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From:   Andy Lutomirski <luto@kernel.org>
To:     x86@kernel.org
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Yonghong Song <yhs@fb.com>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Andy Lutomirski <luto@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>
Subject: [PATCH 09/11] x86/fault: Rename no_context() to kernelmode_fixup_or_oops()
Date:   Sun, 31 Jan 2021 09:24:40 -0800
Message-Id: <5b0ad34afeeee15032393367b0945a5032903162.1612113550.git.luto@kernel.org>
In-Reply-To: <cover.1612113550.git.luto@kernel.org>
References: <cover.1612113550.git.luto@kernel.org>
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The name no_context() has never been very clear.  It's only called for
faults from kernel mode, so rename it and change the no-longer-useful
user_mode(regs) check to a WARN_ON_ONCE.

Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/mm/fault.c | 28 ++++++++++------------------
 1 file changed, 10 insertions(+), 18 deletions(-)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 177b612c7f33..04cc98ec2423 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -693,17 +693,10 @@ page_fault_oops(struct pt_regs *regs, unsigned long error_code,
 }
 
 static noinline void
-no_context(struct pt_regs *regs, unsigned long error_code,
-	   unsigned long address, int signal, int si_code)
+kernelmode_fixup_or_oops(struct pt_regs *regs, unsigned long error_code,
+			 unsigned long address, int signal, int si_code)
 {
-	if (user_mode(regs)) {
-		/*
-		 * This is an implicit supervisor-mode access from user
-		 * mode.  Bypass all the kernel-mode recovery code and just
-		 * OOPS.
-		 */
-		goto oops;
-	}
+	WARN_ON_ONCE(user_mode(regs));
 
 	/* Are we prepared to handle this kernel fault? */
 	if (fixup_exception(regs, X86_TRAP_PF, error_code, address)) {
@@ -743,7 +736,6 @@ no_context(struct pt_regs *regs, unsigned long error_code,
 	if (is_prefetch(regs, error_code, address))
 		return;
 
-oops:
 	page_fault_oops(regs, error_code, address);
 }
 
@@ -790,7 +782,7 @@ __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
 	struct task_struct *tsk = current;
 
 	if (!user_mode(regs)) {
-		no_context(regs, error_code, address, pkey, si_code);
+		kernelmode_fixup_or_oops(regs, error_code, address, pkey, si_code);
 		return;
 	}
 
@@ -922,7 +914,7 @@ do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
 {
 	/* Kernel mode? Handle exceptions or die: */
 	if (!user_mode(regs)) {
-		no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
+		kernelmode_fixup_or_oops(regs, error_code, address, SIGBUS, BUS_ADRERR);
 		return;
 	}
 
@@ -1382,8 +1374,8 @@ void do_user_addr_fault(struct pt_regs *regs,
 		 * has unlocked the mm for us if we get here.
 		 */
 		if (!user_mode(regs))
-			no_context(regs, error_code, address, SIGBUS,
-				   BUS_ADRERR);
+			kernelmode_fixup_or_oops(regs, error_code, address,
+						 SIGBUS, BUS_ADRERR);
 		return;
 	}
 
@@ -1403,15 +1395,15 @@ void do_user_addr_fault(struct pt_regs *regs,
 		return;
 
 	if (fatal_signal_pending(current) && !user_mode(regs)) {
-		no_context(regs, error_code, address, 0, 0);
+		kernelmode_fixup_or_oops(regs, error_code, address, 0, 0);
 		return;
 	}
 
 	if (fault & VM_FAULT_OOM) {
 		/* Kernel mode? Handle exceptions or die: */
 		if (!user_mode(regs)) {
-			no_context(regs, error_code, address,
-				   SIGSEGV, SEGV_MAPERR);
+			kernelmode_fixup_or_oops(regs, error_code, address,
+						 SIGSEGV, SEGV_MAPERR);
 			return;
 		}
 
-- 
2.29.2