From 2140a9942b84dd4bf559dd1215b8f43c36ece5b5 Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Fri, 3 Feb 2017 02:03:25 -0700 Subject: [PATCH] x86/entry/64: Relax pvops stub clobber specifications Except for the error_exit case, none of the code paths following the {DIS,EN}ABLE_INTERRUPTS() invocations being modified here make any assumptions on register values, so all registers can be clobbered there. In the error_exit case a minor adjustment to register usage (at once eliminating an instruction) also allows for this to be true. Signed-off-by: Jan Beulich Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/5894556D02000078001366D3@prv-mh.provo.novell.com Signed-off-by: Ingo Molnar --- arch/x86/entry/entry_64.S | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 044d18ebc43c..d2b2a2948ffe 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -212,7 +212,7 @@ entry_SYSCALL_64_fastpath: * If we see that no exit work is required (which we are required * to check with IRQs off), then we can go straight to SYSRET64. */ - DISABLE_INTERRUPTS(CLBR_NONE) + DISABLE_INTERRUPTS(CLBR_ANY) TRACE_IRQS_OFF movq PER_CPU_VAR(current_task), %r11 testl $_TIF_ALLWORK_MASK, TASK_TI_flags(%r11) @@ -233,7 +233,7 @@ entry_SYSCALL_64_fastpath: * raise(3) will trigger this, for example. IRQs are off. */ TRACE_IRQS_ON - ENABLE_INTERRUPTS(CLBR_NONE) + ENABLE_INTERRUPTS(CLBR_ANY) SAVE_EXTRA_REGS movq %rsp, %rdi call syscall_return_slowpath /* returns with IRQs disabled */ @@ -343,7 +343,7 @@ ENTRY(stub_ptregs_64) * Called from fast path -- disable IRQs again, pop return address * and jump to slow path */ - DISABLE_INTERRUPTS(CLBR_NONE) + DISABLE_INTERRUPTS(CLBR_ANY) TRACE_IRQS_OFF popq %rax jmp entry_SYSCALL64_slow_path @@ -518,7 +518,7 @@ common_interrupt: interrupt do_IRQ /* 0(%rsp): old RSP */ ret_from_intr: - DISABLE_INTERRUPTS(CLBR_NONE) + DISABLE_INTERRUPTS(CLBR_ANY) TRACE_IRQS_OFF decl PER_CPU_VAR(irq_count) @@ -1051,7 +1051,7 @@ END(paranoid_entry) * On entry, ebx is "no swapgs" flag (1: don't need swapgs, 0: need it) */ ENTRY(paranoid_exit) - DISABLE_INTERRUPTS(CLBR_NONE) + DISABLE_INTERRUPTS(CLBR_ANY) TRACE_IRQS_OFF_DEBUG testl %ebx, %ebx /* swapgs needed? */ jnz paranoid_exit_no_swapgs @@ -1156,10 +1156,9 @@ END(error_entry) * 0: user gsbase is loaded, we need SWAPGS and standard preparation for return to usermode */ ENTRY(error_exit) - movl %ebx, %eax - DISABLE_INTERRUPTS(CLBR_NONE) + DISABLE_INTERRUPTS(CLBR_ANY) TRACE_IRQS_OFF - testl %eax, %eax + testl %ebx, %ebx jnz retint_kernel jmp retint_user END(error_exit)