Subject: [PATCH v10 00/27] powerpc, mm: Memory Protection Keys

From: Ram Pai <[email-masked]>
Date: Thu, 18 Jan 2018 17:50:21 -0800

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

These patches along with the pte-bit freeing patch series
enables the protection key feature on powerpc; 4k and 64k
hashpage kernels.

Will send the documentation and selftest patches separately

All patches can be found at --
https://github.com/rampai/memorykeys.git memkey.v10

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
platform.

ISA3.0 section 5.7.13 describes the detailed
specifications.

Highlevel view of the design:
---------------------------
When an application associates a key with a address
address range, program the key in the Linux PTE.
When the MMU detects a page fault, allocate a hash
page and program the key into HPTE. And finally
when the MMU detects a key violation; due to
invalid application access, invoke the registered
signal handler and provide the violated key number.

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

History:
-------
version v10:
	(1) key-fault in page-fault handler
		is handled as normal fault
		and not as a bad fault.
	(2) changed device tree scanning to 
		unflattened device tree.
	(3) fixed a bug in the logic that detected
		the total number of available pkeys.
	(4) dropped two patches. (i) sysfs interface
		(ii) sys_pkey_modif() syscall

version v9:
	(1) used jump-labels to optimize code
		-- Balbir
	(2) fixed a register initialization bug noted
		by Balbir
	(3) fixed inappropriate use of paca to pass
		siginfo and keys to signal handler
	(4) Cleanup of comment style not to be right 
		justified -- mpe
	(5) restructured the patches to depend on the
		availability of VM_PKEY_BIT4 in
		include/linux/mm.h
	(6) Incorporated comments from Dave Hansen
		towards changes to selftest and got
		them tested on x86.

version v8:
	(1) Contents of the AMR register withdrawn from
	the siginfo structure. Applications can always
	read the AMR register.
	(2) AMR/IAMR/UAMOR are now available through 
		ptrace system call. -- thanks to Thiago
	(3) code changes to handle legacy power cpus
	that do not support execute-disable.
	(4) incorporates many code improvement
		suggestions.

version v7:
	(1) refers to device tree property to enable
		protection keys.
	(2) adds 4K PTE support.
	(3) fixes a couple of bugs noticed by Thiago
	(4) decouples this patch series from arch-
	 independent code. This patch series can
	 now stand by itself, with one kludge
	patch(2).
version v7:
	(1) refers to device tree property to enable
		protection keys.
	(2) adds 4K PTE support.
	(3) fixes a couple of bugs noticed by Thiago
	(4) decouples this patch series from arch-
	 independent code. This patch series can
	 now stand by itself, with one kludge
	 patch(2).

version v6:
	(1) selftest changes are broken down into 20
		incremental patches.
	(2) A separate key allocation mask that
		includes PKEY_DISABLE_EXECUTE is 
		added for powerpc
	(3) pkey feature is enabled for 64K HPT case
		only. RPT and 4k HPT is disabled.
	(4) Documentation is updated to better 
		capture the semantics.
	(5) introduced arch_pkeys_enabled() to find
		if an arch enables pkeys. Correspond-
		ing change the logic that displays
		key value in smaps.
	(6) code rearranged in many places based on
		comments from Dave Hansen, Balbir,
		Anshuman.	
	(7) fixed one bug where a bogus key could be
		associated successfully in
		pkey_mprotect().

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 units
	(4) page faults handlers captures the fault-
		ing 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
	 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
		patches.
	(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
		do_page_fault()
	(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 (26):
  mm, powerpc, x86: define VM_PKEY_BITx bits if CONFIG_ARCH_HAS_PKEYS
    is enabled
  mm, powerpc, x86: introduce an additional vma bit for powerpc pkey
  powerpc: initial pkey plumbing
  powerpc: track allocation status of all pkeys
  powerpc: helper function to read,write AMR,IAMR,UAMOR registers
  powerpc: helper functions to initialize AMR, IAMR and UAMOR registers
  powerpc: cleanup AMR, IAMR when a key is allocated or freed
  powerpc: implementation for arch_set_user_pkey_access()
  powerpc: ability to create execute-disabled pkeys
  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: Program HPTE key protection bits
  powerpc: helper to validate key-access permissions of a pte
  powerpc: check key protection for user page access
  powerpc: implementation for arch_vma_access_permitted()
  powerpc: Handle exceptions caused by pkey violation
  powerpc: introduce get_mm_addr_key() helper
  powerpc: Deliver SEGV signal on pkey violation
  powerpc: Enable pkey subsystem
  powerpc: sys_pkey_alloc() and sys_pkey_free() system calls
  powerpc: sys_pkey_mprotect() system call
  mm, x86 : introduce arch_pkeys_enabled()
  mm: display pkey in smaps if arch_pkeys_enabled() is true

Thiago Jung Bauermann (1):
  powerpc/ptrace: Add memory protection key regset

 arch/powerpc/Kconfig                          |   15 +
 arch/powerpc/include/asm/book3s/64/mmu-hash.h |    5 +
 arch/powerpc/include/asm/book3s/64/mmu.h      |   10 +
 arch/powerpc/include/asm/book3s/64/pgtable.h  |   48 +++-
 arch/powerpc/include/asm/bug.h                |    1 +
 arch/powerpc/include/asm/cputable.h           |   16 +-
 arch/powerpc/include/asm/mman.h               |   13 +-
 arch/powerpc/include/asm/mmu.h                |    9 +
 arch/powerpc/include/asm/mmu_context.h        |   22 ++
 arch/powerpc/include/asm/pkeys.h              |  229 ++++++++++++
 arch/powerpc/include/asm/processor.h          |    5 +
 arch/powerpc/include/asm/reg.h                |    1 -
 arch/powerpc/include/asm/systbl.h             |    3 +
 arch/powerpc/include/asm/unistd.h             |    6 +-
 arch/powerpc/include/uapi/asm/elf.h           |    1 +
 arch/powerpc/include/uapi/asm/mman.h          |    6 +
 arch/powerpc/include/uapi/asm/unistd.h        |    3 +
 arch/powerpc/kernel/exceptions-64s.S          |    2 +-
 arch/powerpc/kernel/process.c                 |    7 +
 arch/powerpc/kernel/ptrace.c                  |   66 ++++
 arch/powerpc/kernel/traps.c                   |   19 +-
 arch/powerpc/mm/Makefile                      |    1 +
 arch/powerpc/mm/fault.c                       |   49 +++-
 arch/powerpc/mm/hash_utils_64.c               |   26 ++
 arch/powerpc/mm/mmu_context_book3s64.c        |    2 +
 arch/powerpc/mm/pkeys.c                       |  469 +++++++++++++++++++++++++
 arch/x86/include/asm/pkeys.h                  |    1 +
 arch/x86/kernel/fpu/xstate.c                  |    5 +
 arch/x86/kernel/setup.c                       |    8 -
 fs/proc/task_mmu.c                            |   16 +-
 include/linux/mm.h                            |   12 +-
 include/linux/pkeys.h                         |    5 +
 include/uapi/linux/elf.h                      |    1 +
 33 files changed, 1040 insertions(+), 42 deletions(-)
 create mode 100644 arch/powerpc/include/asm/pkeys.h
 create mode 100644 arch/powerpc/mm/pkeys.c