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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 <torvalds@linux-foundation.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Jessica Yu <jeyu@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
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 <mingo@kernel.org>
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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 <torvalds@linux-foundation.org>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
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 <mingo@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
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
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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 <linux@roeck-us.net>
Reported-by: Guenter Roeck <linux@roeck-us.net>
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>
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 <mingo@kernel.org>
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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 <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>
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 <mingo@kernel.org>
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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 <gidisrael@gmail.com>
Cc: Greg Ungerer <gerg@linux-m68k.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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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) <peterz@infradead.org>
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/41a6d33971462ebd944a1c60ad4bf5be86c17b77.1487712920.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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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 <linux/compiler.h> 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 <gidisrael@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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Link: http://lkml.kernel.org/r/1477894241.1103202.772260161.1B0A5995@webmail.messagingengine.com
Signed-off-by: Benjamin Peterson <bp@benjamin.pe>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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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 <dvyukov@google.com>
Acked-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: <stable@vger.kernel.org> [4.0+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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The __latent_entropy gcc attribute can be used only on functions and
variables. If it is on a function then the plugin will instrument it for
gathering control-flow entropy. If the attribute is on a variable then
the plugin will initialize it with random contents. The variable must
be an integer, an integer array type or a structure with integer fields.
These specific functions have been selected because they are init
functions (to help gather boot-time entropy), are called at unpredictable
times, or they have variable loops, each of which provide some level of
latent entropy.
Signed-off-by: Emese Revfy <re.emese@gmail.com>
[kees: expanded commit message]
Signed-off-by: Kees Cook <keescook@chromium.org>
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There are three usercopy warnings which are currently being silenced for
gcc 4.6 and newer:
1) "copy_from_user() buffer size is too small" compile warning/error
This is a static warning which happens when object size and copy size
are both const, and copy size > object size. I didn't see any false
positives for this one. So the function warning attribute seems to
be working fine here.
Note this scenario is always a bug and so I think it should be
changed to *always* be an error, regardless of
CONFIG_DEBUG_STRICT_USER_COPY_CHECKS.
2) "copy_from_user() buffer size is not provably correct" compile warning
This is another static warning which happens when I enable
__compiletime_object_size() for new compilers (and
CONFIG_DEBUG_STRICT_USER_COPY_CHECKS). It happens when object size
is const, but copy size is *not*. In this case there's no way to
compare the two at build time, so it gives the warning. (Note the
warning is a byproduct of the fact that gcc has no way of knowing
whether the overflow function will be called, so the call isn't dead
code and the warning attribute is activated.)
So this warning seems to only indicate "this is an unusual pattern,
maybe you should check it out" rather than "this is a bug".
I get 102(!) of these warnings with allyesconfig and the
__compiletime_object_size() gcc check removed. I don't know if there
are any real bugs hiding in there, but from looking at a small
sample, I didn't see any. According to Kees, it does sometimes find
real bugs. But the false positive rate seems high.
3) "Buffer overflow detected" runtime warning
This is a runtime warning where object size is const, and copy size >
object size.
All three warnings (both static and runtime) were completely disabled
for gcc 4.6 with the following commit:
2fb0815c9ee6 ("gcc4: disable __compiletime_object_size for GCC 4.6+")
That commit mistakenly assumed that the false positives were caused by a
gcc bug in __compiletime_object_size(). But in fact,
__compiletime_object_size() seems to be working fine. The false
positives were instead triggered by #2 above. (Though I don't have an
explanation for why the warnings supposedly only started showing up in
gcc 4.6.)
So remove warning #2 to get rid of all the false positives, and re-enable
warnings #1 and #3 by reverting the above commit.
Furthermore, since #1 is a real bug which is detected at compile time,
upgrade it to always be an error.
Having done all that, CONFIG_DEBUG_STRICT_USER_COPY_CHECKS is no longer
needed.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Although sparse declares __builtin_bswap*(), it can't actually do
constant folding inside them (yet). As such, things like
switch (protocol) {
case htons(ETH_P_IP):
break;
}
which we do all over the place cause sparse to warn that it expects a
constant instead of a function call.
Disable __HAVE_BUILTIN_BSWAP*__ if __CHECKER__ is defined to avoid this.
