generic bug: use show_regs() instead of dump_stack()

The current generic bug implementation has a call to dump_stack() in case a
WARN_ON(whatever) gets hit.  Since report_bug(), which calls dump_stack(),
gets called from an exception handler we can do better: just pass the
pt_regs structure to report_bug() and pass it to show_regs() in case of a
warning.  This will give more debug informations like register contents,
etc...  In addition this avoids some pointless lines that dump_stack()
emits, since it includes a stack backtrace of the exception handler which
is of no interest in case of a warning.  E.g.  on s390 the following lines
are currently always present in a stack backtrace if dump_stack() gets
called from report_bug():

 [<000000000001517a>] show_trace+0x92/0xe8)
 [<0000000000015270>] show_stack+0xa0/0xd0
 [<00000000000152ce>] dump_stack+0x2e/0x3c
 [<0000000000195450>] report_bug+0x98/0xf8
 [<0000000000016cc8>] illegal_op+0x1fc/0x21c
 [<00000000000227d6>] sysc_return+0x0/0x10

Acked-by: Jeremy Fitzhardinge <jeremy@goop.org>
Acked-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Kyle McMartin <kyle@parisc-linux.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 2 deletions

diff --git a/include/linux/bug.h b/include/linux/bug.h
index 42aa0a54b6f4..54398d2c6d8d 100644
--- a/include/linux/bug.h
+++ b/include/linux/bug.h
@@ -10,6 +10,8 @@ enum bug_trap_type {
 	BUG_TRAP_TYPE_BUG = 2,
 };
 
+struct pt_regs;
+
 #ifdef CONFIG_GENERIC_BUG
 #include <asm-generic/bug.h>
 
@@ -20,7 +22,7 @@ static inline int is_warning_bug(const struct bug_entry *bug)
 
 const struct bug_entry *find_bug(unsigned long bugaddr);
 
-enum bug_trap_type report_bug(unsigned long bug_addr);
+enum bug_trap_type report_bug(unsigned long bug_addr, struct pt_regs *regs);
 
 int  module_bug_finalize(const Elf_Ehdr *, const Elf_Shdr *,
 			 struct module *);
@@ -31,7 +33,8 @@ int is_valid_bugaddr(unsigned long addr);
 
 #else	/* !CONFIG_GENERIC_BUG */
 
-static inline enum bug_trap_type report_bug(unsigned long bug_addr)
+static inline enum bug_trap_type report_bug(unsigned long bug_addr,
+					    struct pt_regs *regs)
 {
 	return BUG_TRAP_TYPE_BUG;
 }