From: Ram Pai <linuxram@us.ibm.com>
To: mpe@ellerman.id.au, mingo@redhat.com, akpm@linux-foundation.org,
corbet@lwn.net, arnd@arndb.de
Cc: linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org,
x86@kernel.org, linux-arch@vger.kernel.org,
linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org,
linux-kernel@vger.kernel.org, dave.hansen@intel.com,
benh@kernel.crashing.org, paulus@samba.org,
khandual@linux.vnet.ibm.com, aneesh.kumar@linux.vnet.ibm.com,
bsingharora@gmail.com, hbabu@us.ibm.com, mhocko@kernel.org,
bauerman@linux.vnet.ibm.com, ebiederm@xmission.com,
linuxram@us.ibm.com
Subject: [PATCH v9 30/51] Documentation/x86: Move protecton key documentation to arch neutral directory
Date: Mon, 6 Nov 2017 00:57:22 -0800 [thread overview]
Message-ID: <1509958663-18737-31-git-send-email-linuxram@us.ibm.com> (raw)
In-Reply-To: <1509958663-18737-1-git-send-email-linuxram@us.ibm.com>
Since PowerPC and Intel both support memory protection keys, moving
the documenation to arch-neutral directory.
Signed-off-by: Ram Pai <linuxram@us.ibm.com>
---
Documentation/vm/protection-keys.txt | 85 +++++++++++++++++++++++++++++++++
Documentation/x86/protection-keys.txt | 85 ---------------------------------
2 files changed, 85 insertions(+), 85 deletions(-)
create mode 100644 Documentation/vm/protection-keys.txt
delete mode 100644 Documentation/x86/protection-keys.txt
diff --git a/Documentation/vm/protection-keys.txt b/Documentation/vm/protection-keys.txt
new file mode 100644
index 0000000..fa46dcb
--- /dev/null
+++ b/Documentation/vm/protection-keys.txt
@@ -0,0 +1,85 @@
+Memory Protection Keys for Userspace (PKU aka PKEYs) is a CPU feature
+which will be found on future Intel CPUs.
+
+Memory Protection Keys provides a mechanism for enforcing page-based
+protections, but without requiring modification of the page tables
+when an application changes protection domains. It works by
+dedicating 4 previously ignored bits in each page table entry to a
+"protection key", giving 16 possible keys.
+
+There is also a new user-accessible register (PKRU) with two separate
+bits (Access Disable and Write Disable) for each key. Being a CPU
+register, PKRU is inherently thread-local, potentially giving each
+thread a different set of protections from every other thread.
+
+There are two new instructions (RDPKRU/WRPKRU) for reading and writing
+to the new register. The feature is only available in 64-bit mode,
+even though there is theoretically space in the PAE PTEs. These
+permissions are enforced on data access only and have no effect on
+instruction fetches.
+
+=========================== Syscalls ===========================
+
+There are 3 system calls which directly interact with pkeys:
+
+ int pkey_alloc(unsigned long flags, unsigned long init_access_rights)
+ int pkey_free(int pkey);
+ int pkey_mprotect(unsigned long start, size_t len,
+ unsigned long prot, int pkey);
+
+Before a pkey can be used, it must first be allocated with
+pkey_alloc(). An application calls the WRPKRU instruction
+directly in order to change access permissions to memory covered
+with a key. In this example WRPKRU is wrapped by a C function
+called pkey_set().
+
+ int real_prot = PROT_READ|PROT_WRITE;
+ pkey = pkey_alloc(0, PKEY_DISABLE_WRITE);
+ ptr = mmap(NULL, PAGE_SIZE, PROT_NONE, MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
+ ret = pkey_mprotect(ptr, PAGE_SIZE, real_prot, pkey);
+ ... application runs here
+
+Now, if the application needs to update the data at 'ptr', it can
+gain access, do the update, then remove its write access:
+
+ pkey_set(pkey, 0); // clear PKEY_DISABLE_WRITE
+ *ptr = foo; // assign something
+ pkey_set(pkey, PKEY_DISABLE_WRITE); // set PKEY_DISABLE_WRITE again
+
+Now when it frees the memory, it will also free the pkey since it
+is no longer in use:
+
+ munmap(ptr, PAGE_SIZE);
+ pkey_free(pkey);
+
+(Note: pkey_set() is a wrapper for the RDPKRU and WRPKRU instructions.
