Messages in this thread | | | Date | Thu, 28 Sep 2006 16:32:56 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH RFC 1/4] Generic BUG handling. |
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On Thu, 28 Sep 2006 15:54:45 -0700 Jeremy Fitzhardinge <jeremy@goop.org> wrote:
> 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 > > 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/function 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/function information. > > Some architectures (powerpc) implement WARN using the same mechanism; > if the illegal instruction was the result of a WARN, then report_bug() > returns 1; otherwise it returns 0.
Neato.
> 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.
What is the locking for these lists? I don't see much in here. It has implications for code which wants to do BUG while holding that lock..
> This patch also converts i386, x86-64 and powerpc to use this > infrastructure. I have only tested i386; x86-64 and powerpc are not > even compile-tested in this patch. > > Because powerpc also records the function name, I added this to i386 > and x86-64 for consistency. Strictly speaking the function name is > redundant with kallsyms, so perhaps it can be dropped from powerpc.
I agree that the function name is a rather gratuitous space-consumer.
> +#ifdef CONFIG_GENERIC_BUG > + /* Support for BUG */ > + struct list_head bug_list; > + struct bug_entry *bug_table; > + unsigned num_bugs;
Shouldn't this be u64? ;)
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