Revision 9cc6d9e5daaa147a9a3e31557efcb331989e77be authored by Nathan Lynch on 29 September 2014, 18:11:36 UTC, committed by Russell King on 30 September 2014, 15:55:23 UTC
Joachim Eastwood reports that commit fbfb872f5f41 "ARM: 8148/1: flush
TLS and thumbee register state during exec" causes a boot-time crash
on a Cortex-M4 nommu system:

Freeing unused kernel memory: 68K (281e5000 - 281f6000)
Unhandled exception: IPSR = 00000005 LR = fffffff1
CPU: 0 PID: 1 Comm: swapper Not tainted 3.17.0-rc6-00313-gd2205fa30aa7 #191
task: 29834000 ti: 29832000 task.ti: 29832000
PC is at flush_thread+0x2e/0x40
LR is at flush_thread+0x21/0x40
pc : [<2800954a>] lr : [<2800953d>] psr: 4100000b
sp : 29833d60 ip : 00000000 fp : 00000001
r10: 00003cf8 r9 : 29b1f000 r8 : 00000000
r7 : 29b0bc00 r6 : 29834000 r5 : 29832000 r4 : 29832000
r3 : ffff0ff0 r2 : 29832000 r1 : 00000000 r0 : 282121f0
xPSR: 4100000b
CPU: 0 PID: 1 Comm: swapper Not tainted 3.17.0-rc6-00313-gd2205fa30aa7 #191
[<2800afa5>] (unwind_backtrace) from [<2800a327>] (show_stack+0xb/0xc)
[<2800a327>] (show_stack) from [<2800a963>] (__invalid_entry+0x4b/0x4c)

The problem is that set_tls is attempting to clear the TLS location in
the kernel-user helper page, which isn't set up on V7M.

Fix this by guarding the write to the kuser helper page with
a CONFIG_KUSER_HELPERS ifdef.

Fixes: fbfb872f5f41 ARM: 8148/1: flush TLS and thumbee register state during exec

Reported-by: Joachim Eastwood <manabian@gmail.com>
Tested-by: Joachim Eastwood <manabian@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Nathan Lynch <nathan_lynch@mentor.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
1 parent ebc7725
Raw File
mono.txt
               Mono(tm) Binary Kernel Support for Linux
               -----------------------------------------

To configure Linux to automatically execute Mono-based .NET binaries
(in the form of .exe files) without the need to use the mono CLR
wrapper, you can use the BINFMT_MISC kernel support.

This will allow you to execute Mono-based .NET binaries just like any
other program after you have done the following:

1) You MUST FIRST install the Mono CLR support, either by downloading
   a binary package, a source tarball or by installing from CVS. Binary
   packages for several distributions can be found at:

	http://go-mono.com/download.html

   Instructions for compiling Mono can be found at:

	http://www.go-mono.com/compiling.html

   Once the Mono CLR support has been installed, just check that
   /usr/bin/mono (which could be located elsewhere, for example
   /usr/local/bin/mono) is working.

2) You have to compile BINFMT_MISC either as a module or into
   the kernel (CONFIG_BINFMT_MISC) and set it up properly.
   If you choose to compile it as a module, you will have
   to insert it manually with modprobe/insmod, as kmod
   cannot be easily supported with binfmt_misc. 
   Read the file 'binfmt_misc.txt' in this directory to know
   more about the configuration process.

3) Add the following entries to /etc/rc.local or similar script
   to be run at system startup:

# Insert BINFMT_MISC module into the kernel
if [ ! -e /proc/sys/fs/binfmt_misc/register ]; then
        /sbin/modprobe binfmt_misc
	# Some distributions, like Fedora Core, perform
	# the following command automatically when the
	# binfmt_misc module is loaded into the kernel
	# or during normal boot up (systemd-based systems).
	# Thus, it is possible that the following line
	# is not needed at all.
	mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
fi

# Register support for .NET CLR binaries
if [ -e /proc/sys/fs/binfmt_misc/register ]; then
	# Replace /usr/bin/mono with the correct pathname to
	# the Mono CLR runtime (usually /usr/local/bin/mono
	# when compiling from sources or CVS).
        echo ':CLR:M::MZ::/usr/bin/mono:' > /proc/sys/fs/binfmt_misc/register
else
        echo "No binfmt_misc support"
        exit 1
fi

4) Check that .exe binaries can be ran without the need of a
   wrapper script, simply by launching the .exe file directly
   from a command prompt, for example:

	/usr/bin/xsd.exe

   NOTE: If this fails with a permission denied error, check
         that the .exe file has execute permissions.
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