Memory Protection Keys for User pages (pkeys) is a CPU feature
which will first appear on Skylake Servers, but will also be
supported on future non-server parts. It provides a mechanism
for enforcing page-based protections, but without requiring
modification of the page tables when an application changes
wishes to change permissions.
Patches to implement execute-only mapping support using pkeys was
merged in to 4.6. But, to do anything else useful with pkeys, an
application needs to be able to set the pkey field in the PTE
(obviously has to be done in-kernel) and make changes to the
"rights" register (using unprivileged instructions).
An application also needs to have an an allocator for the keys
themselves. If two different parts of an application both want
to protect their data with pkeys, they first need to know which
key to use for their individual purposes.
This set introduces 5 system calls, in 3 logical groups:
1. PTE pkey setting (sys_pkey_mprotect(), patches #1-3)
2. Key allocation (sys_pkey_alloc() / sys_pkey_free(), patch #4)
3. Rights register manipulation (sys_pkey_set/get(), patch #5)
These patches build on top of "core" pkeys support already in
4.6. This set is specifically built on f87e0434a, which is
tip/x86/urgent since it contained a documentation fix.
I have manpages written for some of these syscalls, and have
submitted them for review to the manpages list.
This set is also available here:
git://git.kernel.org/pub/scm/linux/kernel/git/daveh/x86-pkeys.git pkeys-v031
I've written a set of unit tests for these interfaces, which is
available as the last patch in the series and integrated in to
kselftests.
=== diffstat ===
Dave Hansen (8):
x86, pkeys: add fault handling for PF_PK page fault bit
mm: implement new pkey_mprotect() system call
x86, pkeys: make mprotect_key() mask off additional vm_flags
x86: wire up mprotect_key() system call
x86, pkeys: allocation/free syscalls
x86, pkeys: add pkey set/get syscalls
pkeys: add details of system call use to Documentation/
x86, pkeys: add self-tests
Documentation/x86/protection-keys.txt | 63 +
arch/alpha/include/uapi/asm/mman.h | 5 +
arch/mips/include/uapi/asm/mman.h | 5 +
arch/parisc/include/uapi/asm/mman.h | 5 +
arch/x86/entry/syscalls/syscall_32.tbl | 5 +
arch/x86/entry/syscalls/syscall_64.tbl | 5 +
arch/x86/include/asm/mmu.h | 8 +
arch/x86/include/asm/mmu_context.h | 25 +-
arch/x86/include/asm/pkeys.h | 83 +-
arch/x86/kernel/fpu/xstate.c | 73 +-
arch/x86/mm/fault.c | 9 +
arch/x86/mm/pkeys.c | 38 +-
arch/xtensa/include/uapi/asm/mman.h | 5 +
include/linux/pkeys.h | 39 +-
include/uapi/asm-generic/mman-common.h | 5 +
mm/mprotect.c | 134 +-
tools/testing/selftests/x86/Makefile | 2 +-
tools/testing/selftests/x86/pkey-helpers.h | 186 +++
tools/testing/selftests/x86/protection_keys.c | 1199 +++++++++++++++++
19 files changed, 1863 insertions(+), 31 deletions(-)
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
From: Dave Hansen <[email protected]>
PF_PK means that a memory access violated the protection key
access restrictions. It is unconditionally an access_error()
because the permissions set on the VMA don't matter (the PKRU
value overrides it), and we never "resolve" PK faults (like
how a COW can "resolve write fault).
Signed-off-by: Dave Hansen <[email protected]>
---
b/arch/x86/mm/fault.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff -puN arch/x86/mm/fault.c~pkeys-105-add-pk-to-fault arch/x86/mm/fault.c
--- a/arch/x86/mm/fault.c~pkeys-105-add-pk-to-fault 2016-04-11 08:38:40.474232702 -0700
+++ b/arch/x86/mm/fault.c 2016-04-11 08:38:40.478232883 -0700
@@ -1107,6 +1107,15 @@ access_error(unsigned long error_code, s
{
/* This is only called for the current mm, so: */
bool foreign = false;
+
+ /*
+ * Read or write was blocked by protection keys. This is
+ * always an unconditional error and can never result in
+ * a follow-up action to resolve the fault, like a COW.
+ */
+ if (error_code & PF_PK)
+ return 1;
+
/*
* Make sure to check the VMA so that we do not perform
* faults just to hit a PF_PK as soon as we fill in a
_
From: Dave Hansen <[email protected]>
This code should be a good demonstration of how to use the new
system calls as well as how to use protection keys in general.
This code shows how to:
1. Manipulate the Protection Keys Rights User (PKRU) register with
sys_pkey_get/set()
2. Set a protection key on memory
3. Fetch and/or modify PKRU from the signal XSAVE state
4. Read the kernel-provided protection key in the siginfo
5. Set up an execute-only mapping
There are currently 13 tests:
test_read_of_write_disabled_region
test_read_of_access_disabled_region
test_write_of_write_disabled_region
test_write_of_access_disabled_region
test_kernel_write_of_access_disabled_region
test_kernel_write_of_write_disabled_region
test_kernel_gup_of_access_disabled_region
test_kernel_gup_write_to_write_disabled_region
test_executing_on_unreadable_memory
test_ptrace_of_child
test_pkey_syscalls_on_non_allocated_pkey
test_pkey_syscalls_bad_args
test_pkey_alloc_exhaust
Each of the tests is run with plain memory (via mmap(MAP_ANON)),
transparent huge pages, and hugetlb.
Signed-off-by: Dave Hansen <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
---
b/tools/testing/selftests/x86/Makefile | 2
b/tools/testing/selftests/x86/pkey-helpers.h | 186 +++
b/tools/testing/selftests/x86/protection_keys.c | 1199 ++++++++++++++++++++++++
3 files changed, 1386 insertions(+), 1 deletion(-)
diff -puN tools/testing/selftests/x86/Makefile~pkeys-130-selftests tools/testing/selftests/x86/Makefile
--- a/tools/testing/selftests/x86/Makefile~pkeys-130-selftests 2016-04-11 08:38:43.915388455 -0700
+++ b/tools/testing/selftests/x86/Makefile 2016-04-11 08:38:43.919388636 -0700
@@ -5,7 +5,7 @@ include ../lib.mk
.PHONY: all all_32 all_64 warn_32bit_failure clean
TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt ptrace_syscall \
- check_initial_reg_state sigreturn ldt_gdt iopl
+ check_initial_reg_state sigreturn ldt_gdt iopl protection_keys
TARGETS_C_32BIT_ONLY := entry_from_vm86 syscall_arg_fault test_syscall_vdso unwind_vdso \
test_FCMOV test_FCOMI test_FISTTP \
vdso_restorer
diff -puN /dev/null tools/testing/selftests/x86/pkey-helpers.h
--- /dev/null 2016-04-04 09:40:43.435149254 -0700
+++ b/tools/testing/selftests/x86/pkey-helpers.h 2016-04-11 08:38:43.919388636 -0700
@@ -0,0 +1,186 @@
+#ifndef _PKEYS_HELPER_H
+#define _PKEYS_HELPER_H
+#define _GNU_SOURCE
+#include <string.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <signal.h>
+#include <assert.h>
+#include <stdlib.h>
+#include <ucontext.h>
+#include <sys/mman.h>
+
+#define NR_PKEYS 16
+
+#ifndef DEBUG_LEVEL
+#define DEBUG_LEVEL 0
+#endif
+#define dprintf_level(level, args...) do { if(level <= DEBUG_LEVEL) printf(args); } while(0)
+#define dprintf1(args...) dprintf_level(1, args)
+#define dprintf2(args...) dprintf_level(2, args)
+#define dprintf3(args...) dprintf_level(3, args)
+#define dprintf4(args...) dprintf_level(4, args)
+
+extern unsigned int shadow_pkru;
+static inline unsigned int __rdpkru(void)
+{
+ unsigned int eax, edx;
+ unsigned int ecx = 0;
+ unsigned int pkru;
+
+ asm volatile(".byte 0x0f,0x01,0xee\n\t"
+ : "=a" (eax), "=d" (edx)
+ : "c" (ecx));
+ pkru = eax;
+ return pkru;
+}
+
+static inline unsigned int _rdpkru(int line)
+{
+ unsigned int pkru = __rdpkru();
+ dprintf4("rdpkru(line=%d) pkru: %x shadow: %x\n", line, pkru, shadow_pkru);
+ assert(pkru == shadow_pkru);
+ return pkru;
+}
+
+#define rdpkru() _rdpkru(__LINE__)
+
+static inline void __wrpkru(unsigned int pkru)
+{
+ unsigned int eax = pkru;
+ unsigned int ecx = 0;
+ unsigned int edx = 0;
+
+return;
+ asm volatile(".byte 0x0f,0x01,0xef\n\t"
+ : : "a" (eax), "c" (ecx), "d" (edx));
+ assert(pkru == __rdpkru());
+}
+
+static inline void wrpkru(unsigned int pkru)
+{
+ dprintf4("%s() changing %08x to %08x\n", __func__, __rdpkru(), pkru);
+ // will do the shadow check for us:
+ rdpkru();
+ __wrpkru(pkru);
+ shadow_pkru = pkru;
+ dprintf4("%s(%08x) pkru: %08x\n", __func__, pkru, __rdpkru());
+}
+
+/*
+ * These are technically racy. since something could
+ * change PKRU between the read and the write.
