linux-kernel - [PATCH 08/13] x86/fault: Don't set thread.cr2, etc before OOPSing

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Message-Id: <d418022aa0fad9cb40467aa7acaf4e95be50ee96.1542667307.git.luto@kernel.org>
Date:   Mon, 19 Nov 2018 14:45:32 -0800
From:   Andy Lutomirski <luto@...nel.org>
To:     x86@...nel.org
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Yu-cheng Yu <yu-cheng.yu@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>
Subject: [PATCH 08/13] x86/fault: Don't set thread.cr2, etc before OOPSing

The fault handling code sets the cr2, trap_nr, and error_code fields
in thread_struct before OOPSing.  No one reads those fields during
an OOPS, so remove the code to set them.

Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
 arch/x86/mm/fault.c | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index fac931d89c23..a6554110ef62 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -621,10 +621,6 @@ pgtable_bad(struct pt_regs *regs, unsigned long error_code,
 	       tsk->comm, address);
 	dump_pagetable(address);
 
-	tsk->thread.cr2		= address;
-	tsk->thread.trap_nr	= X86_TRAP_PF;
-	tsk->thread.error_code	= error_code;
-
 	if (__die("Bad pagetable", regs, error_code))
 		sig = 0;
 
@@ -753,10 +749,6 @@ no_context(struct pt_regs *regs, unsigned long error_code,
 	if (task_stack_end_corrupted(tsk))
 		printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
 
-	tsk->thread.cr2		= address;
-	tsk->thread.trap_nr	= X86_TRAP_PF;
-	tsk->thread.error_code	= error_code;
-
 	sig = SIGKILL;
 	if (__die("Oops", regs, error_code))
 		sig = 0;
-- 
2.17.2