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2021-06-14Documentation: kdump: update kdump guideBaoquan He
Some parts of the guide are aged, hence need be updated. 1) The backup area of the 1st 640K on X86_64 has been removed by below commits, update the description accordingly. commit 7c321eb2b843 ("x86/kdump: Remove the backup region handling") commit 6f599d84231f ("x86/kdump: Always reserve the low 1M when the crashkernel option is specified") 2) Sort out the descripiton of "crashkernel syntax" part. 3) And some other minor cleanups. Signed-off-by: Baoquan He <bhe@redhat.com> Acked-by: Dave Young <dyoung@redhat.com> Link: https://lore.kernel.org/r/20210609083218.GB591017@MiWiFi-R3L-srv [jc: added blank line to fix added build warning] Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2020-12-15kdump: append uts_namespace.name offset to VMCOREINFOAlexander Egorenkov
The offset of the field 'init_uts_ns.name' has changed since commit 9a56493f6942 ("uts: Use generic ns_common::count"). Make the offset of the field 'uts_namespace.name' available in VMCOREINFO because tools like 'crash-utility' and 'makedumpfile' must be able to read it from crash dumps. Link: https://lore.kernel.org/r/159644978167.604812.1773586504374412107.stgit@localhost.localdomain Link: https://lkml.kernel.org/r/20200930102328.396488-1-egorenar@linux.ibm.com Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com> Acked-by: lijiang <lijiang@redhat.com> Acked-by: Baoquan He <bhe@redhat.com> Cc: Dave Young <dyoung@redhat.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: "Eric W . Biederman" <ebiederm@xmission.com> Cc: Kirill Tkhai <ktkhai@virtuozzo.com> Cc: Kees Cook <keescook@chromium.org> Cc: Christian Brauner <christian.brauner@ubuntu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-10-13Merge tag 'printk-for-5.10' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux Pull printk updates from Petr Mladek: "The big new thing is the fully lockless ringbuffer implementation, including the support for continuous lines. It will allow to store and read messages in any situation wihtout the risk of deadlocks and without the need of temporary per-CPU buffers. The access is still serialized by logbuf_lock. It synchronizes few more operations, for example, temporary buffer for formatting the message, syslog and kmsg_dump operations. The lock removal is being discussed and should be ready for the next release. The continuous lines are handled exactly the same way as before to avoid regressions in user space. It means that they are appended to the last message when the caller is the same. Only the last message can be extended. The data ring includes plain text of the messages. Except for an integer at the beginning of each message that points back to the descriptor ring with other metadata. The dictionary has to stay. journalctl uses it to filter the log. It allows to show messages related to a given device. The dictionary values are stored in the descriptor ring with the other metadata. This is the first part of the printk rework as discussed at Plumbers 2019, see https://lore.kernel.org/r/87k1acz5rx.fsf@linutronix.de. The next big step will be handling consoles by kthreads during the normal system operation. It will require special handling of situations when the kthreads could not get scheduled, for example, early boot, suspend, panic. Other changes: - Add John Ogness as a reviewer for printk subsystem. He is author of the rework and is familiar with the code and history. - Fix locking in serial8250_do_startup() to prevent lockdep report. - Few code cleanups" * tag 'printk-for-5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux: (27 commits) printk: Use fallthrough pseudo-keyword printk: reduce setup_text_buf size to LOG_LINE_MAX printk: avoid and/or handle record truncation printk: remove dict ring printk: move dictionary keys to dev_printk_info printk: move printk_info into separate array printk: reimplement log_cont using record extension printk: ringbuffer: add finalization/extension support printk: ringbuffer: change representation of states printk: ringbuffer: clear initial reserved fields printk: ringbuffer: add BLK_DATALESS() macro printk: ringbuffer: relocate get_data() printk: ringbuffer: avoid memcpy() on state_var printk: ringbuffer: fix setting state in desc_read() kernel.h: Move oops_in_progress to printk.h scripts/gdb: update for lockless printk ringbuffer scripts/gdb: add utils.read_ulong() docs: vmcoreinfo: add lockless printk ringbuffer vmcoreinfo printk: reduce LOG_BUF_SHIFT range for H8300 printk: ringbuffer: support dataless records ...
