- May 19, 2022
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Josh Poimboeuf authored
With CONFIG_GENERIC_BUG_RELATIVE_POINTERS, the addr/file relative pointers are calculated weirdly: based on the beginning of the bug_entry struct address, rather than their respective pointer addresses. Make the relative pointers less surprising to both humans and tools by calculating them the normal way. Signed-off-by:
Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by:
Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by:
Mark Rutland <mark.rutland@arm.com> Acked-by:
Catalin Marinas <catalin.marinas@arm.com> Tested-by: Mark Rutland <mark.rutland@arm.com> [arm64] Link: https://lkml.kernel.org/r/f0e05be797a16f4fc2401eeb88c8450dcbe61df6.1652362951.git.jpoimboe@kernel.org
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- Apr 01, 2021
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Andrew Scull authored
Set bug_get_file_line()'s output parameter values directly rather than first nullifying them and then conditionally setting new values. Signed-off-by:
Andrew Scull <ascull@google.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: "Steven Rostedt (VMware)" <rostedt@goodmis.org> Acked-by:
Will Deacon <will@kernel.org> Signed-off-by:
Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20210318143311.839894-4-ascull@google.com
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Andrew Scull authored
There is some non-trivial config-based logic to get the file name and line number associated with a bug. Factor this out to a getter that can be resused. Signed-off-by:
Steven Rostedt (VMware) <rostedt@goodmis.org> Acked-by:
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Andrew Scull authored
report_bug() will return early if it cannot find a bug corresponding to the provided address. The subsequent test for the bug will always be true so remove it. Fixes: 1b4cfe3c ("lib/bug.c: exclude non-BUG/WARN exceptions from report_bug()") Signed-off-by:
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- Feb 08, 2021
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Christoph Hellwig authored
Except for two lockdep asserts module_mutex is only used in module.c. Remove the two asserts given that the functions they are in are not exported and just called from the module code, and mark module_mutex static. Reviewed-by:
Miroslav Benes <mbenes@suse.cz> Signed-off-by:
Christoph Hellwig <hch@lst.de> Signed-off-by:
Jessica Yu <jeyu@kernel.org>
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- Jun 01, 2020
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Peter Zijlstra authored
While doing some tracing, I found a huge portion of the per-cpu buffer was taken by printk/serial output because we're disabling the trace far too late (after printing the CUT string). Improve matters for architectures that have GENERIC_BUG + _BUG_FLAGS by killing the tracer in the exception handler before printing anything much. Link: https://lkml.kernel.org/r/20200528145240.GF706495@hirez.programming.kicks-ass.net Signed-off-by:
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- Sep 26, 2019
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Kees Cook authored
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: 6b15f678 ("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>
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- Mar 10, 2018
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Kees Cook authored
Commit b8347c21 ("x86/debug: Handle warnings before the notifier chain, to fix KGDB crash") changed the ordering of fixups, and did not take into account the case of x86 processing non-WARN() and non-BUG() exceptions. This would lead to output of a false BUG line with no other information. In the case of a refcount exception, it would be immediately followed by the refcount WARN(), producing very strange double-"cut here": lkdtm: attempting bad refcount_inc() overflow ------------[ cut here ]------------ Kernel BUG at 0000000065f29de5 [verbose debug info unavailable] ------------[ cut here ]------------ refcount_t overflow at lkdtm_REFCOUNT_INC_OVERFLOW+0x6b/0x90 in cat[3065], uid/euid: 0/0 WARNING: CPU: 0 PID: 3065 at kernel/panic.c:657 refcount_error_report+0x9a/0xa4 ... In the prior ordering, exceptions were searched first: do_trap_no_signal(struct task_struct *tsk, int trapnr, char *str, ... if (fixup_exception(regs, trapnr)) return 0; - if (fixup_bug(regs, trapnr)) - return 0; - As a result, fixup_bugs()'s is_valid_bugaddr() didn't take into account needing to search the exception list first, since that had already happened. So, instead of searching the exception list twice (once in is_valid_bugaddr() and then again in fixup_exception()), just add a simple sanity check to report_bug() that will immediately bail out if a BUG() (or WARN()) entry is not found. Link: http://lkml.kernel.org/r/20180301225934.GA34350@beast Fixes: b8347c21 ("x86/debug: Handle warnings before the notifier chain, to fix KGDB crash") Signed-off-by:
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Kees Cook authored