+ An example implementation can be found in
+ tools/testing/selftests/x86/protection_keys.c)
+
+=========================== Behavior ===========================
+
+The kernel attempts to make protection keys consistent with the
+behavior of a plain mprotect(). For instance if you do this:
+
+ mprotect(ptr, size, PROT_NONE);
+ something(ptr);
+
+you can expect the same effects with protection keys when doing this:
+
+ pkey = pkey_alloc(0, PKEY_DISABLE_WRITE | PKEY_DISABLE_READ);
+ pkey_mprotect(ptr, size, PROT_READ|PROT_WRITE, pkey);
+ something(ptr);
+
+That should be true whether something() is a direct access to 'ptr'
+like:
+
+ *ptr = foo;
+
+or when the kernel does the access on the application's behalf like
+with a read():
+
+ read(fd, ptr, 1);
+
+The kernel will send a SIGSEGV in both cases, but si_code will be set
+to SEGV_PKERR when violating protection keys versus SEGV_ACCERR when
+the plain mprotect() permissions are violated.
diff --git a/Documentation/x86/protection-keys.txt b/Documentation/x86/protection-keys.txt
deleted file mode 100644
index fa46dcb..0000000
--- a/Documentation/x86/protection-keys.txt
+++ /dev/null
@@ -1,85 +0,0 @@
-Memory Protection Keys for Userspace (PKU aka PKEYs) is a CPU feature
-which will be found on future Intel CPUs.
-
-Memory Protection Keys provides a mechanism for enforcing page-based
-protections, but without requiring modification of the page tables
-when an application changes protection domains. It works by
-dedicating 4 previously ignored bits in each page table entry to a
-"protection key", giving 16 possible keys.
-
-There is also a new user-accessible register (PKRU) with two separate
-bits (Access Disable and Write Disable) for each key. Being a CPU
-register, PKRU is inherently thread-local, potentially giving each
-thread a different set of protections from every other thread.
-
-There are two new instructions (RDPKRU/WRPKRU) for reading and writing
-to the new register. The feature is only available in 64-bit mode,
-even though there is theoretically space in the PAE PTEs. These
-permissions are enforced on data access only and have no effect on
-instruction fetches.
-
-=========================== Syscalls ===========================
-
-There are 3 system calls which directly interact with pkeys:
-
- int pkey_alloc(unsigned long flags, unsigned long init_access_rights)
- int pkey_free(int pkey);
- int pkey_mprotect(unsigned long start, size_t len,
- unsigned long prot, int pkey);
-
-Before a pkey can be used, it must first be allocated with
-pkey_alloc(). An application calls the WRPKRU instruction
-directly in order to change access permissions to memory covered
-with a key. In this example WRPKRU is wrapped by a C function
-called pkey_set().
-
- int real_prot = PROT_READ|PROT_WRITE;
- pkey = pkey_alloc(0, PKEY_DISABLE_WRITE);
- ptr = mmap(NULL, PAGE_SIZE, PROT_NONE, MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
- ret = pkey_mprotect(ptr, PAGE_SIZE, real_prot, pkey);
- ... application runs here
-
-Now, if the application needs to update the data at 'ptr', it can
-gain access, do the update, then remove its write access:
-
- pkey_set(pkey, 0); // clear PKEY_DISABLE_WRITE
- *ptr = foo; // assign something
- pkey_set(pkey, PKEY_DISABLE_WRITE); // set PKEY_DISABLE_WRITE again
-
-Now when it frees the memory, it will also free the pkey since it
-is no longer in use:
-
- munmap(ptr, PAGE_SIZE);
- pkey_free(pkey);
-
-(Note: pkey_set() is a wrapper for the RDPKRU and WRPKRU instructions.
- An example implementation can be found in
- tools/testing/selftests/x86/protection_keys.c)
-
-=========================== Behavior ===========================
-
-The kernel attempts to make protection keys consistent with the
-behavior of a plain mprotect(). For instance if you do this:
-
- mprotect(ptr, size, PROT_NONE);
- something(ptr);
-
-you can expect the same effects with protection keys when doing this:
-
- pkey = pkey_alloc(0, PKEY_DISABLE_WRITE | PKEY_DISABLE_READ);
- pkey_mprotect(ptr, size, PROT_READ|PROT_WRITE, pkey);
- something(ptr);
-
-That should be true whether something() is a direct access to 'ptr'
-like:
-
- *ptr = foo;
-
-or when the kernel does the access on the application's behalf like
-with a read():
-
- read(fd, ptr, 1);
-
-The kernel will send a SIGSEGV in both cases, but si_code will be set
-to SEGV_PKERR when violating protection keys versus SEGV_ACCERR when
-the plain mprotect() permissions are violated.
