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![Kees Cook](/assets/img/avatar_default.png)
The original clean up of "cut here" missed the WARN_ON() case (that does
not have a printk message), which was fixed recently by adding an explicit
printk of "cut here". This had the downside of adding a printk() to every
WARN_ON() caller, which reduces the utility of using an instruction
exception to streamline the resulting code. By making this a new BUGFLAG,
all of these can be removed and "cut here" can be handled by the exception
handler.
This was very pronounced on PowerPC, but the effect can be seen on x86 as
well. The resulting text size of a defconfig build shows some small
savings from this patch:
text data bss dec hex filename
19691167 5134320 1646664 26472151 193eed7 vmlinux.before
19676362 5134260 1663048 26473670 193f4c6 vmlinux.after
This change also opens the door for creating something like BUG_MSG(),
where a custom printk() before issuing BUG(), without confusing the "cut
here" line.
Link: http://lkml.kernel.org/r/201908200943.601DD59DCE@keescook
Fixes: 6b15f678fb
("include/asm-generic/bug.h: fix "cut here" for WARN_ON for __WARN_TAINT architectures")
Signed-off-by: Kees Cook <keescook@chromium.org>
Reported-by: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Drew Davenport <ddavenport@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
240 lines
6.6 KiB
C
240 lines
6.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_GENERIC_BUG_H
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#define _ASM_GENERIC_BUG_H
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#include <linux/compiler.h>
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#define CUT_HERE "------------[ cut here ]------------\n"
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#ifdef CONFIG_GENERIC_BUG
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#define BUGFLAG_WARNING (1 << 0)
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#define BUGFLAG_ONCE (1 << 1)
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#define BUGFLAG_DONE (1 << 2)
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#define BUGFLAG_NO_CUT_HERE (1 << 3) /* CUT_HERE already sent */
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#define BUGFLAG_TAINT(taint) ((taint) << 8)
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#define BUG_GET_TAINT(bug) ((bug)->flags >> 8)
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#endif
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#ifndef __ASSEMBLY__
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#include <linux/kernel.h>
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#ifdef CONFIG_BUG
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#ifdef CONFIG_GENERIC_BUG
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struct bug_entry {
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#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
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unsigned long bug_addr;
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#else
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signed int bug_addr_disp;
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#endif
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#ifdef CONFIG_DEBUG_BUGVERBOSE
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#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
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const char *file;
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#else
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signed int file_disp;
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#endif
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unsigned short line;
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#endif
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unsigned short flags;
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};
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#endif /* CONFIG_GENERIC_BUG */
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/*
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* Don't use BUG() or BUG_ON() unless there's really no way out; one
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* example might be detecting data structure corruption in the middle
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* of an operation that can't be backed out of. If the (sub)system
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* can somehow continue operating, perhaps with reduced functionality,
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* it's probably not BUG-worthy.
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*
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* If you're tempted to BUG(), think again: is completely giving up
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* really the *only* solution? There are usually better options, where
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* users don't need to reboot ASAP and can mostly shut down cleanly.
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*/
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#ifndef HAVE_ARCH_BUG
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#define BUG() do { \
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printk("BUG: failure at %s:%d/%s()!\n", __FILE__, __LINE__, __func__); \
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barrier_before_unreachable(); \
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panic("BUG!"); \
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} while (0)
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#endif
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#ifndef HAVE_ARCH_BUG_ON
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#define BUG_ON(condition) do { if (unlikely(condition)) BUG(); } while (0)
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#endif
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/*
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* WARN(), WARN_ON(), WARN_ON_ONCE, and so on can be used to report
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* significant kernel issues that need prompt attention if they should ever
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* appear at runtime.
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*
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* Do not use these macros when checking for invalid external inputs
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* (e.g. invalid system call arguments, or invalid data coming from
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* network/devices), and on transient conditions like ENOMEM or EAGAIN.
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* These macros should be used for recoverable kernel issues only.
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* For invalid external inputs, transient conditions, etc use
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* pr_err[_once/_ratelimited]() followed by dump_stack(), if necessary.
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* Do not include "BUG"/"WARNING" in format strings manually to make these
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* conditions distinguishable from kernel issues.
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*
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* Use the versions with printk format strings to provide better diagnostics.
