[tip:x86/asm] x86/asm/entry/64: Save all regs on interrupt entry

tip-bot for Andy Lutomirski
2015-07-07T10:53:55Z

Commit-ID: ff467594f2a4be01a0fa5e9ffc223fa930d232dd
Gitweb: http://git.kernel.org/tip/ff467594f2a4be01a0fa5e9ffc223fa930d232dd
Author: Andy Lutomirski <luto@kernel.org>
AuthorDate: Fri, 3 Jul 2015 12:44:29 -0700
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 7 Jul 2015 10:59:07 +0200

x86/asm/entry/64: Save all regs on interrupt entry

To prepare for the big rewrite of the error and interrupt exit
paths, we will need pt_regs completely filled in.

It's already completely filled in when error_exit runs, so rearrange
interrupt handling to match it. This will slow down interrupt
handling very slightly (eight instructions), but the
simplification it enables will be more than worth it.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Denys Vlasenko <vda.linux@googlemail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: paulmck@linux.vnet.ibm.com
Link: http://lkml.kernel.org/r/d8a766a7f558b30e6e01352854628a2d9943460c.1435952415.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/entry/calling.h | 3 ---
arch/x86/entry/entry_64.S | 29 +++++++++--------------------
2 files changed, 9 insertions(+), 23 deletions(-)

diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h
index 519207f..3c71dd9 100644
--- a/arch/x86/entry/calling.h
+++ b/arch/x86/entry/calling.h
@@ -135,9 +135,6 @@ For 32-bit we have the following conventions - kernel is built with
movq %rbp, 4*8+\offset(%rsp)
movq %rbx, 5*8+\offset(%rsp)
.endm
- .macro SAVE_EXTRA_REGS_RBP offset=0
- movq %rbp, 4*8+\offset(%rsp)
- .endm

.macro RESTORE_EXTRA_REGS offset=0
movq 0*8+\offset(%rsp), %r15
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 4ca5b78..65029f4 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -502,21 +502,13 @@ END(irq_entries_start)
/* 0(%rsp): ~(interrupt number) */
.macro interrupt func
cld
- /*
- * Since nothing in interrupt handling code touches r12...r15 members
- * of "struct pt_regs", and since interrupts can nest, we can save
- * four stack slots and simultaneously provide
- * an unwind-friendly stack layout by saving "truncated" pt_regs
- * exactly up to rbp slot, without these members.
- */
- ALLOC_PT_GPREGS_ON_STACK -RBP
- SAVE_C_REGS -RBP
- /* this goes to 0(%rsp) for unwinder, not for saving the value: */
- SAVE_EXTRA_REGS_RBP -RBP
+ ALLOC_PT_GPREGS_ON_STACK
+ SAVE_C_REGS
+ SAVE_EXTRA_REGS

- leaq -RBP(%rsp), %rdi /* arg1 for \func (pointer to pt_regs) */
+ movq %rsp,%rdi /* arg1 for \func (pointer to pt_regs) */

- testb $3, CS-RBP(%rsp)
+ testb $3, CS(%rsp)
jz 1f
SWAPGS
1:
@@ -553,9 +545,7 @@ ret_from_intr:
decl PER_CPU_VAR(irq_count)

/* Restore saved previous stack */
- popq %rsi
- /* return code expects complete pt_regs - adjust rsp accordingly: */
- leaq -RBP(%rsi), %rsp
+ popq %rsp

testb $3, CS(%rsp)
jz retint_kernel
@@ -580,7 +570,7 @@ retint_swapgs: /* return to user-space */
TRACE_IRQS_IRETQ

SWAPGS
- jmp restore_c_regs_and_iret
+ jmp restore_regs_and_iret

/* Returning to kernel space */
retint_kernel:
@@ -604,6 +594,8 @@ retint_kernel:
* At this label, code paths which return to kernel and to user,
* which come from interrupts/exception and from syscalls, merge.
*/
+restore_regs_and_iret:
+ RESTORE_EXTRA_REGS
restore_c_regs_and_iret:
RESTORE_C_REGS
REMOVE_PT_GPREGS_FROM_STACK 8
@@ -674,12 +666,10 @@ retint_signal:
jz retint_swapgs
TRACE_IRQS_ON
ENABLE_INTERRUPTS(CLBR_NONE)
- SAVE_EXTRA_REGS
movq $-1, ORIG_RAX(%rsp)
xorl %esi, %esi /* oldset */
movq %rsp, %rdi /* &pt_regs */
call do_notify_resume
- RESTORE_EXTRA_REGS
DISABLE_INTERRUPTS(CLBR_NONE)
TRACE_IRQS_OFF
GET_THREAD_INFO(%rcx)
@@ -1160,7 +1150,6 @@ END(error_entry)
*/
ENTRY(error_exit)
movl %ebx, %eax
- RESTORE_EXTRA_REGS
DISABLE_INTERRUPTS(CLBR_NONE)
TRACE_IRQS_OFF
testl %eax, %eax