Fixes: 7322dd755e7d ("byteswap: try to avoid __builtin_constant_p gcc bug")
Link: http://lkml.kernel.org/r/1470914102-26389-1-git-send-email-johannes@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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gcc as far back as at least 3.04 documents the function attribute
__malloc__. Add a shorthand for attaching that to a function
declaration. This was also suggested by Andi Kleen way back in 2002
[1], but didn't get applied, perhaps because gcc at that time generated
the exact same code with and without this attribute.
This attribute tells the compiler that the return value (if non-NULL)
can be assumed not to alias any other valid pointers at the time of the
call.
Please note that the documentation for a range of gcc versions (starting
from around 4.7) contained a somewhat confusing and self-contradicting
text:
The malloc attribute is used to tell the compiler that a function may
be treated as if any non-NULL pointer it returns cannot alias any other
pointer valid when the function returns and *that the memory has
undefined content*. [...] Standard functions with this property include
malloc and *calloc*.
(emphasis mine). The intended meaning has later been clarified [2]:
This tells the compiler that a function is malloc-like, i.e., that the
pointer P returned by the function cannot alias any other pointer valid
when the function returns, and moreover no pointers to valid objects
occur in any storage addressed by P.
What this means is that we can apply the attribute to kmalloc and
friends, and it is ok for the returned memory to have well-defined
contents (__GFP_ZERO). But it is not ok to apply it to kmemdup(), nor
to other functions which both allocate and possibly initialize the
memory with existing pointers. So unless someone is doing something
pretty perverted kstrdup() should also be a fine candidate.
[1] http://thread.gmane.org/gmane.linux.kernel/57172
[2] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56955
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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gcc support for __builtin_bswap16() was supposedly added for powerpc in
gcc 4.6, and was then later added for other architectures in gcc 4.8.
However, Stephen Rothwell reported that attempting to use it on powerpc
in gcc 4.6 fails with:
lib/vsprintf.c:160:2: error: initializer element is not constant
lib/vsprintf.c:160:2: error: (near initialization for 'decpair[0]')
lib/vsprintf.c:160:2: error: initializer element is not constant
lib/vsprintf.c:160:2: error: (near initialization for 'decpair[1]')
...
I'm not entirely sure what those errors mean, but I don't see them on
gcc 4.8. So let's consider gcc 4.8 to be the official starting point
for __builtin_bswap16().
Arnd Bergmann adds:
"I found the commit in gcc-4.8 that replaced the powerpc-specific
implementation of __builtin_bswap16 with an architecture-independent
one. Apparently the powerpc version (gcc-4.6 and 4.7) just mapped to
the lhbrx/sthbrx instructions, so it ended up not being a constant,
though the intent of the patch was mainly to add support for the
builtin to x86:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52624
has the patch that went into gcc-4.8 and more information."
Fixes: 7322dd755e7d ("byteswap: try to avoid __builtin_constant_p gcc bug")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Tested-by: Stephen Rothwell <sfr@canb.auug.org.au>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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-ftracer can duplicate asm blocks causing compilation to fail in
noclone functions. For example, KVM declares a global variable
in an asm like
asm("2: ... \n
.pushsection data \n
.global vmx_return \n
vmx_return: .long 2b");
and -ftracer causes a double declaration.
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Marek <mmarek@suse.cz>
Cc: stable@vger.kernel.org
Cc: kvm@vger.kernel.org
Reported-by: Linda Walsh <lkml@tlinx.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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The patch "slab.h: sprinkle __assume_aligned attributes" causes *tons* of
whinges if you do 'make C=2' with sparse 0.5.0:
CHECK drivers/media/usb/pwc/pwc-if.c
include/linux/slab.h:307:43: error: attribute '__assume_aligned__': unknown attribute
include/linux/slab.h:308:58: error: attribute '__assume_aligned__': unknown attribute
include/linux/slab.h:337:73: error: attribute '__assume_aligned__': unknown attribute
include/linux/slab.h:375:74: error: attribute '__assume_aligned__': unknown attribute
include/linux/slab.h:378:80: error: attribute '__assume_aligned__': unknown attribute
sparse apparently pretends to be gcc >= 4.9, yet isn't prepared to handle
all the function attributes supported by those gccs and complains loudly.
So hide the definition of __assume_aligned from it (so that the generic
one in compiler.h gets used).
