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linux/arch/s390/Kconfig
Gerald Schaefer c1821c2e97 [S390] noexec protection 
This provides a noexec protection on s390 hardware. Our hardware does
not have any bits left in the pte for a hw noexec bit, so this is a
different approach using shadow page tables and a special addressing
mode that allows separate address spaces for code and data.

As a special feature of our "secondary-space" addressing mode, separate
page tables can be specified for the translation of data addresses
(storage operands) and instruction addresses. The shadow page table is
used for the instruction addresses and the standard page table for the
data addresses.
The shadow page table is linked to the standard page table by a pointer
in page->lru.next of the struct page corresponding to the page that
contains the standard page table (since page->private is not really
private with the pte_lock and the page table pages are not in the LRU
list).
Depending on the software bits of a pte, it is either inserted into
both page tables or just into the standard (data) page table. Pages of
a vma that does not have the VM_EXEC bit set get mapped only in the
data address space. Any try to execute code on such a page will cause a
page translation exception. The standard reaction to this is a SIGSEGV
with two exceptions: the two system call opcodes 0x0a77 (sys_sigreturn)
and 0x0aad (sys_rt_sigreturn) are allowed. They are stored by the
kernel to the signal stack frame. Unfortunately, the signal return
mechanism cannot be modified to use an SA_RESTORER because the
exception unwinding code depends on the system call opcode stored
behind the signal stack frame.

This feature requires that user space is executed in secondary-space
mode and the kernel in home-space mode, which means that the addressing
modes need to be switched and that the noexec protection only works
for user space.
After switching the addressing modes, we cannot use the mvcp/mvcs
instructions anymore to copy between kernel and user space. A new
mvcos instruction has been added to the z9 EC/BC hardware which allows
to copy between arbitrary address spaces, but on older hardware the
page tables need to be walked manually.

Signed-off-by: Gerald Schaefer <geraldsc@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2007-02-05 21:18:17 +01:00

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#
# For a description of the syntax of this configuration file,
# see Documentation/kbuild/kconfig-language.txt.
#
config MMU
bool
default y
config LOCKDEP_SUPPORT
bool
default y
config STACKTRACE_SUPPORT
bool
default y
config RWSEM_GENERIC_SPINLOCK
bool
config RWSEM_XCHGADD_ALGORITHM
bool
default y
config ARCH_HAS_ILOG2_U32
bool
default n
config ARCH_HAS_ILOG2_U64
bool
default n
config GENERIC_HWEIGHT
bool
default y
config GENERIC_CALIBRATE_DELAY
bool
default y
config GENERIC_TIME
def_bool y
mainmenu "Linux Kernel Configuration"
config S390
bool
default y
source "init/Kconfig"
menu "Base setup"
comment "Processor type and features"
config 64BIT
bool "64 bit kernel"
help
Select this option if you have a 64 bit IBM zSeries machine
and want to use the 64 bit addressing mode.
config 32BIT
bool
default y if !64BIT
config SMP
bool "Symmetric multi-processing support"
---help---
This enables support for systems with more than one CPU. If you have
a system with only one CPU, like most personal computers, say N. If
you have a system with more than one CPU, say Y.
If you say N here, the kernel will run on single and multiprocessor
machines, but will use only one CPU of a multiprocessor machine. If
you say Y here, the kernel will run on many, but not all,
singleprocessor machines. On a singleprocessor machine, the kernel
will run faster if you say N here.
See also the <file:Documentation/smp.txt> and the SMP-HOWTO
available at <http://www.tldp.org/docs.html#howto>.
Even if you don't know what to do here, say Y.
config NR_CPUS
int "Maximum number of CPUs (2-64)"
range 2 64
depends on SMP
default "32"
help
This allows you to specify the maximum number of CPUs which this
kernel will support. The maximum supported value is 64 and the
minimum value which makes sense is 2.
This is purely to save memory - each supported CPU adds
approximately sixteen kilobytes to the kernel image.
config HOTPLUG_CPU
bool "Support for hot-pluggable CPUs"
depends on SMP
select HOTPLUG
default n
help
Say Y here to be able to turn CPUs off and on. CPUs
can be controlled through /sys/devices/system/cpu/cpu#.
