linux-toradex.git/include/asm-generic/sections.h, branch v5.10-rc3

sections.h: dereference_function_descriptor() returns void pointer

2020-08-11T10:06:15+00:00

The function dereference_function_descriptor() takes on hppa64, ppc64
and ia64 a pointer to a function descriptor and returns a (void) pointer
to the dereferenced function.
To make cross-arch coding easier, on all other architectures the
dereference_function_descriptor() macro should return a void pointer
too.

Signed-off-by: Helge Deller

vmlinux.lds.h: Create section for protection against instrumentation

2020-05-19T13:47:20+00:00

Some code pathes, especially the low level entry code, must be protected
against instrumentation for various reasons:

 - Low level entry code can be a fragile beast, especially on x86.

 - With NO_HZ_FULL RCU state needs to be established before using it.

Having a dedicated section for such code allows to validate with tooling
that no unsafe functions are invoked.

Add the .noinstr.text section and the noinstr attribute to mark
functions. noinstr implies notrace. Kprobes will gain a section check
later.

Provide also a set of markers: instrumentation_begin()/end()

These are used to mark code inside a noinstr function which calls
into regular instrumentable text section as safe.

The instrumentation markers are only active when CONFIG_DEBUG_ENTRY is
enabled as the end marker emits a NOP to prevent the compiler from merging
the annotation points. This means the objtool verification requires a
kernel compiled with this option.

Signed-off-by: Thomas Gleixner 
Reviewed-by: Alexandre Chartre 
Acked-by: Peter Zijlstra 
Link: https://lkml.kernel.org/r/20200505134100.075416272@linutronix.de

locking/lockdep: check for freed initmem in static_obj()

2019-04-29T08:47:10+00:00

The following warning occurred on s390:
WARNING: CPU: 0 PID: 804 at kernel/locking/lockdep.c:1025 lockdep_register_key+0x30/0x150

This is because the check in static_obj() assumes that all memory within
[_stext, _end] belongs to static objects, which at least for s390 isn't
true. The init section is also part of this range, and freeing it allows
the buddy allocator to allocate memory from it. We have virt == phys for
the kernel on s390, so that such allocations would then have addresses
within the range [_stext, _end].

To fix this, introduce arch_is_kernel_initmem_freed(), similar to
arch_is_kernel_text/data(), and add it to the checks in static_obj().
This will always return 0 on architectures that do not define
arch_is_kernel_initmem_freed. On s390, it will return 1 if initmem has
been freed and the address is in the range [__init_begin, __init_end].

Signed-off-by: Gerald Schaefer 
Reviewed-by: Heiko Carstens 
Signed-off-by: Martin Schwidefsky

mm: move is_kernel_rodata() to asm-generic/sections.h

2018-10-16T10:53:27+00:00

Export this routine so that we can use it later in devm_kstrdup_const()
and devm_kfree().

Signed-off-by: Bartosz Golaszewski 
Reviewed-by: Bjorn Andersson 
Acked-by: Mike Rapoport 
Acked-by: Rasmus Villemoes 
Reviewed-by: Geert Uytterhoeven 
Reviewed-by: Andy Shevchenko 
Signed-off-by: Greg Kroah-Hartman

sections: split dereference_function_descriptor()

2018-01-09T09:45:37+00:00

There are two format specifiers to print out a pointer in symbolic
format: '%pS/%ps' and '%pF/%pf'. On most architectures, the two
mean exactly the same thing, but some architectures (ia64, ppc64,
parisc64) use an indirect pointer for C function pointers, where
the function pointer points to a function descriptor (which in
turn contains the actual pointer to the code). The '%pF/%pf, when
used appropriately, automatically does the appropriate function
descriptor dereference on such architectures.

The "when used appropriately" part is tricky. Basically this is
a subtle ABI detail, specific to some platforms, that made it to
the API level and people can be unaware of it and miss the whole
"we need to dereference the function" business out. [1] proves
that point (note that it fixes only '%pF' and '%pS', there might
be '%pf' and '%ps' cases as well).

It appears that we can handle everything within the affected
arches and make '%pS/%ps' smart enough to retire '%pF/%pf'.
Function descriptors live in .opd elf section and all affected
arches (ia64, ppc64, parisc64) handle it properly for kernel
and modules. So we, technically, can decide if the dereference
is needed by simply looking at the pointer: if it belongs to
.opd section then we need to dereference it.

The kernel and modules have their own .opd sections, obviously,
that's why we need to split dereference_function_descriptor()
and use separate kernel and module dereference arch callbacks.

This patch does the first step, it
a) adds dereference_kernel_function_descriptor() function.
b) adds a weak alias to dereference_module_function_descriptor()
   function.