--
1.7.1
next prev parent reply other threads:[~2017-11-06 8:59 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-06 8:56 [PATCH v9 00/51] powerpc, mm: Memory Protection Keys Ram Pai
2017-11-06 8:56 ` [PATCH v9 01/51] mm, powerpc, x86: define VM_PKEY_BITx bits if CONFIG_ARCH_HAS_PKEYS is enabled Ram Pai
2017-11-06 8:56 ` [PATCH v9 02/51] mm, powerpc, x86: introduce an additional vma bit for powerpc pkey Ram Pai
2017-11-06 8:56 ` [PATCH v9 03/51] powerpc: initial pkey plumbing Ram Pai
2017-11-06 8:56 ` [PATCH v9 04/51] powerpc: track allocation status of all pkeys Ram Pai
2017-11-06 8:56 ` [PATCH v9 05/51] powerpc: helper function to read, write AMR, IAMR, UAMOR registers Ram Pai
2017-11-06 8:56 ` [PATCH v9 06/51] powerpc: helper functions to initialize AMR, IAMR and " Ram Pai
2017-11-06 8:56 ` [PATCH v9 07/51] powerpc: cleanup AMR, IAMR when a key is allocated or freed Ram Pai
2017-11-06 8:57 ` [PATCH v9 08/51] powerpc: implementation for arch_set_user_pkey_access() Ram Pai
2017-11-06 8:57 ` [PATCH v9 09/51] powerpc: ability to create execute-disabled pkeys Ram Pai
2017-11-06 8:57 ` [PATCH v9 10/51] powerpc: store and restore the pkey state across context switches Ram Pai
2017-11-06 8:57 ` [PATCH v9 11/51] powerpc: introduce execute-only pkey Ram Pai
2017-11-06 8:57 ` [PATCH v9 12/51] powerpc: ability to associate pkey to a vma Ram Pai
2017-11-06 8:57 ` [PATCH v9 13/51] powerpc: implementation for arch_override_mprotect_pkey() Ram Pai
2017-11-06 8:57 ` [PATCH v9 14/51] powerpc: map vma key-protection bits to pte key bits Ram Pai
2017-11-06 8:57 ` [PATCH v9 15/51] powerpc: Program HPTE key protection bits Ram Pai
2017-11-06 8:57 ` [PATCH v9 16/51] powerpc: helper to validate key-access permissions of a pte Ram Pai
2017-11-06 8:57 ` [PATCH v9 17/51] powerpc: check key protection for user page access Ram Pai
2017-11-06 8:57 ` [PATCH v9 18/51] powerpc: implementation for arch_vma_access_permitted() Ram Pai
2017-11-06 8:57 ` [PATCH v9 19/51] powerpc: Handle exceptions caused by pkey violation Ram Pai
2017-11-06 8:57 ` [PATCH v9 20/51] powerpc: introduce get_mm_addr_key() helper Ram Pai
2017-11-06 8:57 ` [PATCH v9 21/51] powerpc: Deliver SEGV signal on pkey violation Ram Pai
2017-11-06 8:57 ` [PATCH v9 22/51] powerpc/ptrace: Add memory protection key regset Ram Pai
2017-11-06 8:57 ` [PATCH v9 23/51] powerpc: Enable pkey subsystem Ram Pai
2017-11-13 0:54 ` Ram Pai
2017-11-06 8:57 ` [PATCH v9 24/51] powerpc: sys_pkey_alloc() and sys_pkey_free() system calls Ram Pai
2017-11-06 8:57 ` [PATCH v9 25/51] powerpc: sys_pkey_mprotect() system call Ram Pai
2017-11-06 8:57 ` [PATCH v9 26/51] powerpc: add sys_pkey_modify() " Ram Pai
2017-11-06 8:57 ` [PATCH v9 27/51] mm, x86 : introduce arch_pkeys_enabled() Ram Pai
2017-11-06 8:57 ` [PATCH v9 28/51] mm: display pkey in smaps if arch_pkeys_enabled() is true Ram Pai
2017-11-06 8:57 ` [PATCH v9 29/51] mm/mprotect, powerpc/mm/pkeys, x86/mm/pkeys: Add sysfs interface Ram Pai
