linux-stable/arch/sh/Kconfig
Linus Torvalds 9471f1f2f5 Merge branch 'expand-stack'
This modifies our user mode stack expansion code to always take the
mmap_lock for writing before modifying the VM layout.

It's actually something we always technically should have done, but
because we didn't strictly need it, we were being lazy ("opportunistic"
sounds so much better, doesn't it?) about things, and had this hack in
place where we would extend the stack vma in-place without doing the
proper locking.

And it worked fine.  We just needed to change vm_start (or, in the case
of grow-up stacks, vm_end) and together with some special ad-hoc locking
using the anon_vma lock and the mm->page_table_lock, it all was fairly
straightforward.

That is, it was all fine until Ruihan Li pointed out that now that the
vma layout uses the maple tree code, we *really* don't just change
vm_start and vm_end any more, and the locking really is broken.  Oops.

It's not actually all _that_ horrible to fix this once and for all, and
do proper locking, but it's a bit painful.  We have basically three
different cases of stack expansion, and they all work just a bit
differently:

 - the common and obvious case is the page fault handling. It's actually
   fairly simple and straightforward, except for the fact that we have
   something like 24 different versions of it, and you end up in a maze
   of twisty little passages, all alike.

 - the simplest case is the execve() code that creates a new stack.
   There are no real locking concerns because it's all in a private new
   VM that hasn't been exposed to anybody, but lockdep still can end up
   unhappy if you get it wrong.

 - and finally, we have GUP and page pinning, which shouldn't really be
   expanding the stack in the first place, but in addition to execve()
   we also use it for ptrace(). And debuggers do want to possibly access
   memory under the stack pointer and thus need to be able to expand the
   stack as a special case.

None of these cases are exactly complicated, but the page fault case in
particular is just repeated slightly differently many many times.  And
ia64 in particular has a fairly complicated situation where you can have
both a regular grow-down stack _and_ a special grow-up stack for the
register backing store.

So to make this slightly more manageable, the bulk of this series is to
first create a helper function for the most common page fault case, and
convert all the straightforward architectures to it.

Thus the new 'lock_mm_and_find_vma()' helper function, which ends up
being used by x86, arm, powerpc, mips, riscv, alpha, arc, csky, hexagon,
loongarch, nios2, sh, sparc32, and xtensa.  So we not only convert more
than half the architectures, we now have more shared code and avoid some
of those twisty little passages.

And largely due to this common helper function, the full diffstat of
this series ends up deleting more lines than it adds.

That still leaves eight architectures (ia64, m68k, microblaze, openrisc,
parisc, s390, sparc64 and um) that end up doing 'expand_stack()'
manually because they are doing something slightly different from the
normal pattern.  Along with the couple of special cases in execve() and
GUP.

So there's a couple of patches that first create 'locked' helper
versions of the stack expansion functions, so that there's a obvious
path forward in the conversion.  The execve() case is then actually
pretty simple, and is a nice cleanup from our old "grow-up stackls are
special, because at execve time even they grow down".

The #ifdef CONFIG_STACK_GROWSUP in that code just goes away, because
it's just more straightforward to write out the stack expansion there
manually, instead od having get_user_pages_remote() do it for us in some
situations but not others and have to worry about locking rules for GUP.

And the final step is then to just convert the remaining odd cases to a
new world order where 'expand_stack()' is called with the mmap_lock held
for reading, but where it might drop it and upgrade it to a write, only
to return with it held for reading (in the success case) or with it
completely dropped (in the failure case).

In the process, we remove all the stack expansion from GUP (where
dropping the lock wouldn't be ok without special rules anyway), and add
it in manually to __access_remote_vm() for ptrace().

Thanks to Adrian Glaubitz and Frank Scheiner who tested the ia64 cases.
Everything else here felt pretty straightforward, but the ia64 rules for
stack expansion are really quite odd and very different from everything
else.  Also thanks to Vegard Nossum who caught me getting one of those
odd conditions entirely the wrong way around.

Anyway, I think I want to actually move all the stack expansion code to
a whole new file of its own, rather than have it split up between
mm/mmap.c and mm/memory.c, but since this will have to be backported to
the initial maple tree vma introduction anyway, I tried to keep the
patches _fairly_ minimal.

