Merge remote-tracking branch 'linus/master' into x86/urgent

1 files changed, 192 insertions, 40 deletions

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index a20e1cb9dc8..3fe8239fd8f 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -55,6 +55,7 @@
 #include <asm/paravirt.h>
 #include <asm/ftrace.h>
 #include <asm/percpu.h>
+#include <linux/err.h>
 
 /* Avoid __ASSEMBLER__'ifying <linux/audit.h> just for this.  */
 #include <linux/elf-em.h>
@@ -548,7 +549,7 @@ badsys:
 #ifdef CONFIG_AUDITSYSCALL
 	/*
 	 * Fast path for syscall audit without full syscall trace.
-	 * We just call audit_syscall_entry() directly, and then
+	 * We just call __audit_syscall_entry() directly, and then
 	 * jump back to the normal fast path.
 	 */
 auditsys:
@@ -558,22 +559,21 @@ auditsys:
 	movq %rdi,%rdx			/* 3rd arg: 1st syscall arg */
 	movq %rax,%rsi			/* 2nd arg: syscall number */
 	movl $AUDIT_ARCH_X86_64,%edi	/* 1st arg: audit arch */
-	call audit_syscall_entry
+	call __audit_syscall_entry
 	LOAD_ARGS 0		/* reload call-clobbered registers */
 	jmp system_call_fastpath
 
 	/*
-	 * Return fast path for syscall audit.  Call audit_syscall_exit()
+	 * Return fast path for syscall audit.  Call __audit_syscall_exit()
 	 * directly and then jump back to the fast path with TIF_SYSCALL_AUDIT
 	 * masked off.
 	 */
 sysret_audit:
 	movq RAX-ARGOFFSET(%rsp),%rsi	/* second arg, syscall return value */
-	cmpq $0,%rsi		/* is it < 0? */
-	setl %al		/* 1 if so, 0 if not */
+	cmpq $-MAX_ERRNO,%rsi	/* is it < -MAX_ERRNO? */
+	setbe %al		/* 1 if so, 0 if not */
 	movzbl %al,%edi		/* zero-extend that into %edi */
-	inc %edi /* first arg, 0->1(AUDITSC_SUCCESS), 1->2(AUDITSC_FAILURE) */
-	call audit_syscall_exit
+	call __audit_syscall_exit
 	movl $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT),%edi
 	jmp sysret_check
 #endif	/* CONFIG_AUDITSYSCALL */
@@ -1480,62 +1480,214 @@ ENTRY(error_exit)
 	CFI_ENDPROC
 END(error_exit)
 
+/*
+ * Test if a given stack is an NMI stack or not.
+ */
+	.macro test_in_nmi reg stack nmi_ret normal_ret
+	cmpq %\reg, \stack
+	ja \normal_ret
+	subq $EXCEPTION_STKSZ, %\reg
+	cmpq %\reg, \stack
+	jb \normal_ret
+	jmp \nmi_ret
+	.endm
 
