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From: Borislav Petkov <bp@suse.de>
To: Andy Lutomirski <luto@kernel.org>, X86 ML <x86@kernel.org>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Brian Gerst <brgerst@gmail.com>,
	Dave Hansen <dave.hansen@intel.com>,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: [PATCH] x86/entry/64: Shorten TEST instructions
Date: Thu, 2 Nov 2017 13:09:26 +0100	[thread overview]
Message-ID: <20171102120926.4srwerqrr7g72e2k@pd.tnic> (raw)
In-Reply-To: <20171102105018.gdpjhixuf2f5v5e5@pd.tnic>

On Thu, Nov 02, 2017 at 11:50:18AM +0100, Borislav Petkov wrote:
> If these paths are slow and adding a TEST and a Jcc would give us the
> additional sanity-checking, then I don't see any downside to it.

Damn, that really shows. Almost 900K iterations less.

./lseek1_processes -s 50

before: average:11994233
after : average:11134599

So we'll have to remember to enable CONFIG_DEBUG_ENTRY from time to
time. :-\

Ok, let's then only shorten the TEST insns:

---
From: Borislav Petkov <bp@suse.de>
Date: Thu, 2 Nov 2017 13:00:49 +0100
Subject: [PATCH] x86/entry/64: Shorten TEST instructions

Convert TESTL to TESTB and save 3 bytes per callsite.

No functionality change.

Signed-off-by: Borislav Petkov <bp@suse.de>
---
 arch/x86/entry/entry_64.S | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 40e9933a2d33..84263c79a119 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -620,7 +620,7 @@ GLOBAL(retint_user)
 GLOBAL(swapgs_restore_regs_and_return_to_usermode)
 #ifdef CONFIG_DEBUG_ENTRY
 	/* Assert that pt_regs indicates user mode. */
-	testl	$3, CS(%rsp)
+	testb	$3, CS(%rsp)
 	jnz	1f
 	ud2
 1:
@@ -653,7 +653,7 @@ retint_kernel:
 GLOBAL(restore_regs_and_return_to_kernel)
 #ifdef CONFIG_DEBUG_ENTRY
 	/* Assert that pt_regs indicates kernel mode. */
-	testl	$3, CS(%rsp)
+	testb	$3, CS(%rsp)
 	jz	1f
 	ud2
 1:
-- 
2.13.0

