[RFC v5 00/38] powerpc: Memory Protection Keys

From: Ram Pai
Date: Wed Jul 05 2017 - 17:33:21 EST

Memory protection keys enable applications to protect its
address space from inadvertent access or corruption from

The overall idea:

A process allocates a key and associates it with
an address range within its address space.
The process then can dynamically set read/write
permissions on the key without involving the
kernel. Any code that violates the permissions
of the address space; as defined by its associated
key, will receive a segmentation fault.

This patch series enables the feature on PPC64 HPTE

ISA3.0 section 5.7.13 describes the detailed specifications.

This patch series has passed all the protection key
tests available in the selftests directory.
The tests are updated to work on both x86 and powerpc.

version v5:
(1) reverted back to the old design -- store the
key in the pte, instead of bypassing it.
The v4 design slowed down the hash page path.
(2) detects key violation when kernel is told to
access user pages.
(3) further refined the patches into smaller consumable
(4) page faults handlers captures the faulting key
from the pte instead of the vma. This closes a
race between where the key update in the vma and
a key fault caused cause by the key programmed
in the pte.
(5) a key created with access-denied should
also set it up to deny write. Fixed it.
(6) protection-key number is displayed in smaps
the x86 way.
version v4:
(1) patches no more depend on the pte bits to program
the hpte -- comment by Balbir
(2) documentation updates
(3) fixed a bug in the selftest.
(4) unlike x86, powerpc lets signal handler change key
permission bits; the change will persist across
signal handler boundaries. Earlier we allowed
the signal handler to modify a field in the siginfo
structure which would than be used by the kernel
to program the key protection register (AMR)
-- resolves a issue raised by Ben.
"Calls to sys_swapcontext with a made-up context
will end up with a crap AMR if done by code who
didn't know about that register".
(5) these changes enable protection keys on 4k-page
kernel aswell.

version v3:
(1) split the patches into smaller consumable
(2) added the ability to disable execute permission
on a key at creation.
(3) rename calc_pte_to_hpte_pkey_bits() to
pte_to_hpte_pkey_bits() -- suggested by Anshuman
(4) some code optimization and clarity in
(5) A bug fix while invalidating a hpte slot in
__hash_page_4K() -- noticed by Aneesh

version v2:
(1) documentation and selftest added
(2) fixed a bug in 4k hpte backed 64k pte where page
invalidation was not done correctly, and
initialization of second-part-of-the-pte was not
done correctly if the pte was not yet Hashed
with a hpte. Reported by Aneesh.
(3) Fixed ABI breakage caused in siginfo structure.
Reported by Anshuman.

version v1: Initial version

Ram Pai (38):
powerpc: Free up four 64K PTE bits in 4K backed HPTE pages
powerpc: Free up four 64K PTE bits in 64K backed HPTE pages
powerpc: introduce pte_set_hash_slot() helper
powerpc: introduce pte_get_hash_gslot() helper
powerpc: capture the PTE format changes in the dump pte report
powerpc: use helper functions in __hash_page_64K() for 64K PTE
powerpc: use helper functions in __hash_page_huge() for 64K PTE
powerpc: use helper functions in __hash_page_4K() for 64K PTE
powerpc: use helper functions in __hash_page_4K() for 4K PTE
powerpc: use helper functions in flush_hash_page()
mm: introduce an additional vma bit for powerpc pkey
mm: ability to disable execute permission on a key at creation
x86: disallow pkey creation with PKEY_DISABLE_EXECUTE
powerpc: initial plumbing for key management
powerpc: helper function to read,write AMR,IAMR,UAMOR registers
powerpc: implementation for arch_set_user_pkey_access()
powerpc: sys_pkey_alloc() and sys_pkey_free() system calls
powerpc: store and restore the pkey state across context switches
powerpc: introduce execute-only pkey
powerpc: ability to associate pkey to a vma
powerpc: implementation for arch_override_mprotect_pkey()
powerpc: map vma key-protection bits to pte key bits.
powerpc: sys_pkey_mprotect() system call
powerpc: Program HPTE key protection bits
powerpc: helper to validate key-access permissions of a pte
powerpc: check key protection for user page access
powerpc: Macro the mask used for checking DSI exception
powerpc: implementation for arch_vma_access_permitted()
powerpc: Handle exceptions caused by pkey violation
powerpc: capture AMR register content on pkey violation
powerpc: introduce get_pte_pkey() helper
powerpc: capture the violated protection key on fault
powerpc: Deliver SEGV signal on pkey violation
procfs: display the protection-key number associated with a vma
selftest: Move protecton key selftest to arch neutral directory
selftest: PowerPC specific test updates to memory protection keys
Documentation: Move protecton key documentation to arch neutral
Documentation: PowerPC specific updates to memory protection keys