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*/
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#ifndef __WARN_FLAGS
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extern __printf(4, 5)
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void warn_slowpath_fmt(const char *file, const int line, unsigned taint,
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const char *fmt, ...);
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#define __WARN() __WARN_printf(TAINT_WARN, NULL)
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#define __WARN_printf(taint, arg...) \
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warn_slowpath_fmt(__FILE__, __LINE__, taint, arg)
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#else
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extern __printf(1, 2) void __warn_printk(const char *fmt, ...);
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#define __WARN() __WARN_FLAGS(BUGFLAG_TAINT(TAINT_WARN))
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#define __WARN_printf(taint, arg...) do { \
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__warn_printk(arg); \
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__WARN_FLAGS(BUGFLAG_NO_CUT_HERE | BUGFLAG_TAINT(taint));\
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} while (0)
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#define WARN_ON_ONCE(condition) ({ \
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int __ret_warn_on = !!(condition); \
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if (unlikely(__ret_warn_on)) \
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__WARN_FLAGS(BUGFLAG_ONCE | \
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BUGFLAG_TAINT(TAINT_WARN)); \
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unlikely(__ret_warn_on); \
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})
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#endif
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/* used internally by panic.c */
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struct warn_args;
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struct pt_regs;
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void __warn(const char *file, int line, void *caller, unsigned taint,
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struct pt_regs *regs, struct warn_args *args);
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#ifndef WARN_ON
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#define WARN_ON(condition) ({ \
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int __ret_warn_on = !!(condition); \
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if (unlikely(__ret_warn_on)) \
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__WARN(); \
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unlikely(__ret_warn_on); \
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})
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#endif
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#ifndef WARN
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#define WARN(condition, format...) ({ \
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int __ret_warn_on = !!(condition); \
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if (unlikely(__ret_warn_on)) \
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__WARN_printf(TAINT_WARN, format); \
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unlikely(__ret_warn_on); \
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})
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#endif
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#define WARN_TAINT(condition, taint, format...) ({ \
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int __ret_warn_on = !!(condition); \
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if (unlikely(__ret_warn_on)) \
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__WARN_printf(taint, format); \
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unlikely(__ret_warn_on); \
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})
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#ifndef WARN_ON_ONCE
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#define WARN_ON_ONCE(condition) ({ \
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static bool __section(.data.once) __warned; \
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int __ret_warn_once = !!(condition); \
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\
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if (unlikely(__ret_warn_once && !__warned)) { \
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__warned = true; \
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WARN_ON(1); \
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} \
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unlikely(__ret_warn_once); \
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})
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#endif
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#define WARN_ONCE(condition, format...) ({ \
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static bool __section(.data.once) __warned; \
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int __ret_warn_once = !!(condition); \
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\
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if (unlikely(__ret_warn_once && !__warned)) { \
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__warned = true; \
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WARN(1, format); \
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} \
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unlikely(__ret_warn_once); \
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})
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#define WARN_TAINT_ONCE(condition, taint, format...) ({ \
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static bool __section(.data.once) __warned; \
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int __ret_warn_once = !!(condition); \
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\
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if (unlikely(__ret_warn_once && !__warned)) { \
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__warned = true; \
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WARN_TAINT(1, taint, format); \
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} \
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unlikely(__ret_warn_once); \
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})
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#else /* !CONFIG_BUG */
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#ifndef HAVE_ARCH_BUG
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#define BUG() do {} while (1)
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#endif
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#ifndef HAVE_ARCH_BUG_ON
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#define BUG_ON(condition) do { if (unlikely(condition)) BUG(); } while (0)
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#endif
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#ifndef HAVE_ARCH_WARN_ON
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#define WARN_ON(condition) ({ \
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int __ret_warn_on = !!(condition); \
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unlikely(__ret_warn_on); \
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})
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#endif
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#ifndef WARN
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#define WARN(condition, format...) ({ \
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int __ret_warn_on = !!(condition); \
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no_printk(format); \
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unlikely(__ret_warn_on); \
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})
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#endif
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#define WARN_ON_ONCE(condition) WARN_ON(condition)
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#define WARN_ONCE(condition, format...) WARN(condition, format)
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#define WARN_TAINT(condition, taint, format...) WARN(condition, format)
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#define WARN_TAINT_ONCE(condition, taint, format...) WARN(condition, format)
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#endif
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/*
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* WARN_ON_SMP() is for cases that the warning is either
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* meaningless for !SMP or may even cause failures.
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* It can also be used with values that are only defined
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* on SMP:
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*
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* struct foo {
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* [...]
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* #ifdef CONFIG_SMP
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* int bar;
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* #endif
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* };
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*
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* void func(struct foo *zoot)
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* {
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* WARN_ON_SMP(!zoot->bar);
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*
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* For CONFIG_SMP, WARN_ON_SMP() should act the same as WARN_ON(),
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* and should be a nop and return false for uniprocessor.
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*
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* if (WARN_ON_SMP(x)) returns true only when CONFIG_SMP is set
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* and x is true.
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*/
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#ifdef CONFIG_SMP
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# define WARN_ON_SMP(x) WARN_ON(x)
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#else
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/*
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* Use of ({0;}) because WARN_ON_SMP(x) may be used either as
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* a stand alone line statement or as a condition in an if ()
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* statement.
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* A simple "0" would cause gcc to give a "statement has no effect"
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* warning.
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*/
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# define WARN_ON_SMP(x) ({0;})
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#endif
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#endif /* __ASSEMBLY__ */
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#endif
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