From: Andy Lutomirski <luto@kernel.org>
To: x86@kernel.org
Cc: linux-kernel@vger.kernel.org, Borislav Petkov <bp@alien8.de>,
Brian Gerst <brgerst@gmail.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Juergen Gross <jgross@suse.com>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Kees Cook <keescook@chromium.org>,
Andy Lutomirski <luto@kernel.org>
Subject: [RFC 04/17] x86/asm/64: Simplify reg restore code in the standard IRET paths
Date: Wed, 6 Sep 2017 14:36:49 -0700 [thread overview]
Message-ID: <704276f098b124c6bbe3a6dab3815736c7d01c4a.1504733277.git.luto@kernel.org> (raw)
In-Reply-To: <cover.1504733277.git.luto@kernel.org>
In-Reply-To: <cover.1504733277.git.luto@kernel.org>
The old code restored all the registers with movq instead of pop.
In theory, this was done because some CPUs have higher movq
throughput, but any gain there would be tiny and is almost certainly
outweighed by the higher text size.
This saves 96 bytes of text.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
arch/x86/entry/calling.h | 9 +++++++++
arch/x86/entry/entry_64.S | 28 ++++++++++++++++++++++------
2 files changed, 31 insertions(+), 6 deletions(-)
diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h
index 05ed3d393da7..0a2c73fe2cfc 100644
--- a/arch/x86/entry/calling.h
+++ b/arch/x86/entry/calling.h
@@ -147,6 +147,15 @@ For 32-bit we have the following conventions - kernel is built with
movq 5*8+\offset(%rsp), %rbx
.endm
+ .macro POP_EXTRA_REGS
+ popq %r15
+ popq %r14
+ popq %r13
+ popq %r12
+ popq %rbp
+ popq %rbx
+ .endm
+
.macro RESTORE_C_REGS_HELPER rstor_rax=1, rstor_rcx=1, rstor_r11=1, rstor_r8910=1, rstor_rdx=1
.if \rstor_r11
movq 6*8(%rsp), %r11
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 2cd01ed9cd59..7f1a83b17b4a 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -521,9 +521,17 @@ GLOBAL(retint_user)
GLOBAL(swapgs_restore_regs_and_return_to_usermode)
SWAPGS
- RESTORE_EXTRA_REGS
- RESTORE_C_REGS
- REMOVE_PT_GPREGS_FROM_STACK 8
+ POP_EXTRA_REGS
+ popq %r11
+ popq %r10
+ popq %r9
+ popq %r8
+ popq %rax
+ popq %rcx
+ popq %rdx
+ popq %rsi
+ popq %rdi
+ addq $8, %rsp
INTERRUPT_RETURN
@@ -546,9 +554,17 @@ retint_kernel:
TRACE_IRQS_IRETQ
GLOBAL(restore_regs_and_return_to_kernel)
- RESTORE_EXTRA_REGS
- RESTORE_C_REGS
- REMOVE_PT_GPREGS_FROM_STACK 8
+ POP_EXTRA_REGS
+ popq %r11
+ popq %r10
+ popq %r9
+ popq %r8
+ popq %rax
+ popq %rcx
+ popq %rdx
+ popq %rsi
+ popq %rdi
+ addq $8, %rsp
INTERRUPT_RETURN
ENTRY(native_iret)
--
2.13.5
next prev parent reply other threads:[~2017-09-06 21:40 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-06 21:36 [RFC 00/17] Pile o' entry stack changes Andy Lutomirski
2017-09-06 21:36 ` [RFC 01/17] x86/asm/64: Remove the restore_c_regs_and_iret label Andy Lutomirski
2017-09-07 9:40 ` Borislav Petkov
2017-09-07 9:46 ` Ingo Molnar
2017-09-07 9:49 ` Ingo Molnar
2017-09-07 9:57 ` Borislav Petkov
2017-09-07 10:29 ` Ingo Molnar
2017-09-06 21:36 ` [RFC 02/17] x86/asm/64: Split the iret-to-user and iret-to-kernel paths Andy Lutomirski
2017-09-06 21:36 ` [RFC 03/17] x86/asm/64: Move SWAPGS into the common iret-to-usermode path Andy Lutomirski
2017-09-06 21:36 ` Andy Lutomirski [this message]
2017-09-12 20:05 ` [RFC 04/17] x86/asm/64: Simplify reg restore code in the standard IRET paths Josh Poimboeuf
2017-09-06 21:36 ` [RFC 05/17] x86/asm/64: Shrink paranoid_exit_restore and make labels local Andy Lutomirski
2017-09-06 21:36 ` [RFC 06/17] x86/asm/64: Use pop instead of movq in syscall_return_via_sysret Andy Lutomirski
2017-09-06 21:36 ` [RFC 07/17] x86/asm/64: Merge the fast and slow SYSRET paths Andy Lutomirski
2017-09-06 21:36 ` [RFC 08/17] x86/asm/64: De-Xen-ify our NMI code Andy Lutomirski
2017-09-07 9:34 ` Juergen Gross
2017-09-07 18:38 ` Andy Lutomirski
2017-09-08 4:26 ` Juergen Gross
2017-09-06 21:36 ` [RFC 09/17] x86/asm/32: Pull MSR_IA32_SYSENTER_CS update code out of native_load_sp0() Andy Lutomirski
2017-09-12 20:06 ` Josh Poimboeuf
2017-09-06 21:36 ` [RFC 10/17] x86/asm/64: Pass sp0 directly to load_sp0() Andy Lutomirski
2017-09-06 21:36 ` [RFC 11/17] x86/asm: Add task_top_of_stack() to find the top of a task's stack Andy Lutomirski
2017-09-06 21:36 ` [RFC 12/17] x86/xen/64: Clean up SP code in cpu_initialize_context() Andy Lutomirski
2017-09-12 20:09 ` Josh Poimboeuf
2017-09-06 21:36 ` [RFC 13/17] x86/boot/64: Stop initializing TSS.sp0 at boot Andy Lutomirski
2017-09-06 21:36 ` [RFC 14/17] x86/asm/64: Remove all remaining direct thread_struct::sp0 reads Andy Lutomirski
2017-09-06 21:37 ` [RFC 15/17] x86/boot/32: Fix cpu_current_top_of_stack initialization at boot Andy Lutomirski
2017-09-06 21:37 ` [RFC 16/17] x86/asm/64: Remove thread_struct::sp0 Andy Lutomirski
2017-09-06 21:37 ` [RFC 17/17] x86/traps: Use a new on_thread_stack() helper to clean up an assertion Andy Lutomirski
2017-09-12 20:11 ` Josh Poimboeuf
2017-09-12 20:25 ` Andrew Cooper
2017-09-06 22:16 ` [RFC 00/17] Pile o' entry stack changes Andi Kleen
2017-09-07 0:01 ` Andy Lutomirski
2017-09-07 7:04 ` Ingo Molnar
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