+ */
+static inline void __pkey_access_allow(int pkey, int do_allow)
+{
+ unsigned int pkru = rdpkru();
+ int bit = pkey * 2;
+
+ if (do_allow)
+ pkru &= (1<<bit);
+ else
+ pkru |= (1<<bit);
+
+ dprintf4("pkru now: %08x\n", rdpkru());
+ wrpkru(pkru);
+}
+
+static inline void __pkey_write_allow(int pkey, int do_allow_write)
+{
+ long pkru = rdpkru();
+ int bit = pkey * 2 + 1;
+
+ if (do_allow_write)
+ pkru &= (1<<bit);
+ else
+ pkru |= (1<<bit);
+
+ wrpkru(pkru);
+ dprintf4("pkru now: %08x\n", rdpkru());
+}
+
+#define PROT_PKEY0 0x10 /* protection key value (bit 0) */
+#define PROT_PKEY1 0x20 /* protection key value (bit 1) */
+#define PROT_PKEY2 0x40 /* protection key value (bit 2) */
+#define PROT_PKEY3 0x80 /* protection key value (bit 3) */
+
+#define PAGE_SIZE 4096
+#define MB (1<<20)
+
+static inline void __cpuid(unsigned int *eax, unsigned int *ebx,
+ unsigned int *ecx, unsigned int *edx)
+{
+ /* ecx is often an input as well as an output. */
+ asm volatile(
+ "cpuid;"
+ : "=a" (*eax),
+ "=b" (*ebx),
+ "=c" (*ecx),
+ "=d" (*edx)
+ : "0" (*eax), "2" (*ecx));
+}
+
+/* Intel-defined CPU features, CPUID level 0x00000007:0 (ecx) */
+#define X86_FEATURE_PKU (1<<3) /* Protection Keys for Userspace */
+#define X86_FEATURE_OSPKE (1<<4) /* OS Protection Keys Enable */
+
+static inline int cpu_has_pku(void)
+{
+ unsigned int eax;
+ unsigned int ebx;
+ unsigned int ecx;
+ unsigned int edx;
+ eax = 0x7;
+ ecx = 0x0;
+ __cpuid(&eax, &ebx, &ecx, &edx);
+
+ if (!(ecx & X86_FEATURE_PKU)) {
+ dprintf2("cpu does not have PKU\n");
+ return 0;
+ }
+ if (!(ecx & X86_FEATURE_OSPKE)) {
+ dprintf2("cpu does not have OSPKE\n");
+ return 0;
+ }
+ return 1;
+}
+
+#define XSTATE_PKRU_BIT (9)
+#define XSTATE_PKRU 0x200
+
+int pkru_xstate_offset(void)
+{
+ unsigned int eax;
+ unsigned int ebx;
+ unsigned int ecx;
+ unsigned int edx;
+ int xstate_offset;
+ int xstate_size;
+ unsigned long XSTATE_CPUID = 0xd;
+ int leaf;
+
+ // assume that XSTATE_PKRU is set in XCR0
+ leaf = XSTATE_PKRU_BIT;
+ {
+ eax = XSTATE_CPUID;
+ // 0x2 !??! from setup_xstate_features() in the kernel
+ ecx = leaf;
+ __cpuid(&eax, &ebx, &ecx, &edx);
+
+ //printf("leaf[%d] offset: %d size: %d\n", leaf, ebx, eax);
+ if (leaf == XSTATE_PKRU_BIT) {
+ xstate_offset = ebx;
+ xstate_size = eax;
+ }
+ }
+
+ if (xstate_size== 0) {
+ printf("could not find size/offset of PKRU in xsave state\n");
+ return 0;
+ }
+
+ return xstate_offset;
+}
+
+#endif /* _PKEYS_HELPER_H */
diff -puN /dev/null tools/testing/selftests/x86/protection_keys.c
--- /dev/null 2016-04-04 09:40:43.435149254 -0700
+++ b/tools/testing/selftests/x86/protection_keys.c 2016-04-11 08:38:43.920388682 -0700
@@ -0,0 +1,1199 @@
+/*
+ * Tests x86 Memory Protection Keys (see Documentation/x86/protection-keys.txt)
+ *
+ * There are examples in here of:
+ * * how to set protection keys on memory
+ * * how to set/clear bits in PKRU (the rights register)
+ * * how to handle SEGV_PKRU signals and extract pkey-relevant
+ * information from the siginfo
+ *
+ * Things to add:
+ * make sure KSM and KSM COW breaking works
+ * prefault pages in at malloc, or not
+ * protect MPX bounds tables with protection keys?
+ * make sure VMA splitting/merging is working correctly
+ * OOMs can destroy mm->mmap (see exit_mmap()), so make sure it is immune to pkeys
+ * look for pkey "leaks" where it is still set on a VMA but "freed" back to the kernel
+ * do a plain mprotect() to a mprotect_pkey() area and make sure the pkey sticks
+ *
+ * Compile like this:
+ * gcc -o protection_keys -O2 -g -std=gnu99 -pthread -Wall protection_keys.c -lrt -ldl -lm
+ * gcc -m32 -o protection_keys_32 -O2 -g -std=gnu99 -pthread -Wall protection_keys.c -lrt -ldl -lm
+ */
+#define _GNU_SOURCE
+#include <errno.h>
+#include <linux/futex.h>
+#include <sys/time.h>
+#include <sys/syscall.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <signal.h>
+#include <assert.h>
+#include <stdlib.h>
+#include <ucontext.h>
+#include <sys/mman.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/ptrace.h>
+
+#include "pkey-helpers.h"
+
+int iteration_nr = 1;
+int test_nr;
+
+unsigned int shadow_pkru;
+
+#define HPAGE_SIZE (1UL<<21)
+#define ARRAY_SIZE(x) (sizeof(x) / sizeof(*(x)))
+#define ALIGN(x, align_to) (((x) + ((align_to)-1)) & ~((align_to)-1))
+#define ALIGN_PTR(p, ptr_align_to) ((typeof(p))ALIGN((unsigned long)(p), ptr_align_to))
+
+extern void abort_hooks(void);
+#define pkey_assert(condition) do { \
+ if (!(condition)) { \
+ printf("assert() at %s::%d test_nr: %d iteration: %d\n", \
+ __FILE__, __LINE__, \
+ test_nr, iteration_nr); \
+ perror("errno at assert"); \
+ abort_hooks(); \
+ assert(condition); \
+ } \
+} while (0)
+#define raw_assert(cond) assert(cond)
+
+void cat_into_file(char *str, char *file)
+{
+ int fd = open(file, O_RDWR);
+ int ret;
+ /*
+ * these need to be raw because they are called under
+ * pkey_assert()
+ */
+ raw_assert(fd >= 0);
+ ret = write(fd, str, strlen(str));
+ if (ret != strlen(str)) {
+ perror("write to file failed");
+ fprintf(stderr, "filename: '%s' str: '%s'\n", file, str);
+ raw_assert(0);
+ }
+ close(fd);
+}
+
+void tracing_on(void)
+{
+#ifdef CONTROL_TRACING
+ char pidstr[32];
+ sprintf(pidstr, "%d", getpid());
+ //cat_into_file("20000", "/sys/kernel/debug/tracing/buffer_size_kb");
+ cat_into_file("0", "/sys/kernel/debug/tracing/tracing_on");
+ cat_into_file("\n", "/sys/kernel/debug/tracing/trace");
+ if (1) {
+ cat_into_file("function_graph", "/sys/kernel/debug/tracing/current_tracer");
+ cat_into_file("1", "/sys/kernel/debug/tracing/options/funcgraph-proc");
+ } else {
+ cat_into_file("nop", "/sys/kernel/debug/tracing/current_tracer");
+ }
+ cat_into_file(pidstr, "/sys/kernel/debug/tracing/set_ftrace_pid");
+ cat_into_file("1", "/sys/kernel/debug/tracing/tracing_on");
+ dprintf1("enabled tracing\n");
+#endif
+}
+
+void tracing_off(void)
+{
+#ifdef CONTROL_TRACING
+ cat_into_file("0", "/sys/kernel/debug/tracing/tracing_on");
+#endif
+}
+
+void abort_hooks(void)
+{
+ fprintf(stderr, "running %s()...\n", __func__);
+ tracing_off();
+#ifdef SLEEP_ON_ABORT
+ sleep(SLEEP_ON_ABORT);
+#endif
+}
+
+void lots_o_noops(void)
+{
+ dprintf1("running %s()\n", __func__);
+ asm(".rept 65536 ; nopl 0x7eeeeeee(%eax) ; .endr");
+ dprintf1("%s() done\n", __func__);
+}
+
+// I'm addicted to the kernel types
+#define u8 uint8_t
+#define u16 uint16_t
+#define u32 uint32_t
+#define u64 uint64_t
+
+#ifdef __i386__
+#define SYS_mprotect_key 380
+#define SYS_pkey_alloc 381
+#define SYS_pkey_free 382
+#define SYS_pkey_get 383
+#define SYS_pkey_set 384
+#define REG_IP_IDX REG_EIP
+#define si_pkey_offset 0x18
+#else
+#define SYS_mprotect_key 329
+#define SYS_pkey_alloc 330
+#define SYS_pkey_free 331
+#define SYS_pkey_get 332
+#define SYS_pkey_set 333
+#define REG_IP_IDX REG_RIP
+#define si_pkey_offset 0x20
+#endif
+
+void dump_mem(void *dumpme, int len_bytes)
+{
+ char *c = (void *)dumpme;
+ int i;
+ for (i = 0; i < len_bytes; i+= sizeof(u64)) {
+ u64 *ptr = (u64 *)(c + i);
+ dprintf1("dump[%03d][@%p]: %016jx\n", i, ptr, *ptr);
+ }
+}
+
+#define __SI_FAULT (3 << 16)
+#define SEGV_BNDERR (__SI_FAULT|3) /* failed address bound checks */
+#define SEGV_PKUERR (__SI_FAULT|4)
+
+static char *si_code_str(int si_code)
+{
+ if (si_code & SEGV_MAPERR)
+ return "SEGV_MAPERR";
+ if (si_code & SEGV_ACCERR)
+ return "SEGV_ACCERR";
+ if (si_code & SEGV_BNDERR)
+ return "SEGV_BNDERR";
+ if (si_code & SEGV_PKUERR)
+ return "SEGV_PKUERR";
+ return "UNKNOWN";
+}
+
+int pkru_faults = 0;
+int last_si_pkey = -1;
+void signal_handler(int signum, siginfo_t* si, void* vucontext)
+{
+ ucontext_t* uctxt = vucontext;
+ int trapno;
+ unsigned long ip;
+ char *fpregs;
+ u32 *pkru_ptr;
+ u64 si_pkey;
+ u32* si_pkey_ptr;
+ int pkru_offset;
+
+ dprintf1(">>>>===============SIGSEGV============================\n");
+ dprintf1("%s()::%d, pkru: 0x%x shadow: %x\n", __func__, __LINE__, __rdpkru(), shadow_pkru);
+
+ trapno = uctxt->uc_mcontext.gregs[REG_TRAPNO];
+ ip = uctxt->uc_mcontext.gregs[REG_IP_IDX];
+ fpregset_t fpregset = uctxt->uc_mcontext.fpregs;
+ fpregs = (void *)fpregset;
+
+ dprintf2("%s() trapno: %d ip: 0x%lx info->si_code: %s/%d\n", __func__, trapno, ip,
+ si_code_str(si->si_code), si->si_code);
+#ifdef __i386__
+ /*
+ * 32-bit has some extra padding so that userspace can tell whether
+ * the XSTATE header is present in addition to the "legacy" FPU
+ * state. We just assume that it is here.
