linux-toradex.git/include/linux/compiler-gcc.h, branch v4.11-rc3

objtool, modules: Discard objtool annotation sections for modules

2017-03-01T19:32:25+00:00

The '__unreachable' and '__func_stack_frame_non_standard' sections are
only used at compile time.  They're discarded for vmlinux but they
should also be discarded for modules.

Since this is a recurring pattern, prefix the section names with
".discard.".  It's a nice convention and vmlinux.lds.h already discards
such sections.

Also remove the 'a' (allocatable) flag from the __unreachable section
since it doesn't make sense for a discarded section.

Suggested-by: Linus Torvalds 
Signed-off-by: Josh Poimboeuf 
Cc: Jessica Yu 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Fixes: d1091c7fa3d5 ("objtool: Improve detection of BUG() and other dead ends")
Link: http://lkml.kernel.org/r/20170301180444.lhd53c5tibc4ns77@treble
Signed-off-by: Ingo Molnar

objtool, compiler.h: Fix __unreachable section relocation size

2017-03-01T13:20:18+00:00

Linus reported the following commit broke module loading on his laptop:

  d1091c7fa3d5 ("objtool: Improve detection of BUG() and other dead ends")

It showed errors like the following:

  module: overflow in relocation type 10 val ffffffffc02afc81
  module: 'nvme' likely not compiled with -mcmodel=kernel

The problem is that the __unreachable section addresses are stored using
the '.long' asm directive, which isn't big enough for .text section
kernel addresses.  Use relative addresses instead:

  ".long %c0b - .\t\n"

Suggested-by: Linus Torvalds 
Reported-by: Linus Torvalds 
Signed-off-by: Josh Poimboeuf 
Cc: Peter Zijlstra 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Fixes: d1091c7fa3d5 ("objtool: Improve detection of BUG() and other dead ends")
Link: http://lkml.kernel.org/r/20170301060504.oltm3iws6fmubnom@treble
Signed-off-by: Ingo Molnar

Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2017-02-28T18:15:59+00:00

Pull objtool fixes from Ingo Molnar:
 "A handful of objtool fixes related to unreachable code, plus a build
  fix for out of tree modules"

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  objtool: Enclose contents of unreachable() macro in a block
  objtool: Prevent GCC from merging annotate_unreachable()
  objtool: Improve detection of BUG() and other dead ends
  objtool: Fix CONFIG_STACK_VALIDATION=y warning for out-of-tree modules

objtool: Enclose contents of unreachable() macro in a block

2017-02-28T06:47:26+00:00

Guenter Roeck reported a boot failure in mips64.  It was bisected to the
following commit:

  d1091c7fa3d5 ("objtool: Improve detection of BUG() and other dead ends")

The unreachable() macro was formerly only composed of a single
statement.  The above commit added a second statement, but neglected to
enclose the statements in a block.

Suggested-by: Guenter Roeck 
Reported-by: Guenter Roeck 
Signed-off-by: Josh Poimboeuf 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Fixes: d1091c7fa3d5 ("objtool: Improve detection of BUG() and other dead ends")
Link: http://lkml.kernel.org/r/20170228042116.glmwmwiohcix7o4a@treble
Signed-off-by: Ingo Molnar

objtool: Prevent GCC from merging annotate_unreachable()

2017-02-25T09:11:23+00:00

0-day bot reported some new objtool warnings which were caused by the
new annotate_unreachable() macro:

  fs/afs/flock.o: warning: objtool: afs_do_unlk()+0x0: duplicate frame pointer save
  fs/afs/flock.o: warning: objtool: afs_do_unlk()+0x0: frame pointer state mismatch
  fs/btrfs/delayed-inode.o: warning: objtool: btrfs_delete_delayed_dir_index()+0x0: duplicate frame pointer save
  fs/btrfs/delayed-inode.o: warning: objtool: btrfs_delete_delayed_dir_index()+0x0: frame pointer state mismatch
  fs/dlm/lock.o: warning: objtool: _grant_lock()+0x0: duplicate frame pointer save
  fs/dlm/lock.o: warning: objtool: _grant_lock()+0x0: frame pointer state mismatch
  fs/ocfs2/alloc.o: warning: objtool: ocfs2_mv_path()+0x0: duplicate frame pointer save
  fs/ocfs2/alloc.o: warning: objtool: ocfs2_mv_path()+0x0: frame pointer state mismatch

It turns out that, for older versions of GCC, if a function has multiple
BUG() incantations, GCC will sometimes merge the corresponding
annotate_unreachable() inline asm statements into a single block.  That
has the undesirable effect of removing one of the entries in the
__unreachable section, confusing objtool greatly.

