From 7664c5a1da4711bb6383117f51b94c8dc8f3f1cd Mon Sep 17 00:00:00 2001 From: Jeremy Fitzhardinge Date: Fri, 8 Dec 2006 02:36:19 -0800 Subject: [PATCH] Generic BUG implementation 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 Cc: Andi Kleen Cc: Hugh Dickens Cc: Michael Ellerman Cc: Paul Mackerras Cc: Benjamin Herrenschmidt Cc: Rusty Russell Signed-off-by: Adrian Bunk Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/asm-generic/bug.h | 16 ++++++++++++++++ include/asm-generic/vmlinux.lds.h | 8 ++++++++ 2 files changed, 24 insertions(+) (limited to 'include/asm-generic') diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h index c92ae0f166ff..47e3561638b1 100644 --- a/include/asm-generic/bug.h +++ b/include/asm-generic/bug.h @@ -4,6 +4,22 @@ #include #ifdef CONFIG_BUG + +#ifdef CONFIG_GENERIC_BUG +#ifndef __ASSEMBLY__ +struct bug_entry { + unsigned long bug_addr; +#ifdef CONFIG_DEBUG_BUGVERBOSE + const char *file; + unsigned short line; +#endif + unsigned short flags; +}; +#endif /* __ASSEMBLY__ */ + +#define BUGFLAG_WARNING (1<<0) +#endif /* CONFIG_GENERIC_BUG */ + #ifndef HAVE_ARCH_BUG #define BUG() do { \ printk("BUG: failure at %s:%d/%s()!\n", __FILE__, __LINE__, __FUNCTION__); \ diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 4d4c62d11059..6e9fcebbf89f 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -218,6 +218,14 @@ .stab.indexstr 0 : { *(.stab.indexstr) } \ .comment 0 : { *(.comment) } +#define BUG_TABLE \ + . = ALIGN(8); \ + __bug_table : AT(ADDR(__bug_table) - LOAD_OFFSET) { \ + __start___bug_table = .; \ + *(__bug_table) \ + __stop___bug_table = .; \ + } + #define NOTES \ .notes : { *(.note.*) } :note -- cgit v1.2.1