The BUG and stack protector reports were still using a raw %p. This changes it to %pB for more meaningful output. Link: http://lkml.kernel.org/r/20180301225704.GA34198@beast Fixes: ad67b74d ("printk: hash addresses printed with %p") Signed-off-by:
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- Nov 18, 2017
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Kees Cook authored
The "cut here" string is used in a few paths. Define it in a single place. Link: http://lkml.kernel.org/r/1510100869-73751-3-git-send-email-keescook@chromium.org Signed-off-by:
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Andi Kleen authored
Some architectures store the WARN_ONCE state in the flags field of the bug_entry. Clear that one too when resetting once state through /sys/kernel/debug/clear_warn_once Pointed out by Michael Ellerman Improves the earlier patch that add clear_warn_once. [ak@linux.intel.com: add a missing ifdef CONFIG_MODULES] Link: http://lkml.kernel.org/r/20171020170633.9593-1-andi@firstfloor.org [akpm@linux-foundation.org: fix unused var warning] [akpm@linux-foundation.org: Use 0200 for clear_warn_once file, per mpe] [akpm@linux-foundation.org: clear BUGFLAG_DONE in clear_once_table(), per mpe] Link: http://lkml.kernel.org/r/20171019204642.7404-1-andi@firstfloor.org Signed-off-by:
Andi Kleen <ak@linux.intel.com> Tested-by:
Michael Ellerman <mpe@ellerman.id.au> Signed-off-by:
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- Nov 02, 2017
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Greg Kroah-Hartman authored
Many source files in the tree are missing licensing information, which makes it harder for compliance tools to determine the correct license. By default all files without license information are under the default license of the kernel, which is GPL version 2. Update the files which contain no license information with the 'GPL-2.0' SPDX license identifier. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This patch is based on work done by Thomas Gleixner and Kate Stewart and Philippe Ombredanne. How this work was done: Patches were generated and checked against linux-4.14-rc6 for a subset of the use cases: - file had no licensing information it it. - file was a */uapi/* one with no licensing information in it, - file was a */uapi/* one with existing licensing information, Further patches will be generated in subsequent months to fix up cases where non-standard license headers were used, and references to license had to be inferred by heuristics based on keywords. The analysis to determine which SPDX License Identifier to be applied to a file was done in a spreadsheet of side by side results from of the output of two independent scanners (ScanCode & Windriver) producing SPDX tag:value files created by Philippe Ombredanne. Philippe prepared the base worksheet, and did an initial spot review of a few 1000 files. The 4.13 kernel was the starting point of the analysis with 60,537 files assessed. Kate Stewart did a file by file comparison of the scanner results in the spreadsheet to determine which SPDX license identifier(s) to be applied to the file. She confirmed any determination that was not immediately clear with lawyers working with the Linux Foundation. Criteria used to select files for SPDX license identifier tagging was: - Files considered eligible had to be source code files. - Make and config files were included as candidates if they contained >5 lines of source - File already had some variant of a license header in it (even if <5 lines). All documentation files were explicitly excluded. The following heuristics were used to determine which SPDX license identifiers to apply. - when both scanners couldn't find any license traces, file was considered to have no license information in it, and the top level COPYING file license applied. For non */uapi/* files that summary was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 11139 and resulted in the first patch in this series. If that file was a */uapi/* path one, it was "GPL-2.0 WITH Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 WITH Linux-syscall-note 930 and resulted in the second patch in this series. - if a file had some form of licensing information in it, and was one of the */uapi/* ones, it was denoted with the Linux-syscall-note if any GPL family license was found in the file or had no licensing in it (per prior point). Results summary: SPDX license identifier # files ---------------------------------------------------|------ GPL-2.0 WITH Linux-syscall-note 270 GPL-2.0+ WITH Linux-syscall-note 169 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17 LGPL-2.1+ WITH Linux-syscall-note 15 GPL-1.0+ WITH Linux-syscall-note 14 ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5 LGPL-2.0+ WITH Linux-syscall-note 4 LGPL-2.1 WITH Linux-syscall-note 3 ((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3 ((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1 and that resulted in the third patch in this series. - when the two scanners agreed on the detected license(s), that became the concluded license(s). - when there was disagreement between the two scanners (one detected a license but the other didn't, or they both detected different licenses) a manual inspection of the file occurred. - In most cases