+ */
+ fpregs += 0x70;
+#endif
+ pkru_offset = pkru_xstate_offset();
+ pkru_ptr = (void *)(&fpregs[pkru_offset]);
+
+ dprintf1("siginfo: %p\n", si);
+ dprintf1(" fpregs: %p\n", fpregs);
+ /*
+ * If we got a PKRU fault, we *HAVE* to have at least one bit set in
+ * here.
+ */
+ dprintf1("pkru_xstate_offset: %d\n", pkru_xstate_offset());
+ //dump_mem(pkru_ptr - 128, 256);
+ pkey_assert(*pkru_ptr);
+
+ si_pkey_ptr = (u32 *)(((u8 *)si) + si_pkey_offset);
+ dprintf1("si_pkey_ptr: %p\n", si_pkey_ptr);
+ dump_mem(si_pkey_ptr - 8, 24);
+ si_pkey = *si_pkey_ptr;
+ pkey_assert(si_pkey < NR_PKEYS);
+ last_si_pkey = si_pkey;
+
+ if ((si->si_code == SEGV_MAPERR) ||
+ (si->si_code == SEGV_ACCERR) ||
+ (si->si_code == SEGV_BNDERR)) {
+ printf("non-PK si_code, exiting...\n");
+ exit(4);
+ }
+
+ //printf("pkru_xstate_offset(): %d\n", pkru_xstate_offset());
+ dprintf1("signal pkru from xsave: %08x\n", *pkru_ptr);
+ // need __ version so we do not do shadow_pkru checking
+ dprintf1("signal pkru from pkru: %08x\n", __rdpkru());
+ dprintf1("si_pkey from siginfo: %jx\n", si_pkey);
+ *(u64 *)pkru_ptr = 0x00000000;
+ dprintf1("WARNING: set PRKU=0 to allow faulting instruction to continue\n");
+ pkru_faults++;
+ dprintf1("<<<<==================================================\n");
+ return;
+ if (trapno == 14) {
+ fprintf(stderr,
+ "ERROR: In signal handler, page fault, trapno = %d, ip = %016lx\n",
+ trapno, ip);
+ fprintf(stderr, "si_addr %p\n", si->si_addr);
+ fprintf(stderr, "REG_ERR: %lx\n", (unsigned long)uctxt->uc_mcontext.gregs[REG_ERR]);
+ //sleep(999);
+ exit(1);
+ } else {
+ fprintf(stderr,"unexpected trap %d! at 0x%lx\n", trapno, ip);
+ fprintf(stderr, "si_addr %p\n", si->si_addr);
+ fprintf(stderr, "REG_ERR: %lx\n", (unsigned long)uctxt->uc_mcontext.gregs[REG_ERR]);
+ exit(2);
+ }
+}
+
+int wait_all_children()
+{
+ int status;
+ return waitpid(-1, &status, 0);
+}
+
+void sig_chld(int x)
+{
+ dprintf2("[%d] SIGCHLD: %d\n", getpid(), x);
+}
+
+void setup_sigsegv_handler()
+{
+ int r,rs;
+ struct sigaction newact;
+ struct sigaction oldact;
+
+ /* #PF is mapped to sigsegv */
+ int signum = SIGSEGV;
+
+ newact.sa_handler = 0; /* void(*)(int)*/
+ newact.sa_sigaction = signal_handler; /* void (*)(int, siginfo_t*, void*) */
+
+ /*sigset_t - signals to block while in the handler */
+ /* get the old signal mask. */
+ rs = sigprocmask(SIG_SETMASK, 0, &newact.sa_mask);
+ pkey_assert(rs == 0);
+
+ /* call sa_sigaction, not sa_handler*/
+ newact.sa_flags = SA_SIGINFO;
+
+ newact.sa_restorer = 0; /* void(*)(), obsolete */
+ r = sigaction(signum, &newact, &oldact);
+ r = sigaction(SIGALRM, &newact, &oldact);
+ pkey_assert(r == 0);
+}
+
+void setup_handlers(void)
+{
+ signal(SIGCHLD, &sig_chld);
+ setup_sigsegv_handler();
+}
+
+pid_t fork_lazy_child(void)
+{
+ pid_t forkret;
+
+ forkret = fork();
+ pkey_assert(forkret >= 0);
+ dprintf3("[%d] fork() ret: %d\n", getpid(), forkret);
+
+ if (!forkret) {
+ /* in the child */
+ while (1) {
+ dprintf1("child sleeping...\n");
+ sleep(30);
+ }
+ }
+ return forkret;
+}
+
+void davecmp(void *_a, void *_b, int len)
+{
+ int i;
+ unsigned long *a = _a;
+ unsigned long *b = _b;
+ for (i = 0; i < len / sizeof(*a); i++) {
+ if (a[i] == b[i])
+ continue;
+
+ dprintf3("[%3d]: a: %016lx b: %016lx\n", i, a[i], b[i]);
+ }
+}
+
+void dumpit(char *f)
+{
+ int fd = open(f, O_RDONLY);
+ char buf[100];
+ int nr_read;
+
+ dprintf2("maps fd: %d\n", fd);
+ do {
+ nr_read = read(fd, &buf[0], sizeof(buf));
+ write(1, buf, nr_read);
+ } while (nr_read > 0);
+ close(fd);
+}
+
+#define PKEY_DISABLE_ACCESS 0x1
+#define PKEY_DISABLE_WRITE 0x2
+
+int sys_pkey_get(int pkey, unsigned long flags)
+{
+ int ret = syscall(SYS_pkey_get, pkey);
+ dprintf1("%s(pkey=%d, flags=%lx) = %x / %d\n", __func__, pkey, flags, ret, ret);
+ return ret;
+}
+
+int sys_pkey_set(int pkey, unsigned long rights, unsigned long flags)
+{
+ int ret = syscall(SYS_pkey_set, pkey, rights, flags);
+ dprintf3("%s(pkey=%d, rights=%lx, flags=%lx) = %x pkru now: %x\n", __func__,
+ pkey, rights, flags, ret, __rdpkru());
+ return ret;
+}
+
+void pkey_disable_set(int pkey, int flags)
+{
+ unsigned long syscall_flags = 0;
+ int ret;
+ int pkey_rights = sys_pkey_get(pkey, syscall_flags);
+ u32 orig_pkru = rdpkru();
+
+ pkey_assert(flags & (PKEY_DISABLE_ACCESS | PKEY_DISABLE_WRITE));
+
+ dprintf1("%s(%d) sys_pkey_get(%d): %x\n", __func__, pkey, pkey, pkey_rights);
+ pkey_assert(pkey_rights >= 0) ;
+
+ pkey_rights |= flags;
+
+ ret = sys_pkey_set(pkey, pkey_rights, syscall_flags);
+ /*pkru and flags have the same format */
+ shadow_pkru |= flags << (pkey * 2);
+ dprintf1("%s(%d) shadow: 0x%x\n", __func__, pkey, shadow_pkru);
+
+ pkey_assert(ret >= 0);
+
+ pkey_rights = sys_pkey_get(pkey, syscall_flags);
+ dprintf1("%s(%d) sys_pkey_get(%d): %x\n", __func__, pkey, pkey, pkey_rights);
+
+ dprintf1("%s(%d) pkru: 0x%x\n", __func__, pkey, rdpkru());
+ if (flags)
+ pkey_assert(rdpkru() > orig_pkru);
+}
+
+void pkey_disable_clear(int pkey, int flags)
+{
+ unsigned long syscall_flags = 0;
+ int ret;
+ int pkey_rights = sys_pkey_get(pkey, syscall_flags);
+ u32 orig_pkru = rdpkru();
+
+ pkey_assert(flags & (PKEY_DISABLE_ACCESS | PKEY_DISABLE_WRITE));
+
+ dprintf1("%s(%d) sys_pkey_get(%d): %x\n", __func__, pkey, pkey, pkey_rights);
+ pkey_assert(pkey_rights >= 0) ;
+
+ pkey_rights |= flags;
+
+ ret = syscall(SYS_pkey_set, pkey, pkey_rights);
+ /* pkru and flags have the same format */
+ shadow_pkru &= ~(flags << (pkey * 2));
+ pkey_assert(ret >= 0);
+
+ pkey_rights = sys_pkey_get(pkey, syscall_flags);
+ dprintf1("%s(%d) sys_pkey_get(%d): %x\n", __func__, pkey, pkey, pkey_rights);
+
+ dprintf1("%s(%d) pkru: 0x%x\n", __func__, pkey, rdpkru());
+ if (flags)
+ assert(rdpkru() > orig_pkru);
+}
+
+void pkey_write_allow(int pkey)
+{
+ pkey_disable_clear(pkey, PKEY_DISABLE_WRITE);
+}
+void pkey_write_deny(int pkey)
+{
+ pkey_disable_set(pkey, PKEY_DISABLE_WRITE);
+}
+void pkey_access_allow(int pkey)
+{
+ pkey_disable_clear(pkey, PKEY_DISABLE_ACCESS);
+}
+void pkey_access_deny(int pkey)
+{
+ pkey_disable_set(pkey, PKEY_DISABLE_ACCESS);
+}
+
+int sys_mprotect_pkey(void *ptr, size_t size, unsigned long orig_prot, unsigned long pkey)
+{
+ int sret;
+
+ dprintf2("%s(0x%p, %zx, prot=%lx, pkey=%lx)\n", __func__,
+ ptr, size, orig_prot, pkey);
+
+ errno = 0;
+ sret = syscall(SYS_mprotect_key, ptr, size, orig_prot, pkey);
+ if (errno) {
+ dprintf2("SYS_mprotect_key sret: %d\n", sret);
+ dprintf2("SYS_mprotect_key prot: 0x%lx\n", orig_prot);
+ dprintf2("SYS_mprotect_key failed, errno: %d\n", errno);
+ if (DEBUG_LEVEL >= 2)
+ perror("SYS_mprotect_pkey");
+ }
+ return sret;
+}
+
+int sys_pkey_alloc(unsigned long flags, unsigned long init_val)
+{
+ int ret = syscall(SYS_pkey_alloc, flags, init_val);
+ dprintf1("%s(flags=%lx, init_val=%lx) syscall ret: %d errno: %d\n", __func__,
+ flags, init_val, ret, errno);
+ return ret;
+}
+
+int alloc_pkey(void)
+{
+ int ret;
+ unsigned long init_val = 0x0;
+
+ dprintf1("alloc_pkey()::%d, pkru: 0x%x shadow: %x\n", __LINE__, __rdpkru(), shadow_pkru);
+ ret = sys_pkey_alloc(0, init_val);
+ /*
+ * pkey_alloc() sets PKRU, so we need to reflect it in
+ * shadow_pkru:
+ */
+ if (ret) {
+ // clear both the bits:
+ shadow_pkru &= ~(0x3 << (ret * 2));
+ // move the new state in from init_val
+ // (remember, we cheated and init_val == pkru format)
+ shadow_pkru |= (init_val << (ret * 2));
+ }
+ dprintf1("alloc_pkey()::%d, pkru: 0x%x shadow: %x\n", __LINE__, __rdpkru(), shadow_pkru);
+ dprintf1("alloc_pkey()::%d errno: %d\n", __LINE__, errno);
+ rdpkru(); // for shadow checking
+ return ret;
+}
+
+int sys_pkey_free(unsigned long pkey)
+{
+ int ret = syscall(SYS_pkey_free, pkey);
+ dprintf1("%s(pkey=%ld) syscall ret: %d\n", __func__, pkey, ret);
+ return ret;
+}
+
+/*
+ * I had a bug where pkey bits could be set by mprotect() but
+ * not cleared. This ensures we get lots of random bit sets
+ * and clears on the vma and pte pkey bits.