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Reported-by: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
Tested-By: Valdis Kletnieks <valdis.kletnieks@vt.edu>
Cc: Christopher Li <sparse@chrisli.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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gcc 4.9 added the function attribute assume_aligned, indicating to the
caller that the returned pointer may be assumed to have a certain minimal
alignment. This is useful if, for example, the return value is passed to
memset(). Add a shorthand macro for that.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Some code may perform racy by design memory reads. This could be
harmless, yet such code may produce KASAN warnings.
To hide such accesses from KASAN this patch introduces
READ_ONCE_NOCHECK() macro. KASAN will not check the memory
accessed by READ_ONCE_NOCHECK(). The KernelThreadSanitizer
(KTSAN) is going to ignore it as well.
This patch creates __read_once_size_nocheck() a clone of
__read_once_size(). The only difference between them is
'no_sanitized_address' attribute appended to '*_nocheck'
function. This attribute tells the compiler that instrumentation
of memory accesses should not be applied to that function. We
declare it as static '__maybe_unsed' because GCC is not capable
to inline such function:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
With KASAN=n READ_ONCE_NOCHECK() is just a clone of READ_ONCE().
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Kostya Serebryany <kcc@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Wolfram Gloger <wmglo@dent.med.uni-muenchen.de>
Cc: kasan-dev <kasan-dev@googlegroups.com>
Link: http://lkml.kernel.org/r/1445243838-17763-2-git-send-email-aryabinin@virtuozzo.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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As gcc major version numbers are going to advance rather rapidly in the
future, there's no real value in separate files for each compiler
version.
Deduplicate some of the macros #defined in each file too.
Neaten comments using normal kernel commenting style.
Signed-off-by: Joe Perches <joe@perches.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Segher Boessenkool <segher@kernel.crashing.org>
Cc: Sasha Levin <levinsasha928@gmail.com>
Cc: Anton Blanchard <anton@samba.org>
Cc: Alan Modra <amodra@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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- Move the inline and noinline blocks together
- Comment neatening
- Alignment of __attribute__ uses
- Consistent naming of __must_be_array macro argument
- Multiline macro neatening
Signed-off-by: Joe Perches <joe@perches.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Segher Boessenkool <segher@kernel.crashing.org>
Cc: Sasha Levin <levinsasha928@gmail.com>
Cc: Anton Blanchard <anton@samba.org>
Cc: Alan Modra <amodra@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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In commit 0b053c951829 ("lib: memzero_explicit: use barrier instead
of OPTIMIZER_HIDE_VAR"), we made memzero_explicit() more robust in
case LTO would decide to inline memzero_explicit() and eventually
find out it could be elimiated as dead store.
While using barrier() works well for the case of gcc, recent efforts
from LLVMLinux people suggest to use llvm as an alternative to gcc,
and there, Stephan found in a simple stand-alone user space example
that llvm could nevertheless optimize and thus elimitate the memset().
A similar issue has been observed in the referenced llvm bug report,
which is regarded as not-a-bug.
Based on some experiments, icc is a bit special on its own, while it
doesn't seem to eliminate the memset(), it could do so with an own
implementation, and then result in similar findings as with llvm.
The fix in this patch now works for all three compilers (also tested
with more aggressive optimization levels). Arguably, in the current
kernel tree it's more of a theoretical issue, but imho, it's better
to be pedantic about it.
It's clearly visible with gcc/llvm though, with the below code: if we
would have used barrier() only here, llvm would have omitted clearing,
not so with barrier_data() variant:
static inline void memzero_explicit(void *s, size_t count)
{
memset(s, 0, count);
barrier_data(s);
}
int main(void)
{
char buff[20];
memzero_explicit(buff, sizeof(buff));
return 0;
}
$ gcc -O2 test.c
$ gdb a.out
(gdb) disassemble main
Dump of assembler code for function main:
0x0000000000400400 <+0>: lea -0x28(%rsp),%rax
0x0000000000400405 <+5>: movq $0x0,-0x28(%rsp)
0x000000000040040e <+14>: movq $0x0,-0x20(%rsp)
0x0000000000400417 <+23>: movl $0x0,-0x18(%rsp)
0x000000000040041f <+31>: xor %eax,%eax
0x0000000000400421 <+33>: retq
End of assembler dump.
