Commit graph

37 commits

Author SHA1 Message Date
Linus Torvalds
c4726e774e gcc plugin fix:
- Lift gcc test into Kconfig
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Merge tag 'gcc-plugins-v4.19-rc1-fix' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull gcc plugin fix from Kees Cook:
 "Lift gcc test into Kconfig. This is for better behavior when the
  kernel is built with Clang, reported by Stefan Agner"

* tag 'gcc-plugins-v4.19-rc1-fix' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  gcc-plugins: Disable when building under Clang
2018-08-26 11:41:08 -07:00
Kees Cook
b04413330c gcc-plugins: Disable when building under Clang
Prior to doing compiler feature detection in Kconfig, attempts to build
GCC plugins with Clang would fail the build, much in the same way missing
GCC plugin headers would fail the build. However, now that this logic
has been lifted into Kconfig, add an explicit test for GCC (instead of
duplicating it in the feature-test script).

Reported-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2018-08-23 10:06:12 -07:00
Alexander Popov
45d9a1e3cc gcc-plugins: Clean up the cgraph_create_edge* macros
Drop useless redefinitions of cgraph_create_edge* macros. Drop the unused
nest argument. Also support gcc-8, which doesn't have freq argument.

Signed-off-by: Alexander Popov <alex.popov@linux.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
2018-07-24 16:14:06 -07:00
Masahiro Yamada
45332b1bdf gcc-plugins: split out Kconfig entries to scripts/gcc-plugins/Kconfig
Collect relevant code into the scripts/gcc-plugins directory.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
2018-07-24 16:11:07 -07:00
Masahiro Yamada
c17d6179ad gcc-plugins: remove unused GCC_PLUGIN_SUBDIR
GCC_PLUGIN_SUBDIR has never been used.  If you really need this in
the future, please re-add it then.

For now, the code is unused. Remove.

'export HOSTLIBS' is not necessary either.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
2018-07-02 19:27:00 -07:00
Masahiro Yamada
59f53855ba gcc-plugins: test plugin support in Kconfig and clean up Makefile
Run scripts/gcc-plugin.sh from Kconfig so that users can enable
GCC_PLUGINS only when the compiler supports building plugins.

Kconfig defines a new symbol, PLUGIN_HOSTCC.  This will contain
the compiler (g++ or gcc) used for building plugins, or empty
if the plugin can not be supported at all.

This allows us to remove all ugly testing in Makefile.gcc-plugins.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Kees Cook <keescook@chromium.org>
2018-06-11 09:16:22 +09:00
Masahiro Yamada
5aadfdeb8d kcov: test compiler capability in Kconfig and correct dependency
As Documentation/kbuild/kconfig-language.txt notes, 'select' should be
be used with care - it forces a lower limit of another symbol, ignoring
the dependency.  Currently, KCOV can select GCC_PLUGINS even if arch
does not select HAVE_GCC_PLUGINS.  This could cause the unmet direct
dependency.

Now that Kconfig can test compiler capability, let's handle this in a
more sophisticated way.

There are two ways to enable KCOV; use the compiler that natively
supports -fsanitize-coverage=trace-pc, or build the SANCOV plugin if
the compiler has ability to build GCC plugins.  Hence, the correct
dependency for KCOV is:

  depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS

You do not need to build the SANCOV plugin if the compiler already
supports -fsanitize-coverage=trace-pc.  Hence, the select should be:

  select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC

With this, GCC_PLUGIN_SANCOV is selected only when necessary, so
scripts/Makefile.gcc-plugins can be cleaner.

I also cleaned up Kconfig and scripts/Makefile.kcov as well.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
2018-06-11 09:14:08 +09:00
Sargun Dhillon
df0ce17331 security: convert security hooks to use hlist
This changes security_hook_heads to use hlist_heads instead of
the circular doubly-linked list heads. This should cut down
the size of the struct by about half.

In addition, it allows mutation of the hooks at the tail of the
callback list without having to modify the head. The longer-term
purpose of this is to enable making the heads read only.

Signed-off-by: Sargun Dhillon <sargun@sargun.me>
Reviewed-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: James Morris <james.morris@microsoft.com>
2018-03-31 13:18:27 +11:00
Kees Cook
b86729109c gcc-plugins: Use dynamic initializers
GCC 8 changed the order of some fields and is very picky about ordering
in static initializers, so instead just move to dynamic initializers,
and drop the redundant already-zero field assignments.