a manual inspection of the information in the file resulted in a clear resolution of the license that should apply (and which scanner probably needed to revisit its heuristics). - When it was not immediately clear, the license identifier was confirmed with lawyers working with the Linux Foundation. - If there was any question as to the appropriate license identifier, the file was flagged for further research and to be revisited later in time. In total, over 70 hours of logged manual review was done on the spreadsheet to determine the SPDX license identifiers to apply to the source files by Kate, Philippe, Thomas and, in some cases, confirmation by lawyers working with the Linux Foundation. Kate also obtained a third independent scan of the 4.13 code base from FOSSology, and compared selected files where the other two scanners disagreed against that SPDX file, to see if there was new insights. The Windriver scanner is based on an older version of FOSSology in part, so they are related. Thomas did random spot checks in about 500 files from the spreadsheets for the uapi headers and agreed with SPDX license identifier in the files he inspected. For the non-uapi files Thomas did random spot checks in about 15000 files. In initial set of patches against 4.14-rc6, 3 files were found to have copy/paste license identifier errors, and have been fixed to reflect the correct identifier. Additionally Philippe spent 10 hours this week doing a detailed manual inspection and review of the 12,461 patched files from the initial patch version early this week with: - a full scancode scan run, collecting the matched texts, detected license ids and scores - reviewing anything where there was a license detected (about 500+ files) to ensure that the applied SPDX license was correct - reviewing anything where there was no detection but the patch license was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied SPDX license was correct This produced a worksheet with 20 files needing minor correction. This worksheet was then exported into 3 different .csv files for the different types of files to be modified. These .csv files were then reviewed by Greg. Thomas wrote a script to parse the csv files and add the proper SPDX tag to the file, in the format that the file expected. This script was further refined by Greg based on the output to detect more types of files automatically and to distinguish between header and source .c files (which need different comment types.) Finally Greg ran the script using the .csv files to generate the patches. Reviewed-by:
Kate Stewart <kstewart@linuxfoundation.org> Reviewed-by:
Philippe Ombredanne <pombredanne@nexb.com> Reviewed-by:
Thomas Gleixner <tglx@linutronix.de> Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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- Mar 30, 2017
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Josh suggested moving the _ONCE logic inside the trap handler, using a bit in the bug_entry::flags field, avoiding the need for the extra variable. Sadly this only works for WARN_ON_ONCE(), since the others have printk() statements prior to triggering the trap. Still, this saves a fair amount of text and some data: text data filename 10682460 4530992 defconfig-build/vmlinux.orig 10665111 4530096 defconfig-build/vmlinux.patched Suggested-by:
Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by:
Ingo Molnar <mingo@kernel.org>
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- Mar 02, 2017
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Ingo Molnar authored
We don't actually need the full rculist.h header in sched.h anymore, we will be able to include the smaller rcupdate.h header instead. But first update code that relied on the implicit header inclusion. Acked-by:
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- Mar 17, 2016
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Josh Poimboeuf authored
The traceoff_on_warning option doesn't have any effect on s390, powerpc, arm64, parisc, and sh because there are two different types of WARN implementations: 1) The above mentioned architectures treat WARN() as a special case of a BUG() exception. They handle warnings in report_bug() in lib/bug.c. 2) All other architectures just call warn_slowpath_*() directly. Their warnings are handled in warn_slowpath_common() in kernel/panic.c. Support traceoff_on_warning on all architectures and prevent any future divergence by using a single common function to emit the warning. Also remove the '()' from '%pS()', because the parentheses look funky: [ 45.607629] WARNING: at /root/warn_mod/warn_mod.c:17 .init_dummy+0x20/0x40 [warn_mod]() Reported-by:
Chunyu Hu <chuhu@redhat.com> Signed-off-by:
Heiko Carstens <heiko.carstens@de.ibm.com> Tested-by:
Prarit Bhargava <prarit@redhat.com> Acked-by:
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Heiko Carstens authored