$ clang -O2 test.c
$ gdb a.out
(gdb) disassemble main
Dump of assembler code for function main:
0x00000000004004f0 <+0>: xorps %xmm0,%xmm0
0x00000000004004f3 <+3>: movaps %xmm0,-0x18(%rsp)
0x00000000004004f8 <+8>: movl $0x0,-0x8(%rsp)
0x0000000000400500 <+16>: lea -0x18(%rsp),%rax
0x0000000000400505 <+21>: xor %eax,%eax
0x0000000000400507 <+23>: retq
End of assembler dump.
As gcc, clang, but also icc defines __GNUC__, it's sufficient to define
this in compiler-gcc.h only to be picked up. For a fallback or otherwise
unsupported compiler, we define it as a barrier. Similarly, for ecc which
does not support gcc inline asm.
Reference: https://llvm.org/bugs/show_bug.cgi?id=15495
Reported-by: Stephan Mueller <smueller@chronox.de>
Tested-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Stephan Mueller <smueller@chronox.de>
Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
Cc: mancha security <mancha1@zoho.com>
Cc: Mark Charlebois <charlebm@gmail.com>
Cc: Behan Webster <behanw@converseincode.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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To be consistent with other compiler attributes introduce __alias(symbol)
macro expanding into __attribute__((alias(#symbol)))
Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Konstantin Serebryany <kcc@google.com>
Cc: Dmitry Chernenkov <dmitryc@google.com>
Signed-off-by: Andrey Konovalov <adech.fo@gmail.com>
Cc: Yuri Gribov <tetra2005@gmail.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Disabling compiler optimizations can be fragile, since a new
optimization could be added to -O0 or -Os that breaks the assumptions
the code is making.
Instead of disabling compiler optimizations, use a dummy inline assembly
(based on RELOC_HIDE) to block the problematic kinds of optimization,
while still allowing other optimizations to be applied to the code.
The dummy inline assembly is added after every OR, and has the
accumulator variable as its input and output. The compiler is forced to
assume that the dummy inline assembly could both depend on the
accumulator variable and change the accumulator variable, so it is
forced to compute the value correctly before the inline assembly, and
cannot assume anything about its value after the inline assembly.
This change should be enough to make crypto_memneq work correctly (with
data-independent timing) even if it is inlined at its call sites. That
can be done later in a followup patch.
Compile-tested on x86_64.
Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.eti.br>
Acked-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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Throughout compiler*.h, many version checks are made. These can be
simplified by using the macro that gcc's documentation recommends.
However, my primary reason for adding this is that I need bug-check
macros that are enabled at certain gcc versions and it's cleaner to use
this macro than the tradition method:
#if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ => 2)
If you add patch level, it gets this ugly:
#if __GNUC__ > 4 || (__GNUC__ == 4 && (__GNUC_MINOR__ > 2 || \
__GNUC_MINOR__ == 2 __GNUC_PATCHLEVEL__ >= 1))
As opposed to:
#if GCC_VERSION >= 40201
While having separate headers for gcc 3 & 4 eliminates some of this
verbosity, they can still be cleaned up by this.
See also:
http://gcc.gnu.org/onlinedocs/cpp/Common-Predefined-Macros.html
Signed-off-by: Daniel Santos <daniel.santos@pobox.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Joe Perches <joe@perches.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Commit 5963e317b1e9d2a ("ftrace/x86: Do not change stacks in DEBUG when
calling lockdep") prevented lockdep calls from the int3 breakpoint handler
from reseting the stack if a function that was called was in the process
of being converted for tracing and had a breakpoint on it. The idea is,
before calling the lockdep code, do a load_idt() to the special IDT that
kept the breakpoint stack from reseting. This worked well as a quick fix
for this kernel release, until a certain config caused a lockup in the
function tracer start up tests.
Investigating it, I found that the load_idt that was used to prevent
the int3 from changing stacks was itself being traced!
Even though the config had CONFIG_OPTIMIZE_INLINING disabled, and
all 'inline' tags were set to always inline, there were still cases that
it did not inline! This was caused by CONFIG_PARAVIRT_GUEST, where it
would add a pointer to the native_load_idt() which made that function
to be traced.
Commit 45959ee7aa645815a ("ftrace: Do not function trace inlined functions")
only touched the 'inline' tags when CONFIG_OPMITIZE_INLINING was enabled.
PARAVIRT_GUEST shows that this was not enough and we need to also
mark always_inline with notrace as well.
Reported-by: Fengguang Wu <wfg@linux.intel.com>
Tested-by: Fengguang Wu <wfg@linux.intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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It's equivalent to __printf, so prefer __scanf.
