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SubjectRe: [PATCH 3/3] x86/mm, tracing: Fix CR2 corruption
On Thu, Jul 04, 2019 at 12:05:22AM +0200, Peter Zijlstra wrote:
> On Wed, Jul 03, 2019 at 04:47:01PM -0400, Steven Rostedt wrote:

> > Yeah, looks like we might be missing a TRACE_IRQS_OFF from the
> > from_usermode_stack_switch path.
>
> Oh bugger, there's a second error_entry call.

---
Subject: x86/entry/64: Simplify idtentry a little
From: Peter Zijlstra <peterz@infradead.org>
Date: Thu Jul 4 10:55:11 CEST 2019

There's a bunch of duplication in idtentry, namely the
.Lfrom_usermode_switch_stack is an explicit paranoid=0 copy of the
normal flow.

Make this explicit by creating a (idtentry_part) helper macro.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/entry/entry_64.S | 100 +++++++++++++++++++++-------------------------
1 file changed, 47 insertions(+), 53 deletions(-)

--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -865,6 +865,51 @@ apicinterrupt IRQ_WORK_VECTOR irq_work
*/
#define CPU_TSS_IST(x) PER_CPU_VAR(cpu_tss_rw) + (TSS_ist + (x) * 8)

+.macro idtentry_part has_error_code:req paranoid:req shift_ist:-1 ist_offset=0
+
+ .if \paranoid
+ call paranoid_entry
+ /* returned flag: ebx=0: need swapgs on exit, ebx=1: don't need it */
+ .else
+ call error_entry
+ .endif
+ UNWIND_HINT_REGS
+
+ .if \paranoid
+ .if \shift_ist != -1
+ TRACE_IRQS_OFF_DEBUG /* reload IDT in case of recursion */
+ .else
+ TRACE_IRQS_OFF
+ .endif
+ .endif
+
+ movq %rsp, %rdi /* pt_regs pointer */
+
+ .if \has_error_code
+ movq ORIG_RAX(%rsp), %rsi /* get error code */
+ movq $-1, ORIG_RAX(%rsp) /* no syscall to restart */
+ .else
+ xorl %esi, %esi /* no error code */
+ .endif
+
+ .if \shift_ist != -1
+ subq $\ist_offset, CPU_TSS_IST(\shift_ist)
+ .endif
+
+ call \do_sym
+
+ .if \shift_ist != -1
+ addq $\ist_offset, CPU_TSS_IST(\shift_ist)
+ .endif
+
+ .if \paranoid
+ jmp paranoid_exit
+ .else
+ jmp error_exit
+ .endif
+
+.endm
+
/**
* idtentry - Generate an IDT entry stub
* @sym: Name of the generated entry point
@@ -935,46 +980,7 @@ ENTRY(\sym)
.Lfrom_usermode_no_gap_\@:
.endif

- .if \paranoid
- call paranoid_entry
- .else
- call error_entry
- .endif
- UNWIND_HINT_REGS
- /* returned flag: ebx=0: need swapgs on exit, ebx=1: don't need it */
-
- .if \paranoid
- .if \shift_ist != -1
- TRACE_IRQS_OFF_DEBUG /* reload IDT in case of recursion */
- .else
- TRACE_IRQS_OFF
- .endif
- .endif
-
- movq %rsp, %rdi /* pt_regs pointer */
-
- .if \has_error_code
- movq ORIG_RAX(%rsp), %rsi /* get error code */
- movq $-1, ORIG_RAX(%rsp) /* no syscall to restart */
- .else
- xorl %esi, %esi /* no error code */
- .endif
-
- .if \shift_ist != -1
- subq $\ist_offset, CPU_TSS_IST(\shift_ist)
- .endif
-
- call \do_sym
-
- .if \shift_ist != -1
- addq $\ist_offset, CPU_TSS_IST(\shift_ist)
- .endif
-
- .if \paranoid
- jmp paranoid_exit
- .else
- jmp error_exit
- .endif
+ idtentry_part has_error_code=\has_error_code paranoid=\paranoid shift_ist=\shift_ist ist_offset=\ist_offset

.if \paranoid == 1
/*
@@ -983,21 +989,9 @@ ENTRY(\sym)
* run in real process context if user_mode(regs).
*/
.Lfrom_usermode_switch_stack_\@:
- call error_entry
-
- movq %rsp, %rdi /* pt_regs pointer */
-
- .if \has_error_code
- movq ORIG_RAX(%rsp), %rsi /* get error code */
- movq $-1, ORIG_RAX(%rsp) /* no syscall to restart */
- .else
- xorl %esi, %esi /* no error code */
+ idtentry_part has_error_code=\has_error_code paranoid=0
.endif

- call \do_sym
-
- jmp error_exit
- .endif
_ASM_NOKPROBE(\sym)
END(\sym)
.endm
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