2020-10-12Merge branch 'printk-rework' into for-linusPetr Mladek
2020-09-24docs: admin-guide: update kdump documentation due to change of crash URLlijiang
Since crash utility has been moved to github, the original URL is no longer available. Let's update it accordingly. Suggested-by: Dave Young <dyoung@redhat.com> Signed-off-by: Lianbo Jiang <lijiang@redhat.com> Link: https://lore.kernel.org/r/a088bff5-1174-25fa-ac26-6e46795f4085@redhat.com Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2020-09-22printk: move dictionary keys to dev_printk_infoJohn Ogness
Dictionaries are only used for SUBSYSTEM and DEVICE properties. The current implementation stores the property names each time they are used. This requires more space than otherwise necessary. Also, because the dictionary entries are currently considered optional, it cannot be relied upon that they are always available, even if the writer wanted to store them. These issues will increase should new dictionary properties be introduced. Rather than storing the subsystem and device properties in the dict ring, introduce a struct dev_printk_info with separate fields to store only the property values. Embed this struct within the struct printk_info to provide guaranteed availability. Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/87mu1jl6ne.fsf@jogness.linutronix.de
2020-09-15printk: ringbuffer: add finalization/extension supportJohn Ogness
Add support for extending the newest data block. For this, introduce a new finalization state (desc_finalized) denoting a committed descriptor that cannot be extended. Until a record is finalized, a writer can reopen that record to append new data. Reopening a record means transitioning from the desc_committed state back to the desc_reserved state. A writer can explicitly finalize a record if there is no intention of extending it. Also, records are automatically finalized when a new record is reserved. This relieves writers of needing to explicitly finalize while also making such records available to readers sooner. (Readers can only traverse finalized records.) Four new memory barrier pairs are introduced. Two of them are insignificant additions (data_realloc:A/desc_read:D and data_realloc:A/data_push_tail:B) because they are alternate path memory barriers that exactly match the purpose, pairing, and context of the two existing memory barrier pairs they provide an alternate path for. The other two new memory barrier pairs are significant additions: desc_reopen_last:A / _prb_commit:B - When reopening a descriptor, ensure the state transitions back to desc_reserved before fully trusting the descriptor data. _prb_commit:B / desc_reserve:D - When committing a descriptor, ensure the state transitions to desc_committed before checking the head ID to see if the descriptor needs to be finalized. Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20200914123354.832-6-john.ogness@linutronix.de
2020-09-15printk: ringbuffer: change representation of statesJohn Ogness
Rather than deriving the state by evaluating bits within the flags area of the state variable, assign the states explicit values and set those values in the flags area. Introduce macros to make it simple to read and write state values for the state variable. Although the functionality is preserved, the binary representation for the states is changed. Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20200914123354.832-5-john.ogness@linutronix.de
2020-09-08scripts/gdb: update for lockless printk ringbufferJohn Ogness
With the introduction of the lockless printk ringbuffer, the data structure for the kernel log buffer was changed. Update the gdb scripts to be able to parse/print the new log buffer structure. Fixes: 896fbe20b4e2333fb55 ("printk: use the lockless ringbuffer") Signed-off-by: John Ogness <john.ogness@linutronix.de> Reported-by: Nick Desaulniers <ndesaulniers@google.com> Tested-by: Nick Desaulniers <ndesaulniers@google.com> Tested-by: Petr Mladek <pmladek@suse.com> [akpm@linux-foundation.org: A typo fix.] Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20200814212525.6118-3-john.ogness@linutronix.de
2020-09-08docs: vmcoreinfo: add lockless printk ringbuffer vmcoreinfoJohn Ogness
With the introduction of the lockless printk ringbuffer, the VMCOREINFO relating to the kernel log buffer was changed. Update the documentation to match those changes. Fixes: 896fbe20b4e2333fb55 ("printk: use the lockless ringbuffer") Reported-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20200814213316.6394-1-john.ogness@linutronix.de
2020-07-02arm64/crash_core: Export TCR_EL1.T1SZ in vmcoreinfoBhupesh Sharma
TCR_EL1.TxSZ, which controls the VA space size, is configured by a single kernel image to support either 48-bit or 52-bit VA space. If the ARMv8.2-LVA optional feature is present and we are running with a 64KB page size, then it is possible to use 52-bits of address space for both userspace and kernel addresses. However, any kernel binary that supports 52-bit must also be able to fall back to 48-bit at early boot time if the hardware feature is not present. Since TCR_EL1.T1SZ indicates the size of the memory region addressed by TTBR1_EL1, export the same in vmcoreinfo. User-space utilities like makedumpfile and crash-utility need to read this value from vmcoreinfo for determining if a virtual address lies in the linear map range. While at it also add documentation for TCR_EL1.T1SZ variable being added to vmcoreinfo. It indicates the size offset of the memory region addressed by TTBR1_EL1. Signed-off-by: Bhupesh Sharma <bhsharma@redhat.com> Tested-by: John Donnelly <john.p.donnelly@oracle.com> Tested-by: Kamlakant Patel <kamlakantp@marvell.com> Tested-by: Amit Daniel Kachhap <amit.kachhap@arm.com> Reviewed-by: James Morse <james.morse@arm.com> Reviewed-by: Amit Daniel Kachhap <amit.kachhap@arm.com> Cc: James Morse <james.morse@arm.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Will Deacon <will@kernel.org> Cc: Steve Capper <steve.capper@arm.com> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Dave Anderson <anderson@redhat.com> Cc: Kazuhito Hagio <k-hagio@ab.jp.nec.com> Cc: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org Cc: kexec@lists.infradead.org Link: https://lore.kernel.org/r/1589395957-24628-3-git-send-email-bhsharma@redhat.com [catalin.marinas@arm.com: removed vabits_actual from the commit log] Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2020-07-02crash_core, vmcoreinfo: Append 'MAX_PHYSMEM_BITS' to vmcoreinfoBhupesh Sharma