Also, while I don't think it's valid to expand the stack from GUP, the
final patch in here is a "warn if some crazy GUP user wants to try to
expand the stack" patch.  That one will be reverted before the final
release, but it's left to catch any odd cases during the merge window
and release candidates.

Reported-by: Ruihan Li <lrh2000@pku.edu.cn>

* branch 'expand-stack':
  gup: add warning if some caller would seem to want stack expansion
  mm: always expand the stack with the mmap write lock held
  execve: expand new process stack manually ahead of time
  mm: make find_extend_vma() fail if write lock not held
  powerpc/mm: convert coprocessor fault to lock_mm_and_find_vma()
  mm/fault: convert remaining simple cases to lock_mm_and_find_vma()
  arm/mm: Convert to using lock_mm_and_find_vma()
  riscv/mm: Convert to using lock_mm_and_find_vma()
  mips/mm: Convert to using lock_mm_and_find_vma()
  powerpc/mm: Convert to using lock_mm_and_find_vma()
  arm64/mm: Convert to using lock_mm_and_find_vma()
  mm: make the page fault mmap locking killable
  mm: introduce new 'lock_mm_and_find_vma()' page fault helper
2023-06-28 20:35:21 -07:00

798 lines
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# SPDX-License-Identifier: GPL-2.0
config SUPERH
def_bool y
select ARCH_32BIT_OFF_T
select ARCH_ENABLE_MEMORY_HOTPLUG if SPARSEMEM && MMU
select ARCH_ENABLE_MEMORY_HOTREMOVE if SPARSEMEM && MMU
select ARCH_HAVE_NMI_SAFE_CMPXCHG if (GUSA_RB || CPU_SH4A)
select ARCH_HAS_BINFMT_FLAT if !MMU
select ARCH_HAS_CPU_FINALIZE_INIT
select ARCH_HAS_CURRENT_STACK_POINTER
select ARCH_HAS_GIGANTIC_PAGE
select ARCH_HAS_GCOV_PROFILE_ALL
select ARCH_HAS_PTE_SPECIAL
select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
select ARCH_HIBERNATION_POSSIBLE if MMU
select ARCH_MIGHT_HAVE_PC_PARPORT
select ARCH_WANT_IPC_PARSE_VERSION
select CPU_NO_EFFICIENT_FFS
select DMA_DECLARE_COHERENT
select GENERIC_ATOMIC64
select GENERIC_CMOS_UPDATE if SH_SH03 || SH_DREAMCAST
select GENERIC_IDLE_POLL_SETUP
select GENERIC_IRQ_SHOW
select GENERIC_LIB_ASHLDI3
select GENERIC_LIB_ASHRDI3
select GENERIC_LIB_LSHRDI3
select GENERIC_PCI_IOMAP if PCI
select GENERIC_SCHED_CLOCK
select GENERIC_SMP_IDLE_THREAD
select GUP_GET_PXX_LOW_HIGH if X2TLB
select HAS_IOPORT if HAS_IOPORT_MAP
select HAVE_ARCH_AUDITSYSCALL
select HAVE_ARCH_KGDB
select HAVE_ARCH_SECCOMP_FILTER
select HAVE_ARCH_TRACEHOOK
select HAVE_DEBUG_BUGVERBOSE
select HAVE_DEBUG_KMEMLEAK
select HAVE_DYNAMIC_FTRACE
select HAVE_FAST_GUP if MMU
select HAVE_FUNCTION_GRAPH_TRACER
select HAVE_FUNCTION_TRACER
select HAVE_FTRACE_MCOUNT_RECORD
select HAVE_HW_BREAKPOINT
select HAVE_IOREMAP_PROT if MMU && !X2TLB
select HAVE_KERNEL_BZIP2
select HAVE_KERNEL_GZIP
select HAVE_KERNEL_LZMA
select HAVE_KERNEL_LZO
select HAVE_KERNEL_XZ
select HAVE_KPROBES
select HAVE_KRETPROBES
select HAVE_MIXED_BREAKPOINTS_REGS
select HAVE_MOD_ARCH_SPECIFIC if DWARF_UNWINDER
select HAVE_NMI
select HAVE_PATA_PLATFORM
select HAVE_PERF_EVENTS
select HAVE_REGS_AND_STACK_ACCESS_API
select HAVE_UID16
select HAVE_SOFTIRQ_ON_OWN_STACK if IRQSTACKS
select HAVE_STACKPROTECTOR
select HAVE_SYSCALL_TRACEPOINTS
select IRQ_FORCED_THREADING
select LOCK_MM_AND_FIND_VMA
select MODULES_USE_ELF_RELA
select NEED_SG_DMA_LENGTH
select NO_DMA if !MMU && !DMA_COHERENT
select NO_GENERIC_PCI_IOPORT_MAP if PCI