Suggested-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>
Signed-off-by: Kees Cook <keescook@chromium.org>
2018-02-05 17:27:46 -08:00
valdis.kletnieks@vt.edu
80d1724316 gcc-plugins: Add include required by GCC release 8
GCC requires another #include to get the gcc-plugins to build cleanly.

Signed-off-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>
Signed-off-by: Kees Cook <keescook@chromium.org>
2018-02-05 17:10:10 -08:00
Greg Kroah-Hartman
b24413180f License cleanup: add SPDX GPL-2.0 license identifier to files with no license
Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.

By default all files without license information are under the default
license of the kernel, which is GPL version 2.

Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier.  The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.

How this work was done:

Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
 - file had no licensing information it it.
 - file was a */uapi/* one with no licensing information in it,
 - file was a */uapi/* one with existing licensing information,

Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.

The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne.  Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.

The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed.  Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.

Criteria used to select files for SPDX license identifier tagging was:
 - Files considered eligible had to be source code files.
 - Make and config files were included as candidates if they contained >5
   lines of source
 - File already had some variant of a license header in it (even if <5
   lines).

All documentation files were explicitly excluded.

The following heuristics were used to determine which SPDX license
identifiers to apply.

 - when both scanners couldn't find any license traces, file was
   considered to have no license information in it, and the top level
   COPYING file license applied.

   For non */uapi/* files that summary was:

   SPDX license identifier                            # files
   ---------------------------------------------------|-------
   GPL-2.0                                              11139

   and resulted in the first patch in this series.

   If that file was a */uapi/* path one, it was "GPL-2.0 WITH
   Linux-syscall-note" otherwise it was "GPL-2.0".  Results of that was:

   SPDX license identifier                            # files
   ---------------------------------------------------|-------
   GPL-2.0 WITH Linux-syscall-note                        930

   and resulted in the second patch in this series.

 - if a file had some form of licensing information in it, and was one
   of the */uapi/* ones, it was denoted with the Linux-syscall-note if
   any GPL family license was found in the file or had no licensing in
   it (per prior point).  Results summary:

   SPDX license identifier                            # files
   ---------------------------------------------------|------
   GPL-2.0 WITH Linux-syscall-note                       270
   GPL-2.0+ WITH Linux-syscall-note                      169
   ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause)    21
   ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)    17
   LGPL-2.1+ WITH Linux-syscall-note                      15
   GPL-1.0+ WITH Linux-syscall-note                       14
   ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause)    5
   LGPL-2.0+ WITH Linux-syscall-note                       4
   LGPL-2.1 WITH Linux-syscall-note                        3
   ((GPL-2.0 WITH Linux-syscall-note) OR MIT)              3
   ((GPL-2.0 WITH Linux-syscall-note) AND MIT)             1

   and that resulted in the third patch in this series.

 - when the two scanners agreed on the detected license(s), that became
   the concluded license(s).

 - when there was disagreement between the two scanners (one detected a
   license but the other didn't, or they both detected different
   licenses) a manual inspection of the file occurred.

 - In most cases a manual inspection of the information in the file
   resulted in a clear resolution of the license that should apply (and
   which scanner probably needed to revisit its heuristics).

 - When it was not immediately clear, the license identifier was
   confirmed with lawyers working with the Linux Foundation.

 - If there was any question as to the appropriate license identifier,
   the file was flagged for further research and to be revisited later
   in time.

In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.

Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights.  The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.

Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.

In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.

Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
 - a full scancode scan run, collecting the matched texts, detected
   license ids and scores
 - reviewing anything where there was a license detected (about 500+
   files) to ensure that the applied SPDX license was correct
 - reviewing anything where there was no detection but the patch license
   was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
   SPDX license was correct

This produced a worksheet with 20 files needing minor correction.  This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.

These .csv files were then reviewed by Greg.  Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected.  This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.)  Finally Greg ran the script using the .csv files to
generate the patches.

Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-11-02 11:10:55 +01:00
Kees Cook
ad05e6ca7b Merge branch 'for-next/gcc-plugin/structleak' into for-next/gcc-plugins 2017-08-07 13:29:04 -07:00
Ard Biesheuvel
f7dd250789 gcc-plugins: structleak: add option to init all vars used as byref args
In the Linux kernel, struct type variables are rarely passed by-value,
and so functions that initialize such variables typically take an input
reference to the variable rather than returning a value that can
subsequently be used in an assignment.

If the initalization function is not part of the same compilation unit,
the lack of an assignment operation defeats any analysis the compiler
can perform as to whether the variable may be used before having been
initialized. This means we may end up passing on such variables
uninitialized, resulting in potential information leaks.

So extend the existing structleak GCC plugin so it will [optionally]
apply to all struct type variables that have their address taken at any
point, rather than only to variables of struct types that have a __user
annotation.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
2017-08-07 11:20:57 -07:00
Kees Cook
9225331b31 randstruct: Enable function pointer struct detection
This enables the automatic structure selection logic in the randstruct
GCC plugin. The selection logic randomizes all structures that contain
only function pointers, unless marked with __no_randomize_layout.

Signed-off-by: Kees Cook <keescook@chromium.org>
2017-08-01 17:04:48 -07:00
Kees Cook
1854c19cae randstruct: Whitelist NIU struct page overloading
The NIU ethernet driver intentionally stores a page struct pointer on
top of the "mapping" field. Whitelist this case:

drivers/net/ethernet/sun/niu.c: In function ‘niu_rx_pkt_ignore’:
drivers/net/ethernet/sun/niu.c:3402:10: note: found mismatched ssa struct pointer types: ‘struct page’ and ‘struct address_space’

    *link = (struct page *) page->mapping;
    ~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Kees Cook <keescook@chromium.org>
2017-06-22 16:21:43 -07:00
Kees Cook
802762cdff randstruct: Whitelist big_key path struct overloading
The big_key payload structure intentionally stores a struct path in
two void pointers to avoid header soup. Whitelist this case:

security/keys/big_key.c: In function ‘big_key_read’:
security/keys/big_key.c:293:16: note: found mismatched rhs struct pointer types: ‘struct path’ and ‘void *’

   struct path *path = (struct path *)&key->payload.data[big_key_path];
                ^~~~

Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
2017-06-22 16:21:42 -07:00
Kees Cook
b07b65846b randstruct: Whitelist UNIXCB cast
This is another false positive in bad cast detection:

net/unix/af_unix.c: In function ‘unix_skb_scm_eq’:
net/unix/af_unix.c:1621:31: note: found mismatched rhs struct pointer types: ‘struct unix_skb_parms’ and ‘char’

  const struct unix_skb_parms *u = &UNIXCB(skb);
                               ^

UNIXCB is:

	#define UNIXCB(skb)     (*(struct unix_skb_parms *)&((skb)->cb))

And ->cb is:

	char                    cb[48] __aligned(8);

This is a rather crazy cast, but appears to be safe in the face of
randomization, so whitelist it in the plugin.

Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Kees Cook <keescook@chromium.org>
2017-06-22 16:21:41 -07:00
Kees Cook
fd466e068e randstruct: Whitelist struct security_hook_heads cast
The LSM initialization routines walk security_hook_heads as an array
of struct list_head instead of via names to avoid a ton of needless
source. Whitelist this to avoid the false positive warning from the
plugin:

security/security.c: In function ‘security_init’:
security/security.c:59:20: note: found mismatched op0 struct pointer types: ‘struct list_head’ and ‘struct security_hook_heads’

  struct list_head *list = (struct list_head *) &security_hook_heads;
                    ^

Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: James Morris <james.l.morris@oracle.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
2017-06-22 16:21:40 -07:00
Kees Cook
313dd1b629 gcc-plugins: Add the randstruct plugin
This randstruct plugin is modified from Brad Spengler/PaX Team's code
in the last public patch of grsecurity/PaX based on my understanding
of the code. Changes or omissions from the original code are mine and
don't reflect the original grsecurity/PaX code.

The randstruct GCC plugin randomizes the layout of selected structures
at compile time, as a probabilistic defense against attacks that need to
know the layout of structures within the kernel. This is most useful for
"in-house" kernel builds where neither the randomization seed nor other
build artifacts are made available to an attacker. While less useful for
distribution kernels (where the randomization seed must be exposed for
third party kernel module builds), it still has some value there since now
all kernel builds would need to be tracked by an attacker.

