arm32/64/elf: Split READ_IMPLIES_EXEC from executable PT_GNU_STACK

The READ_IMPLIES_EXEC work-around was designed for old toolchains that
lacked the ELF PT_GNU_STACK marking under the assumption that toolchains
that couldn't specify executable permission flags for the stack may not
know how to do it correctly for any memory region.

This logic is sensible for having ancient binaries coexist in a system
with possibly NX memory, but was implemented in a way that equated having
a PT_GNU_STACK marked executable as being as "broken" as lacking the
PT_GNU_STACK marking entirely. Things like unmarked assembly and stack
trampolines may cause PT_GNU_STACK to need an executable bit, but they
do not imply all mappings must be executable.

This confusion has led to situations where modern programs with explicitly
marked executable stack are forced into the READ_IMPLIES_EXEC state when
no such thing is needed. (And leads to unexpected failures when mmap()ing
regions of device driver memory that wish to disallow VM_EXEC[1].)

In looking for other reasons for the READ_IMPLIES_EXEC behavior, Jann
Horn noted that glibc thread stacks have always been marked RWX (until
2003 when they started tracking the PT_GNU_STACK flag instead[2]). And
musl doesn't support executable stacks at all[3]. As such, no breakage
for multithreaded applications is expected from this change.

This changes arm32 and arm64 compat together, to keep behavior the same.

[1] https://lkml.kernel.org/r/20190418055759.GA3155@mellanox.com
[2] https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=54ee14b3882
[3] https://lkml.kernel.org/r/20190423192534.GN23599@brightrain.aerifal.cx

Suggested-by: Hector Marco-Gisbert <hecmargi@upv.es>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lkml.kernel.org/r/20200327064820.12602-6-keescook@chromium.org

arm32/64/elf: Add tables to document READ_IMPLIES_EXEC

Add tables to document the current behavior of READ_IMPLIES_EXEC in
preparation for changing the behavior for both arm64 and arm.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lkml.kernel.org/r/20200327064820.12602-5-keescook@chromium.org

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>

ARM: enable elf_fdpic on systems with an MMU

Provide the necessary changes to be able to execute ELF-FDPIC binaries
on ARM systems with an MMU.

The default for CONFIG_BINFMT_ELF_FDPIC is also set to n if the regular
ELF loader is already configured so not to force FDPIC support on
everyone. Given that CONFIG_BINFMT_ELF depends on CONFIG_MMU, this means
CONFIG_BINFMT_ELF_FDPIC will still default to y when !MMU.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Mickael GUENE <mickael.guene@st.com>
Tested-by: Vincent Abriou <vincent.abriou@st.com>
Tested-by: Andras Szemzo <szemzo.andras@gmail.com>

arm_elf_read_implies_exec(): remove unused argument

The first argument to elf_read_implies_exec() is either the actual
header structure or a pointer to that structure whether one looks
at fs/binfmt_elf.c or fs/binfmt_elf_fdpic.c. This ought to be fixed
of course, but in the mean time let's sidestep the issue by removing
that first argument from arm_elf_read_implies_exec() as it is unused
anyway.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Mickael GUENE <mickael.guene@st.com>
Tested-by: Vincent Abriou <vincent.abriou@st.com>
Tested-by: Andras Szemzo <szemzo.andras@gmail.com>

Disintegrate asm/system.h for ARM

Disintegrate asm/system.h for ARM.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Russell King <linux@arm.linux.org.uk>
cc: linux-arm-kernel@lists.infradead.org

arm: convert core files from module.h to export.h

Many of the core ARM kernel files are not modules, but just
including module.h for exporting symbols. Now these files can
use the lighter footprint export.h for this role.

There are probably lots more, but ARM files of mach-* and plat-*
don't get coverage via a simple yesconfig build. They will have
to be cleaned up and tested via using their respective configs.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

ARM: 6878/1: fix personality flag propagation across an exec

Our SET_PERSONALITY() implementation was overwriting all existing
personality flags, including ADDR_NO_RANDOMIZE, making them unavailable
to processes being exec'd after a call to personality() in user space.
This prevents the gdb test suite from running successfully.

Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

ARM: 5883/1: Revert "disable NX support for OABI-supporting kernels"

This reverts commit 14f0aa359365e8a93a77b71e3b840274b9b4dcb1.

That commit was needed earlier because system call restarting for
OABI (compat) required an executable stack and thus had problems
with NX. Since ab72b00734ae4d0b ("ARM: Fix signal restart issues
with NX and OABI compat") has reworked the code to not require an
executable stack anymore, we can re-enable NX support for kernels
with OABI (compat) support.

Signed-off-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

[ARM] disable NX support for OABI-supporting kernels

Our signal syscall restart handling for these kernels still uses
the userspace stack to build code for restarting the syscall.
Unfortunately, fixing this is non-trivial, and so for the time
being, we resolve the problem by disabling NX support.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

[ARM] 5404/1: Fix condition in arm_elf_read_implies_exec() to set READ_IMPLIES_EXEC

READ_IMPLIES_EXEC must be set when:
o binary _is_ an executable stack (i.e. not EXSTACK_DISABLE_X)
o processor architecture is _under_ ARMv6 (XN bit is supported from ARMv6)

Signed-off-by: Makito SHIOKAWA <lkhmkt@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

[ARM] fix VFP+softfloat binaries

2.6.28-rc tightened up the ELF architecture checks on ARM. For
non-EABI it only allows VFP if the hardware supports it. However,
the kernel fails to also inspect the soft-float flag, so it
incorrectly rejects binaries using soft-VFP.

The fix is simple: also check that EF_ARM_SOFT_FLOAT isn't set
before rejecting VFP binaries on non-VFP hardware.

Acked-by: Mikael Pettersson <mikpe@it.uu.se>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

[ARM] Improve non-executable support

Add support for detecting non-executable stack binaries, and adjust
permissions to prevent execution from data and stack areas. Also,
ensure that READ_IMPLIES_EXEC is enabled for older CPUs where that
is true, and for any executable-stack binary.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>