1. 16 Jul, 2007 1 commit
    • Heiko Carstens's avatar
      generic bug: use show_regs() instead of dump_stack() · 608e2619
      Heiko Carstens authored
      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: default avatarJeremy Fitzhardinge <jeremy@goop.org>
      Acked-by: default avatarHaavard 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: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      608e2619
  2. 08 Dec, 2006 1 commit
    • Jeremy Fitzhardinge's avatar
      [PATCH] Generic BUG implementation · 7664c5a1
      Jeremy Fitzhardinge authored
      This patch adds common handling for kernel BUGs, for use by architectures as
      they wish.  The code is derived from arch/powerpc.
      
      The advantages of having common BUG handling are:
       - consistent BUG reporting across architectures
       - shared implementation of out-of-line file/line data
       - implement CONFIG_DEBUG_BUGVERBOSE consistently
      
      This means that in inline impact of BUG is just the illegal instruction
      itself, which is an improvement for i386 and x86-64.
      
      A BUG is represented in the instruction stream as an illegal instruction,
      which has file/line information associated with it.  This extra information is
      stored in the __bug_table section in the ELF file.
      
      When the kernel gets an illegal instruction, it first confirms it might
      possibly be from a BUG (ie, in kernel mode, the right illegal instruction).
      It then calls report_bug().  This searches __bug_table for a matching
      instruction pointer, and if found, prints the corresponding file/line
      information.  If report_bug() determines that it wasn't a BUG which caused the
      trap, it returns BUG_TRAP_TYPE_NONE.
      
      Some architectures (powerpc) implement WARN using the same mechanism; if the
      illegal instruction was the result of a WARN, then report_bug(Q) returns
      CONFIG_DEBUG_BUGVERBOSE; otherwise it returns BUG_TRAP_TYPE_BUG.
      
      lib/bug.c keeps a list of loaded modules which can be searched for __bug_table
      entries.  The architecture must call
      module_bug_finalize()/module_bug_cleanup() from its corresponding
      module_finalize/cleanup functions.
      
      Unsetting CONFIG_DEBUG_BUGVERBOSE will reduce the kernel size by some amount.
      At the very least, filename and line information will not be recorded for each
      but, but architectures may decide to store no extra information per BUG at
      all.
      
      Unfortunately, gcc doesn't have a general way to mark an asm() as noreturn, so
      architectures will generally have to include an infinite loop (or similar) in
      the BUG code, so that gcc knows execution won't continue beyond that point.
      gcc does have a __builtin_trap() operator which may be useful to achieve the
      same effect, unfortunately it cannot be used to actually implement the BUG
      itself, because there's no way to get the instruction's address for use in
      generating the __bug_table entry.
      
      [randy.dunlap@oracle.com: Handle BUG=n, GENERIC_BUG=n to prevent build errors]
      [bunk@stusta.de: include/linux/bug.h must always #include <linux/module.h]
      Signed-off-by: default avatarJeremy Fitzhardinge <jeremy@goop.org>
      Cc: Andi Kleen <ak@muc.de>
      Cc: Hugh Dickens <hugh@veritas.com>
      Cc: Michael Ellerman <michael@ellerman.id.au>
      Cc: Paul Mackerras <paulus@samba.org>
      Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
      Cc: Rusty Russell <rusty@rustcorp.com.au>
      Signed-off-by: default avatarAdrian Bunk <bunk@stusta.de>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      7664c5a1