In more performance sensitive scenarios, GCC_PLUGIN_RANDSTRUCT_PERFORMANCE
can be selected to make a best effort to restrict randomization to
cacheline-sized groups of elements, and will not randomize bitfields. This
comes at the cost of reduced randomization.

Two annotations are defined,__randomize_layout and __no_randomize_layout,
which respectively tell the plugin to either randomize or not to
randomize instances of the struct in question. Follow-on patches enable
the auto-detection logic for selecting structures for randomization
that contain only function pointers. It is disabled here to assist with
bisection.

Since any randomized structs must be initialized using designated
initializers, __randomize_layout includes the __designated_init annotation
even when the plugin is disabled so that all builds will require
the needed initialization. (With the plugin enabled, annotations for
automatically chosen structures are marked as well.)

The main differences between this implemenation and grsecurity are:
- disable automatic struct selection (to be enabled in follow-up patch)
- add designated_init attribute at runtime and for manual marking
- clarify debugging output to differentiate bad cast warnings
- add whitelisting infrastructure
- support gcc 7's DECL_ALIGN and DECL_MODE changes (Laura Abbott)
- raise minimum required GCC version to 4.7

Earlier versions of this patch series were ported by Michael Leibowitz.

Signed-off-by: Kees Cook <keescook@chromium.org>
2017-06-22 16:15:45 -07:00
Kees Cook
1132e1e448 gcc-plugins: Detail c-common.h location for GCC 4.6
The c-common.h file moved in stock gcc 4.7, not gcc 4.6. However, most
people building plugins with gcc 4.6 are using the Debian or Ubuntu
version, which includes a patch to move the headers to the 4.7 location.
In case anyone trips over this with a stock gcc 4.6, add a pointer to the
patch used by Debian/Ubuntu.

Signed-off-by: Kees Cook <keescook@chromium.org>
2017-05-28 10:23:02 -07:00
Linus Torvalds
794fe7891d Fixes a typo in sancov plugin, exposed in earlier compiler versions
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Merge tag 'gcc-plugins-v4.11-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull gcc-plugins fix from Kees Cook:
 "Fixes a typo in sancov plugin, exposed in earlier compiler versions"

* tag 'gcc-plugins-v4.11-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  gcc-plugins: fix sancov_plugin for gcc-5
2017-03-09 18:05:41 -08:00
Arnd Bergmann
dcc235279a gcc-plugins: fix sancov_plugin for gcc-5
The name of the local variable was inadvertantly changed from
sancov_plugin_pass_info to sancov_pass_info:

scripts/gcc-plugins/sancov_plugin.c: In function ‘int plugin_init(plugin_name_args*, plugin_gcc_version*)’:
scripts/gcc-plugins/sancov_plugin.c:136:67: error: ‘sancov_plugin_pass_info’ was not declared in this scope

This changes the conditional reference to this variable as well.

Fixes: 5a45a4c5c3 ("gcc-plugins: consolidate on PASS_INFO macro")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Kees Cook <keescook@chromium.org>
2017-02-27 14:10:10 -08:00
Kees Cook
c054ee3bbf Merge branch 'for-next/gcc-plugin/structleak' into for-linus/gcc-plugins 2017-02-21 21:12:57 -08:00
Kees Cook
c61f13eaa1 gcc-plugins: Add structleak for more stack initialization
This plugin detects any structures that contain __user attributes and
makes sure it is being fully initialized so that a specific class of
information exposure is eliminated. (This plugin was originally designed
to block the exposure of siginfo in CVE-2013-2141.)

Ported from grsecurity/PaX. This version adds a verbose option to the
plugin and the Kconfig.

Signed-off-by: Kees Cook <keescook@chromium.org>
2017-01-18 12:02:35 -08:00
Kees Cook
5a45a4c5c3 gcc-plugins: consolidate on PASS_INFO macro
Now that PASS_INFO() exists, use it in the other existing gcc plugins,
instead of always open coding the same thing.

Based on updates to the grsecurity/PaX gcc plugins.