Say N if you want to disable CPU hotplug.
config DEFAULT_MIGRATION_COST
int
default "1000000"
config MATHEMU
bool "IEEE FPU emulation"
depends on MARCH_G5
help
This option is required for IEEE compliant floating point arithmetic
on older S/390 machines. Say Y unless you know your machine doesn't
need this.
config COMPAT
bool "Kernel support for 31 bit emulation"
depends on 64BIT
help
Select this option if you want to enable your system kernel to
handle system-calls from ELF binaries for 31 bit ESA. This option
(and some other stuff like libraries and such) is needed for
executing 31 bit applications. It is safe to say "Y".
config SYSVIPC_COMPAT
bool
depends on COMPAT && SYSVIPC
default y
config AUDIT_ARCH
bool
default y
config S390_SWITCH_AMODE
bool "Switch kernel/user addressing modes"
help
This option allows to switch the addressing modes of kernel and user
space. The kernel parameter switch_amode=on will enable this feature,
default is disabled. Enabling this (via kernel parameter) on machines
earlier than IBM System z9-109 EC/BC will reduce system performance.
Note that this option will also be selected by selecting the execute
protection option below. Enabling the execute protection via the
noexec kernel parameter will also switch the addressing modes,
independent of the switch_amode kernel parameter.
config S390_EXEC_PROTECT
bool "Data execute protection"
select S390_SWITCH_AMODE
help
This option allows to enable a buffer overflow protection for user
space programs and it also selects the addressing mode option above.
The kernel parameter noexec=on will enable this feature and also
switch the addressing modes, default is disabled. Enabling this (via
kernel parameter) on machines earlier than IBM System z9-109 EC/BC
will reduce system performance.
comment "Code generation options"
choice
prompt "Processor type"
default MARCH_G5
config MARCH_G5
bool "S/390 model G5 and G6"
depends on !64BIT
help
Select this to build a 31 bit kernel that works
on all S/390 and zSeries machines.
config MARCH_Z900
bool "IBM eServer zSeries model z800 and z900"
help
Select this to optimize for zSeries machines. This
will enable some optimizations that are not available
on older 31 bit only CPUs.
config MARCH_Z990
bool "IBM eServer zSeries model z890 and z990"
help
Select this enable optimizations for model z890/z990.
This will be slightly faster but does not work on
older machines such as the z900.
config MARCH_Z9_109
bool "IBM System z9"
help
Select this to enable optimizations for IBM System z9-109, IBM
System z9 Enterprise Class (z9 EC), and IBM System z9 Business
Class (z9 BC). The kernel will be slightly faster but will not
work on older machines such as the z990, z890, z900, and z800.
endchoice
config PACK_STACK
bool "Pack kernel stack"
help
This option enables the compiler option -mkernel-backchain if it
is available. If the option is available the compiler supports
the new stack layout which dramatically reduces the minimum stack
frame size. With an old compiler a non-leaf function needs a
minimum of 96 bytes on 31 bit and 160 bytes on 64 bit. With
-mkernel-backchain the minimum size drops to 16 byte on 31 bit
and 24 byte on 64 bit.
Say Y if you are unsure.
config SMALL_STACK
bool "Use 4kb/8kb for kernel stack instead of 8kb/16kb"
depends on PACK_STACK && !LOCKDEP
help
If you say Y here and the compiler supports the -mkernel-backchain
option the kernel will use a smaller kernel stack size. For 31 bit
the reduced size is 4kb instead of 8kb and for 64 bit it is 8kb
instead of 16kb. This allows to run more thread on a system and
reduces the pressure on the memory management for higher order
page allocations.
Say N if you are unsure.
config CHECK_STACK
bool "Detect kernel stack overflow"
help
This option enables the compiler option -mstack-guard and
-mstack-size if they are available. If the compiler supports them
it will emit additional code to each function prolog to trigger
an illegal operation if the kernel stack is about to overflow.
Say N if you are unsure.
config STACK_GUARD
int "Size of the guard area (128-1024)"
range 128 1024
depends on CHECK_STACK
default "256"
help
This allows you to specify the size of the guard area at the lower
end of the kernel stack. If the kernel stack points into the guard
area on function entry an illegal operation is triggered. The size
needs to be a power of 2. Please keep in mind that the size of an
interrupt frame is 184 bytes for 31 bit and 328 bytes on 64 bit.