Right now user-space tools like 'makedumpfile' and 'crash' need to rely on a best-guess method of determining value of 'MAX_PHYSMEM_BITS' supported by underlying kernel. This value is used in user-space code to calculate the bit-space required to store a section for SPARESMEM (similar to the existing calculation method used in the kernel implementation): #define SECTIONS_SHIFT (MAX_PHYSMEM_BITS - SECTION_SIZE_BITS) Now, regressions have been reported in user-space utilities like 'makedumpfile' and 'crash' on arm64, with the recently added kernel support for 52-bit physical address space, as there is no clear method of determining this value in user-space (other than reading kernel CONFIG flags). As per suggestion from makedumpfile maintainer (Kazu), it makes more sense to append 'MAX_PHYSMEM_BITS' to vmcoreinfo in the core code itself rather than in arch-specific code, so that the user-space code for other archs can also benefit from this addition to the vmcoreinfo and use it as a standard way of determining 'SECTIONS_SHIFT' value in user-land. A reference 'makedumpfile' implementation which reads the 'MAX_PHYSMEM_BITS' value from vmcoreinfo in a arch-independent fashion is available here: While at it also update vmcoreinfo documentation for 'MAX_PHYSMEM_BITS' variable being added to vmcoreinfo. 'MAX_PHYSMEM_BITS' defines the maximum supported physical address space memory. Signed-off-by: Bhupesh Sharma <bhsharma@redhat.com> Tested-by: John Donnelly <john.p.donnelly@oracle.com> Acked-by: Dave Young <dyoung@redhat.com> Cc: Boris Petkov <bp@alien8.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: James Morse <james.morse@arm.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Will Deacon <will@kernel.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Paul Mackerras <paulus@samba.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Dave Anderson <anderson@redhat.com> Cc: Kazuhito Hagio <k-hagio@ab.jp.nec.com> Cc: x86@kernel.org Cc: linuxppc-dev@lists.ozlabs.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org Cc: kexec@lists.infradead.org Link: https://lore.kernel.org/r/1589395957-24628-2-git-send-email-bhsharma@redhat.com Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2020-06-08kernel: add panic_on_taintRafael Aquini
Analogously to the introduction of panic_on_warn, this patch introduces a kernel option named panic_on_taint in order to provide a simple and generic way to stop execution and catch a coredump when the kernel gets tainted by any given flag. This is useful for debugging sessions as it avoids having to rebuild the kernel to explicitly add calls to panic() into the code sites that introduce the taint flags of interest. For instance, if one is interested in proceeding with a post-mortem analysis at the point a given code path is hitting a bad page (i.e. unaccount_page_cache_page(), or slab_bug()), a coredump can be collected by rebooting the kernel with 'panic_on_taint=0x20' amended to the command line. Another, perhaps less frequent, use for this option would be as a means for assuring a security policy case where only a subset of taints, or no single taint (in paranoid mode), is allowed for the running system. The optional switch 'nousertaint' is handy in this particular scenario, as it will avoid userspace induced crashes by writes to sysctl interface /proc/sys/kernel/tainted causing false positive hits for such policies. [akpm@linux-foundation.org: tweak kernel-parameters.txt wording] Suggested-by: Qian Cai <cai@lca.pw> Signed-off-by: Rafael Aquini <aquini@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Luis Chamberlain <mcgrof@kernel.org> Cc: Dave Young <dyoung@redhat.com> Cc: Baoquan He <bhe@redhat.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Kees Cook <keescook@chromium.org> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Adrian Bunk <bunk@kernel.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Laura Abbott <labbott@redhat.com> Cc: Jeff Mahoney <jeffm@suse.com> Cc: Jiri Kosina <jikos@kernel.org> Cc: Takashi Iwai <tiwai@suse.de> Link: http://lkml.kernel.org/r/20200515175502.146720-1-aquini@redhat.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-05-11Documentation/vmcoreinfo: Add documentation for 'KERNELPACMASK'Amit Daniel Kachhap
Add documentation for KERNELPACMASK variable being added to the vmcoreinfo. It indicates the PAC bits mask information of signed kernel pointers if Armv8.3-A Pointer Authentication feature is present. Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Dave Young <dyoung@redhat.com> Cc: Baoquan He <bhe@redhat.com> Link: https://lore.kernel.org/r/1589202116-18265-2-git-send-email-amit.kachhap@arm.com Signed-off-by: Will Deacon <will@kernel.org>
2019-07-15docs: admin-guide: add kdump documentation into itMauro Carvalho Chehab
The Kdump documentation describes procedures with admins use in order to solve issues on their systems. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>