Signed-off-by: Kees Cook <keescook@chromium.org>
2017-01-13 14:20:03 -08:00
Kees Cook
8d4973a1c0 gcc-plugins: add PASS_INFO and build_const_char_string()
This updates the GCC plugins gcc-common.h from PaX Team to include
more helpers and header files, specifically adds the PASS_INFO()
macro to make plugin declarations nicer and a helper for proper
const string building.

Signed-off-by: Kees Cook <keescook@chromium.org>
2017-01-10 16:50:57 -08:00
Kees Cook
81d873a871 gcc-plugins: update gcc-common.h for gcc-7
This updates gcc-common.h from Emese Revfy for gcc 7. This fixes issues seen
by Kugan and Arnd. Build tested with gcc 5.4 and 7 snapshot.

Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
2017-01-03 12:08:59 -08:00
Kees Cook
9988f4d577 latent_entropy: fix ARM build error on earlier gcc
This fixes build errors seen on gcc-4.9.3 or gcc-5.3.1 for an ARM:

arm-soc/init/initramfs.c: In function 'error':
arm-soc/init/initramfs.c:50:1: error: unrecognizable insn:
 }
 ^
(insn 26 25 27 5 (set (reg:SI 111 [ local_entropy.243 ])
        (rotatert:SI (reg:SI 116 [ local_entropy.243 ])
            (const_int -30 [0xffffffffffffffe2]))) -1
     (nil))

Patch from PaX Team <pageexec@freemail.hu>

Reported-by: Arnd Bergmann <arnd@arndb.de>
Reported-by: Brad Spengler <spender@grsecurity.net>
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
2017-01-03 12:08:59 -08:00
Masanari Iida
9165dabb25 treewide: Fix printk() message errors
This patch fix spelling typos in printk and kconfig.

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
2016-12-14 10:54:27 +01:00
Kees Cook
58bea4144d latent_entropy: Fix wrong gcc code generation with 64 bit variables
The stack frame size could grow too large when the plugin used long long
on 32-bit architectures when the given function had too many basic blocks.

The gcc warning was:

drivers/pci/hotplug/ibmphp_ebda.c: In function 'ibmphp_access_ebda':
drivers/pci/hotplug/ibmphp_ebda.c:409:1: warning: the frame size of 1108 bytes is larger than 1024 bytes [-Wframe-larger-than=]

This switches latent_entropy from u64 to unsigned long.

Thanks to PaX Team and Emese Revfy for the patch.

Signed-off-by: Kees Cook <keescook@chromium.org>
2016-10-31 11:30:41 -07:00
Kees Cook
da7389ac6c gcc-plugins: Export symbols needed by gcc
This explicitly exports symbols that gcc expects from plugins.

Based on code from Emese Revfy.

Signed-off-by: Kees Cook <keescook@chromium.org>
2016-10-31 10:40:13 -07:00
Emese Revfy
38addce8b6 gcc-plugins: Add latent_entropy plugin
This adds a new gcc plugin named "latent_entropy". It is designed to
extract as much possible uncertainty from a running system at boot time as
possible, hoping to capitalize on any possible variation in CPU operation
(due to runtime data differences, hardware differences, SMP ordering,
thermal timing variation, cache behavior, etc).

At the very least, this plugin is a much more comprehensive example for
how to manipulate kernel code using the gcc plugin internals.

The need for very-early boot entropy tends to be very architecture or
system design specific, so this plugin is more suited for those sorts
of special cases. The existing kernel RNG already attempts to extract
entropy from reliable runtime variation, but this plugin takes the idea to
a logical extreme by permuting a global variable based on any variation
in code execution (e.g. a different value (and permutation function)
is used to permute the global based on loop count, case statement,
if/then/else branching, etc).

To do this, the plugin starts by inserting a local variable in every
marked function. The plugin then adds logic so that the value of this
variable is modified by randomly chosen operations (add, xor and rol) and
random values (gcc generates separate static values for each location at
compile time and also injects the stack pointer at runtime). The resulting
value depends on the control flow path (e.g., loops and branches taken).

Before the function returns, the plugin mixes this local variable into
the latent_entropy global variable. The value of this global variable
is added to the kernel entropy pool in do_one_initcall() and _do_fork(),
though it does not credit any bytes of entropy to the pool; the contents
of the global are just used to mix the pool.

Additionally, the plugin can pre-initialize arrays with build-time
random contents, so that two different kernel builds running on identical
hardware will not have the same starting values.