+ */
+int alloc_random_pkey(void)
+{
+ int max_nr_pkey_allocs;
+ int ret;
+ int i;
+ int alloced_pkeys[NR_PKEYS];
+ int nr_alloced = 0;
+ int random_index;
+ memset(alloced_pkeys, 0, sizeof(alloced_pkeys));
+
+ /* allocate every possible key and make a note of which ones we got */
+ max_nr_pkey_allocs = NR_PKEYS;
+ max_nr_pkey_allocs = 1;
+ for (i = 0; i < max_nr_pkey_allocs; i++) {
+ int new_pkey = alloc_pkey();
+ if (new_pkey < 0)
+ break;
+ alloced_pkeys[nr_alloced++] = new_pkey;
+ }
+
+ pkey_assert(nr_alloced > 0);
+ /* select a random one out of the allocated ones */
+ random_index = rand() % nr_alloced;
+ ret = alloced_pkeys[random_index];
+ /* now zero it out so we don't free it next */
+ alloced_pkeys[random_index] = 0;
+
+ /* go through the allocated ones that we did not want and free them */
+ for (i = 0; i < nr_alloced; i++) {
+ int free_ret;
+ if (!alloced_pkeys[i])
+ continue;
+ free_ret = sys_pkey_free(alloced_pkeys[i]);
+ pkey_assert(!free_ret);
+ }
+ return ret;
+}
+
+int mprotect_pkey(void *ptr, size_t size, unsigned long orig_prot, unsigned long pkey)
+{
+ int nr_iterations = 0; // random() % 100;
+ int ret;
+
+ while (0) {
+ int rpkey = alloc_random_pkey();
+ ret = sys_mprotect_pkey(ptr, size, orig_prot, pkey);
+ dprintf1("sys_mprotect_pkey(%p, %zx, prot=0x%lx, pkey=%ld) ret: %d\n",
+ ptr, size, orig_prot, pkey, ret);
+ if (nr_iterations-- < 0)
+ break;
+
+ sys_pkey_free(rpkey);
+ }
+ pkey_assert(pkey < NR_PKEYS);
+
+ ret = sys_mprotect_pkey(ptr, size, orig_prot, pkey);
+ dprintf1("mprotect_pkey(%p, %zx, prot=0x%lx, pkey=%ld) ret: %d\n", ptr, size, orig_prot, pkey, ret);
+ pkey_assert(!ret);
+ return ret;
+}
+
+struct pkey_malloc_record {
+ void *ptr;
+ long size;
+};
+struct pkey_malloc_record *pkey_malloc_records;
+long nr_pkey_malloc_records;
+void record_pkey_malloc(void *ptr, long size)
+{
+ long i;
+ struct pkey_malloc_record *rec = NULL;
+
+ for (i = 0; i < nr_pkey_malloc_records; i++) {
+ rec = &pkey_malloc_records[i];
+ // find a free record
+ if (rec)
+ break;
+ }
+ if (!rec) {
+ // every record is full
+ size_t old_nr_records = nr_pkey_malloc_records;
+ size_t new_nr_records = (nr_pkey_malloc_records * 2 + 1);
+ size_t new_size = new_nr_records * sizeof(struct pkey_malloc_record);
+ dprintf2("new_nr_records: %zd\n", new_nr_records);
+ dprintf2("new_size: %zd\n", new_size);
+ pkey_malloc_records = realloc(pkey_malloc_records, new_size);
+ pkey_assert(pkey_malloc_records != NULL);
+ rec = &pkey_malloc_records[nr_pkey_malloc_records];
+ // realloc() does not initalize memory, so zero it from
+ // the first new record all the way to the end.
+ for (i = 0; i < new_nr_records - old_nr_records; i++)
+ memset(rec + i, 0, sizeof(*rec));
+ }
+ dprintf3("filling malloc record[%d/%p]: {%p, %ld}\n",
+ (int)(rec - pkey_malloc_records), rec, ptr, size);
+ rec->ptr = ptr;
+ rec->size = size;
+ nr_pkey_malloc_records++;
+}
+
+void free_pkey_malloc(void *ptr)
+{
+ long i;
+ int ret;
+ dprintf3("%s(%p)\n", __func__, ptr);
+ for (i = 0; i < nr_pkey_malloc_records; i++) {
+ struct pkey_malloc_record *rec = &pkey_malloc_records[i];
+ dprintf4("looking for ptr %p at record[%ld/%p]: {%p, %ld}\n",
+ ptr, i, rec, rec->ptr, rec->size);
+ if ((ptr < rec->ptr) ||
+ (ptr >= rec->ptr + rec->size))
+ continue;
+
+ dprintf3("found ptr %p at record[%ld/%p]: {%p, %ld}\n",
+ ptr, i, rec, rec->ptr, rec->size);
+ nr_pkey_malloc_records--;
+ ret = munmap(rec->ptr, rec->size);
+ dprintf3("munmap ret: %d\n", ret);
+ pkey_assert(!ret);
+ dprintf3("clearing rec->ptr, rec: %p\n", rec);
+ rec->ptr = NULL;
+ dprintf3("done clearing rec->ptr, rec: %p\n", rec);
+ return;
+ }
+ pkey_assert(false);
+}
+
+
+void *malloc_pkey_with_mprotect(long size, int prot, u16 pkey)
+{
+ void *ptr;
+ int ret;
+
+ rdpkru();
+ dprintf1("doing %s(size=%ld, prot=0x%x, pkey=%d)\n", __func__, size, prot, pkey);
+ pkey_assert(pkey < NR_PKEYS);
+ ptr = mmap(NULL, size, prot, MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
+ pkey_assert(ptr != (void *)-1);
+ ret = mprotect_pkey((void *)ptr, PAGE_SIZE, prot, pkey);
+ pkey_assert(!ret);
+ record_pkey_malloc(ptr, size);
+ rdpkru();
+
+ dprintf1("%s() for pkey %d @ %p\n", __func__, pkey, ptr);
+ return ptr;
+}
+
+void *malloc_pkey_anon_huge(long size, int prot, u16 pkey)
+{
+ int ret;
+ void *ptr;
+
+ dprintf1("doing %s(size=%ld, prot=0x%x, pkey=%d)\n", __func__, size, prot, pkey);
+ // Guarantee we can fit at least one huge page in the resulting
+ // allocation by allocating space for 2:
+ size = ALIGN(size, HPAGE_SIZE * 2);
+ ptr = mmap(NULL, size, PROT_NONE, MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
+ pkey_assert(ptr != (void *)-1);
+ record_pkey_malloc(ptr, size);
+ mprotect_pkey(ptr, size, prot, pkey);
+
+ dprintf1("unaligned ptr: %p\n", ptr);
+ ptr = ALIGN_PTR(ptr, HPAGE_SIZE);
+ dprintf1(" aligned ptr: %p\n", ptr);
+ ret = madvise(ptr, HPAGE_SIZE, MADV_HUGEPAGE);
+ dprintf1("MADV_HUGEPAGE ret: %d\n", ret);
+ ret = madvise(ptr, HPAGE_SIZE, MADV_WILLNEED);
+ dprintf1("MADV_WILLNEED ret: %d\n", ret);
+ memset(ptr, 0, HPAGE_SIZE);
+
+ dprintf1("mmap()'d thp for pkey %d @ %p\n", pkey, ptr);
+ return ptr;
+}
+
+void *malloc_pkey_hugetlb(long size, int prot, u16 pkey)
+{
+ void *ptr;
+ int flags = MAP_ANONYMOUS|MAP_PRIVATE|MAP_HUGETLB;
+
+ dprintf1("doing %s(%ld, %x, %x)\n", __func__, size, prot, pkey);
+ size = ALIGN(size, HPAGE_SIZE * 2);
+ pkey_assert(pkey < NR_PKEYS);
+ ptr = mmap(NULL, size, PROT_NONE, flags, -1, 0);
+ pkey_assert(ptr != (void *)-1);
+ mprotect_pkey(ptr, size, prot, pkey);
+
+ record_pkey_malloc(ptr, size);
+
+ dprintf1("mmap()'d hugetlbfs for pkey %d @ %p\n", pkey, ptr);
+ return ptr;
+}
+
+void *malloc_pkey_mmap_dax(long size, int prot, u16 pkey)
+{
+ void *ptr;
+ int fd;
+
+ dprintf1("doing %s(size=%ld, prot=0x%x, pkey=%d)\n", __func__, size, prot, pkey);
+ pkey_assert(pkey < NR_PKEYS);
+ fd = open("/dax/foo", O_RDWR);
+ pkey_assert(fd >= 0);
+
+ ptr = mmap(0, size, prot, MAP_SHARED, fd, 0);
+ pkey_assert(ptr != (void *)-1);
+
+ mprotect_pkey(ptr, size, prot, pkey);
+
+ record_pkey_malloc(ptr, size);
+
+ dprintf1("mmap()'d for pkey %d @ %p\n", pkey, ptr);
+ close(fd);
+ return ptr;
+}
+
+//void *malloc_pkey_with_mprotect(long size, int prot, u16 pkey)
+void *(*pkey_malloc[])(long size, int prot, u16 pkey) = {
+
+ malloc_pkey_with_mprotect,
+ malloc_pkey_anon_huge,
+ malloc_pkey_hugetlb,
+// can not do direct with the mprotect_pkey() API
+// malloc_pkey_mmap_direct,
+// malloc_pkey_mmap_dax,
+};
+
+void *malloc_pkey(long size, int prot, u16 pkey)
+{
+ void *ret;
+ static int malloc_type = 0;
+ int nr_malloc_types = ARRAY_SIZE(pkey_malloc);
+
+ pkey_assert(pkey < NR_PKEYS);
+ pkey_assert(malloc_type < nr_malloc_types);
+ ret = pkey_malloc[malloc_type](size, prot, pkey);
+ pkey_assert(ret != (void *)-1);
+ malloc_type++;
+ if (malloc_type >= nr_malloc_types)
+ malloc_type = (random()%nr_malloc_types);
+
+ dprintf3("%s(%ld, prot=%x, pkey=%x) returning: %p\n", __func__, size, prot, pkey, ret);
+ return ret;
+}
+
+int last_pkru_faults = 0;
+void expected_pk_fault(int pkey)
+{
+ dprintf2("%s(): last_pkru_faults: %d pkru_faults: %d\n",
+ __func__, last_pkru_faults, pkru_faults);
+ dprintf2("%s(%d): last_si_pkey: %d\n", __func__, pkey, last_si_pkey);
+ pkey_assert(last_pkru_faults + 1 == pkru_faults);
+ pkey_assert(last_si_pkey == pkey);
+ /*
+ * The signal handler shold have cleared out PKRU to let the
+ * test program continue. We now have to restore it.
