4.14-stable review patch. If anyone has any objections, please let me know.
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From: Andy Lutomirski luto@kernel.org
commit 548c3050ea8d16997ae27f9e080a8338a606fc93 upstream.
When I added entry_SYSCALL_64_after_hwframe(), I left TRACE_IRQS_OFF before it. This means that users of entry_SYSCALL_64_after_hwframe() were responsible for invoking TRACE_IRQS_OFF, and the one and only user (Xen, added in the same commit) got it wrong.
I think this would manifest as a warning if a Xen PV guest with CONFIG_DEBUG_LOCKDEP=y were used with context tracking. (The context tracking bit is to cause lockdep to get invoked before we turn IRQs back on.) I haven't tested that for real yet because I can't get a kernel configured like that to boot at all on Xen PV.
Move TRACE_IRQS_OFF below the label.
Signed-off-by: Andy Lutomirski luto@kernel.org Cc: Boris Ostrovsky boris.ostrovsky@oracle.com 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: Juergen Gross jgross@suse.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Gleixner tglx@linutronix.de Fixes: 8a9949bc71a7 ("x86/xen/64: Rearrange the SYSCALL entries") Link: http://lkml.kernel.org/r/9150aac013b7b95d62c2336751d5b6e91d2722aa.1511325444... Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/entry/entry_64.S | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -148,8 +148,6 @@ ENTRY(entry_SYSCALL_64) movq %rsp, PER_CPU_VAR(rsp_scratch) movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp
- TRACE_IRQS_OFF - /* Construct struct pt_regs on stack */ pushq $__USER_DS /* pt_regs->ss */ pushq PER_CPU_VAR(rsp_scratch) /* pt_regs->sp */ @@ -170,6 +168,8 @@ GLOBAL(entry_SYSCALL_64_after_hwframe) sub $(6*8), %rsp /* pt_regs->bp, bx, r12-15 not saved */ UNWIND_HINT_REGS extra=0
+ TRACE_IRQS_OFF + /* * If we need to do entry work or if we guess we'll need to do * exit work, go straight to the slow path.