linux-kernel - [RFC][PATCH 3/8] x86/mm: break out user address space handling

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Date:   Fri, 07 Sep 2018 12:48:57 -0700
From:   Dave Hansen <dave.hansen@...ux.intel.com>
To:     linux-kernel@...r.kernel.org
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>,
        sean.j.christopherson@...el.com, peterz@...radead.org,
        tglx@...utronix.de, x86@...nel.org, luto@...nel.org
Subject: [RFC][PATCH 3/8] x86/mm: break out user address space handling


From: Dave Hansen <dave.hansen@...ux.intel.com>

The last patch broke out kernel address space handing into its own
helper.  Now, do the same for user address space handling.

Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Sean Christopherson <sean.j.christopherson@...el.com>
Cc: "Peter Zijlstra (Intel)" <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: x86@...nel.org
Cc: Andy Lutomirski <luto@...nel.org>
---

 b/arch/x86/mm/fault.c |   47 ++++++++++++++++++++++++++++-------------------
 1 file changed, 28 insertions(+), 19 deletions(-)

diff -puN arch/x86/mm/fault.c~pkeys-fault-warnings-01 arch/x86/mm/fault.c
--- a/arch/x86/mm/fault.c~pkeys-fault-warnings-01	2018-09-07 11:21:46.663751901 -0700
+++ b/arch/x86/mm/fault.c	2018-09-07 11:21:46.667751901 -0700
@@ -1203,6 +1203,7 @@ static inline bool smap_violation(int er
 	return true;
 }
 
+/* Handle faults in the kernel portion of the address space */
 static void
 do_kern_addr_space_fault(struct pt_regs *regs, unsigned long hw_error_code,
 			 unsigned long address)
@@ -1252,14 +1253,11 @@ do_kern_addr_space_fault(struct pt_regs
 }
 NOKPROBE_SYMBOL(do_kern_addr_space_fault);
 
-/*
- * This routine handles page faults.  It determines the address,
- * and the problem, and then passes it off to one of the appropriate
- * routines.
- */
-static noinline void
-__do_page_fault(struct pt_regs *regs, unsigned long hw_error_code,
-		unsigned long address)
+/* Handle faults in the user portion of the address space */
+static inline
+void do_user_addr_space_fault(struct pt_regs *regs,
+			      unsigned long hw_error_code,
+			      unsigned long address)
 {
 	unsigned long sw_error_code;
 	struct vm_area_struct *vma;
@@ -1272,17 +1270,6 @@ __do_page_fault(struct pt_regs *regs, un
 	tsk = current;
 	mm = tsk->mm;
 
-	prefetchw(&mm->mmap_sem);
-
-	if (unlikely(kmmio_fault(regs, address)))
-		return;
-
-	/* Was the fault on kernel-controlled part of the address space? */
-	if (unlikely(fault_in_kernel_space(address))) {
-		do_kern_addr_space_fault(regs, hw_error_code, address);
-		return;
-	}
-
 	/* kprobes don't want to hook the spurious faults: */
 	if (unlikely(kprobes_fault(regs)))
 		return;
@@ -1486,6 +1473,28 @@ good_area:
 
 	check_v8086_mode(regs, address, tsk);
 }
+NOKPROBE_SYMBOL(do_user_addr_space_fault);
+
+/*
+ * This routine handles page faults.  It determines the address,
+ * and the problem, and then passes it off to one of the appropriate
+ * routines.
+ */
+static noinline void
+__do_page_fault(struct pt_regs *regs, unsigned long hw_error_code,
+		unsigned long address)
+{
+	prefetchw(&current->mm->mmap_sem);
+
+	if (unlikely(kmmio_fault(regs, address)))
+		return;
+
+	/* Was the fault on kernel-controlled part of the address space? */
+	if (unlikely(fault_in_kernel_space(address)))
+		do_kern_addr_space_fault(regs, hw_error_code, address);
+	else
+		do_user_addr_space_fault(regs, hw_error_code, address);
+}
 NOKPROBE_SYMBOL(__do_page_fault);
 
 static nokprobe_inline void
_