linux-toradex.git/include/linux/compiler.h, branch v4.19-rc5

module: use relative references for __ksymtab entries

2018-08-22T17:52:47+00:00

An ordinary arm64 defconfig build has ~64 KB worth of __ksymtab entries,
each consisting of two 64-bit fields containing absolute references, to
the symbol itself and to a char array containing its name, respectively.

When we build the same configuration with KASLR enabled, we end up with an
additional ~192 KB of relocations in the .init section, i.e., one 24 byte
entry for each absolute reference, which all need to be processed at boot
time.

Given how the struct kernel_symbol that describes each entry is completely
local to module.c (except for the references emitted by EXPORT_SYMBOL()
itself), we can easily modify it to contain two 32-bit relative references
instead.  This reduces the size of the __ksymtab section by 50% for all
64-bit architectures, and gets rid of the runtime relocations entirely for
architectures implementing KASLR, either via standard PIE linking (arm64)
or using custom host tools (x86).

Note that the binary search involving __ksymtab contents relies on each
section being sorted by symbol name.  This is implemented based on the
input section names, not the names in the ksymtab entries, so this patch
does not interfere with that.

Given that the use of place-relative relocations requires support both in
the toolchain and in the module loader, we cannot enable this feature for
all architectures.  So make it dependent on whether
CONFIG_HAVE_ARCH_PREL32_RELOCATIONS is defined.

Link: http://lkml.kernel.org/r/20180704083651.24360-4-ard.biesheuvel@linaro.org
Signed-off-by: Ard Biesheuvel 
Acked-by: Jessica Yu 
Acked-by: Michael Ellerman 
Reviewed-by: Will Deacon 
Acked-by: Ingo Molnar 
Cc: Arnd Bergmann 
Cc: Benjamin Herrenschmidt 
Cc: Bjorn Helgaas 
Cc: Catalin Marinas 
Cc: James Morris 
Cc: James Morris 
Cc: Josh Poimboeuf 
Cc: Kees Cook 
Cc: Nicolas Pitre 
Cc: Paul Mackerras 
Cc: Petr Mladek 
Cc: Russell King 
Cc: "Serge E. Hallyn" 
Cc: Sergey Senozhatsky 
Cc: Steven Rostedt 
Cc: Thomas Garnier 
Cc: Thomas Gleixner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

linux/compiler.h: don't use bool

2018-08-22T17:52:47+00:00

Appararently, it's possible to have a non-trivial TU include a few
headers, including linux/build_bug.h, without ending up with
linux/types.h.  So the 0day bot sent me

config: um-x86_64_defconfig (attached as .config)

>> include/linux/compiler.h:316:3: error: unknown type name 'bool'; did you mean '_Bool'?
      bool __cond = !(condition);    \

for something I'm working on.

Rather than contributing to the #include madness and including
linux/types.h from compiler.h, just use int.

Link: http://lkml.kernel.org/r/20180817101036.20969-1-linux@rasmusvillemoes.dk
Signed-off-by: Rasmus Villemoes 
Cc: Christopher Li 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

branch-check: fix long->int truncation when profiling branches

2018-06-04T21:28:20+00:00

The function __builtin_expect returns long type (see the gcc
documentation), and so do macros likely and unlikely. Unfortunatelly, when
CONFIG_PROFILE_ANNOTATED_BRANCHES is selected, the macros likely and
unlikely expand to __branch_check__ and __branch_check__ truncates the
long type to int. This unintended truncation may cause bugs in various
kernel code (we found a bug in dm-writecache because of it), so it's
better to fix __branch_check__ to return long.

Link: http://lkml.kernel.org/r/alpine.LRH.2.02.1805300818140.24812@file01.intranet.prod.int.rdu2.redhat.com

Cc: Ingo Molnar 
Cc: stable@vger.kernel.org
Fixes: 1f0d69a9fc815 ("tracing: profile likely and unlikely annotations")
Signed-off-by: Mikulas Patocka 
Signed-off-by: Steven Rostedt (VMware)

bug.h: work around GCC PR82365 in BUG()

2018-02-21T23:35:43+00:00

Looking at functions with large stack frames across all architectures
led me discovering that BUG() suffers from the same problem as
fortify_panic(), which I've added a workaround for already.

In short, variables that go out of scope by calling a noreturn function
or __builtin_unreachable() keep using stack space in functions
afterwards.

A workaround that was identified is to insert an empty assembler
statement just before calling the function that doesn't return.  I'm
adding a macro "barrier_before_unreachable()" to document this, and
insert calls to that in all instances of BUG() that currently suffer
from this problem.

The files that saw the largest change from this had these frame sizes
before, and much less with my patch:

  fs/ext4/inode.c:82:1: warning: the frame size of 1672 bytes is larger than 800 bytes [-Wframe-larger-than=]
  fs/ext4/namei.c:434:1: warning: the frame size of 904 bytes is larger than 800 bytes [-Wframe-larger-than=]
  fs/ext4/super.c:2279:1: warning: the frame size of 1160 bytes is larger than 800 bytes [-Wframe-larger-than=]
  fs/ext4/xattr.c:146:1: warning: the frame size of 1168 bytes is larger than 800 bytes [-Wframe-larger-than=]
  fs/f2fs/inode.c:152:1: warning: the frame size of 1424 bytes is larger than 800 bytes [-Wframe-larger-than=]
  net/netfilter/ipvs/ip_vs_core.c:1195:1: warning: the frame size of 1068 bytes is larger than 800 bytes [-Wframe-larger-than=]
  net/netfilter/ipvs/ip_vs_core.c:395:1: warning: the frame size of 1084 bytes is larger than 800 bytes [-Wframe-larger-than=]
  net/netfilter/ipvs/ip_vs_ftp.c:298:1: warning: the frame size of 928 bytes is larger than 800 bytes [-Wframe-larger-than=]
  net/netfilter/ipvs/ip_vs_ftp.c:418:1: warning: the frame size of 908 bytes is larger than 800 bytes [-Wframe-larger-than=]
  net/netfilter/ipvs/ip_vs_lblcr.c:718:1: warning: the frame size of 960 bytes is larger than 800 bytes [-Wframe-larger-than=]
  drivers/net/xen-netback/netback.c:1500:1: warning: the frame size of 1088 bytes is larger than 800 bytes [-Wframe-larger-than=]

In case of ARC and CRIS, it turns out that the BUG() implementation
actually does return (or at least the compiler thinks it does),
resulting in lots of warnings about uninitialized variable use and
leaving noreturn functions, such as:

  block/cfq-iosched.c: In function 'cfq_async_queue_prio':
  block/cfq-iosched.c:3804:1: error: control reaches end of non-void function [-Werror=return-type]
  include/linux/dmaengine.h: In function 'dma_maxpq':
  include/linux/dmaengine.h:1123:1: error: control reaches end of non-void function [-Werror=return-type]

This makes them call __builtin_trap() instead, which should normally
dump the stack and kill the current process, like some of the other
architectures already do.

I tried adding barrier_before_unreachable() to panic() and
fortify_panic() as well, but that had very little effect, so I'm not
submitting that patch.

Vineet said:

: For ARC, it is double win.
:
: 1. Fixes 3 -Wreturn-type warnings
:
: | ../net/core/ethtool.c:311:1: warning: control reaches end of non-void function
: [-Wreturn-type]
: | ../kernel/sched/core.c:3246:1: warning: control reaches end of non-void function
: [-Wreturn-type]
: | ../include/linux/sunrpc/svc_xprt.h:180:1: warning: control reaches end of
: non-void function [-Wreturn-type]
:
: 2.  bloat-o-meter reports code size improvements as gcc elides the
:    generated code for stack return.

Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82365
Link: http://lkml.kernel.org/r/20171219114112.939391-1-arnd@arndb.de
Signed-off-by: Arnd Bergmann 
Acked-by: Vineet Gupta 	[arch/arc]
Tested-by: Vineet Gupta 	[arch/arc]
Cc: Mikael Starvik 
Cc: Jesper Nilsson 
Cc: Tony Luck 
Cc: Fenghua Yu 
Cc: Geert Uytterhoeven 
Cc: "David S. Miller" 
Cc: Christopher Li 
Cc: Thomas Gleixner 
Cc: Peter Zijlstra 
Cc: Kees Cook 
Cc: Ingo Molnar 
Cc: Josh Poimboeuf 
Cc: Will Deacon 
Cc: "Steven Rostedt (VMware)" 
Cc: Mark Rutland 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6

2018-02-12T16:57:21+00:00

Pull crypto fixes from Herbert Xu:
 "This fixes the following issues:

   - oversize stack frames on mn10300 in sha3-generic

   - warning on old compilers in sha3-generic

   - API error in sun4i_ss_prng

   - potential dead-lock in sun4i_ss_prng

   - null-pointer dereference in sha512-mb

   - endless loop when DECO acquire fails in caam

   - kernel oops when hashing empty message in talitos"

* 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6:
  crypto: sun4i_ss_prng - convert lock to _bh in sun4i_ss_prng_generate
  crypto: sun4i_ss_prng - fix return value of sun4i_ss_prng_generate
  crypto: caam - fix endless loop when DECO acquire fails
  crypto: sha3-generic - Use __optimize to support old compilers
  compiler-gcc.h: __nostackprotector needs gcc-4.4 and up
  compiler-gcc.h: Introduce __optimize function attribute
  crypto: sha3-generic - deal with oversize stack frames
  crypto: talitos - fix Kernel Oops on hashing an empty file
  crypto: sha512-mb - initialize pending lengths correctly

compiler-gcc.h: Introduce __optimize function attribute

2018-02-08T11:37:10+00:00

Create a new function attribute __optimize, which allows to specify an
optimization level on a per-function basis.

Signed-off-by: Geert Uytterhoeven 
Acked-by: Ard Biesheuvel 
Signed-off-by: Herbert Xu

compiler.h: Add read_word_at_a_time() function.

2018-02-01T20:20:21+00:00

Sometimes we know that it's safe to do potentially out-of-bounds access
because we know it won't cross a page boundary.  Still, KASAN will
report this as a bug.

Add read_word_at_a_time() function which is supposed to be used in such
cases.  In read_word_at_a_time() KASAN performs relaxed check - only the
first byte of access is validated.

Signed-off-by: Andrey Ryabinin 
Signed-off-by: Linus Torvalds

compiler.h, kasan: Avoid duplicating __read_once_size_nocheck()

2018-02-01T20:20:21+00:00

Instead of having two identical __read_once_size_nocheck() functions
with different attributes, consolidate all the difference in new macro
__no_kasan_or_inline and use it. No functional changes.

Signed-off-by: Andrey Ryabinin 
Signed-off-by: Linus Torvalds

compiler.h: Remove ACCESS_ONCE()

2017-12-12T12:22:10+00:00

There are no longer any kernelspace uses of ACCESS_ONCE(), so we can
remove the definition from .

This patch removes the ACCESS_ONCE() definition, and updates comments
which referred to it. At the same time, some inconsistent and redundant
whitespace is removed from comments.

Tested-by: Paul E. McKenney 
Signed-off-by: Mark Rutland 
Cc: Arnaldo Carvalho de Melo 
Cc: Joe Perches 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: apw@canonical.com
Link: http://lkml.kernel.org/r/20171127103824.36526-4-mark.rutland@arm.com
Signed-off-by: Ingo Molnar

Merge branch 'linus' into core/objtool, to pick up dependent commits

2017-11-14T06:21:44+00:00

Signed-off-by: Ingo Molnar