+ */
+ if (__rdpkru() != 0) {
+ pkey_assert(0);
+ }
+ __wrpkru(shadow_pkru);
+ dprintf1("%s() set PKRU=%x to restore state after signal nuked it\n",
+ __func__, shadow_pkru);
+ last_pkru_faults = pkru_faults;
+ last_si_pkey = -1;
+}
+
+void do_not_expect_pk_fault(void)
+{
+ pkey_assert(last_pkru_faults == pkru_faults);
+}
+
+int test_fds[10] = { -1 };
+int nr_test_fds;
+void __save_test_fd(int fd)
+{
+ pkey_assert(fd >= 0);
+ pkey_assert(nr_test_fds < ARRAY_SIZE(test_fds));
+ test_fds[nr_test_fds] = fd;
+ nr_test_fds++;
+}
+
+int get_test_read_fd(void)
+{
+ int test_fd = open("/etc/passwd", O_RDONLY);
+ __save_test_fd(test_fd);
+ return test_fd;
+}
+
+void close_test_fds(void)
+{
+ int i;
+
+ for (i = 0; i < nr_test_fds; i++) {
+ if (test_fds[i] < 0)
+ continue;
+ close(test_fds[i]);
+ test_fds[i] = -1;
+ }
+ nr_test_fds = 0;
+}
+
+#define barrier() __asm__ __volatile__("": : :"memory")
+__attribute__((noinline)) int read_ptr(int *ptr)
+{
+ /*
+ * Keep GCC from optimizing this away somehow
+ */
+ barrier();
+ return *ptr;
+}
+
+void test_read_of_write_disabled_region(int *ptr, u16 pkey)
+{
+ int ptr_contents;
+ dprintf1("disabling write access to PKEY[1], doing read\n");
+ pkey_write_deny(pkey);
+ ptr_contents = read_ptr(ptr);
+ dprintf1("*ptr: %d\n", ptr_contents);
+ dprintf1("\n");
+}
+void test_read_of_access_disabled_region(int *ptr, u16 pkey)
+{
+ int ptr_contents;
+ rdpkru();
+ dprintf1("disabling access to PKEY[%02d], doing read @ %p\n", pkey, ptr);
+ pkey_access_deny(pkey);
+ ptr_contents = read_ptr(ptr);
+ dprintf1("*ptr: %d\n", ptr_contents);
+ expected_pk_fault(pkey);
+}
+void test_write_of_write_disabled_region(int *ptr, u16 pkey)
+{
+ dprintf1("disabling write access to PKEY[%02d], doing write\n", pkey);
+ pkey_write_deny(pkey);
+ *ptr = __LINE__;
+ expected_pk_fault(pkey);
+}
+void test_write_of_access_disabled_region(int *ptr, u16 pkey)
+{
+ dprintf1("disabling access to PKEY[%02d], doing write\n", pkey);
+ pkey_access_deny(pkey);
+ *ptr = __LINE__;
+ expected_pk_fault(pkey);
+}
+void test_kernel_write_of_access_disabled_region(int *ptr, u16 pkey)
+{
+ int ret;
+ int test_fd = get_test_read_fd();
+
+ dprintf1("disabling access to PKEY[%02d], having kernel read() to buffer\n", pkey);
+ pkey_access_deny(pkey);
+ ret = read(test_fd, ptr, 1);
+ dprintf1("read ret: %d\n", ret);
+ pkey_assert(ret);
+}
+void test_kernel_write_of_write_disabled_region(int *ptr, u16 pkey)
+{
+ int ret;
+ int test_fd = get_test_read_fd();
+
+ pkey_write_deny(pkey);
+ ret = read(test_fd, ptr, 100);
+ dprintf1("read ret: %d\n", ret);
+ if (ret < 0 && (DEBUG_LEVEL > 0))
+ perror("read");
+ pkey_assert(ret);
+}
+
+void test_kernel_gup_of_access_disabled_region(int *ptr, u16 pkey)
+{
+ int pipe_ret, vmsplice_ret;
+ struct iovec iov;
+ int pipe_fds[2];
+
+ pipe_ret = pipe(pipe_fds);
+
+ pkey_assert(pipe_ret == 0);
+ dprintf1("disabling access to PKEY[%02d], having kernel vmsplice from buffer\n", pkey);
+ pkey_access_deny(pkey);
+ iov.iov_base = ptr;
+ iov.iov_len = PAGE_SIZE;
+ vmsplice_ret = vmsplice(pipe_fds[1], &iov, 1, SPLICE_F_GIFT);
+ dprintf1("vmsplice() ret: %d\n", vmsplice_ret);
+ pkey_assert(vmsplice_ret == -1);
+
+ close(pipe_fds[0]);
+ close(pipe_fds[1]);
+}
+
+void test_kernel_gup_write_to_write_disabled_region(int *ptr, u16 pkey)
+{
+ int ignored = 0xdada;
+ int futex_ret;
+ int some_int = __LINE__;
+
+ dprintf1("disabling write to PKEY[%02d], doing futex gunk in buffer\n", pkey);
+ *ptr = some_int;
+ pkey_write_deny(pkey);
+ futex_ret = syscall(SYS_futex, ptr, FUTEX_WAIT, some_int-1, NULL, &ignored, ignored);
+ if (DEBUG_LEVEL > 0)
+ perror("futex");
+ dprintf1("futex() ret: %d\n", futex_ret);
+ //pkey_assert(vmsplice_ret == -1);
+}
+
+/* Assumes that all pkeys other than 'pkey' are unallocated */
+void test_pkey_syscalls_on_non_allocated_pkey(int *ptr, u16 pkey)
+{
+ int err;
+ int i;
+
+ /* Note: 0 is the default pkey, so don't mess with it */
+ for (i = 1; i < NR_PKEYS; i++) {
+ if (pkey == i)
+ continue;
+
+ dprintf1("trying get/set/free to non-allocated pkey: %2d\n", i);
+ err = sys_pkey_free(i);
+ pkey_assert(err);
+
+ err = sys_pkey_get(i, 0);
+ pkey_assert(err < 0);
+
+ err = sys_pkey_free(i);
+ pkey_assert(err);
+
+ err = sys_mprotect_pkey(ptr, PAGE_SIZE, PROT_READ, i);
+ pkey_assert(err);
+ }
+}
+
+/* Assumes that all pkeys other than 'pkey' are unallocated */
+void test_pkey_syscalls_bad_args(int *ptr, u16 pkey)
+{
+ int err;
+ int bad_flag = (PKEY_DISABLE_ACCESS | PKEY_DISABLE_WRITE) + 1;
+ int bad_pkey = NR_PKEYS+99;
+
+ err = sys_pkey_get(bad_pkey, bad_flag);
+ pkey_assert(err < 0);
+
+ /* pass a known-invalid pkey in: */
+ err = sys_mprotect_pkey(ptr, PAGE_SIZE, PROT_READ, bad_pkey);
+ pkey_assert(err);
+}
+
+/* Assumes that all pkeys other than 'pkey' are unallocated */
+void test_pkey_alloc_exhaust(int *ptr, u16 pkey)
+{
+ unsigned long flags;
+ unsigned long init_val;
+ int err;
+ int allocated_pkeys[NR_PKEYS] = {0};
+ int nr_allocated_pkeys = 0;
+ int i;
+
+ for (i = 0; i < NR_PKEYS*2; i++) {
+ int new_pkey;
+ dprintf1("%s() alloc loop: %d\n", __func__, i);
+ flags = 0;
+ init_val = 0;
+ pkey_assert(!flags);
+ pkey_assert(!init_val);
+ new_pkey = sys_pkey_alloc(flags, init_val);
+ dprintf2("%s() errno: %d ENOSPC: %d\n", __func__, errno, ENOSPC);
+ if ((new_pkey == -1) && (errno == ENOSPC)) {
+ dprintf2("%s() failed to allocate pkey after %d tries with ENOSPC\n",
+ __func__, nr_allocated_pkeys);
+ break;
+ }
+ pkey_assert(nr_allocated_pkeys < NR_PKEYS);
+ allocated_pkeys[nr_allocated_pkeys++] = new_pkey;
+ }
+
+ dprintf1("%s()::%d\n", __func__, __LINE__);
+
+ /*
+ * ensure it did not reach the end of the loop without
+ * failure:
+ * */
+ pkey_assert(i < NR_PKEYS*2);
+
+ /*
+ * There are 16 pkeys suported in hardware. One is taken
+ * up for the default (0) and another can be taken up by
+ * an execute-only mapping. Ensure that we can allocate
+ * at least 14 (16-2).