The minimum size for the stack guard should be 256 for 31 bit and
512 for 64 bit.
config WARN_STACK
bool "Emit compiler warnings for function with broken stack usage"
help
This option enables the compiler options -mwarn-framesize and
-mwarn-dynamicstack. If the compiler supports these options it
will generate warnings for function which either use alloca or
create a stack frame bigger then CONFIG_WARN_STACK_SIZE.
Say N if you are unsure.
config WARN_STACK_SIZE
int "Maximum frame size considered safe (128-2048)"
range 128 2048
depends on WARN_STACK
default "256"
help
This allows you to specify the maximum frame size a function may
have without the compiler complaining about it.
config ARCH_POPULATES_NODE_MAP
def_bool y
source "mm/Kconfig"
config HOLES_IN_ZONE
def_bool y
comment "I/O subsystem configuration"
config MACHCHK_WARNING
bool "Process warning machine checks"
help
Select this option if you want the machine check handler on IBM S/390 or
zSeries to process warning machine checks (e.g. on power failures).
If unsure, say "Y".
config QDIO
tristate "QDIO support"
---help---
This driver provides the Queued Direct I/O base support for
IBM mainframes.
For details please refer to the documentation provided by IBM at
<http://www10.software.ibm.com/developerworks/opensource/linux390>
To compile this driver as a module, choose M here: the
module will be called qdio.
If unsure, say Y.
config QDIO_DEBUG
bool "Extended debugging information"
depends on QDIO
help
Say Y here to get extended debugging output in
/sys/kernel/debug/s390dbf/qdio...
Warning: this option reduces the performance of the QDIO module.
If unsure, say N.
comment "Misc"
config PREEMPT
bool "Preemptible Kernel"
help
This option reduces the latency of the kernel when reacting to
real-time or interactive events by allowing a low priority process to
be preempted even if it is in kernel mode executing a system call.
This allows applications to run more reliably even when the system is
under load.
Say N if you are unsure.
config IPL
bool "Builtin IPL record support"
help
If you want to use the produced kernel to IPL directly from a
device, you have to merge a bootsector specific to the device
into the first bytes of the kernel. You will have to select the
IPL device.
choice
prompt "IPL method generated into head.S"
depends on IPL
default IPL_TAPE
help
Select "tape" if you want to IPL the image from a Tape.
Select "vm_reader" if you are running under VM/ESA and want
to IPL the image from the emulated card reader.
config IPL_TAPE
bool "tape"
config IPL_VM
bool "vm_reader"
endchoice
source "fs/Kconfig.binfmt"
config PROCESS_DEBUG
bool "Show crashed user process info"
help
Say Y to print all process fault locations to the console. This is
a debugging option; you probably do not want to set it unless you
are an S390 port maintainer.
config PFAULT
bool "Pseudo page fault support"
help
Select this option, if you want to use PFAULT pseudo page fault
handling under VM. If running native or in LPAR, this option
has no effect. If your VM does not support PFAULT, PAGEEX
pseudo page fault handling will be used.
Note that VM 4.2 supports PFAULT but has a bug in its
implementation that causes some problems.
Everybody who wants to run Linux under VM != VM4.2 should select
this option.
config SHARED_KERNEL
bool "VM shared kernel support"
help
Select this option, if you want to share the text segment of the
Linux kernel between different VM guests. This reduces memory
usage with lots of guests but greatly increases kernel size.
You should only select this option if you know what you are
doing and want to exploit this feature.
config CMM
tristate "Cooperative memory management"
help
Select this option, if you want to enable the kernel interface
to reduce the memory size of the system. This is accomplished
by allocating pages of memory and put them "on hold". This only
makes sense for a system running under VM where the unused pages
will be reused by VM for other guest systems. The interface
allows an external monitor to balance memory of many systems.
Everybody who wants to run Linux under VM should select this
option.
config CMM_PROC
bool "/proc interface to cooperative memory management"
depends on CMM
help
Select this option to enable the /proc interface to the
cooperative memory management.
config CMM_IUCV
bool "IUCV special message interface to cooperative memory management"
depends on CMM && (SMSGIUCV=y || CMM=SMSGIUCV)
help
Select this option to enable the special message interface to
the cooperative memory management.
config VIRT_TIMER
bool "Virtual CPU timer support"
help
This provides a kernel interface for virtual CPU timers.
