Merge branch 'for-next/bti-user' into for-next/bti

Merge in user support for Branch Target Identification, which narrowly
missed the cut for 5.7 after a late ABI concern.

* for-next/bti-user:
  arm64: bti: Document behaviour for dynamically linked binaries
  arm64: elf: Fix allnoconfig kernel build with !ARCH_USE_GNU_PROPERTY
  arm64: BTI: Add Kconfig entry for userspace BTI
  mm: smaps: Report arm64 guarded pages in smaps
  arm64: mm: Display guarded pages in ptdump
  KVM: arm64: BTI: Reset BTYPE when skipping emulated instructions
  arm64: BTI: Reset BTYPE when skipping emulated instructions
  arm64: traps: Shuffle code to eliminate forward declarations
  arm64: unify native/compat instruction skipping
  arm64: BTI: Decode BYTPE bits when printing PSTATE
  arm64: elf: Enable BTI at exec based on ELF program properties
  elf: Allow arch to tweak initial mmap prot flags
  arm64: Basic Branch Target Identification support
  ELF: Add ELF program property parsing support
  ELF: UAPI and Kconfig additions for ELF program properties

1 files changed, 25 insertions, 0 deletions

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 40fb05d96c60..43be825d0730 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -9,6 +9,7 @@ config ARM64
 	select ACPI_MCFG if (ACPI && PCI)
 	select ACPI_SPCR_TABLE if ACPI
 	select ACPI_PPTT if ACPI
+	select ARCH_BINFMT_ELF_STATE
 	select ARCH_HAS_DEBUG_VIRTUAL
 	select ARCH_HAS_DEVMEM_IS_ALLOWED
 	select ARCH_HAS_DMA_PREP_COHERENT
@@ -32,6 +33,7 @@ config ARM64
 	select ARCH_HAS_SYSCALL_WRAPPER
 	select ARCH_HAS_TEARDOWN_DMA_OPS if IOMMU_SUPPORT
 	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
+	select ARCH_HAVE_ELF_PROT
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
 	select ARCH_INLINE_READ_LOCK if !PREEMPTION
 	select ARCH_INLINE_READ_LOCK_BH if !PREEMPTION
@@ -61,6 +63,7 @@ config ARM64
 	select ARCH_INLINE_SPIN_UNLOCK_IRQRESTORE if !PREEMPTION
 	select ARCH_KEEP_MEMBLOCK
 	select ARCH_USE_CMPXCHG_LOCKREF
+	select ARCH_USE_GNU_PROPERTY
 	select ARCH_USE_QUEUED_RWLOCKS
 	select ARCH_USE_QUEUED_SPINLOCKS
 	select ARCH_SUPPORTS_MEMORY_FAILURE
@@ -1584,6 +1587,28 @@ endmenu
 
 menu "ARMv8.5 architectural features"
 
+config ARM64_BTI
+	bool "Branch Target Identification support"
+	default y
+	help
+	  Branch Target Identification (part of the ARMv8.5 Extensions)
+	  provides a mechanism to limit the set of locations to which computed
+	  branch instructions such as BR or BLR can jump.
+
+	  To make use of BTI on CPUs that support it, say Y.
+
+	  BTI is intended to provide complementary protection to other control
+	  flow integrity protection mechanisms, such as the Pointer
+	  authentication mechanism provided as part of the ARMv8.3 Extensions.
+	  For this reason, it does not make sense to enable this option without
+	  also enabling support for pointer authentication.  Thus, when
+	  enabling this option you should also select ARM64_PTR_AUTH=y.
+
+	  Userspace binaries must also be specifically compiled to make use of
+	  this mechanism.  If you say N here or the hardware does not support
+	  BTI, such binaries can still run, but you get no additional
+	  enforcement of branch destinations.
+
 config ARM64_E0PD
 	bool "Enable support for E0PD"
 	default y