+ */
+ pkey_assert(i >= NR_PKEYS-2);
+
+ for (i = 0; i < nr_allocated_pkeys; i++) {
+ err = sys_pkey_free(allocated_pkeys[i]);
+ pkey_assert(!err);
+ }
+}
+
+void test_ptrace_of_child(int *ptr, u16 pkey)
+{
+ __attribute__((__unused__)) int peek_result;
+ pid_t child_pid;
+ void *ignored = 0;
+ long ret;
+ int status;
+ /*
+ * This is the "control" for our little expermient. Make sure
+ * we can always access it when ptracing.
+ */
+ int *plain_ptr_unaligned = malloc(HPAGE_SIZE);
+ int *plain_ptr = ALIGN_PTR(plain_ptr_unaligned, PAGE_SIZE);
+
+ /*
+ * Fork a child which is an exact copy of this process, of course.
+ * That means we can do all of our tests via ptrace() and then plain
+ * memory access and ensure they work differently.
+ */
+ child_pid = fork_lazy_child();
+ dprintf1("[%d] child pid: %d\n", getpid(), child_pid);
+
+ ret = ptrace(PTRACE_ATTACH, child_pid, ignored, ignored);
+ if (ret)
+ perror("attach");
+ dprintf1("[%d] attach ret: %ld %d\n", getpid(), ret, __LINE__);
+ pkey_assert(ret != -1);
+ ret = waitpid(child_pid, &status, WUNTRACED);
+ if ((ret != child_pid) || !(WIFSTOPPED(status)) ) {
+ fprintf(stderr, "weird waitpid result %ld stat %x\n", ret, status);
+ pkey_assert(0);
+ }
+ dprintf2("waitpid ret: %ld\n", ret);
+ dprintf2("waitpid status: %d\n", status);
+
+ pkey_access_deny(pkey);
+ pkey_write_deny(pkey);
+
+ /* Write access, untested for now:
+ ret = ptrace(PTRACE_POKEDATA, child_pid, peek_at, data);
+ pkey_assert(ret != -1);
+ dprintf1("poke at %p: %ld\n", peek_at, ret);
+ */
+
+ /*
+ * Try to access the pkey-protected "ptr" via ptrace:
+ */
+ ret = ptrace(PTRACE_PEEKDATA, child_pid, ptr, ignored);
+ /* expect it to work, without an error: */
+ pkey_assert(ret != -1);
+ /* Now access from the current task, and expect an exception: */
+ peek_result = read_ptr(ptr);
+ expected_pk_fault(pkey);
+
+ /*
+ * Try to access the NON-pkey-protected "ptr" via ptrace:
+ */
+ ret = ptrace(PTRACE_PEEKDATA, child_pid, plain_ptr, ignored);
+ /* expect it to work, without an error: */
+ pkey_assert(ret != -1);
+ /* Now access from the current task, and expect NO exception: */
+ peek_result = read_ptr(ptr);
+ do_not_expect_pk_fault();
+
+ ret = ptrace(PTRACE_DETACH, child_pid, ignored, 0);
+ pkey_assert(ret != -1);
+
+ ret = kill(child_pid, SIGKILL);
+ pkey_assert(ret != -1);
+
+ free(plain_ptr_unaligned);
+}
+
+void test_executing_on_unreadable_memory(int *ptr, u16 pkey)
+{
+ void *p1;
+ int ptr_contents;
+ int ret;
+
+ p1 = ALIGN_PTR(&lots_o_noops, PAGE_SIZE);
+
+ madvise(p1, PAGE_SIZE, MADV_DONTNEED);
+ lots_o_noops();
+ ptr_contents = read_ptr(p1);
+ dprintf2("ptr (%p) contents@%d: %x\n", p1, __LINE__, ptr_contents);
+
+ ret = mprotect_pkey(p1, PAGE_SIZE, PROT_EXEC, (u64)pkey);
+ pkey_assert(!ret);
+ pkey_access_deny(pkey);
+
+ dprintf2("pkru: %x\n", rdpkru());
+
+ /*
+ * Make sure this is an *instruction* fault
+ */
+ madvise(p1, PAGE_SIZE, MADV_DONTNEED);
+ lots_o_noops();
+ do_not_expect_pk_fault();
+ ptr_contents = read_ptr(p1);
+ dprintf2("ptr (%p) contents@%d: %x\n", p1, __LINE__, ptr_contents);
+ expected_pk_fault(pkey);
+}
+
+void test_mprotect_pkey_on_unsupported_cpu(int *ptr, u16 pkey)
+{
+ int size = PAGE_SIZE;
+ int sret;
+
+ if (cpu_has_pku()) {
+ dprintf1("SKIP: %s: no CPU support\n", __func__);
+ return;
+ }
+
+ sret = syscall(SYS_mprotect_key, ptr, size, PROT_READ, pkey);
+ pkey_assert(sret < 0);
+}
+
+void (*pkey_tests[])(int *ptr, u16 pkey) = {
+ test_read_of_write_disabled_region,
+ test_read_of_access_disabled_region,
+ test_write_of_write_disabled_region,
+ test_write_of_access_disabled_region,
+ test_kernel_write_of_access_disabled_region,
+ test_kernel_write_of_write_disabled_region,
+ test_kernel_gup_of_access_disabled_region,
+ test_kernel_gup_write_to_write_disabled_region,
+ test_executing_on_unreadable_memory,
+ test_ptrace_of_child,
+ test_pkey_syscalls_on_non_allocated_pkey,
+ test_pkey_syscalls_bad_args,
+ test_pkey_alloc_exhaust,
+};
+
+void run_tests_once(void)
+{
+ int *ptr;
+ int prot = PROT_READ|PROT_WRITE;
+
+ for (test_nr = 0; test_nr < ARRAY_SIZE(pkey_tests); test_nr++) {
+ int pkey;
+ int orig_pkru_faults = pkru_faults;
+
+ dprintf1("======================\n");
+ dprintf1("test %d starting...\n", test_nr);
+
+ tracing_on();
+ pkey = alloc_random_pkey();
+ dprintf1("test %d starting with pkey: %d\n", test_nr, pkey);
+ ptr = malloc_pkey(PAGE_SIZE, prot, pkey);
+ //dumpit("/proc/self/maps");
+ pkey_tests[test_nr](ptr, pkey);
+ //sleep(999);
+ dprintf1("freeing test memory: %p\n", ptr);
+ free_pkey_malloc(ptr);
+ sys_pkey_free(pkey);
+
+ dprintf1("pkru_faults: %d\n", pkru_faults);
+ dprintf1("orig_pkru_faults: %d\n", orig_pkru_faults);
+
+ tracing_off();
+ close_test_fds();
+
+ printf("test %2d PASSED (itertation %d)\n", test_nr, iteration_nr);
+ dprintf1("======================\n\n");
+ }
+ iteration_nr++;
+}
+
+int main()
+{
+ int nr_iterations = 22;
+ setup_handlers();
+
+ printf("has pku: %d\n", cpu_has_pku());
+
+ if (!cpu_has_pku()) {
+ int size = PAGE_SIZE;
+ int *ptr;
+
+ printf("running PKEY tests for unsupported CPU/OS\n");
+
+ ptr = mmap(NULL, size, PROT_NONE, MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
+ assert(ptr != (void *)-1);
+ test_mprotect_pkey_on_unsupported_cpu(ptr, 1);
+ exit(0);
+ }
+
+ printf("pkru: %x\n", rdpkru());
+ pkey_assert(!rdpkru());
+ cat_into_file("10", "/proc/sys/vm/nr_hugepages");
+
+ while (nr_iterations-- > 0)
+ run_tests_once();
+
+ printf("done (all tests OK)\n");
+ return 0;
+}
+
_
From: Dave Hansen <[email protected]>
This is all that we need to get the new system call itself
working on x86.
Signed-off-by: Dave Hansen <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
---
b/arch/x86/entry/syscalls/syscall_32.tbl | 1 +
b/arch/x86/entry/syscalls/syscall_64.tbl | 1 +
2 files changed, 2 insertions(+)
diff -puN arch/x86/entry/syscalls/syscall_32.tbl~pkeys-114-x86-mprotect_key arch/x86/entry/syscalls/syscall_32.tbl
--- a/arch/x86/entry/syscalls/syscall_32.tbl~pkeys-114-x86-mprotect_key 2016-04-11 08:38:41.821293673 -0700
+++ b/arch/x86/entry/syscalls/syscall_32.tbl 2016-04-11 08:38:41.826293899 -0700
@@ -386,3 +386,4 @@
377 i386 copy_file_range sys_copy_file_range
378 i386 preadv2 sys_preadv2
379 i386 pwritev2 sys_pwritev2
+380 i386 pkey_mprotect sys_pkey_mprotect
diff -puN arch/x86/entry/syscalls/syscall_64.tbl~pkeys-114-x86-mprotect_key arch/x86/entry/syscalls/syscall_64.tbl
--- a/arch/x86/entry/syscalls/syscall_64.tbl~pkeys-114-x86-mprotect_key 2016-04-11 08:38:41.823293763 -0700
+++ b/arch/x86/entry/syscalls/syscall_64.tbl 2016-04-11 08:38:41.826293899 -0700
@@ -335,6 +335,7 @@
326 common copy_file_range sys_copy_file_range
327 64 preadv2 sys_preadv2
328 64 pwritev2 sys_pwritev2
+329 common pkey_mprotect sys_pkey_mprotect
#
# x32-specific system call numbers start at 512 to avoid cache impact
_
From: Dave Hansen <[email protected]>
This patch adds two new system calls:
int pkey_alloc(unsigned long flags, unsigned long init_access_rights)
int pkey_free(int pkey);
These implement an "allocator" for the protection keys
themselves, which can be thought of as analogous to the allocator
that the kernel has for file descriptors. The kernel tracks
which numbers are in use, and only allows operations on keys that
are valid. A key which was not obtained by pkey_alloc() may not,
for instance, be passed to pkey_mprotect() (or the forthcoming
get/set syscalls).