select OLD_SIGACTION
select OLD_SIGSUSPEND
select PCI_DOMAINS if PCI
select PERF_EVENTS
select PERF_USE_VMALLOC
select RTC_LIB
select SPARSE_IRQ
select TRACE_IRQFLAGS_SUPPORT
help
The SuperH is a RISC processor targeted for use in embedded systems
and consumer electronics; it was also used in the Sega Dreamcast
gaming console. The SuperH port has a home page at
<http://www.linux-sh.org/>.
config GENERIC_BUG
def_bool y
depends on BUG
config GENERIC_HWEIGHT
def_bool y
config GENERIC_CALIBRATE_DELAY
bool
config GENERIC_LOCKBREAK
def_bool y
depends on SMP && PREEMPTION
config ARCH_SUSPEND_POSSIBLE
def_bool n
config ARCH_HIBERNATION_POSSIBLE
def_bool n
config SYS_SUPPORTS_APM_EMULATION
bool
select ARCH_SUSPEND_POSSIBLE
config SYS_SUPPORTS_SMP
bool
config SYS_SUPPORTS_NUMA
bool
config STACKTRACE_SUPPORT
def_bool y
config LOCKDEP_SUPPORT
def_bool y
config ARCH_HAS_ILOG2_U32
def_bool n
config ARCH_HAS_ILOG2_U64
def_bool n
config NO_IOPORT_MAP
def_bool !PCI
depends on !SH_SH4202_MICRODEV && !SH_SHMIN && !SH_HP6XX && \
!SH_SOLUTION_ENGINE
config IO_TRAPPED
bool
config SWAP_IO_SPACE
bool
config DMA_COHERENT
bool
config DMA_NONCOHERENT
def_bool !NO_DMA && !DMA_COHERENT
select ARCH_HAS_DMA_PREP_COHERENT
select ARCH_HAS_SYNC_DMA_FOR_DEVICE
select DMA_DIRECT_REMAP
config PGTABLE_LEVELS
default 3 if X2TLB
default 2
menu "System type"
#
# Processor families
#
config CPU_SH2
bool
select SH_INTC
config CPU_SH2A
bool
select CPU_SH2
select UNCACHED_MAPPING
config CPU_J2
bool
select CPU_SH2
select OF
select OF_EARLY_FLATTREE
config CPU_SH3
bool
select CPU_HAS_INTEVT
select CPU_HAS_SR_RB
select SH_INTC
select SYS_SUPPORTS_SH_TMU
config CPU_SH4
bool
select ARCH_SUPPORTS_HUGETLBFS if MMU
select CPU_HAS_INTEVT
select CPU_HAS_SR_RB
select CPU_HAS_FPU if !CPU_SH4AL_DSP
select SH_INTC
select SYS_SUPPORTS_SH_TMU
config CPU_SH4A
bool
select CPU_SH4
config CPU_SH4AL_DSP
bool
select CPU_SH4A
select CPU_HAS_DSP
config CPU_SHX2
bool
config CPU_SHX3
bool
select DMA_COHERENT
select SYS_SUPPORTS_SMP
select SYS_SUPPORTS_NUMA
config ARCH_SHMOBILE
bool
select ARCH_SUSPEND_POSSIBLE
select PM
config CPU_HAS_PMU
depends on CPU_SH4 || CPU_SH4A
default y
bool
choice
prompt "Processor sub-type selection"
#
# Processor subtypes
#
# SH-2 Processor Support
config CPU_SUBTYPE_SH7619
bool "Support SH7619 processor"
select CPU_SH2
select SYS_SUPPORTS_SH_CMT
config CPU_SUBTYPE_J2
bool "Support J2 processor"
select CPU_J2
select SYS_SUPPORTS_SMP
select GENERIC_CLOCKEVENTS_BROADCAST if SMP
# SH-2A Processor Support
config CPU_SUBTYPE_SH7201
bool "Support SH7201 processor"
select CPU_SH2A
select CPU_HAS_FPU
select SYS_SUPPORTS_SH_MTU2
config CPU_SUBTYPE_SH7203
bool "Support SH7203 processor"
select CPU_SH2A
select CPU_HAS_FPU
select SYS_SUPPORTS_SH_CMT
select SYS_SUPPORTS_SH_MTU2
select PINCTRL
config CPU_SUBTYPE_SH7206
bool "Support SH7206 processor"
select CPU_SH2A
select SYS_SUPPORTS_SH_CMT
select SYS_SUPPORTS_SH_MTU2
config CPU_SUBTYPE_SH7263
bool "Support SH7263 processor"
select CPU_SH2A
select CPU_HAS_FPU
select SYS_SUPPORTS_SH_CMT
select SYS_SUPPORTS_SH_MTU2
config CPU_SUBTYPE_SH7264
bool "Support SH7264 processor"
select CPU_SH2A
select CPU_HAS_FPU
select SYS_SUPPORTS_SH_CMT
select SYS_SUPPORTS_SH_MTU2
select PINCTRL
config CPU_SUBTYPE_SH7269
bool "Support SH7269 processor"
select CPU_SH2A
select CPU_HAS_FPU
select SYS_SUPPORTS_SH_CMT
select SYS_SUPPORTS_SH_MTU2
select PINCTRL
config CPU_SUBTYPE_MXG
bool "Support MX-G processor"
select CPU_SH2A
select SYS_SUPPORTS_SH_MTU2
help
Select MX-G if running on an R8A03022BG part.
# SH-3 Processor Support
config CPU_SUBTYPE_SH7705
bool "Support SH7705 processor"
select CPU_SH3
config CPU_SUBTYPE_SH7706
bool "Support SH7706 processor"
select CPU_SH3
help
Select SH7706 if you have a 133 Mhz SH-3 HD6417706 CPU.
config CPU_SUBTYPE_SH7707
bool "Support SH7707 processor"
select CPU_SH3
help
Select SH7707 if you have a 60 Mhz SH-3 HD6417707 CPU.
config CPU_SUBTYPE_SH7708
bool "Support SH7708 processor"
select CPU_SH3
help
Select SH7708 if you have a 60 Mhz SH-3 HD6417708S or
if you have a 100 Mhz SH-3 HD6417708R CPU.
config CPU_SUBTYPE_SH7709
bool "Support SH7709 processor"
select CPU_SH3
help
Select SH7709 if you have a 80 Mhz SH-3 HD6417709 CPU.
config CPU_SUBTYPE_SH7710
bool "Support SH7710 processor"
select CPU_SH3
select CPU_HAS_DSP
help
Select SH7710 if you have a SH3-DSP SH7710 CPU.
config CPU_SUBTYPE_SH7712
bool "Support SH7712 processor"
select CPU_SH3
select CPU_HAS_DSP
help
Select SH7712 if you have a SH3-DSP SH7712 CPU.
config CPU_SUBTYPE_SH7720
bool "Support SH7720 processor"
select CPU_SH3
select CPU_HAS_DSP
select SYS_SUPPORTS_SH_CMT
select USB_OHCI_SH if USB_OHCI_HCD
select PINCTRL
help
Select SH7720 if you have a SH3-DSP SH7720 CPU.
config CPU_SUBTYPE_SH7721
bool "Support SH7721 processor"
select CPU_SH3
select CPU_HAS_DSP
select SYS_SUPPORTS_SH_CMT
select USB_OHCI_SH if USB_OHCI_HCD
help
Select SH7721 if you have a SH3-DSP SH7721 CPU.
# SH-4 Processor Support
config CPU_SUBTYPE_SH7750
bool "Support SH7750 processor"
select CPU_SH4
help
Select SH7750 if you have a 200 Mhz SH-4 HD6417750 CPU.
config CPU_SUBTYPE_SH7091
bool "Support SH7091 processor"
select CPU_SH4
help
Select SH7091 if you have an SH-4 based Sega device (such as
the Dreamcast, Naomi, and Naomi 2).
config CPU_SUBTYPE_SH7750R
bool "Support SH7750R processor"
select CPU_SH4
config CPU_SUBTYPE_SH7750S
bool "Support SH7750S processor"
select CPU_SH4
config CPU_SUBTYPE_SH7751
bool "Support SH7751 processor"
select CPU_SH4
help
Select SH7751 if you have a 166 Mhz SH-4 HD6417751 CPU,
or if you have a HD6417751R CPU.
config CPU_SUBTYPE_SH7751R
bool "Support SH7751R processor"
select CPU_SH4
config CPU_SUBTYPE_SH7760
bool "Support SH7760 processor"
select CPU_SH4
config CPU_SUBTYPE_SH4_202
bool "Support SH4-202 processor"
select CPU_SH4
# SH-4A Processor Support
config CPU_SUBTYPE_SH7723
bool "Support SH7723 processor"
select CPU_SH4A
select CPU_SHX2
select ARCH_SHMOBILE
select ARCH_SPARSEMEM_ENABLE
select SYS_SUPPORTS_SH_CMT
select PINCTRL
help
Select SH7723 if you have an SH-MobileR2 CPU.
config CPU_SUBTYPE_SH7724
bool "Support SH7724 processor"
select CPU_SH4A
select CPU_SHX2
select ARCH_SHMOBILE
select ARCH_SPARSEMEM_ENABLE
select SYS_SUPPORTS_SH_CMT
select PINCTRL
help
Select SH7724 if you have an SH-MobileR2R CPU.
config CPU_SUBTYPE_SH7734
bool "Support SH7734 processor"
select CPU_SH4A
select CPU_SHX2
select PINCTRL
help
Select SH7734 if you have a SH4A SH7734 CPU.
config CPU_SUBTYPE_SH7757
bool "Support SH7757 processor"
select CPU_SH4A
select CPU_SHX2
select PINCTRL
help
Select SH7757 if you have a SH4A SH7757 CPU.
config CPU_SUBTYPE_SH7763
bool "Support SH7763 processor"
select CPU_SH4A
select USB_OHCI_SH if USB_OHCI_HCD
help
Select SH7763 if you have a SH4A SH7763(R5S77631) CPU.
config CPU_SUBTYPE_SH7770
bool "Support SH7770 processor"
select CPU_SH4A
config CPU_SUBTYPE_SH7780
bool "Support SH7780 processor"
select CPU_SH4A
config CPU_SUBTYPE_SH7785
bool "Support SH7785 processor"
select CPU_SH4A
select CPU_SHX2
select ARCH_SPARSEMEM_ENABLE
select SYS_SUPPORTS_NUMA
select PINCTRL
config CPU_SUBTYPE_SH7786
bool "Support SH7786 processor"
select CPU_SH4A
select CPU_SHX3
select CPU_HAS_PTEAEX
select GENERIC_CLOCKEVENTS_BROADCAST if SMP
select USB_OHCI_SH if USB_OHCI_HCD
select USB_EHCI_SH if USB_EHCI_HCD
select PINCTRL
config CPU_SUBTYPE_SHX3
bool "Support SH-X3 processor"
select CPU_SH4A
select CPU_SHX3
select GENERIC_CLOCKEVENTS_BROADCAST if SMP
select GPIOLIB
select PINCTRL
# SH4AL-DSP Processor Support
config CPU_SUBTYPE_SH7343
bool "Support SH7343 processor"
select CPU_SH4AL_DSP
select ARCH_SHMOBILE
select SYS_SUPPORTS_SH_CMT
config CPU_SUBTYPE_SH7722
bool "Support SH7722 processor"
select CPU_SH4AL_DSP
select CPU_SHX2
select ARCH_SHMOBILE
select ARCH_SPARSEMEM_ENABLE
select SYS_SUPPORTS_NUMA
select SYS_SUPPORTS_SH_CMT
select PINCTRL
config CPU_SUBTYPE_SH7366
bool "Support SH7366 processor"
select CPU_SH4AL_DSP
select CPU_SHX2
select ARCH_SHMOBILE
select ARCH_SPARSEMEM_ENABLE
select SYS_SUPPORTS_NUMA
select SYS_SUPPORTS_SH_CMT
endchoice
source "arch/sh/mm/Kconfig"
source "arch/sh/Kconfig.cpu"
source "arch/sh/boards/Kconfig"
menu "Timer and clock configuration"
config SH_PCLK_FREQ
int "Peripheral clock frequency (in Hz)"
depends on SH_CLK_CPG_LEGACY
default "31250000" if CPU_SUBTYPE_SH7619
default "33333333" if CPU_SUBTYPE_SH7770 || \
CPU_SUBTYPE_SH7760 || \
CPU_SUBTYPE_SH7705 || \
CPU_SUBTYPE_SH7203 || \
CPU_SUBTYPE_SH7206 || \
CPU_SUBTYPE_SH7263 || \
CPU_SUBTYPE_MXG
default "60000000" if CPU_SUBTYPE_SH7751 || CPU_SUBTYPE_SH7751R
default "66000000" if CPU_SUBTYPE_SH4_202
default "50000000"
help
This option is used to specify the peripheral clock frequency.
This is necessary for determining the reference clock value on
platforms lacking an RTC.
config SH_CLK_CPG
def_bool y
config SH_CLK_CPG_LEGACY
depends on SH_CLK_CPG
def_bool y if !CPU_SUBTYPE_SH7785 && !ARCH_SHMOBILE && \
!CPU_SHX3 && !CPU_SUBTYPE_SH7757 && \
!CPU_SUBTYPE_SH7734 && !CPU_SUBTYPE_SH7264 && \
!CPU_SUBTYPE_SH7269
endmenu
menu "CPU Frequency scaling"
source "drivers/cpufreq/Kconfig"
endmenu
source "arch/sh/drivers/Kconfig"
endmenu
menu "Kernel features"
source "kernel/Kconfig.hz"
config KEXEC
bool "kexec system call (EXPERIMENTAL)"
depends on MMU
select KEXEC_CORE
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 it is independent of the system firmware. And like a reboot
you can start any kernel with it, not just Linux.
The name comes from the similarity to the exec system call.
It is an ongoing process to be certain the hardware in a machine
is properly shutdown, so do not be surprised if this code does not
initially work for you. As of this writing the exact hardware
interface is strongly in flux, so no good recommendation can be
made.
config CRASH_DUMP
bool "kernel crash dumps (EXPERIMENTAL)"
depends on BROKEN_ON_SMP
help
Generate crash dump after being started by kexec.
This should be normally only set in special crash dump kernels
which are loaded in the main kernel with kexec-tools into
a specially reserved region and then later executed after
a crash by kdump/kexec. The crash dump kernel must be compiled
to a memory address not used by the main kernel using
PHYSICAL_START.
For more details see Documentation/admin-guide/kdump/kdump.rst
config KEXEC_JUMP
bool "kexec jump (EXPERIMENTAL)"
depends on KEXEC && HIBERNATION
help
Jump between original kernel and kexeced kernel and invoke
code via KEXEC
config PHYSICAL_START
hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
default MEMORY_START
help
This gives the physical address where the kernel is loaded
and is ordinarily the same as MEMORY_START.
Different values are primarily used in the case of kexec on panic
where the fail safe kernel needs to run at a different address
than the panic-ed kernel.
config SMP
bool "Symmetric multi-processing support"
depends on SYS_SUPPORTS_SMP
help
This enables support for systems with more than one CPU. If you have
a system with only one CPU, say N. If you have a system with more
than one CPU, say Y.
If you say N here, the kernel will run on uni- 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,
uniprocessor machines. On a uniprocessor machine, the kernel
will run faster if you say N here.
People using multiprocessor machines who say Y here should also say
Y to "Enhanced Real Time Clock Support", below.
See also <file:Documentation/admin-guide/lockup-watchdogs.rst> and the SMP-HOWTO
available at <https://www.tldp.org/docs.html#howto>.
If you don't know what to do here, say N.
config NR_CPUS
int "Maximum number of CPUs (2-32)"
range 2 32
depends on SMP
default "4" if CPU_SUBTYPE_SHX3
default "2"
help
This allows you to specify the maximum number of CPUs which this
kernel will support. The maximum supported value is 32 and the
minimum value which makes sense is 2.
This is purely to save memory - each supported CPU adds
approximately eight kilobytes to the kernel image.
config HOTPLUG_CPU
bool "Support for hot-pluggable CPUs (EXPERIMENTAL)"
depends on SMP
help
Say Y here to experiment with turning CPUs off and on. CPUs
can be controlled through /sys/devices/system/cpu.
config GUSA
def_bool y
depends on !SMP
help
This enables support for gUSA (general UserSpace Atomicity).
This is the default implementation for both UP and non-ll/sc
CPUs, and is used by the libc, amongst others.
For additional information, design information can be found
in <http://lc.linux.or.jp/lc2002/papers/niibe0919p.pdf>.
This should only be disabled for special cases where alternate
atomicity implementations exist.
config GUSA_RB
bool "Implement atomic operations by roll-back (gRB) (EXPERIMENTAL)"
depends on GUSA && CPU_SH3 || (CPU_SH4 && !CPU_SH4A)
help
Enabling this option will allow the kernel to implement some
atomic operations using a software implementation of load-locked/
store-conditional (LLSC). On machines which do not have hardware
LLSC, this should be more efficient than the other alternative of
disabling interrupts around the atomic sequence.
config HW_PERF_EVENTS
bool "Enable hardware performance counter support for perf events"
depends on PERF_EVENTS && CPU_HAS_PMU
default y
help
Enable hardware performance counter support for perf events. If