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
-- 

  reply	other threads:[~2017-11-02 12:09 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-11-02  7:58 [PATCH v2 00/20] Pile o' entry/exit/sp0 changes Andy Lutomirski
2017-11-02  7:58 ` [PATCH v2 01/20] x86/asm/64: Remove the restore_c_regs_and_iret label Andy Lutomirski
2017-11-02 10:49   ` [tip:x86/asm] x86/entry/64: " tip-bot for Andy Lutomirski
2017-11-02  7:58 ` [PATCH v2 02/20] x86/asm/64: Split the iret-to-user and iret-to-kernel paths Andy Lutomirski
2017-11-02 10:49   ` [tip:x86/asm] x86/entry/64: Split the IRET-to-user and IRET-to-kernel paths tip-bot for Andy Lutomirski
2017-11-02 10:50   ` [PATCH v2 02/20] x86/asm/64: Split the iret-to-user and iret-to-kernel paths Borislav Petkov
2017-11-02 12:09     ` Borislav Petkov [this message]
2017-11-02 12:48       ` [tip:x86/asm] x86/entry/64: Shorten TEST instructions tip-bot for Borislav Petkov
2017-11-02  7:59 ` [PATCH v2 03/20] x86/asm/64: Move SWAPGS into the common iret-to-usermode path Andy Lutomirski
2017-11-02 10:49   ` [tip:x86/asm] x86/entry/64: Move SWAPGS into the common IRET-to-usermode path tip-bot for Andy Lutomirski
2017-11-02  7:59 ` [PATCH v2 04/20] x86/asm/64: Simplify reg restore code in the standard IRET paths Andy Lutomirski
2017-11-02 10:50   ` [tip:x86/asm] x86/entry/64: " tip-bot for Andy Lutomirski
2017-11-02  7:59 ` [PATCH v2 05/20] x86/asm/64: Shrink paranoid_exit_restore and make labels local Andy Lutomirski
2017-11-02 10:50   ` [tip:x86/asm] x86/entry/64: " tip-bot for Andy Lutomirski
2017-11-02  7:59 ` [PATCH v2 06/20] x86/asm/64: Use pop instead of movq in syscall_return_via_sysret Andy Lutomirski
2017-11-02 10:51   ` [tip:x86/asm] x86/entry/64: " tip-bot for Andy Lutomirski
2017-11-02  7:59 ` [PATCH v2 07/20] x86/asm/64: Merge the fast and slow SYSRET paths Andy Lutomirski
2017-11-02 10:51   ` [tip:x86/asm] x86/entry/64: " tip-bot for Andy Lutomirski
2017-11-02  7:59 ` [PATCH v2 08/20] x86/entry/64: Use POP instead of MOV to restore regs on NMI return Andy Lutomirski
2017-11-02 10:51   ` [tip:x86/asm] " tip-bot for Andy Lutomirski
2017-11-02  7:59 ` [PATCH v2 09/20] x86/entry/64: Remove the RESTORE_..._REGS infrastructure Andy Lutomirski
2017-11-02 10:52   ` [tip:x86/asm] " tip-bot for Andy Lutomirski
2017-11-02  7:59 ` [PATCH v2 10/20] xen: add xen nmi trap entry Andy Lutomirski
2017-11-02 10:52   ` [tip:x86/asm] xen, x86/entry/64: Add xen NMI " tip-bot for Juergen Gross
2017-11-02  7:59 ` [PATCH v2 11/20] x86/asm/64: De-Xen-ify our NMI code Andy Lutomirski
2017-11-02 10:53   ` [tip:x86/asm] x86/entry/64: " tip-bot for Andy Lutomirski
2017-11-02  7:59 ` [PATCH v2 12/20] x86/asm/32: Pull MSR_IA32_SYSENTER_CS update code out of native_load_sp0() Andy Lutomirski
2017-11-02 10:53   ` [tip:x86/asm] x86/entry/32: Pull the " tip-bot for Andy Lutomirski
2017-11-02  7:59 ` [PATCH v2 13/20] x86/asm/64: Pass sp0 directly to load_sp0() Andy Lutomirski
2017-11-02  9:48   ` Ingo Molnar
2017-11-02  9:53     ` Ingo Molnar
2017-11-02 10:32     ` Andy Lutomirski
2017-11-02 10:53   ` [tip:x86/asm] x86/entry/64: Pass SP0 " tip-bot for Andy Lutomirski
2017-11-02  7:59 ` [PATCH v2 14/20] x86/asm: Add task_top_of_stack() to find the top of a task's stack Andy Lutomirski
2017-11-02 10:54   ` [tip:x86/asm] x86/entry: " tip-bot for Andy Lutomirski
2017-11-02  7:59 ` [PATCH v2 15/20] x86/xen/64: Clean up SP code in cpu_initialize_context() Andy Lutomirski
2017-11-02  9:56   ` Juergen Gross
2017-11-02 10:54   ` [tip:x86/asm] x86/xen/64, x86/entry/64: " tip-bot for Andy Lutomirski
2017-11-02  7:59 ` [PATCH v2 16/20] x86/boot/64: Stop initializing TSS.sp0 at boot Andy Lutomirski
2017-11-02 10:55   ` [tip:x86/asm] x86/entry/64: " tip-bot for Andy Lutomirski
2017-11-02  7:59 ` [PATCH v2 17/20] x86/asm/64: Remove all remaining direct thread_struct::sp0 reads Andy Lutomirski
2017-11-02 10:55   ` [tip:x86/asm] x86/entry/64: " tip-bot for Andy Lutomirski
2017-11-02  7:59 ` [PATCH v2 18/20] x86/boot/32: Fix cpu_current_top_of_stack initialization at boot Andy Lutomirski
2017-11-02 10:56   ` [tip:x86/asm] x86/entry/32: " tip-bot for Andy Lutomirski
2017-11-02  7:59 ` [PATCH v2 19/20] x86/asm/64: Remove thread_struct::sp0 Andy Lutomirski
2017-11-02 10:56   ` [tip:x86/asm] x86/entry/64: " tip-bot for Andy Lutomirski
2017-11-02  7:59 ` [PATCH v2 20/20] x86/traps: Use a new on_thread_stack() helper to clean up an assertion Andy Lutomirski
2017-11-02 10:56   ` [tip:x86/asm] " tip-bot for Andy Lutomirski

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