These system calls are also very important given the kernel's use
of pkeys to implement execute-only support. These help ensure
that userspace can never assume that it has control of a key
unless it first asks the kernel.
The 'init_access_rights' argument to pkey_alloc() specifies the
rights that will be established for the returned pkey. For
instance:
pkey = pkey_alloc(flags, PKEY_DENY_WRITE);
will allocate 'pkey', but also sets the bits in PKRU[1] such that
writing to 'pkey' is already denied. This keeps userspace from
needing to have knowledge about manipulating PKRU with the
RDPKRU/WRPKRU instructions. Userspace is still free to use these
instructions as it wishes, but this facility ensures it is no
longer required.
The kernel does _not_ enforce that this interface must be used for
changes to PKRU, even for keys it does not control.
This allocation mechanism could be implemented in userspace.
Even if we did it in userspace, we would still need additional
user/kernel interfaces to tell userspace which keys are being
used by the kernel internally (such as for execute-only
mappings). Having the kernel provide this facility completely
removes the need for these additional interfaces, or having an
implementation of this in userspace at all.
Note that we have to make changes to all of the architectures
that do not use mman-common.h because we use the new
PKEY_DENY_ACCESS/WRITE macros in arch-independent code.
1. PKRU is the Protection Key Rights User register. It is a
usermode-accessible register that controls whether writes
and/or access to each individual pkey is allowed or denied.
Signed-off-by: Dave Hansen <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
---
b/arch/alpha/include/uapi/asm/mman.h | 5 +
b/arch/mips/include/uapi/asm/mman.h | 5 +
b/arch/parisc/include/uapi/asm/mman.h | 5 +
b/arch/x86/entry/syscalls/syscall_32.tbl | 2
b/arch/x86/entry/syscalls/syscall_64.tbl | 2
b/arch/x86/include/asm/mmu.h | 8 +++
b/arch/x86/include/asm/mmu_context.h | 10 +++
b/arch/x86/include/asm/pkeys.h | 78 +++++++++++++++++++++++++++++--
b/arch/x86/kernel/fpu/xstate.c | 3 +
b/arch/x86/mm/pkeys.c | 38 +++++++++++----
b/arch/xtensa/include/uapi/asm/mman.h | 5 +
b/include/linux/pkeys.h | 30 +++++++++--
b/include/uapi/asm-generic/mman-common.h | 5 +
b/mm/mprotect.c | 55 +++++++++++++++++++++
14 files changed, 231 insertions(+), 20 deletions(-)
diff -puN arch/alpha/include/uapi/asm/mman.h~pkeys-116-syscalls-allocation arch/alpha/include/uapi/asm/mman.h
--- a/arch/alpha/include/uapi/asm/mman.h~pkeys-116-syscalls-allocation 2016-04-11 08:38:42.253313227 -0700
+++ b/arch/alpha/include/uapi/asm/mman.h 2016-04-11 08:38:42.277314313 -0700
@@ -78,4 +78,9 @@
#define MAP_HUGE_SHIFT 26
#define MAP_HUGE_MASK 0x3f
+#define PKEY_DISABLE_ACCESS 0x1
+#define PKEY_DISABLE_WRITE 0x2
+#define PKEY_ACCESS_MASK (PKEY_DISABLE_ACCESS |\
+ PKEY_DISABLE_WRITE)
+
#endif /* __ALPHA_MMAN_H__ */
diff -puN arch/mips/include/uapi/asm/mman.h~pkeys-116-syscalls-allocation arch/mips/include/uapi/asm/mman.h
--- a/arch/mips/include/uapi/asm/mman.h~pkeys-116-syscalls-allocation 2016-04-11 08:38:42.255313317 -0700
+++ b/arch/mips/include/uapi/asm/mman.h 2016-04-11 08:38:42.277314313 -0700
@@ -105,4 +105,9 @@
#define MAP_HUGE_SHIFT 26
#define MAP_HUGE_MASK 0x3f
+#define PKEY_DISABLE_ACCESS 0x1
+#define PKEY_DISABLE_WRITE 0x2
+#define PKEY_ACCESS_MASK (PKEY_DISABLE_ACCESS |\
+ PKEY_DISABLE_WRITE)
+
#endif /* _ASM_MMAN_H */
diff -puN arch/parisc/include/uapi/asm/mman.h~pkeys-116-syscalls-allocation arch/parisc/include/uapi/asm/mman.h
--- a/arch/parisc/include/uapi/asm/mman.h~pkeys-116-syscalls-allocation 2016-04-11 08:38:42.256313362 -0700
+++ b/arch/parisc/include/uapi/asm/mman.h 2016-04-11 08:38:42.277314313 -0700
@@ -75,4 +75,9 @@
#define MAP_HUGE_SHIFT 26
#define MAP_HUGE_MASK 0x3f
+#define PKEY_DISABLE_ACCESS 0x1
+#define PKEY_DISABLE_WRITE 0x2
+#define PKEY_ACCESS_MASK (PKEY_DISABLE_ACCESS |\
+ PKEY_DISABLE_WRITE)
+
#endif /* __PARISC_MMAN_H__ */
diff -puN arch/x86/entry/syscalls/syscall_32.tbl~pkeys-116-syscalls-allocation arch/x86/entry/syscalls/syscall_32.tbl
--- a/arch/x86/entry/syscalls/syscall_32.tbl~pkeys-116-syscalls-allocation 2016-04-11 08:38:42.258313453 -0700
+++ b/arch/x86/entry/syscalls/syscall_32.tbl 2016-04-11 08:38:42.279314403 -0700
@@ -387,3 +387,5 @@
378 i386 preadv2 sys_preadv2
379 i386 pwritev2 sys_pwritev2
380 i386 pkey_mprotect sys_pkey_mprotect
+381 i386 pkey_alloc sys_pkey_alloc
+382 i386 pkey_free sys_pkey_free
diff -puN arch/x86/entry/syscalls/syscall_64.tbl~pkeys-116-syscalls-allocation arch/x86/entry/syscalls/syscall_64.tbl
--- a/arch/x86/entry/syscalls/syscall_64.tbl~pkeys-116-syscalls-allocation 2016-04-11 08:38:42.259313498 -0700
+++ b/arch/x86/entry/syscalls/syscall_64.tbl 2016-04-11 08:38:42.279314403 -0700
@@ -336,6 +336,8 @@
327 64 preadv2 sys_preadv2
328 64 pwritev2 sys_pwritev2
329 common pkey_mprotect sys_pkey_mprotect
+330 common pkey_alloc sys_pkey_alloc
+331 common pkey_free sys_pkey_free
#
# x32-specific system call numbers start at 512 to avoid cache impact
diff -puN arch/x86/include/asm/mmu_context.h~pkeys-116-syscalls-allocation arch/x86/include/asm/mmu_context.h
--- a/arch/x86/include/asm/mmu_context.h~pkeys-116-syscalls-allocation 2016-04-11 08:38:42.261313589 -0700
+++ b/arch/x86/include/asm/mmu_context.h 2016-04-11 08:38:42.279314403 -0700
@@ -108,7 +108,16 @@ static inline void enter_lazy_tlb(struct
static inline int init_new_context(struct task_struct *tsk,
struct mm_struct *mm)
{
+ #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
+ if (boot_cpu_has(X86_FEATURE_OSPKE)) {
+ /* pkey 0 is the default and always allocated */
+ mm->context.pkey_allocation_map = 0x1;
+ /* -1 means unallocated or invalid */
+ mm->context.execute_only_pkey = -1;
+ }
+ #endif
init_new_context_ldt(tsk, mm);
+
return 0;
}
static inline void destroy_context(struct mm_struct *mm)
@@ -354,5 +363,4 @@ static inline bool arch_pte_access_permi
{
return __pkru_allows_pkey(pte_flags_pkey(pte_flags(pte)), write);
}
-
#endif /* _ASM_X86_MMU_CONTEXT_H */
diff -puN arch/x86/include/asm/mmu.h~pkeys-116-syscalls-allocation arch/x86/include/asm/mmu.h
--- a/arch/x86/include/asm/mmu.h~pkeys-116-syscalls-allocation 2016-04-11 08:38:42.263313679 -0700
+++ b/arch/x86/include/asm/mmu.h 2016-04-11 08:38:42.280314449 -0700
@@ -23,6 +23,14 @@ typedef struct {
const struct vdso_image *vdso_image; /* vdso image in use */
atomic_t perf_rdpmc_allowed; /* nonzero if rdpmc is allowed */
+#ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
+ /*
+ * One bit per protection key says whether userspace can
+ * use it or not. protected by mmap_sem.
+ */
+ u16 pkey_allocation_map;
+ s16 execute_only_pkey;
+#endif
} mm_context_t;
#ifdef CONFIG_SMP
diff -puN arch/x86/include/asm/pkeys.h~pkeys-116-syscalls-allocation arch/x86/include/asm/pkeys.h
--- a/arch/x86/include/asm/pkeys.h~pkeys-116-syscalls-allocation 2016-04-11 08:38:42.264313725 -0700
+++ b/arch/x86/include/asm/pkeys.h 2016-04-11 08:38:42.280314449 -0700
@@ -1,12 +1,8 @@
#ifndef _ASM_X86_PKEYS_H
#define _ASM_X86_PKEYS_H
-#define PKEY_DEDICATED_EXECUTE_ONLY 15
-/*
- * Consider the PKEY_DEDICATED_EXECUTE_ONLY key unavailable.
- */
#define arch_max_pkey() (boot_cpu_has(X86_FEATURE_OSPKE) ? \
- PKEY_DEDICATED_EXECUTE_ONLY : 1)
+ 16 : 1)
extern int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
unsigned long init_val);
@@ -40,4 +36,76 @@ extern int __arch_set_user_pkey_access(s
#define ARCH_VM_PKEY_FLAGS (VM_PKEY_BIT0 | VM_PKEY_BIT1 | VM_PKEY_BIT2 | VM_PKEY_BIT3)
+#define mm_pkey_allocation_map(mm) (mm->context.pkey_allocation_map)
+#define mm_set_pkey_allocated(mm, pkey) do { \
+ mm_pkey_allocation_map(mm) |= (1 << pkey); \
+} while (0)
+#define mm_set_pkey_free(mm, pkey) do { \
+ mm_pkey_allocation_map(mm) &= ~(1 << pkey); \
+} while (0)
+
+/*
+ * This is called from mprotect_pkey().