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
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When gcc inlines a function, it does not mark it with the mcount
prologue, which in turn means that inlined functions are not traced
by the function tracer. But if CONFIG_OPTIMIZE_INLINING is set, then
gcc is allowed not to inline a function that is marked inline.
Depending on the options and the compiler, a function may or may
not be traced by the function tracer, depending on whether gcc
decides to inline a function or not. This has caused several
problems in the pass becaues gcc is not always consistent with
what it decides to inline between different gcc versions.
Some places should not be traced (like paravirt native_* functions)
and these are mostly marked as inline. When gcc decides not to
inline the function, and if that function should not be traced, then
the ftrace function tracer will suddenly break when it use to work
fine. This becomes even harder to debug when different versions of
gcc will not inline that function, making the same kernel and config
work for some gcc versions and not work for others.
By making all functions marked inline to not be traced will remove
the ambiguity that gcc adds when it comes to tracing functions marked
inline. All gcc versions will be consistent with what functions are
traced and having volatile working code will be removed.
Note, only the inline macro when CONFIG_OPTIMIZE_INLINING is set needs
to have notrace added, as the attribute __always_inline will force
the function to be inlined and then not traced.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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commit c5e631cf65f ("ARRAY_SIZE: check for type") added __must_be_array().
But sparse can't parse this gcc extention.
Now make C=2 makes following sparse errors a lot.
kernel/futex.c:2699:25: error: No right hand side of '+'-expression
Because __must_be_array() is used for ARRAY_SIZE() macro and it is
used very widely.
This patch fixes it.
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
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Unify identical gcc3.x and gcc4.x macros.
Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
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We should use the __same_type() helper in __must_be_array().
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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A __naked function is defined in C but with a body completely implemented
by asm(), including any prologue and epilogue. These asm() bodies expect
standard calling conventions for parameter passing. Older GCCs implement
that correctly, but 4.[56] currently do not, see GCC PR44290. In the
Linux kernel this breaks ARM, causing most arch/arm/mm/copypage-*.c
modules to get miscompiled, resulting in kernel crashes during bootup.
Part of the kernel fix is to augment the __naked function attribute to
also imply noinline and noclone. This patch implements that, and has been
verified to fix boot failures with gcc-4.5 compiled 2.6.34 and 2.6.35-rc1
kernels. The patch is a no-op with older GCCs.
Signed-off-by: Mikael Pettersson <mikpe@it.uu.se>
Signed-off-by: Khem Raj <raj.khem@gmail.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
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I wrote some code which is used as compile-time checker, and the
code should be elided after compile.
So I need to annotate the code as "always unused", compared to
"maybe unused".
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <4AEE2CEC.8040206@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
|
|
This is a fix for the following crash observed in 2.6.29-rc3:
http://lkml.org/lkml/2009/1/29/150
On ARM it doesn't make sense to trace a naked function because then
mcount is called without stack and frame pointer being set up and there
is no chance to restore the lr register to the value before mcount was
called.
Reported-by: Matthias Kaehlcke <matthias@kaehlcke.net>
Tested-by: Matthias Kaehlcke <matthias@kaehlcke.net>
Cc: Abhishek Sagar <sagar.abhishek@gmail.com>
Cc: Steven Rostedt <rostedt@home.goodmis.org>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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Requested by C. Lameter
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Mike Travis <travis@sgi.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Richard Henderson <rth@twiddle.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
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- include the gcc version-dependent header files from the generic gcc
header file, rather than the other way around (iow: don't make the
non-gcc header file have to know about gcc versions)
- don't include compiler-gcc4.h for gcc 5 (for whenever it gets
released). That's just confusing and made us do odd things in the
gcc4 header file (testing that we really had version 4!)
- generate the name from the __GNUC__ version directly, rather than
having a mess of #if conditionals.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
fix the condition to match intention: always use the old inlining
behavior on all gcc versions below 4.
this should solve the UML build problem.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Stephen Rothwell reported that linux-next did not build on powerpc64.
make optimized inlining dependent on architecture opt-in.