Christian Borntraeger reported that panic_on_warn doesn't have any effect on s390. The panic_on_warn feature was introduced with 9e3961a0 ("kernel: add panic_on_warn"). However it did care only for the case when WANT_WARN_ON_SLOWPATH is defined. This is turn is only the case for architectures which do not have an own __WARN_TAINT defined. Other architectures which do have __WARN_TAINT defined call report_bug() for warnings within lib/bug.c which does not call panic() in case panic_on_warn is set. Let's simply enable the panic_on_warn feature by adding the same code like it was added to warn_slowpath_common() in panic.c. This enables panic_on_warn also for arm64, parisc, powerpc, s390 and sh. Signed-off-by:
Christian Borntraeger <borntraeger@de.ibm.com> Tested-by:
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- May 28, 2015
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Peter Zijlstra authored
Currently the RCU usage in module is an inconsistent mess of RCU and RCU-sched, this is broken for CONFIG_PREEMPT where synchronize_rcu() does not imply synchronize_sched(). Most usage sites use preempt_{dis,en}able() which is RCU-sched, but (most of) the modification sites use synchronize_rcu(). With the exception of the module bug list, which actually uses RCU. Convert everything over to RCU-sched. Furthermore add lockdep asserts to all sites, because it's not at all clear to me the required locking is observed, esp. on exported functions. Cc: Rusty Russell <rusty@rustcorp.com.au> Acked-by:"Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Signed-off-by:
Rusty Russell <rusty@rustcorp.com.au>
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- Nov 11, 2014
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Masami Hiramatsu authored
Actually since module_bug_list should be used in BUG context, we may not need this. But for someone who want to use this from normal context, this makes module_bug_list an RCU list. Signed-off-by:
Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Signed-off-by:
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- Jun 04, 2014
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Fabian Frederick authored
- Coalesce formats - "WARNING:" prefix unchanged to keep bug format. - printk(KERN_DEFAULT not converted. - define pr_fmt without prefix to avoid any default prefix update (suggested by Joe Perches). Signed-off-by:
Fabian Frederick <fabf@skynet.be> Cc: Jeremy Fitzhardinge <jeremy@goop.org> Cc: Joe Perches <joe@perches.com> Signed-off-by:
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- Jan 21, 2013
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Rusty Russell authored
Fix up all callers as they were before, with make one change: an unsigned module taints the kernel, but doesn't turn off lockdep. Signed-off-by:
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- Jan 12, 2013
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Rusty Russell authored
Prarit's excellent bug report: > In recent Fedora releases (F17 & F18) some users have reported seeing > messages similar to > > [ 15.478160] kvm: Could not allocate 304 bytes percpu data > [ 15.478174] PERCPU: allocation failed, size=304 align=32, alloc from > reserved chunk failed > > during system boot. In some cases, users have also reported seeing this > message along with a failed load of other modules. > > What is happening is systemd is loading an instance of the kvm module for > each cpu found (see commit e9bda3b3). When the module load occurs the kernel > currently allocates the modules percpu data area prior to checking to see > if the module is already loaded or is in the process of being loaded. If > the module is already loaded, or finishes load, the module loading code > releases the current instance's module's percpu data. Now we have a new state MODULE_STATE_UNFORMED, we can insert the module into the list (and thus guarantee its uniqueness) before we allocate the per-cpu region. Reported-by:
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- Jan 26, 2012
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Prarit Bhargava authored
rsyslog will display KERN_EMERG messages on a connected terminal. However, these messages are useless/undecipherable for a general user. For example, after a softlockup we get: Message from syslogd@intel-s3e37-04 at Jan 25 14:18:06 ... kernel:Stack: Message from syslogd@intel-s3e37-04 at Jan 25 14:18:06 ... kernel:Call Trace: Message from syslogd@intel-s3e37-04 at Jan 25 14:18:06 ... kernel:Code: ff ff a8 08 75 25 31 d2 48 8d 86 38 e0 ff ff 48 89 d1 0f 01 c8 0f ae f0 48 8b 86 38 e0 ff ff a8 08 75 08 b1 01 4c 89 e0 0f 01 c9 <e8> ea 69 dd ff 4c 29 e8 48 89 c7 e8 0f bc da ff 49 89 c4 49 89 This happens because the printk levels for these messages are incorrect. Only an informational message should be displayed on a terminal. I modified the printk levels for various messages in the kernel and tested the output by using the drivers/misc/lkdtm.c kernel modules (ie, softlockups, panics, hard lockups, etc.) and confirmed that the console output was still the same and that the output to the terminals was correct. For example, in the case of a softlockup we now see the much more informative: Message from syslogd@intel-s3e37-04 at Jan 25 10:18:06 ... BUG: soft lockup - CPU4 stuck for 60s! instead of the above confusing messages. AFAICT, the messages no longer have to be KERN_EMERG. In the most important case of a panic we set console_verbose(). As for the other less severe cases the correct data is output to the console and /var/log/messages. Successfully tested by me using the drivers/misc/lkdtm.c module. Signed-off-by:
Ingo Molnar <mingo@elte.hu>
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- Oct 05, 2010
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Linus Torvalds authored
With all the recent module loading cleanups, we've minimized the code that sits under module_mutex, fixing various deadlocks and making it possible to do most of the module loading in parallel. However, that whole conversion totally missed the rather obscure code that adds a new module to the list for BUG() handling. That code was doubly obscure because (a) the code itself lives in lib/bugs.c (for dubious reasons) and (b) it gets called from the architecture-specific "module_finalize()" rather than from generic code. Calling it from arch-specific code makes no sense what-so-ever to begin with, and is now actively wrong since that code isn't protected by the module loading lock any more. So this commit moves the "module_bug_{finalize,cleanup}()" calls away from the arch-specific code, and into the generic code - and in the process protects it with the module_mutex so that the list operations are now safe. Future fixups: - move the module list handling code into kernel/module.c where it belongs. - get rid of 'module_bug_list' and just use the regular list of modules (called 'modules' - imagine that) that we already create and maintain for other reasons. Reported-and-tested-by:
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- Aug 11, 2010
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Anton Blanchard authored
We are missing the oops end marker for the exception based WARN implementation in lib/bug.c. This is useful for logfile analysis tools. Signed-off-by:
Anton Blanchard <anton@samba.org> Cc: Ingo Molnar <mingo@elte.hu> Cc: Arjan van de Ven <arjan@infradead.org> Cc: "Kirill A. Shutemov" <kirill@shutemov.name> Signed-off-by:
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Anton Blanchard authored
There are a few issues with the exception based WARN implementation in lib/bug.c: - Inconsistent printk flags. The "cut here" line is printed at KERN_EMERG, so the console and all logged in users see the single line: ------------[ cut here ]------------ for each WARN. Fix this so we print everything at KERN_WARNING to match the kernel/panic.c version. - The lib/bug.c WARN would print "Badness at". Change it to match the kernel/panic.c version which prints "WARNING: at". - Print the list of modules, similar to kernel/panic.c of modules, similar to kernel/panic.c [akpm@linux-foundation.org: coding-style fixes] Signed-off-by:
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- May 19, 2010
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Ben Hutchings authored
WARN() is used in some places to report firmware or hardware bugs that are then worked-around. These bugs do not affect the stability of the kernel and should not set the flag for TAINT_WARN. To allow for this, add WARN_TAINT() and WARN_TAINT_ONCE() macros that take a taint number as argument. Architectures that implement warnings using trap instructions instead of calls to warn_slowpath_*() now implement __WARN_TAINT(taint) instead of __WARN(). Signed-off-by:
Ben Hutchings <ben@decadent.org.uk> Acked-by:
Helge Deller <deller@gmx.de> Tested-by:
Paul Mundt <lethal@linux-sh.org> Signed-off-by:
David Woodhouse <David.Woodhouse@intel.com>
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- Dec 16, 2008
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Jan Beulich authored
Impact: reduce bug table size This allows reducing the bug table size by half. Perhaps there are other 64-bit architectures that could also make use of this. Signed-off-by:
Jan Beulich <jbeulich@novell.com> Signed-off-by:
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- Jul 04, 2008
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Paul Mundt authored
Commit 95b570c9 ("Taint kernel after WARN_ON(condition)") introduced a TAINT_WARN that was implemented for all architectures using the generic warn_on_slowpath(), which excluded any architecture that set HAVE_ARCH_WARN_ON. As all of the architectures that implement their own WARN_ON() all go through the report_bug() path (specifically handling BUG_TRAP_TYPE_WARN), taint the kernel there as well for consistency. Tested on avr32 and sh. Also relevant for s390, parisc, and powerpc. Signed-off-by:
Haavard Skinnemoen <hskinnemoen@atmel.com> Signed-off-by:
Kyle McMartin <kyle@mcmartin.ca> Signed-off-by:
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- Jul 16, 2007
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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:
Jeremy Fitzhardinge <jeremy@goop.org> Acked-by:
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- Dec 08, 2006
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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:
Adrian Bunk <bunk@stusta.de> Signed-off-by:
Andrew Morton <akpm@osdl.org> Signed-off-by:
Linus Torvalds <torvalds@osdl.org>
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