[PATCH 4.9 35/38] Revert "x86/entry/64: Add missing irqflags tracing to native_load_gs_index()"

Greg Kroah-Hartman
2017-12-04T16:03:07Z

This reverts commit 0d794d0d018f23fb09c50f6ae26868bd6ae343d6 which is
commit 0d794d0d018f23fb09c50f6ae26868bd6ae343d6 upstream.

Andy writes:

I think the thing to do is to revert the patch from -stable.
The bug it fixes is very minor, and the regression is that it
made a pre-existing bug in some nearly-undebuggable core resume
code much easier to hit. I don't feel comfortable with a
backport of the latter fix until it has a good long soak in
Linus' tree.

Reported-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/entry/entry_64.S | 10 ++--------
1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index be9df513141e..e7b0e7ff4c58 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -54,19 +54,15 @@ ENTRY(native_usergs_sysret64)
ENDPROC(native_usergs_sysret64)
#endif /* CONFIG_PARAVIRT */

-.macro TRACE_IRQS_FLAGS flags:req
+.macro TRACE_IRQS_IRETQ
#ifdef CONFIG_TRACE_IRQFLAGS
- bt $9, \flags /* interrupts off? */
+ bt $9, EFLAGS(%rsp) /* interrupts off? */
jnc 1f
TRACE_IRQS_ON
1:
#endif
.endm

-.macro TRACE_IRQS_IRETQ
- TRACE_IRQS_FLAGS EFLAGS(%rsp)
-.endm
-
/*
* When dynamic function tracer is enabled it will add a breakpoint
* to all locations that it is about to modify, sync CPUs, update
@@ -872,13 +868,11 @@ idtentry simd_coprocessor_error do_simd_coprocessor_error has_error_code=0
ENTRY(native_load_gs_index)
pushfq
DISABLE_INTERRUPTS(CLBR_ANY & ~CLBR_RDI)
- TRACE_IRQS_OFF
SWAPGS
.Lgs_change:
movl %edi, %gs
2: ALTERNATIVE "", "mfence", X86_BUG_SWAPGS_FENCE
SWAPGS
- TRACE_IRQS_FLAGS (%rsp)
popfq
ret
END(native_load_gs_index)
--
2.15.1