2017-12-18 18:54 ` Dave Hansen
2017-12-18 22:18 ` Ram Pai
2017-12-18 22:28 ` Dave Hansen
2017-12-18 23:15 ` Ram Pai
2017-12-19 8:31 ` Gabriel Paubert
2017-12-19 16:22 ` Ram Pai
2017-12-19 21:34 ` Benjamin Herrenschmidt
2017-12-20 17:50 ` Ram Pai
2017-12-20 22:49 ` Benjamin Herrenschmidt
2017-12-19 10:50 ` Michael Ellerman
2017-12-19 16:32 ` Ram Pai
2017-11-06 8:57 ` Ram Pai [this message]
2017-11-06 8:57 ` [PATCH v9 31/51] Documentation/vm: PowerPC specific updates to memory protection keys Ram Pai
2017-11-06 8:57 ` [PATCH v9 32/51] selftest/x86: Move protecton key selftest to arch neutral directory Ram Pai
2017-11-06 8:57 ` [PATCH v9 33/51] selftest/vm: rename all references to pkru to a generic name Ram Pai
2017-11-06 8:57 ` [PATCH v9 34/51] selftest/vm: move generic definitions to header file Ram Pai
2017-11-06 8:57 ` [PATCH v9 35/51] selftest/vm: typecast the pkey register Ram Pai
2017-11-06 8:57 ` [PATCH v9 36/51] selftest/vm: generic function to handle shadow key register Ram Pai
2017-11-06 8:57 ` [PATCH v9 37/51] selftest/vm: fix the wrong assert in pkey_disable_set() Ram Pai
2017-11-06 8:57 ` [PATCH v9 38/51] selftest/vm: fixed bugs in pkey_disable_clear() Ram Pai
2017-11-06 8:57 ` [PATCH v9 39/51] selftest/vm: clear the bits in shadow reg when a pkey is freed Ram Pai
2017-11-06 8:57 ` [PATCH v9 40/51] selftest/vm: fix alloc_random_pkey() to make it really random Ram Pai
2017-11-06 8:57 ` [PATCH v9 41/51] selftest/vm: introduce two arch independent abstraction Ram Pai
2017-11-06 8:57 ` [PATCH v9 42/51] selftest/vm: pkey register should match shadow pkey Ram Pai
2017-11-06 8:57 ` [PATCH v9 43/51] selftest/vm: generic cleanup Ram Pai
2017-11-06 8:57 ` [PATCH v9 44/51] selftest/vm: powerpc implementation for generic abstraction Ram Pai
2017-11-09 18:47 ` Breno Leitao
2017-11-09 23:37 ` Ram Pai
2017-11-10 11:36 ` Breno Leitao
2017-11-06 8:57 ` [PATCH v9 45/51] selftest/vm: fix an assertion in test_pkey_alloc_exhaust() Ram Pai
2017-11-06 8:57 ` [PATCH v9 46/51] selftest/vm: associate key on a mapped page and detect access violation Ram Pai
2017-11-06 8:57 ` [PATCH v9 47/51] selftest/vm: associate key on a mapped page and detect write violation Ram Pai
2017-11-06 8:57 ` [PATCH v9 48/51] selftest/vm: detect write violation on a mapped access-denied-key page Ram Pai
2017-11-06 8:57 ` [PATCH v9 49/51] selftest/vm: sub-page allocator Ram Pai
2017-11-06 8:57 ` [PATCH v9 50/51] selftests/powerpc: Add ptrace tests for Protection Key register Ram Pai
2017-11-06 8:57 ` [PATCH v9 51/51] selftests/powerpc: Add core file test " Ram Pai
2017-11-06 21:28 ` [PATCH v9 00/51] powerpc, mm: Memory Protection Keys Florian Weimer
2017-11-07 1:22 ` Ram Pai
2017-11-07 7:32 ` Florian Weimer
2017-11-07 22:39 ` Ram Pai
2017-11-07 22:47 ` Dave Hansen
2017-11-07 23:44 ` Ram Pai
2017-11-09 22:23 ` Ram Pai
2017-11-10 18:10 ` Christophe LEROY
2017-11-12 20:45 ` Ram Pai
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