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Subject: [RFC][PATCH 4/8] x86/mm: add clarifying comments for user addr space
To:     linux-kernel@vger.kernel.org
Cc:     Dave Hansen <dave.hansen@linux.intel.com>,
        sean.j.christopherson@intel.com, peterz@infradead.org,
        tglx@linutronix.de, x86@kernel.org, luto@kernel.org
From:   Dave Hansen <dave.hansen@linux.intel.com>
Date:   Fri, 07 Sep 2018 12:48:58 -0700
References: <20180907194852.3C351B82@viggo.jf.intel.com>
In-Reply-To: <20180907194852.3C351B82@viggo.jf.intel.com>
Message-Id: <20180907194858.FD74A39F@viggo.jf.intel.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


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

The SMAP and Reserved checking do not have nice comments.  Add
some to clarify and make it match everything else.

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

 b/arch/x86/mm/fault.c |    8 ++++++++
 1 file changed, 8 insertions(+)

diff -puN arch/x86/mm/fault.c~pkeys-fault-warnings-02 arch/x86/mm/fault.c
--- a/arch/x86/mm/fault.c~pkeys-fault-warnings-02	2018-09-07 11:21:47.182751900 -0700
+++ b/arch/x86/mm/fault.c	2018-09-07 11:21:47.185751900 -0700
@@ -1274,9 +1274,17 @@ void do_user_addr_space_fault(struct pt_
 	if (unlikely(kprobes_fault(regs)))
 		return;
 
+	/*
+	 * Reserved bits are never expected to be set on
+	 * entries in the user portion of the page tables.
+	 */
 	if (unlikely(hw_error_code & X86_PF_RSVD))
 		pgtable_bad(regs, hw_error_code, address);
 
+	/*
+	 * Check for invalid kernel (supervisor) access to user
+	 * pages in the user address space.
+	 */
 	if (unlikely(smap_violation(hw_error_code, regs))) {
 		bad_area_nosemaphore(regs, hw_error_code, address, NULL);
 		return;
_