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).
Use ARM_EXIT_KEEP() so that some architectures can dump exit text at link time
thanks to Stephen Boyd <sboyd@codeaurora.org> (although since we always
define GENERIC_BUG this might be academic.)
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>

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index c208fd97c180a09004967d52a7a2d6a5a3be1b27..c7a76421ba2c3d113d983ca73b09816f9df0dec9 100644 (file)
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -215,6 +215,10 @@ config ARM_PATCH_PHYS_VIRT_16BIT
          to allow physical memory down to a theoretical minimum of 64K
          boundaries.
 
+config GENERIC_BUG
+       def_bool y
+       depends on BUG
+
 source "init/Kconfig"
 
 source "kernel/Kconfig.freezer"

diff --git a/arch/arm/include/asm/bug.h b/arch/arm/include/asm/bug.h
index 4d88425a41693e3778a62250bf09eac6446b1d3d..9abe7a07d5acdde3eea377cda3634e5f5c838115 100644 (file)
--- a/arch/arm/include/asm/bug.h
+++ b/arch/arm/include/asm/bug.h
@@ -3,21 +3,58 @@
 
 
 #ifdef CONFIG_BUG
-#ifdef CONFIG_DEBUG_BUGVERBOSE
-extern void __bug(const char *file, int line) __attribute__((noreturn));
-
-/* give file/line information */
-#define BUG()          __bug(__FILE__, __LINE__)
 
+/*
+ * Use a suitable undefined instruction to use for ARM/Thumb2 bug handling.
+ * We need to be careful not to conflict with those used by other modules and
+ * the register_undef_hook() system.
+ */
+#ifdef CONFIG_THUMB2_KERNEL
+#define BUG_INSTR_VALUE 0xde02
+#define BUG_INSTR_TYPE ".hword "
 #else
+#define BUG_INSTR_VALUE 0xe7f001f2
+#define BUG_INSTR_TYPE ".word "
+#endif
 
-/* this just causes an oops */
-#define BUG()          do { *(int *)0 = 0; } while (1)
 
-#endif
+#define BUG() _BUG(__FILE__, __LINE__, BUG_INSTR_VALUE)
+#define _BUG(file, line, value) __BUG(file, line, value)
+
+#ifdef CONFIG_DEBUG_BUGVERBOSE
+
+/*
+ * The extra indirection is to ensure that the __FILE__ string comes through
+ * OK. Many version of gcc do not support the asm %c parameter which would be
+ * preferable to this unpleasantness. We use mergeable string sections to
+ * avoid multiple copies of the string appearing in the kernel image.
+ */
+
+#define __BUG(__file, __line, __value)                         \
+do {                                                           \
+       BUILD_BUG_ON(sizeof(struct bug_entry) != 12);           \
+       asm volatile("1:\t" BUG_INSTR_TYPE #__value "\n"        \
+               ".pushsection .rodata.str, \"aMS\", %progbits, 1\n" \
+               "2:\t.asciz " #__file "\n"                      \
+               ".popsection\n"                                 \
+               ".pushsection __bug_table,\"a\"\n"              \
+               "3:\t.word 1b, 2b\n"                            \
+               "\t.hword " #__line ", 0\n"                     \
+               ".popsection");                                 \
+       unreachable();                                          \
+} while (0)
+
+#else  /* not CONFIG_DEBUG_BUGVERBOSE */
+
+#define __BUG(__file, __line, __value)                         \
+do {                                                           \
+       asm volatile(BUG_INSTR_TYPE #__value);                  \
+       unreachable();                                          \
+} while (0)
+#endif  /* CONFIG_DEBUG_BUGVERBOSE */
 
 #define HAVE_ARCH_BUG
-#endif
+#endif  /* CONFIG_BUG */
 
 #include <asm-generic/bug.h>
 

diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index bc9f9da782cb85ff3eb0171b9c0d5b8630397c90..74969248c375ee3d5c60f0a98f2d5018252fa50f 100644 (file)
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -21,6 +21,7 @@
 #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 +271,8 @@ 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 +304,24 @@ 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);
 
@@ -706,16 +727,6 @@ 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 bf977f8514f60191e478e8e25a696c93d2802b87..7b2541efd9f8cc1980fc57422eb7d19b2a15f716 100644 (file)
--- a/arch/arm/kernel/vmlinux.lds.S
+++ b/arch/arm/kernel/vmlinux.lds.S
@@ -21,7 +21,8 @@
 #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
 #else
 #define ARM_EXIT_KEEP(x)