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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add CONFIG_OPTIMIZE_INLINING=y.
allow gcc to optimize the kernel image's size by uninlining
functions that have been marked 'inline'. Previously gcc was
forced by Linux to always-inline these functions via a gcc
attribute:
#define inline inline __attribute__((always_inline))
Especially when the user has already selected
CONFIG_OPTIMIZE_FOR_SIZE=y this can make a huge difference in
kernel image size (using a standard Fedora .config):
text data bss dec hex filename
5613924 562708 3854336 10030968 990f78 vmlinux.before
5486689 562708 3854336 9903733 971e75 vmlinux.after
that's a 2.3% text size reduction (!).
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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To be consistent with the use of attributes in the rest of the kernel
replace all use of __attribute_pure__ with __pure and delete the definition
of __attribute_pure__.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Cc: Russell King <rmk@arm.linux.org.uk>
Acked-by: Mauro Carvalho Chehab <mchehab@infradead.org>
Cc: Bryan Wu <bryan.wu@analog.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Replace worthless comments with actual preprocessor errors when including
the wrong versions of the compiler.h files.
[akpm@linux-foundation.org: make it work]
Signed-off-by: Robert P. J. Day <rpjday@mindspring.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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__used is defined to be __attribute__((unused)) for all pre-3.3 gcc
compilers to suppress warnings for unused functions because perhaps they
are referenced only in inline assembly. It is defined to be
__attribute__((used)) for gcc 3.3 and later so that the code is still
emitted for such functions.
__maybe_unused is defined to be __attribute__((unused)) for both function
and variable use if it could possibly be unreferenced due to the evaluation
of preprocessor macros. Function prototypes shall be marked with
__maybe_unused if the actual definition of the function is dependant on
preprocessor macros.
No update to compiler-intel.h is necessary because ICC supports both
__attribute__((used)) and __attribute__((unused)) as specified by the gcc
manual.
__attribute_used__ is deprecated and will be removed once all current
code is converted to using __used.
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Adrian Bunk <bunk@stusta.de>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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We can use a gcc extension to ensure that ARRAY_SIZE() is handed an array,
not a pointer. This is especially important when code is changed from a
fixed array to a pointer. I assume the Intel compiler doesn't support
__builtin_types_compatible_p.
[jdike@addtoit.com: uml: update UML definition of ARRAY_SIZE]
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Extend the set of "__attribute__" shortcut macros, and remove identical
(and now superfluous) definitions from a couple of source files.
based on a page at robert love's blog:
http://rlove.org/log/2005102601
extend the set of shortcut macros defined in compiler-gcc.h with the
following:
#define __packed __attribute__((packed))
#define __weak __attribute__((weak))
#define __naked __attribute__((naked))
#define __noreturn __attribute__((noreturn))
#define __pure __attribute__((pure))
#define __aligned(x) __attribute__((aligned(x)))
#define __printf(a,b) __attribute__((format(printf,a,b)))
Once these are in place, it's up to subsystem maintainers to decide if they
want to take advantage of them. there is already a strong precedent for
using shortcuts like this in the source tree.
The ones that might give people pause are "__aligned" and "__printf", but
shortcuts for both of those are already in use, and in some ways very
confusingly. note the two very different definitions for a macro named
"ALIGNED":
drivers/net/sgiseeq.c:#define ALIGNED(x) ((((unsigned long)(x)) + 0xf) & ~(0xf))
drivers/scsi/ultrastor.c:#define ALIGNED(x) __attribute__((aligned(x)))
also:
include/acpi/platform/acgcc.h:
#define ACPI_PRINTF_LIKE(c) __attribute__ ((__format__ (__printf__, c, c+1)))
Given the precedent, then, it seems logical to at least standardize on a
consistent set of these macros.
Signed-off-by: Robert P. J. Day <rpjday@mindspring.com>
Acked-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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In the process of optimising our per cpu data code, I found a ppc64
compiler bug that has been around forever. Basically the current
RELOC_HIDE can end up trashing r30. Details of the bug can be found at
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25572
This bug is present in all compilers before 4.1. It is masked by the
fact that our current per cpu data code is inefficient and causes
other loads that end up marking r30 as used.
A workaround identified by Alan Modra is to use the =r asm constraint
instead of =g.
Signed-off-by: Anton Blanchard <anton@samba.org>
[ Verified that this makes no real difference on x86[-64] */
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Remove various things which were checking for gcc-1.x and gcc-2.x compilers.
From: Adrian Bunk <bunk@stusta.de>
Some documentation updates and removes some code paths for gcc < 3.2.
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
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