ARM: 7017/1: Use generic BUG() handler

ARM uses its own BUG() handler which makes its output slightly different
from other archtectures.

One of the problems is that the ARM implementation doesn't report the
function
with the BUG() in it, but always reports the PC being in __bug(). The
generic
implementation doesn't have this problem.

Currently we get something like:

kernel BUG at fs/proc/breakme.c:35!
Unable to handle kernel NULL pointer dereference at virtual address
00000000
...
PC is at __bug+0x20/0x2c

With this patch it displays:

kernel BUG at fs/proc/breakme.c:35!
Internal error: Oops - undefined instruction: 0 [#1] PREEMPT SMP
...
PC is at write_breakme+0xd0/0x1b4

This implementation uses an undefined instruction to implement BUG, and
sets up
a bug table containing the relevant information. Many versions of gcc do
not
support %c properly for ARM (inserting a # when they shouldn't) so we
work
around this using distasteful macro magic.

v1: Initial version to replace existing ARM BUG() implementation with
something
more similar to other architectures.

v2: Add Thumb support, remove backtrace whitespace output changes.
Change to
use macros instead of requiring the asm %d flag to work (thanks to
Dave Martin <dave.martin@linaro.org>)

v3: Remove old BUG() implementation in favor of this one.
Remove the Backtrace: message (will submit this separately).
Rebase to linux-2.6.git master.

v4: Allow BUGS in modules (these were not reported correctly in v3)
(thanks to Stephen Boyd <sboyd@codeaurora.org> for suggesting that.)
Remove __bug() as this is no longer needed.

v5: Add %progbits as the section flags.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Tested-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
(cherry picked from commit 87e040b6456fd3416a1f6831c1eedaef5c0a94ff)

Change-Id: Ic7692288dff6e4a15c732eb030295bd196a87fb4
Signed-off-by: Manoj Chourasia <mchourasia@nvidia.com>
Reviewed-on: http://git-master/r/117356
Reviewed-by: Automatic_Commit_Validation_User
Tested-by: Vishal Singh <vissingh@nvidia.com>
Reviewed-by: Sandeep Trasi <strasi@nvidia.com>
(cherry picked from commit 6708ffd0b44f4d09d8fe745471641545655091fb)
Reviewed-on: http://git-master/r/119328
Reviewed-by: Bob Johnston <bjohnston@nvidia.com>
Reviewed-by: Varun Wadekar <vwadekar@nvidia.com>

2 files changed, 43 insertions, 11 deletions

diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 4ef9f0d04e5a..2534d2a1a164 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -4,6 +4,8 @@
  *  Copyright (C) 1995-2009 Russell King
  *  Fragments that appear the same as linux/arch/i386/kernel/traps.c (C) Linus Torvalds
  *
+ * Copyright (c) 2012, NVIDIA CORPORATION.  All rights reserved.
+ *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
@@ -21,6 +23,7 @@
 #include <linux/kdebug.h>
 #include <linux/module.h>
 #include <linux/kexec.h>
+#include <linux/bug.h>
 #include <linux/delay.h>
 #include <linux/init.h>
 #include <linux/sched.h>
@@ -270,6 +273,8 @@ void die(const char *str, struct pt_regs *regs, int err)
 	spin_lock_irq(&die_lock);
 	console_verbose();
 	bust_spinlocks(1);
+	if (!user_mode(regs))
+		report_bug(regs->ARM_pc, regs);
 	ret = __die(str, err, thread, regs);
 
 	if (regs && kexec_should_crash(thread->task))
@@ -301,6 +306,24 @@ void arm_notify_die(const char *str, struct pt_regs *regs,
 	}
 }
 
+#ifdef CONFIG_GENERIC_BUG
+
+int is_valid_bugaddr(unsigned long pc)
+{
+#ifdef CONFIG_THUMB2_KERNEL
+	unsigned short bkpt;
+#else
+	unsigned long bkpt;
+#endif
+
+	if (probe_kernel_address((unsigned *)pc, bkpt))
+		return 0;
+
+	return bkpt == BUG_INSTR_VALUE;
+}
+
+#endif
+
 static LIST_HEAD(undef_hook);
 static DEFINE_SPINLOCK(undef_lock);
 
@@ -708,16 +731,6 @@ baddataabort(int code, unsigned long instr, struct pt_regs *regs)
 	arm_notify_die("unknown data abort code", regs, &info, instr, 0);
 }
 
-void __attribute__((noreturn)) __bug(const char *file, int line)
-{
-	printk(KERN_CRIT"kernel BUG at %s:%d!\n", file, line);
-	*(int *)0 = 0;
-
-	/* Avoid "noreturn function does return" */
-	for (;;);
-}
-EXPORT_SYMBOL(__bug);
-
 void __readwrite_bug(const char *fn)
 {
 	printk("%s called, but not implemented\n", fn);
diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S
index 4e66f62b8d41..1719a8ccde9c 100644
--- a/arch/arm/kernel/vmlinux.lds.S
+++ b/arch/arm/kernel/vmlinux.lds.S
@@ -1,3 +1,21 @@
+/*
+ * arch/arm/kernel/vmlinux.lds.S
+ *
+ * Copyright (c) 2012, NVIDIA CORPORATION.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
 /* ld script to make ARM Linux kernel
  * taken from the i386 version by Russell King
  * Written by Martin Mares <mj@atrey.karlin.mff.cuni.cz>
@@ -21,7 +39,8 @@
 #define ARM_CPU_KEEP(x)
 #endif
 
-#if defined(CONFIG_SMP_ON_UP) && !defined(CONFIG_DEBUG_SPINLOCK)
+#if (defined(CONFIG_SMP_ON_UP) && !defined(CONFIG_DEBUG_SPINLOCK)) || \
+	defined(CONFIG_GENERIC_BUG)
 #define ARM_EXIT_KEEP(x)	x
 #define ARM_EXIT_DISCARD(x)
 #else