linux-kernel - [PATCH v3] arch/x86: get rid of KERN_CONT in show_fault

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Date:   Tue, 26 Jun 2018 09:28:43 +0200
From:   Dmitry Vyukov <dvyukov@...il.com>
To:     tglx@...utronix.de, mingo@...hat.com, x86@...nel.org,
        linux-kernel@...r.kernel.org, sergey.senozhatsky.work@...il.com,
        andy.shevchenko@...il.com
Cc:     Dmitry Vyukov <dvyukov@...gle.com>
Subject: [PATCH v3] arch/x86: get rid of KERN_CONT in show_fault_oops()

From: Dmitry Vyukov <dvyukov@...gle.com>

KERN_CONT leads to split lines in kernel output
and complicates useful changes to printk like
printing context before each line.

Only acceptable use of continuations is basically
boot-time testing.

Get rid of it.

Also tidy up code around as asked by reviewers.

Signed-off-by: Dmitry Vyukov <dvyukov@...gle.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>

---

Changes since v1:
 - use pr_alert() instead of printk(KERN_ALERT)

Changes since v2:
 - drop unnecessary parenthesis
 - remove once used nx_warning and smep_warning
---
 arch/x86/mm/fault.c | 21 +++++++--------------
 1 file changed, 7 insertions(+), 14 deletions(-)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 9a84a0d08727..a73575cacfd9 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -641,11 +641,6 @@ static int is_f00f_bug(struct pt_regs *regs, unsigned long address)
 	return 0;
 }
 
-static const char nx_warning[] = KERN_CRIT
-"kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n";
-static const char smep_warning[] = KERN_CRIT
-"unable to execute userspace code (SMEP?) (uid: %d)\n";
-
 static void
 show_fault_oops(struct pt_regs *regs, unsigned long error_code,
 		unsigned long address)
@@ -664,20 +659,18 @@ show_fault_oops(struct pt_regs *regs, unsigned long error_code,
 		pte = lookup_address_in_pgd(pgd, address, &level);
 
 		if (pte && pte_present(*pte) && !pte_exec(*pte))
-			printk(nx_warning, from_kuid(&init_user_ns, current_uid()));
+			pr_crit("kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n",
+				from_kuid(&init_user_ns, current_uid()));
 		if (pte && pte_present(*pte) && pte_exec(*pte) &&
 				(pgd_flags(*pgd) & _PAGE_USER) &&
 				(__read_cr4() & X86_CR4_SMEP))
-			printk(smep_warning, from_kuid(&init_user_ns, current_uid()));
+			pr_crit("unable to execute userspace code (SMEP?) (uid: %d)\n",
+				from_kuid(&init_user_ns, current_uid()));
 	}
 
-	printk(KERN_ALERT "BUG: unable to handle kernel ");
-	if (address < PAGE_SIZE)
-		printk(KERN_CONT "NULL pointer dereference");
-	else
-		printk(KERN_CONT "paging request");
-
-	printk(KERN_CONT " at %px\n", (void *) address);
+	pr_alert("BUG: unable to handle kernel %s at %px\n",
+		address < PAGE_SIZE ? "NULL pointer dereference" :
+		"paging request", (void *) address);
 
 	dump_pagetable(address);
 }
-- 
2.18.0.rc2.346.g013aa6912e-goog