 	/* runs on exception stack */
 ENTRY(nmi)
 	INTR_FRAME
 	PARAVIRT_ADJUST_EXCEPTION_FRAME
-	pushq_cfi $-1
+	/*
+	 * We allow breakpoints in NMIs. If a breakpoint occurs, then
+	 * the iretq it performs will take us out of NMI context.
+	 * This means that we can have nested NMIs where the next
+	 * NMI is using the top of the stack of the previous NMI. We
+	 * can't let it execute because the nested NMI will corrupt the
+	 * stack of the previous NMI. NMI handlers are not re-entrant
+	 * anyway.
+	 *
+	 * To handle this case we do the following:
+	 *  Check the a special location on the stack that contains
+	 *  a variable that is set when NMIs are executing.
+	 *  The interrupted task's stack is also checked to see if it
+	 *  is an NMI stack.
+	 *  If the variable is not set and the stack is not the NMI
+	 *  stack then:
+	 *    o Set the special variable on the stack
+	 *    o Copy the interrupt frame into a "saved" location on the stack
+	 *    o Copy the interrupt frame into a "copy" location on the stack
+	 *    o Continue processing the NMI
+	 *  If the variable is set or the previous stack is the NMI stack:
+	 *    o Modify the "copy" location to jump to the repeate_nmi
+	 *    o return back to the first NMI
+	 *
+	 * Now on exit of the first NMI, we first clear the stack variable
+	 * The NMI stack will tell any nested NMIs at that point that it is
+	 * nested. Then we pop the stack normally with iret, and if there was
+	 * a nested NMI that updated the copy interrupt stack frame, a
+	 * jump will be made to the repeat_nmi code that will handle the second
+	 * NMI.
+	 */
+
+	/* Use %rdx as out temp variable throughout */
+	pushq_cfi %rdx
+
+	/*
+	 * Check the special variable on the stack to see if NMIs are
+	 * executing.
+	 */
+	cmp $1, -8(%rsp)
+	je nested_nmi
+
+	/*
+	 * Now test if the previous stack was an NMI stack.
+	 * We need the double check. We check the NMI stack to satisfy the
+	 * race when the first NMI clears the variable before returning.
+	 * We check the variable because the first NMI could be in a
+	 * breakpoint routine using a breakpoint stack.
+	 */
+	lea 6*8(%rsp), %rdx
+	test_in_nmi rdx, 4*8(%rsp), nested_nmi, first_nmi
+
+nested_nmi:
+	/*
+	 * Do nothing if we interrupted the fixup in repeat_nmi.
+	 * It's about to repeat the NMI handler, so we are fine
+	 * with ignoring this one.
+	 */
+	movq $repeat_nmi, %rdx
+	cmpq 8(%rsp), %rdx
+	ja 1f
+	movq $end_repeat_nmi, %rdx
+	cmpq 8(%rsp), %rdx
+	ja nested_nmi_out
+
+1:
+	/* Set up the interrupted NMIs stack to jump to repeat_nmi */
+	leaq -6*8(%rsp), %rdx
+	movq %rdx, %rsp
+	CFI_ADJUST_CFA_OFFSET 6*8
+	pushq_cfi $__KERNEL_DS
+	pushq_cfi %rdx
+	pushfq_cfi
+	pushq_cfi $__KERNEL_CS
+	pushq_cfi $repeat_nmi
+
+	/* Put stack back */
+	addq $(11*8), %rsp
+	CFI_ADJUST_CFA_OFFSET -11*8
+
+nested_nmi_out:
+	popq_cfi %rdx
+
+	/* No need to check faults here */
+	INTERRUPT_RETURN
+
+first_nmi:
+	/*
+	 * Because nested NMIs will use the pushed location that we
+	 * stored in rdx, we must keep that space available.
+	 * Here's what our stack frame will look like:
+	 * +-------------------------+
+	 * | original SS             |
+	 * | original Return RSP     |
+	 * | original RFLAGS         |
+	 * | original CS             |
+	 * | original RIP            |
+	 * +-------------------------+
+	 * | temp storage for rdx    |
+	 * +-------------------------+
+	 * | NMI executing variable  |
+	 * +-------------------------+