Documentation/vm/protection-keys.txt | 130 +++
Documentation/x86/protection-keys.txt | 85 --
arch/powerpc/Kconfig | 16 +
arch/powerpc/include/asm/book3s/64/hash-4k.h | 20 +
arch/powerpc/include/asm/book3s/64/hash-64k.h | 60 +-
arch/powerpc/include/asm/book3s/64/hash.h | 7 +-
arch/powerpc/include/asm/book3s/64/mmu-hash.h | 10 +
arch/powerpc/include/asm/book3s/64/mmu.h | 10 +
arch/powerpc/include/asm/book3s/64/pgtable.h | 96 ++-
arch/powerpc/include/asm/mman.h | 16 +-
arch/powerpc/include/asm/mmu_context.h | 5 +
arch/powerpc/include/asm/paca.h | 4 +
arch/powerpc/include/asm/pkeys.h | 159 +++
arch/powerpc/include/asm/processor.h | 5 +
arch/powerpc/include/asm/reg.h | 7 +-
arch/powerpc/include/asm/systbl.h | 3 +
arch/powerpc/include/asm/unistd.h | 6 +-
arch/powerpc/include/uapi/asm/ptrace.h | 3 +-
arch/powerpc/include/uapi/asm/unistd.h | 3 +
arch/powerpc/kernel/asm-offsets.c | 6 +
arch/powerpc/kernel/exceptions-64s.S | 2 +-
arch/powerpc/kernel/process.c | 18 +
arch/powerpc/kernel/setup_64.c | 8 +
arch/powerpc/kernel/signal_32.c | 5 +
arch/powerpc/kernel/signal_64.c | 4 +
arch/powerpc/kernel/traps.c | 14 +
arch/powerpc/mm/Makefile | 1 +
arch/powerpc/mm/dump_linuxpagetables.c | 3 +-
arch/powerpc/mm/fault.c | 26 +
arch/powerpc/mm/hash64_4k.c | 14 +-
arch/powerpc/mm/hash64_64k.c | 124 ++-
arch/powerpc/mm/hash_utils_64.c | 68 +-
arch/powerpc/mm/hugetlbpage-hash64.c | 16 +-
arch/powerpc/mm/mmu_context_book3s64.c | 5 +
arch/powerpc/mm/pkeys.c | 243 ++++
arch/x86/kernel/fpu/xstate.c | 3 +
fs/proc/task_mmu.c | 6 +-
include/linux/mm.h | 18 +-
include/uapi/asm-generic/mman-common.h | 4 +-
tools/testing/selftests/vm/Makefile | 1 +
tools/testing/selftests/vm/pkey-helpers.h | 365 ++++++
tools/testing/selftests/vm/protection_keys.c | 1488 +++++++++++++++++++++++++
tools/testing/selftests/x86/Makefile | 2 +-
tools/testing/selftests/x86/pkey-helpers.h | 219 ----
tools/testing/selftests/x86/protection_keys.c | 1395 -----------------------
45 files changed, 2872 insertions(+), 1831 deletions(-)
create mode 100644 Documentation/vm/protection-keys.txt
delete mode 100644 Documentation/x86/protection-keys.txt
create mode 100644 arch/powerpc/include/asm/pkeys.h
create mode 100644 arch/powerpc/mm/pkeys.c
create mode 100644 tools/testing/selftests/vm/pkey-helpers.h
create mode 100644 tools/testing/selftests/vm/protection_keys.c
delete mode 100644 tools/testing/selftests/x86/pkey-helpers.h
delete mode 100644 tools/testing/selftests/x86/protection_keys.c