22:59           ` Andy Lutomirski
2015-08-12  1:02             ` Paul E. McKenney
2015-08-12 13:13             ` Frederic Weisbecker
2015-08-11 22:38     ` Frederic Weisbecker
2015-08-11 22:51       ` Andy Lutomirski
2015-08-11 23:22         ` Frederic Weisbecker
2015-08-11 23:33           ` Andy Lutomirski
2015-08-12 13:32             ` Frederic Weisbecker
2015-08-12 14:59               ` Andy Lutomirski
2015-08-18 22:34                 ` Frederic Weisbecker
2015-08-18 22:40                   ` Andy Lutomirski
2015-08-19 17:18                     ` Frederic Weisbecker
2015-08-19 18:02                       ` Andy Lutomirski
2015-07-03 19:44 ` [PATCH v5 15/17] x86/entry: Remove exception_enter from most trap handlers Andy Lutomirski
2015-07-07 10:53   ` [tip:x86/asm] x86/entry: Remove exception_enter() " tip-bot for Andy Lutomirski
2015-07-03 19:44 ` [PATCH v5 16/17] x86/entry: Remove SCHEDULE_USER and asm/context-tracking.h Andy Lutomirski
2015-07-07 10:54   ` [tip:x86/asm] x86/entry: Remove SCHEDULE_USER and asm/ context-tracking.h tip-bot for Andy Lutomirski
2015-07-03 19:44 ` [PATCH v5 17/17] x86/irq: Document how IRQ context tracking works and add an assertion Andy Lutomirski
2015-07-07 10:54   ` [tip:x86/asm] x86/irq, context_tracking: Document how IRQ context tracking works and add an RCU assertion tip-bot for Andy Lutomirski
2015-07-14 23:26     ` Frederic Weisbecker
2015-07-14 23:33       ` Andy Lutomirski
2015-07-18 13:23         ` Frederic Weisbecker
2015-07-18 14:10           ` Paul E. McKenney
2015-07-07 11:12 ` [PATCH v5 00/17] x86: Rewrite exit-to-userspace code Ingo Molnar
2015-07-07 16:03   ` Andy Lutomirski
2015-07-07 17:55     ` [PATCH] x86/entry/64: Fix warning on compat syscalls with CONFIG_AUDITSYSCALL=n Andy Lutomirski
2015-07-08  9:57       ` [tip:x86/asm] x86/entry/64: Fix IRQ state confusion and related warning on compat syscalls with CONFIG_AUDITSYSCALL =n tip-bot for Andy Lutomirski
2015-07-08 19:12       ` tip-bot for Andy Lutomirski

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