So, for the time being, we will have:
1) dereference_function_descriptor()
   A generic function, that simply dereferences the pointer. There is
   bunch of places that call it: kgdbts, init/main.c, extable, etc.

2) dereference_kernel_function_descriptor()
   A function to call on kernel symbols that does kernel .opd section
   address range test.

3) dereference_module_function_descriptor()
   A function to call on modules' symbols that does modules' .opd
   section address range test.

[1] https://marc.info/?l=linux-kernel&m=150472969730573

Link: http://lkml.kernel.org/r/20171109234830.5067-2-sergey.senozhatsky@gmail.com
To: Fenghua Yu 
To: Benjamin Herrenschmidt 
To: Paul Mackerras 
To: Michael Ellerman 
To: James Bottomley 
Cc: Andrew Morton 
Cc: Jessica Yu 
Cc: Steven Rostedt 
Cc: linux-ia64@vger.kernel.org
Cc: linux-parisc@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Sergey Senozhatsky 
Tested-by: Tony Luck  #ia64
Tested-by: Santosh Sivaraj  #powerpc
Tested-by: Helge Deller  #parisc64
Signed-off-by: Petr Mladek

kernel debug: support resetting WARN*_ONCE

2017-11-18T00:10:00+00:00

I like _ONCE warnings because it's guaranteed that they don't flood the
log.

During testing I find it useful to reset the state of the once warnings,
so that I can rerun tests and see if they trigger again, or can
guarantee that a test run always hits the same warnings.

This patch adds a debugfs interface to reset all the _ONCE warnings so
that they appear again:

  echo 1 > /sys/kernel/debug/clear_warn_once

This is implemented by putting all the warning booleans into a special
section, and clearing it.

[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/20171017221455.6740-1-andi@firstfloor.org
Signed-off-by: Andi Kleen 
Tested-by: Michael Ellerman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

License cleanup: add SPDX GPL-2.0 license identifier to files with no license

2017-11-02T10:10:55+00:00

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 
Reviewed-by: Philippe Ombredanne 
Reviewed-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

irq: Make the irqentry text section unconditional

2017-08-10T14:28:53+00:00

Generate irqentry and softirqentry text sections without
any Kconfig dependencies. This will add extra sections, but
there should be no performace impact.

Suggested-by: Ingo Molnar 
Signed-off-by: Masami Hiramatsu 
Cc: Ananth N Mavinakayanahalli 
Cc: Anil S Keshavamurthy 
Cc: Chris Zankel 
Cc: David S . Miller 
Cc: Francis Deslauriers 
Cc: Jesper Nilsson 
Cc: Linus Torvalds 
Cc: Max Filippov 
Cc: Mikael Starvik 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Yoshinori Sato 
Cc: linux-arch@vger.kernel.org
Cc: linux-cris-kernel@axis.com
Cc: mathieu.desnoyers@efficios.com
Link: http://lkml.kernel.org/r/150172789110.27216.3955739126693102122.stgit@devbox
Signed-off-by: Ingo Molnar

mm: fix section name for .data..ro_after_init

2017-04-01T00:13:30+00:00

A section name for .data..ro_after_init was added by both:

    commit d07a980c1b8d ("s390: add proper __ro_after_init support")

and

    commit d7c19b066dcf ("mm: kmemleak: scan .data.ro_after_init")

The latter adds incorrect wrapping around the existing s390 section, and
came later.  I'd prefer the s390 naming, so this moves the s390-specific
name up to the asm-generic/sections.h and renames the section as used by
kmemleak (and in the future, kernel/extable.c).

Link: http://lkml.kernel.org/r/20170327192213.GA129375@beast
Signed-off-by: Kees Cook 
Acked-by: Heiko Carstens 	[s390 parts]
Acked-by: Jakub Kicinski 
Cc: Eddie Kovsky 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: kmemleak: scan .data.ro_after_init

2016-11-11T16:12:37+00:00

Limit the number of kmemleak false positives by including
.data.ro_after_init in memory scanning.  To achieve this we need to add
symbols for start and end of the section to the linker scripts.

The problem was been uncovered by commit 56989f6d8568 ("genetlink: mark
families as __ro_after_init").

Link: http://lkml.kernel.org/r/1478274173-15218-1-git-send-email-jakub.kicinski@netronome.com
Reviewed-by: Catalin Marinas 
Signed-off-by: Jakub Kicinski 
Cc: Arnd Bergmann 
Cc: Cong Wang 
Cc: Johannes Berg 
Cc: Martin Schwidefsky 
Cc: Heiko Carstens 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds