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Filename Latest commit message Latest commit date
Josh Poimboeuf dd88a0a0c8 objtool: Handle GCC stack pointer adjustment bug
Arnd Bergmann reported the following warning with GCC 7.1.1:

  fs/fs_pin.o: warning: objtool: pin_kill()+0x139: stack state mismatch: cfa1=7+88 cfa2=7+96

And the kbuild robot reported the following warnings with GCC 5.4.1:

  fs/fs_pin.o: warning: objtool: pin_kill()+0x182: return with modified stack frame
  fs/quota/dquot.o: warning: objtool: dquot_alloc_inode()+0x140: stack state mismatch: cfa1=7+120 cfa2=7+128
  fs/quota/dquot.o: warning: objtool: dquot_free_inode()+0x11a: stack state mismatch: cfa1=7+112 cfa2=7+120

Those warnings are caused by an unusual GCC non-optimization where it
uses an intermediate register to adjust the stack pointer.  It does:

  lea    0x8(%rsp), %rcx
  ...
  mov    %rcx, %rsp

Instead of the obvious:

  add    $0x8, %rsp

It makes no sense to use an intermediate register, so I opened a GCC bug
to track it:

  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81813

But it's not exactly a high-priority bug and it looks like we'll be
stuck with this issue for a while.  So for now we have to track register
values when they're loaded with stack pointer offsets.

This is kind of a big workaround for a tiny problem, but c'est la vie.
I hope to eventually create a GCC plugin to implement a big chunk of
objtool's functionality.  Hopefully at that point we'll be able to
remove of a lot of these GCC-isms from the objtool code.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/6a41a96884c725e7f05413bb7df40cfe824b2444.1504028945.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-08-30 10:48:41 +02:00
arch x86/entry/64: Use ENTRY() instead of ALIGN+GLOBAL for stub32_clone() 2017-08-29 13:23:30 +02:00
block blk-mq: don't leak preempt counter/q_usage_counter when allocating rq failed 2017-08-02 08:23:57 -06:00
certs
crypto
Documentation Merge branch 'x86/urgent' into x86/asm, to pick up fixes 2017-08-10 13:14:15 +02:00
drivers x86/lguest: Remove lguest support 2017-08-24 09:57:28 +02:00
firmware
fs Changes since last update: 2017-08-07 18:16:22 -07:00
include x86/lguest: Remove lguest support 2017-08-24 09:57:28 +02:00
init
ipc ipc: add missing container_of()s for randstruct 2017-08-02 17:16:12 -07:00
kernel futex: Remove unnecessary warning from get_futex_key 2017-08-09 14:00:54 -07:00
lib Merge branch 'x86/urgent' into x86/asm, to pick up fixes 2017-08-10 13:14:15 +02:00
mm mm: take memory hotplug lock within numa_zonelist_order_handler() 2017-08-02 17:16:11 -07:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-08-09 10:14:04 -07:00
samples samples/bpf: fix bpf tunnel cleanup 2017-07-31 22:02:47 -07:00
scripts Merge branch 'x86/urgent' into x86/asm, to pick up fixes 2017-08-10 13:14:15 +02:00
security
sound ASoC: Fixes for v4.13 2017-08-02 17:11:45 +02:00
tools objtool: Handle GCC stack pointer adjustment bug 2017-08-30 10:48:41 +02:00
usr
virt KVM/ARM Fixes for v4.13-rc4 2017-08-03 17:59:58 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS x86/lguest: Remove lguest support 2017-08-24 09:57:28 +02:00
Makefile Linux 4.13-rc4 2017-08-06 18:44:49 -07:00
README

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

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

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.