Default is disabled.
config VIRT_CPU_ACCOUNTING
bool "Base user process accounting on virtual cpu timer"
depends on VIRT_TIMER
help
Select this option to use CPU timer deltas to do user
process accounting.
config APPLDATA_BASE
bool "Linux - VM Monitor Stream, base infrastructure"
depends on PROC_FS && VIRT_TIMER=y
help
This provides a kernel interface for creating and updating z/VM APPLDATA
monitor records. The monitor records are updated at certain time
intervals, once the timer is started.
Writing 1 or 0 to /proc/appldata/timer starts(1) or stops(0) the timer,
i.e. enables or disables monitoring on the Linux side.
A custom interval value (in seconds) can be written to
/proc/appldata/interval.
Defaults are 60 seconds interval and timer off.
The /proc entries can also be read from, showing the current settings.
config APPLDATA_MEM
tristate "Monitor memory management statistics"
depends on APPLDATA_BASE && VM_EVENT_COUNTERS
help
This provides memory management related data to the Linux - VM Monitor
Stream, like paging/swapping rate, memory utilisation, etc.
Writing 1 or 0 to /proc/appldata/memory creates(1) or removes(0) a z/VM
APPLDATA monitor record, i.e. enables or disables monitoring this record
on the z/VM side.
Default is disabled.
The /proc entry can also be read from, showing the current settings.
This can also be compiled as a module, which will be called
appldata_mem.o.
config APPLDATA_OS
tristate "Monitor OS statistics"
depends on APPLDATA_BASE
help
This provides OS related data to the Linux - VM Monitor Stream, like
CPU utilisation, etc.
Writing 1 or 0 to /proc/appldata/os creates(1) or removes(0) a z/VM
APPLDATA monitor record, i.e. enables or disables monitoring this record
on the z/VM side.
Default is disabled.
This can also be compiled as a module, which will be called
appldata_os.o.
config APPLDATA_NET_SUM
tristate "Monitor overall network statistics"
depends on APPLDATA_BASE
help
This provides network related data to the Linux - VM Monitor Stream,
currently there is only a total sum of network I/O statistics, no
per-interface data.
Writing 1 or 0 to /proc/appldata/net_sum creates(1) or removes(0) a z/VM
APPLDATA monitor record, i.e. enables or disables monitoring this record
on the z/VM side.
Default is disabled.
This can also be compiled as a module, which will be called
appldata_net_sum.o.
config NO_IDLE_HZ
bool "No HZ timer ticks in idle"
help
Switches the regular HZ timer off when the system is going idle.
This helps z/VM to detect that the Linux system is idle. VM can
then "swap-out" this guest which reduces memory usage. It also
reduces the overhead of idle systems.
The HZ timer can be switched on/off via /proc/sys/kernel/hz_timer.
hz_timer=0 means HZ timer is disabled. hz_timer=1 means HZ
timer is active.
config NO_IDLE_HZ_INIT
bool "HZ timer in idle off by default"
depends on NO_IDLE_HZ
help
The HZ timer is switched off in idle by default. That means the
HZ timer is already disabled at boot time.
config S390_HYPFS_FS
bool "s390 hypervisor file system support"
select SYS_HYPERVISOR
default y
help
This is a virtual file system intended to provide accounting
information in an s390 hypervisor environment.
config KEXEC
bool "kexec system call"
help
kexec is a system call that implements the ability to shutdown your
current kernel, and to start another kernel. It is like a reboot
but is independent of hardware/microcode support.
endmenu
source "net/Kconfig"
config PCMCIA
bool
default n
source "drivers/base/Kconfig"
source "drivers/connector/Kconfig"
source "drivers/scsi/Kconfig"
source "drivers/s390/Kconfig"
source "drivers/net/Kconfig"
source "fs/Kconfig"
menu "Instrumentation Support"
source "arch/s390/oprofile/Kconfig"
config KPROBES
bool "Kprobes (EXPERIMENTAL)"
depends on EXPERIMENTAL && MODULES
help
Kprobes allows you to trap at almost any kernel address and
execute a callback function. register_kprobe() establishes
a probepoint and specifies the callback. Kprobes is useful
for kernel debugging, non-intrusive instrumentation and testing.
If in doubt, say "N".
endmenu
source "arch/s390/Kconfig.debug"
source "security/Kconfig"
source "crypto/Kconfig"
source "lib/Kconfig"
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