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Josh Poimboeuf 08b393d01c objtool: Support GCC 8 '-fnoreorder-functions'
Since the following commit:

  cd77849a69 ("objtool: Fix GCC 8 cold subfunction detection for aliased functions")

... if the kernel is built with EXTRA_CFLAGS='-fno-reorder-functions',
objtool can get stuck in an infinite loop.

That flag causes the new GCC 8 cold subfunctions to be placed in .text
instead of .text.unlikely.  But it also has an unfortunate quirk: in the
symbol table, the subfunction (e.g., nmi_panic.cold.7) is nested inside
the parent (nmi_panic).

That function overlap confuses objtool, and causes it to get into an
infinite loop in next_insn_same_func().  Here's Allan's description of
the loop:

  "Objtool iterates through the instructions in nmi_panic using
  next_insn_same_func. Once it reaches the end of nmi_panic at 0x534 it
  jumps to 0x528 as that's the start of nmi_panic.cold.7. However, since
  the instructions starting at 0x528 are still associated with nmi_panic
  objtool will get stuck in a loop, continually jumping back to 0x528
  after reaching 0x534."

Fix it by shortening the length of the parent function so that the
functions no longer overlap.

Reported-and-analyzed-by: Allan Xavier <allan.x.xavier@oracle.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Allan Xavier <allan.x.xavier@oracle.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.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/9e704c52bee651129b036be14feda317ae5606ae.1530136978.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2018-07-02 09:42:11 +02:00
Documentation USB fixes for 4.18-rc3 2018-07-01 11:50:16 -07:00
LICENSES LICENSES: Add Linux-OpenIB license text 2018-04-27 16:41:53 -06:00
arch Merge branch 'parisc-4.18-1' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux 2018-06-30 14:16:30 -07:00
block for-linus-20180629 2018-06-30 10:47:46 -07:00
certs certs/blacklist: fix const confusion 2018-06-26 09:43:03 -07:00
crypto Revert changes to convert to ->poll_mask() and aio IOCB_CMD_POLL 2018-06-28 10:40:47 -07:00
drivers Staging/IIO fixes for 4.18-rc3 2018-07-01 12:20:20 -07:00
firmware kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
fs for-4.18-rc2-tag 2018-07-01 12:38:16 -07:00
include Staging/IIO fixes for 4.18-rc3 2018-07-01 12:20:20 -07:00
init Kbuild fixes for v4.18 2018-06-30 13:05:30 -07:00
ipc ipc: use new return type vm_fault_t 2018-06-15 07:55:25 +09:00
kernel Add a missing export required by riscv and unicore 2018-07-01 10:45:13 -07:00
lib for-linus-20180629 2018-06-30 10:47:46 -07:00
mm slub: fix failure when we delete and create a slab cache 2018-06-28 11:16:44 -07:00
net net: handle NULL ->poll gracefully 2018-06-29 06:51:51 -07:00
samples VFIO updates for v4.18 2018-06-12 13:11:26 -07:00
scripts Kbuild fixes for v4.18 2018-06-30 13:05:30 -07:00
security selinux/stable-4.18 PR 20180629 2018-06-30 11:15:12 -07:00
sound ALSA: seq: Fix UBSAN warning at SNDRV_SEQ_IOCTL_QUERY_NEXT_CLIENT ioctl 2018-06-25 11:18:04 +02:00
tools objtool: Support GCC 8 '-fnoreorder-functions' 2018-07-02 09:42:11 +02:00
usr kbuild: rename built-in.o to built-in.a 2018-03-26 02:01:19 +09:00
virt KVM: arm64: Prevent KVM_COMPAT from being selected 2018-06-21 17:17:50 +01:00
.clang-format clang-format: add configuration file 2018-04-11 10:28:35 -07:00
.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 Merge branch 'asoc-4.17' into asoc-4.18 for compress dependencies 2018-04-26 12:24:28 +01:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS/CREDITS: Drop METAG ARCHITECTURE 2018-03-05 16:34:24 +00:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig kconfig: add basic helper macros to scripts/Kconfig.include 2018-05-29 03:31:19 +09:00
MAINTAINERS proc: add Alexey to MAINTAINERS 2018-06-28 11:16:44 -07:00
Makefile Linux 4.18-rc3 2018-07-01 16:04:53 -07:00
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.