+	 * | Saved SS                |
+	 * | Saved Return RSP        |
+	 * | Saved RFLAGS            |
+	 * | Saved CS                |
+	 * | Saved RIP               |
+	 * +-------------------------+
+	 * | copied SS               |
+	 * | copied Return RSP       |
+	 * | copied RFLAGS           |
+	 * | copied CS               |
+	 * | copied RIP              |
+	 * +-------------------------+
+	 * | pt_regs                 |
+	 * +-------------------------+
+	 *
+	 * The saved RIP is used to fix up the copied RIP that a nested
+	 * NMI may zero out. The original stack frame and the temp storage
+	 * is also used by nested NMIs and can not be trusted on exit.
+	 */
+	/* Set the NMI executing variable on the stack. */
+	pushq_cfi $1
+
+	/* Copy the stack frame to the Saved frame */
+	.rept 5
+	pushq_cfi 6*8(%rsp)
+	.endr
+
+	/* Make another copy, this one may be modified by nested NMIs */
+	.rept 5
+	pushq_cfi 4*8(%rsp)
+	.endr
+
+	/* Do not pop rdx, nested NMIs will corrupt it */
+	movq 11*8(%rsp), %rdx
+
+	/*
+	 * Everything below this point can be preempted by a nested
+	 * NMI if the first NMI took an exception. Repeated NMIs
+	 * caused by an exception and nested NMI will start here, and
+	 * can still be preempted by another NMI.
+	 */
+restart_nmi:
+	pushq_cfi $-1		/* ORIG_RAX: no syscall to restart */
 	subq $ORIG_RAX-R15, %rsp
 	CFI_ADJUST_CFA_OFFSET ORIG_RAX-R15
+	/*
+	 * Use save_paranoid to handle SWAPGS, but no need to use paranoid_exit
+	 * as we should not be calling schedule in NMI context.
+	 * Even with normal interrupts enabled. An NMI should not be
+	 * setting NEED_RESCHED or anything that normal interrupts and
+	 * exceptions might do.
+	 */
 	call save_paranoid
 	DEFAULT_FRAME 0
 	/* paranoidentry do_nmi, 0; without TRACE_IRQS_OFF */
 	movq %rsp,%rdi
 	movq $-1,%rsi
 	call do_nmi
-#ifdef CONFIG_TRACE_IRQFLAGS
-	/* paranoidexit; without TRACE_IRQS_OFF */
-	/* ebx:	no swapgs flag */
-	DISABLE_INTERRUPTS(CLBR_NONE)
 	testl %ebx,%ebx				/* swapgs needed? */
 	jnz nmi_restore
-	testl $3,CS(%rsp)
-	jnz nmi_userspace
 nmi_swapgs:
 	SWAPGS_UNSAFE_STACK
 nmi_restore:
 	RESTORE_ALL 8
+	/* Clear the NMI executing stack variable */
+	movq $0, 10*8(%rsp)
 	jmp irq_return
-nmi_userspace:
-	GET_THREAD_INFO(%rcx)
-	movl TI_flags(%rcx),%ebx
-	andl $_TIF_WORK_MASK,%ebx
-	jz nmi_swapgs
-	movq %rsp,%rdi			/* &pt_regs */
-	call sync_regs
-	movq %rax,%rsp			/* switch stack for scheduling */
-	testl $_TIF_NEED_RESCHED,%ebx
-	jnz nmi_schedule
-	movl %ebx,%edx			/* arg3: thread flags */
-	ENABLE_INTERRUPTS(CLBR_NONE)
-	xorl %esi,%esi 			/* arg2: oldset */
-	movq %rsp,%rdi 			/* arg1: &pt_regs */
-	call do_notify_resume
-	DISABLE_INTERRUPTS(CLBR_NONE)
-	jmp nmi_userspace
-nmi_schedule:
-	ENABLE_INTERRUPTS(CLBR_ANY)
-	call schedule
-	DISABLE_INTERRUPTS(CLBR_ANY)
-	jmp nmi_userspace
-	CFI_ENDPROC
-#else
-	jmp paranoid_exit
 	CFI_ENDPROC
-#endif
 END(nmi)
 
+	/*
+	 * If an NMI hit an iret because of an exception or breakpoint,
+	 * it can lose its NMI context, and a nested NMI may come in.
+	 * In that case, the nested NMI will change the preempted NMI's
+	 * stack to jump to here when it does the final iret.
+	 */
+repeat_nmi:
+	INTR_FRAME
+	/* Update the stack variable to say we are still in NMI */
+	movq $1, 5*8(%rsp)
+
+	/* copy the saved stack back to copy stack */
+	.rept 5
+	pushq_cfi 4*8(%rsp)
+	.endr
+
+	jmp restart_nmi
+	CFI_ENDPROC
+end_repeat_nmi:
+
 ENTRY(ignore_sysret)
 	CFI_STARTPROC
 	mov $-ENOSYS,%eax