Signed-off-by: Emese Revfy <re.emese@gmail.com>
[kees: expanded commit message and code comments]
Signed-off-by: Kees Cook <keescook@chromium.org>
2016-10-10 14:51:44 -07:00
Emese Revfy
caefd8c9a9 gcc-plugins: Add support for plugin subdirectories
This adds support for building more complex gcc plugins that live in a
subdirectory instead of just in a single source file.

Reported-by: PaX Team <pageexec@freemail.hu>
Signed-off-by: Emese Revfy <re.emese@gmail.com>
[kees: clarified commit message]
Signed-off-by: Kees Cook <keescook@chromium.org>
2016-08-08 17:53:05 -07:00
Emese Revfy
7040c83bfb gcc-plugins: Automate make rule generation
There's no reason to repeat the same names in the Makefile when the .so
files have already been listed. The .o list can be generated from them.

Reported-by: PaX Team <pageexec@freemail.hu>
Signed-off-by: Emese Revfy <re.emese@gmail.com>
[kees: clarified commit message]
Signed-off-by: Kees Cook <keescook@chromium.org>
2016-08-08 17:52:20 -07:00
Emese Revfy
543c37cb16 Add sancov plugin
The sancov gcc plugin inserts a __sanitizer_cov_trace_pc() call
at the start of basic blocks.

This plugin is a helper plugin for the kcov feature. It supports
all gcc versions with plugin support (from gcc-4.5 on).
It is based on the gcc commit "Add fuzzing coverage support" by Dmitry Vyukov
(https://gcc.gnu.org/viewcvs/gcc?limit_changes=0&view=revision&revision=231296).

Signed-off-by: Emese Revfy <re.emese@gmail.com>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Michal Marek <mmarek@suse.com>
2016-06-07 22:57:10 +02:00
Emese Revfy
0dae776c6b Add Cyclomatic complexity GCC plugin
Add a very simple plugin to demonstrate the GCC plugin infrastructure. This GCC
plugin computes the cyclomatic complexity of each function.

The complexity M of a function's control flow graph is defined as:
M = E - N + 2P
where
E = the number of edges
N = the number of nodes
P = the number of connected components (exit nodes).

Signed-off-by: Emese Revfy <re.emese@gmail.com>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Michal Marek <mmarek@suse.com>
2016-06-07 22:57:10 +02:00
Emese Revfy
6b90bd4ba4 GCC plugin infrastructure
This patch allows to build the whole kernel with GCC plugins. It was ported from
grsecurity/PaX. The infrastructure supports building out-of-tree modules and
building in a separate directory. Cross-compilation is supported too.
Currently the x86, arm, arm64 and uml architectures enable plugins.

The directory of the gcc plugins is scripts/gcc-plugins. You can use a file or a directory
there. The plugins compile with these options:
 * -fno-rtti: gcc is compiled with this option so the plugins must use it too
 * -fno-exceptions: this is inherited from gcc too
 * -fasynchronous-unwind-tables: this is inherited from gcc too
 * -ggdb: it is useful for debugging a plugin (better backtrace on internal
    errors)
 * -Wno-narrowing: to suppress warnings from gcc headers (ipa-utils.h)
 * -Wno-unused-variable: to suppress warnings from gcc headers (gcc_version
    variable, plugin-version.h)

The infrastructure introduces a new Makefile target called gcc-plugins. It
supports all gcc versions from 4.5 to 6.0. The scripts/gcc-plugin.sh script
chooses the proper host compiler (gcc-4.7 can be built by either gcc or g++).
This script also checks the availability of the included headers in
scripts/gcc-plugins/gcc-common.h.

The gcc-common.h header contains frequently included headers for GCC plugins
and it has a compatibility layer for the supported gcc versions.

The gcc-generate-*-pass.h headers automatically generate the registration
structures for GIMPLE, SIMPLE_IPA, IPA and RTL passes.

Note that 'make clean' keeps the *.so files (only the distclean or mrproper
targets clean all) because they are needed for out-of-tree modules.

Based on work created by the PaX Team.

Signed-off-by: Emese Revfy <re.emese@gmail.com>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Michal Marek <mmarek@suse.com>
2016-06-07 22:57:10 +02:00