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Peter Zijlstra 07b487eb57 ftrace/x86_64: Emulate call function while updating in breakpoint handler 
commit 9e298e8604 upstream.

Nicolai Stange discovered[1] that if live kernel patching is enabled, and the
function tracer started tracing the same function that was patched, the
conversion of the fentry call site during the translation of going from
calling the live kernel patch trampoline to the iterator trampoline, would
have as slight window where it didn't call anything.

As live kernel patching depends on ftrace to always call its code (to
prevent the function being traced from being called, as it will redirect
it). This small window would allow the old buggy function to be called, and
this can cause undesirable results.

Nicolai submitted new patches[2] but these were controversial. As this is
similar to the static call emulation issues that came up a while ago[3].
But after some debate[4][5] adding a gap in the stack when entering the
breakpoint handler allows for pushing the return address onto the stack to
easily emulate a call.

[1] http://lkml.kernel.org/r/20180726104029.7736-1-nstange@suse.de
[2] http://lkml.kernel.org/r/20190427100639.15074-1-nstange@suse.de
[3] http://lkml.kernel.org/r/3cf04e113d71c9f8e4be95fb84a510f085aa4afa.1541711457.git.jpoimboe@redhat.com
[4] http://lkml.kernel.org/r/CAHk-=wh5OpheSU8Em_Q3Hg8qw_JtoijxOdPtHru6d+5K8TWM=A@mail.gmail.com
[5] http://lkml.kernel.org/r/CAHk-=wjvQxY4DvPrJ6haPgAa6b906h=MwZXO6G8OtiTGe=N7_w@mail.gmail.com

[
  Live kernel patching is not implemented on x86_32, thus the emulate
  calls are only for x86_64.
]

Cc: Andy Lutomirski <luto@kernel.org>
Cc: Nicolai Stange <nstange@suse.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: the arch/x86 maintainers <x86@kernel.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Miroslav Benes <mbenes@suse.cz>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Joe Lawrence <joe.lawrence@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Mimi Zohar <zohar@linux.ibm.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Nayna Jain <nayna@linux.ibm.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Joerg Roedel <jroedel@suse.de>
Cc: "open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@vger.kernel.org>
Cc: stable@vger.kernel.org
Fixes: b700e7f03d ("livepatch: kernel: add support for live patching")
Tested-by: Nicolai Stange <nstange@suse.de>
Reviewed-by: Nicolai Stange <nstange@suse.de>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
[ Changed to only implement emulated calls for x86_64 ]
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-05-25 18:23:31 +02:00
arch ftrace/x86_64: Emulate call function while updating in breakpoint handler 2019-05-25 18:23:31 +02:00
block bfq: update internal depth state when queue depth changes 2019-05-16 19:41:17 +02:00
certs export.h: remove VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR() 2018-08-22 23:21:44 +09:00
crypto crypto: ccm - fix incompatibility between "ccm" and "ccm_base" 2019-05-22 07:37:43 +02:00
Documentation dcache: sort the freeing-without-RCU-delay mess for good. 2019-05-25 18:23:26 +02:00
drivers iommu/tegra-smmu: Fix invalid ASID bits on Tegra30/114 2019-05-25 18:23:30 +02:00
firmware kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
fs ceph: flush dirty inodes before proceeding with remount 2019-05-25 18:23:31 +02:00
include udlfb: introduce a rendering mutex 2019-05-25 18:23:30 +02:00
init init: initialize jump labels before command line option parsing 2019-05-16 19:41:23 +02:00
ipc ipc/shm.c: use ERR_CAST() for shm_lock() error return 2018-10-05 16:32:04 -07:00
kernel userfaultfd: use RCU to free the task struct when fork fails 2019-05-22 07:37:41 +02:00
lib iov_iter: optimize page_copy_sane() 2019-05-22 07:37:45 +02:00
LICENSES LICENSES: Remove CC-BY-SA-4.0 license text 2018-10-18 11:28:50 +02:00
mm hugetlb: use same fault hash key for shared and private mappings 2019-05-22 07:37:40 +02:00
net vsock/virtio: Initialize core virtio vsock before registering the driver 2019-05-25 18:23:22 +02:00
samples samples: mei: use /dev/mei0 instead of /dev/mei 2019-02-15 08:10:11 +01:00
scripts fs: stream_open - opener for stream-like files so that read and write can run simultaneously without deadlock 2019-05-08 07:21:51 +02:00
security selinux: do not report error on connect(AF_UNSPEC) 2019-05-16 19:41:30 +02:00
sound ALSA: hda/realtek - Fix for Lenovo B50-70 inverted internal microphone bug 2019-05-22 07:37:44 +02:00
tools objtool: Fix function fallthrough detection 2019-05-22 07:37:35 +02:00
usr initramfs: move gen_initramfs_list.sh from scripts/ to usr/ 2018-08-22 23:21:44 +09:00
virt KVM: fix spectrev1 gadgets 2019-05-16 19:41:22 +02:00
.clang-format clang-format: Set IndentWrappedFunctionNames false 2018-08-01 18:38:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Add hch to .get_maintainer.ignore 2015-08-21 14:30:10 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
.mailmap libnvdimm-for-4.19_misc 2018-08-25 18:13:10 -07:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS 9p: remove Ron Minnich from MAINTAINERS 2018-08-17 16:20:26 -07:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS platform/x86: Add Intel AtomISP2 dummy / power-management driver 2019-04-20 09:16:02 +02:00
Makefile Linux 4.19.45 2019-05-22 07:37:46 +02:00
README Docs: Added a pointer to the formatted docs to README 2018-03-21 09:02:53 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.