A workaround for this issue is to ensure that each instance of the
inline asm statement uses a different label, so that GCC sees the
statements are unique and leaves them alone.  The inline asm ‘%=’ token
could be used for that, but unfortunately older versions of GCC don't
support it.  So I implemented a poor man's version of it with the
__LINE__ macro.

Reported-by: kbuild test robot 
Signed-off-by: Josh Poimboeuf 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Fixes: d1091c7fa3d5 ("objtool: Improve detection of BUG() and other dead ends")
Link: http://lkml.kernel.org/r/0c14b00baf9f68d1b0221ddb6c88b925181c8be8.1487997036.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar

compiler-gcc.h: add a new macro to wrap gcc attribute

2017-02-25T01:46:56+00:00

Add __mode(x) into compiler-gcc.h as part of a cleanup task I've taken
up, to replace gcc specific attributes with macros.

The next patch is a cleanup of the m68k subsystem and it requires a new
macro to wrap __attribute__ ((mode (...)))

Link: http://lkml.kernel.org/r/1485540901-1988-2-git-send-email-gidisrael@gmail.com
Signed-off-by: Gideon Israel Dsouza 
Cc: Greg Ungerer 
Cc: Geert Uytterhoeven 
Cc: Paul Gortmaker 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

objtool: Improve detection of BUG() and other dead ends

2017-02-24T08:10:52+00:00

The BUG() macro's use of __builtin_unreachable() via the unreachable()
macro tells gcc that the instruction is a dead end, and that it's safe
to assume the current code path will not execute past the previous
instruction.

On x86, the BUG() macro is implemented with the 'ud2' instruction.  When
objtool's branch analysis sees that instruction, it knows the current
code path has come to a dead end.

Peter Zijlstra has been working on a patch to change the WARN macros to
use 'ud2'.  That patch will break objtool's assumption that 'ud2' is
always a dead end.

Generally it's best for objtool to avoid making those kinds of
assumptions anyway.  The more ignorant it is of kernel code internals,
the better.

So create a more generic way for objtool to detect dead ends by adding
an annotation to the unreachable() macro.  The annotation stores a
pointer to the end of the unreachable code path in an '__unreachable'
section.  Objtool can read that section to find the dead ends.

Tested-by: Peter Zijlstra (Intel) 
Signed-off-by: Josh Poimboeuf 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/41a6d33971462ebd944a1c60ad4bf5be86c17b77.1487712920.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar

crypto: Replaced gcc specific attributes with macros from compiler.h

2017-01-12T16:24:39+00:00

Continuing from this commit: 52f5684c8e1e
("kernel: use macros from compiler.h instead of __attribute__((...))")

I submitted 4 total patches. They are part of task I've taken up to
increase compiler portability in the kernel. I've cleaned up the
subsystems under /kernel /mm /block and /security, this patch targets
/crypto.

There is  which provides macros for various gcc specific
constructs. Eg: __weak for __attribute__((weak)). I've cleaned all
instances of gcc specific attributes with the right macros for the crypto
subsystem.

I had to make one additional change into compiler-gcc.h for the case when
one wants to use this: __attribute__((aligned) and not specify an alignment
factor. From the gcc docs, this will result in the largest alignment for
that data type on the target machine so I've named the macro
__aligned_largest. Please advise if another name is more appropriate.

Signed-off-by: Gideon Israel Dsouza 
Signed-off-by: Herbert Xu

compiler-gcc.h: use "proved" instead of "proofed"

2016-12-13T02:55:09+00:00

Link: http://lkml.kernel.org/r/1477894241.1103202.772260161.1B0A5995@webmail.messagingengine.com
Signed-off-by: Benjamin Peterson 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kasan: update kasan_global for gcc 7

2016-12-01T00:32:52+00:00

kasan_global struct is part of compiler/runtime ABI.  gcc revision
241983 has added a new field to kasan_global struct.  Update kernel
definition of kasan_global struct to include the new field.

Without this patch KASAN is broken with gcc 7.

Link: http://lkml.kernel.org/r/1479219743-28682-1-git-send-email-dvyukov@google.com
Signed-off-by: Dmitry Vyukov 
Acked-by: Andrey Ryabinin 
Cc: Alexander Potapenko 
Cc: 	[4.0+]
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds