Re: [GIT PULL] Protection Keys (pkeys) support

From: Ingo Molnar
Date: Tue Nov 15 2016 - 05:42:41 EST


* Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:

> On Mon, Mar 21, 2016 at 12:34 AM, Ingo Molnar <mingo@xxxxxxxxxx> wrote:
> >
> > Furthermore, I'd reorganize the 'arch settings' section into 4 groups, the
> > following way:
> >
> > 1) Options that are fundamentally only set on x86-32 kernels:
> >
> > 2) Options that are fundamentally only set on x86-64 kernels:
> >
> > 3) Bi-arch options and options that are not yet implemented for both
> >
> > 4) All other options are moved as selects to their respective config entries.
>
> Yes, that sounds much better than what we have now.

... a late update a few months later:

JFYI, I've pushed out a series of changes that implements all this:

c763ea2650df x86/kconfig: Sort the 'config X86' selects alphabetically
953fee1d82f3 x86/kconfig: Clean up 32-bit compat options
39f88911b9dc x86/kconfig: Clean up IA32_EMULATION select
52c8e6017c76 x86/kconfig, x86/pkeys: Move pkeys selects to X86_INTEL_MEMORY_PROTECTION_KEYS
d94e068573f2 x86/kconfig: Move 64-bit only arch Kconfig selects to 'config X86_64'
341c787e34af x86/kconfig: Move 32-bit only arch Kconfig selects to 'config X86_32'

Combo patch is below. Full tree can be found at:

git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/build

The remaining 'if X86_64' options are all features that are selected for the
64-bit kernel but could be used on the 32-bit kernel as well (just nobody bothered
porting it yet). I kept those in the generic section for the time being.

Thanks,

Ingo

---
arch/x86/Kconfig | 68 ++++++++++++++++++++++++++++++++++----------------------
1 file changed, 41 insertions(+), 27 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index bada636d1065..e01f101d4413 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -9,28 +9,50 @@ config 64BIT
config X86_32
def_bool y
depends on !64BIT
+ # Options that are inherently 32-bit kernel only:
+ select ARCH_WANT_IPC_PARSE_VERSION
+ select CLKSRC_I8253
+ select CLONE_BACKWARDS
+ select HAVE_AOUT
+ select HAVE_GENERIC_DMA_COHERENT
+ select MODULES_USE_ELF_REL
+ select OLD_SIGACTION

config X86_64
def_bool y
depends on 64BIT
+ # Options that are inherently 64-bit kernel only:
+ select ARCH_HAS_GIGANTIC_PAGE
+ select ARCH_SUPPORTS_INT128
+ select ARCH_USE_CMPXCHG_LOCKREF
+ select HAVE_ARCH_SOFT_DIRTY
+ select MODULES_USE_ELF_RELA
+ select X86_DEV_DMA_OPS

-### Arch settings
+#
+# Arch settings
+#
+# ( Note that options that are marked 'if X86_64' could in principle be
+# ported to 32-bit as well. )
+#
config X86
def_bool y
+ #
+ # Note: keep this list sorted alphabetically
+ #
select ACPI_LEGACY_TABLES_LOOKUP if ACPI
select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
select ANON_INODES
select ARCH_CLOCKSOURCE_DATA
select ARCH_DISCARD_MEMBLOCK
- select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
+ select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
select ARCH_HAS_DEVMEM_IS_ALLOWED
select ARCH_HAS_ELF_RANDOMIZE
select ARCH_HAS_FAST_MULTIPLIER
select ARCH_HAS_GCOV_PROFILE_ALL
- select ARCH_HAS_GIGANTIC_PAGE if X86_64
select ARCH_HAS_KCOV if X86_64
- select ARCH_HAS_PMEM_API if X86_64
select ARCH_HAS_MMIO_FLUSH
+ select ARCH_HAS_PMEM_API if X86_64
select ARCH_HAS_SG_CHAIN
select ARCH_HAS_UBSAN_SANITIZE_ALL
select ARCH_HAVE_NMI_SAFE_CMPXCHG
@@ -39,23 +61,17 @@ config X86
select ARCH_MIGHT_HAVE_PC_SERIO
select ARCH_SUPPORTS_ATOMIC_RMW
select ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
- select ARCH_SUPPORTS_INT128 if X86_64
select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
select ARCH_USE_BUILTIN_BSWAP
- select ARCH_USE_CMPXCHG_LOCKREF if X86_64
select ARCH_USE_QUEUED_RWLOCKS
select ARCH_USE_QUEUED_SPINLOCKS
select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH if SMP
- select ARCH_WANTS_DYNAMIC_TASK_STRUCT
select ARCH_WANT_FRAME_POINTERS
- select ARCH_WANT_IPC_PARSE_VERSION if X86_32
+ select ARCH_WANTS_DYNAMIC_TASK_STRUCT
select BUILDTIME_EXTABLE_SORT
select CLKEVT_I8253
- select CLKSRC_I8253 if X86_32
select CLOCKSOURCE_VALIDATE_LAST_CYCLE
select CLOCKSOURCE_WATCHDOG
- select CLONE_BACKWARDS if X86_32
- select COMPAT_OLD_SIGACTION if IA32_EMULATION
select DCACHE_WORD_ACCESS
select EDAC_ATOMIC_SCRUB
select EDAC_SUPPORT
@@ -77,7 +93,6 @@ config X86
select HAVE_ACPI_APEI if ACPI
select HAVE_ACPI_APEI_NMI if ACPI
select HAVE_ALIGNED_STRUCT_PAGE if SLUB
- select HAVE_AOUT if X86_32
select HAVE_ARCH_AUDITSYSCALL
select HAVE_ARCH_HARDENED_USERCOPY
select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
@@ -88,12 +103,10 @@ config X86
select HAVE_ARCH_MMAP_RND_BITS if MMU
select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
select HAVE_ARCH_SECCOMP_FILTER
- select HAVE_ARCH_SOFT_DIRTY if X86_64
select HAVE_ARCH_TRACEHOOK
select HAVE_ARCH_TRANSPARENT_HUGEPAGE
- select HAVE_ARCH_WITHIN_STACK_FRAMES
- select HAVE_EBPF_JIT if X86_64
select HAVE_ARCH_VMAP_STACK if X86_64
+ select HAVE_ARCH_WITHIN_STACK_FRAMES
select HAVE_CC_STACKPROTECTOR
select HAVE_CMPXCHG_DOUBLE
select HAVE_CMPXCHG_LOCAL
@@ -106,6 +119,7 @@ config X86
select HAVE_DMA_CONTIGUOUS
select HAVE_DYNAMIC_FTRACE
select HAVE_DYNAMIC_FTRACE_WITH_REGS
+ select HAVE_EBPF_JIT if X86_64
select HAVE_EFFICIENT_UNALIGNED_ACCESS
select HAVE_EXIT_THREAD
select HAVE_FENTRY if X86_64
@@ -113,7 +127,6 @@ config X86
select HAVE_FUNCTION_GRAPH_TRACER
select HAVE_FUNCTION_TRACER
select HAVE_GCC_PLUGINS
- select HAVE_GENERIC_DMA_COHERENT if X86_32
select HAVE_HW_BREAKPOINT
select HAVE_IDE
select HAVE_IOREMAP_PROT
@@ -142,15 +155,11 @@ config X86
select HAVE_PERF_REGS
select HAVE_PERF_USER_STACK_DUMP
select HAVE_REGS_AND_STACK_ACCESS_API
+ select HAVE_STACK_VALIDATION if X86_64
select HAVE_SYSCALL_TRACEPOINTS
- select HAVE_UID16 if X86_32 || IA32_EMULATION
select HAVE_UNSTABLE_SCHED_CLOCK
select HAVE_USER_RETURN_NOTIFIER
select IRQ_FORCED_THREADING
- select MODULES_USE_ELF_RELA if X86_64
- select MODULES_USE_ELF_REL if X86_32
- select OLD_SIGACTION if X86_32
- select OLD_SIGSUSPEND3 if X86_32 || IA32_EMULATION
select PERF_EVENTS
select RTC_LIB
select RTC_MC146818_LIB
@@ -160,11 +169,7 @@ config X86
select THREAD_INFO_IN_TASK
select USER_STACKTRACE_SUPPORT
select VIRT_TO_BUS
- select X86_DEV_DMA_OPS if X86_64
select X86_FEATURE_NAMES if PROC_FS
- select HAVE_STACK_VALIDATION if X86_64
- select ARCH_USES_HIGH_VMA_FLAGS if X86_INTEL_MEMORY_PROTECTION_KEYS
- select ARCH_HAS_PKEYS if X86_INTEL_MEMORY_PROTECTION_KEYS

config INSTRUCTION_DECODER
def_bool y
@@ -1737,6 +1742,8 @@ config X86_INTEL_MEMORY_PROTECTION_KEYS
def_bool y
# Note: only available in 64-bit mode
depends on CPU_SUP_INTEL && X86_64
+ select ARCH_USES_HIGH_VMA_FLAGS
+ select ARCH_HAS_PKEYS
---help---
Memory Protection Keys provides a mechanism for enforcing
page-based protections, but without requiring modification of the
@@ -2092,7 +2099,7 @@ config DEBUG_HOTPLUG_CPU0
config COMPAT_VDSO
def_bool n
prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
- depends on X86_32 || IA32_EMULATION
+ depends on COMPAT_32
---help---
Certain buggy versions of glibc will crash if they are
presented with a 32-bit vDSO that is not mapped at the address
@@ -2694,9 +2701,10 @@ source "fs/Kconfig.binfmt"
config IA32_EMULATION
bool "IA32 Emulation"
depends on X86_64
+ select ARCH_WANT_OLD_COMPAT_IPC
select BINFMT_ELF
select COMPAT_BINFMT_ELF
- select ARCH_WANT_OLD_COMPAT_IPC
+ select COMPAT_OLD_SIGACTION
---help---
Include code to run legacy 32-bit programs under a
64-bit kernel. You should likely turn this on, unless you're
@@ -2721,6 +2729,12 @@ config X86_X32
elf32_x86_64 support enabled to compile a kernel with this
option set.

+config COMPAT_32
+ def_bool y
+ depends on IA32_EMULATION || X86_32
+ select HAVE_UID16
+ select OLD_SIGSUSPEND3
+
config COMPAT
def_bool y
depends on IA32_EMULATION || X86_X32