disabled, perf events will use software events only.
source "drivers/sh/Kconfig"
endmenu
menu "Boot options"
config USE_BUILTIN_DTB
bool "Use builtin DTB"
default n
depends on SH_DEVICE_TREE
help
Link a device tree blob for particular hardware into the kernel,
suppressing use of the DTB pointer provided by the bootloader.
This option should only be used with legacy bootloaders that are
not capable of providing a DTB to the kernel, or for experimental
hardware without stable device tree bindings.
config BUILTIN_DTB_SOURCE
string "Source file for builtin DTB"
default ""
depends on USE_BUILTIN_DTB
help
Base name (without suffix, relative to arch/sh/boot/dts) for the
a DTS file that will be used to produce the DTB linked into the
kernel.
config ZERO_PAGE_OFFSET
hex
default "0x00010000" if PAGE_SIZE_64KB || SH_RTS7751R2D || \
SH_7751_SOLUTION_ENGINE
default "0x00004000" if PAGE_SIZE_16KB || SH_SH03
default "0x00002000" if PAGE_SIZE_8KB
default "0x00001000"
help
This sets the default offset of zero page.
config BOOT_LINK_OFFSET
hex
default "0x00210000" if SH_SHMIN
default "0x00810000" if SH_7780_SOLUTION_ENGINE
default "0x009e0000" if SH_TITAN
default "0x01800000" if SH_SDK7780
default "0x02000000" if SH_EDOSK7760
default "0x00800000"
help
This option allows you to set the link address offset of the zImage.
This can be useful if you are on a board which has a small amount of
memory.
config ENTRY_OFFSET
hex
default "0x00001000" if PAGE_SIZE_4KB
default "0x00002000" if PAGE_SIZE_8KB
default "0x00004000" if PAGE_SIZE_16KB
default "0x00010000" if PAGE_SIZE_64KB
default "0x00000000"
config ROMIMAGE_MMCIF
bool "Include MMCIF loader in romImage (EXPERIMENTAL)"
depends on CPU_SUBTYPE_SH7724
help
Say Y here to include experimental MMCIF loading code in
romImage. With this enabled it is possible to write the romImage
kernel image to an MMC card and boot the kernel straight from
the reset vector. At reset the processor Mask ROM will load the
first part of the romImage which in turn loads the rest the kernel
image to RAM using the MMCIF hardware block.
choice
prompt "Kernel command line"
optional
default CMDLINE_OVERWRITE
help
Setting this option allows the kernel command line arguments
to be set.
config CMDLINE_OVERWRITE
bool "Overwrite bootloader kernel arguments"
help
Given string will overwrite any arguments passed in by
a bootloader.
config CMDLINE_EXTEND
bool "Extend bootloader kernel arguments"
help
Given string will be concatenated with arguments passed in
by a bootloader.
endchoice
config CMDLINE
string "Kernel command line arguments string"
depends on CMDLINE_OVERWRITE || CMDLINE_EXTEND
default "console=ttySC1,115200"
endmenu
menu "Bus options"
config SUPERHYWAY
tristate "SuperHyway Bus support"
depends on CPU_SUBTYPE_SH4_202
config MAPLE
bool "Maple Bus support"
depends on SH_DREAMCAST
help
The Maple Bus is SEGA's serial communication bus for peripherals
on the Dreamcast. Without this bus support you won't be able to
get your Dreamcast keyboard etc to work, so most users
probably want to say 'Y' here, unless you are only using the
Dreamcast with a serial line terminal or a remote network
connection.
endmenu
menu "Power management options (EXPERIMENTAL)"
source "kernel/power/Kconfig"
source "drivers/cpuidle/Kconfig"
endmenu