+ *
+ * Returns true if the protection keys is valid.
+ */
+static inline bool validate_pkey(int pkey)
+{
+ if (pkey < 0)
+ return false;
+ return (pkey < arch_max_pkey());
+}
+
+static inline
+bool mm_pkey_is_allocated(struct mm_struct *mm, unsigned long pkey)
+{
+ if (!validate_pkey(pkey))
+ return true;
+
+ return mm_pkey_allocation_map(mm) & (1 << pkey);
+}
+
+static inline
+int mm_pkey_alloc(struct mm_struct *mm)
+{
+ int all_pkeys_mask = ((1 << arch_max_pkey()) - 1);
+ int ret;
+
+ /*
+ * Are we out of pkeys? We must handle this specially
+ * because ffz() behavior is undefined if there are no
+ * zeros.
+ */
+ if (mm_pkey_allocation_map(mm) == all_pkeys_mask)
+ return -1;
+
+ ret = ffz(mm_pkey_allocation_map(mm));
+
+ mm_set_pkey_allocated(mm, ret);
+
+ return ret;
+}
+
+static inline
+int mm_pkey_free(struct mm_struct *mm, int pkey)
+{
+ /*
+ * pkey 0 is special, always allocated and can never
+ * be freed.
+ */
+ if (!pkey || !validate_pkey(pkey))
+ return -EINVAL;
+ if (!mm_pkey_is_allocated(mm, pkey))
+ return -EINVAL;
+
+ mm_set_pkey_free(mm, pkey);
+
+ return 0;
+}
+
+extern int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
+ unsigned long init_val);
+extern int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
+ unsigned long init_val);
+
#endif /*_ASM_X86_PKEYS_H */
diff -puN arch/x86/kernel/fpu/xstate.c~pkeys-116-syscalls-allocation arch/x86/kernel/fpu/xstate.c
--- a/arch/x86/kernel/fpu/xstate.c~pkeys-116-syscalls-allocation 2016-04-11 08:38:42.266313815 -0700
+++ b/arch/x86/kernel/fpu/xstate.c 2016-04-11 08:38:42.281314494 -0700
@@ -5,6 +5,7 @@
*/
#include <linux/compat.h>
#include <linux/cpu.h>
+#include <linux/mman.h>
#include <linux/pkeys.h>
#include <asm/fpu/api.h>
@@ -778,6 +779,7 @@ const void *get_xsave_field_ptr(int xsav
return get_xsave_addr(&fpu->state.xsave, xsave_state);
}
+#ifdef CONFIG_ARCH_HAS_PKEYS
/*
* Set xfeatures (aka XSTATE_BV) bit for a feature that we want
@@ -943,3 +945,4 @@ int arch_set_user_pkey_access(struct tas
return -EINVAL;
return __arch_set_user_pkey_access(tsk, pkey, init_val);
}
+#endif /* CONFIG_ARCH_HAS_PKEYS */
diff -puN arch/x86/mm/pkeys.c~pkeys-116-syscalls-allocation arch/x86/mm/pkeys.c
--- a/arch/x86/mm/pkeys.c~pkeys-116-syscalls-allocation 2016-04-11 08:38:42.267313860 -0700
+++ b/arch/x86/mm/pkeys.c 2016-04-11 08:38:42.281314494 -0700
@@ -21,8 +21,19 @@
int __execute_only_pkey(struct mm_struct *mm)
{
+ bool need_to_set_mm_pkey = false;
+ int execute_only_pkey = mm->context.execute_only_pkey;
int ret;
+ /* Do we need to assign a pkey for mm's execute-only maps? */
+ if (execute_only_pkey == -1) {
+ /* Go allocate one to use, which might fail */
+ execute_only_pkey = mm_pkey_alloc(mm);
+ if (!validate_pkey(execute_only_pkey))
+ return -1;
+ need_to_set_mm_pkey = true;
+ }
+
/*
* We do not want to go through the relatively costly
* dance to set PKRU if we do not need to. Check it
@@ -32,22 +43,33 @@ int __execute_only_pkey(struct mm_struct
* can make fpregs inactive.
*/
preempt_disable();
- if (fpregs_active() &&
- !__pkru_allows_read(read_pkru(), PKEY_DEDICATED_EXECUTE_ONLY)) {
+ if (!need_to_set_mm_pkey &&
+ fpregs_active() &&
+ !__pkru_allows_read(read_pkru(), execute_only_pkey)) {
preempt_enable();
- return PKEY_DEDICATED_EXECUTE_ONLY;
+ return execute_only_pkey;
}
preempt_enable();
- ret = __arch_set_user_pkey_access(current, PKEY_DEDICATED_EXECUTE_ONLY,
+
+ /*
+ * Set up PKRU so that it denies access for everything
+ * other than execution.
+ */
+ ret = __arch_set_user_pkey_access(current, execute_only_pkey,
PKEY_DISABLE_ACCESS);
/*
* If the PKRU-set operation failed somehow, just return
* 0 and effectively disable execute-only support.
*/
- if (ret)
- return 0;
+ if (ret) {
+ mm_set_pkey_free(mm, execute_only_pkey);
+ return -1;
+ }
- return PKEY_DEDICATED_EXECUTE_ONLY;
+ /* We got one, store it and use it from here on out */
+ if (need_to_set_mm_pkey)
+ mm->context.execute_only_pkey = execute_only_pkey;
+ return execute_only_pkey;
}
static inline bool vma_is_pkey_exec_only(struct vm_area_struct *vma)
@@ -55,7 +77,7 @@ static inline bool vma_is_pkey_exec_only
/* Do this check first since the vm_flags should be hot */
if ((vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)) != VM_EXEC)
return false;
- if (vma_pkey(vma) != PKEY_DEDICATED_EXECUTE_ONLY)
+ if (vma_pkey(vma) != vma->vm_mm->context.execute_only_pkey)
return false;
return true;
diff -puN arch/xtensa/include/uapi/asm/mman.h~pkeys-116-syscalls-allocation arch/xtensa/include/uapi/asm/mman.h
--- a/arch/xtensa/include/uapi/asm/mman.h~pkeys-116-syscalls-allocation 2016-04-11 08:38:42.269313951 -0700
+++ b/arch/xtensa/include/uapi/asm/mman.h 2016-04-11 08:38:42.281314494 -0700
@@ -117,4 +117,9 @@
#define MAP_HUGE_SHIFT 26
#define MAP_HUGE_MASK 0x3f
+#define PKEY_DISABLE_ACCESS 0x1
+#define PKEY_DISABLE_WRITE 0x2
+#define PKEY_ACCESS_MASK (PKEY_DISABLE_ACCESS |\
+ PKEY_DISABLE_WRITE)
+
#endif /* _XTENSA_MMAN_H */
diff -puN include/linux/pkeys.h~pkeys-116-syscalls-allocation include/linux/pkeys.h
--- a/include/linux/pkeys.h~pkeys-116-syscalls-allocation 2016-04-11 08:38:42.270313996 -0700
+++ b/include/linux/pkeys.h 2016-04-11 08:38:42.281314494 -0700
@@ -4,11 +4,6 @@
#include <linux/mm_types.h>
#include <asm/mmu_context.h>
-#define PKEY_DISABLE_ACCESS 0x1
-#define PKEY_DISABLE_WRITE 0x2
-#define PKEY_ACCESS_MASK (PKEY_DISABLE_ACCESS |\
- PKEY_DISABLE_WRITE)
-
#ifdef CONFIG_ARCH_HAS_PKEYS
#include <asm/pkeys.h>
#else /* ! CONFIG_ARCH_HAS_PKEYS */
@@ -17,7 +12,6 @@
#define arch_override_mprotect_pkey(vma, prot, pkey) (0)
#define PKEY_DEDICATED_EXECUTE_ONLY 0
#define ARCH_VM_PKEY_FLAGS 0
-#endif /* ! CONFIG_ARCH_HAS_PKEYS */
/*
* This is called from mprotect_pkey().
@@ -31,4 +25,28 @@ static inline bool validate_pkey(int pke
return (pkey < arch_max_pkey());
}
+static inline bool mm_pkey_is_allocated(struct mm_struct *mm, int pkey)
+{
+ return (pkey == 0);
+}
+
+static inline int mm_pkey_alloc(struct mm_struct *mm)
+{
+ return -1;
+}
+
+static inline int mm_pkey_free(struct mm_struct *mm, int pkey)
+{
+ WARN_ONCE(1, "free of protection key when disabled");
+ return -EINVAL;
+}
+
+static inline int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
+ unsigned long init_val)
+{
+ return 0;
+}
+
+#endif /* ! CONFIG_ARCH_HAS_PKEYS */
+
#endif /* _LINUX_PKEYS_H */
diff -puN include/uapi/asm-generic/mman-common.h~pkeys-116-syscalls-allocation include/uapi/asm-generic/mman-common.h
--- a/include/uapi/asm-generic/mman-common.h~pkeys-116-syscalls-allocation 2016-04-11 08:38:42.272314087 -0700
+++ b/include/uapi/asm-generic/mman-common.h 2016-04-11 08:38:42.282314539 -0700
@@ -72,4 +72,9 @@
#define MAP_HUGE_SHIFT 26
#define MAP_HUGE_MASK 0x3f
+#define PKEY_DISABLE_ACCESS 0x1
+#define PKEY_DISABLE_WRITE 0x2
+#define PKEY_ACCESS_MASK (PKEY_DISABLE_ACCESS |\
+ PKEY_DISABLE_WRITE)
+
#endif /* __ASM_GENERIC_MMAN_COMMON_H */
diff -puN mm/mprotect.c~pkeys-116-syscalls-allocation mm/mprotect.c
--- a/mm/mprotect.c~pkeys-116-syscalls-allocation 2016-04-11 08:38:42.274314177 -0700
+++ b/mm/mprotect.c 2016-04-11 08:38:42.282314539 -0700
@@ -23,11 +23,13 @@
#include <linux/mmu_notifier.h>
#include <linux/migrate.h>
#include <linux/perf_event.h>
+#include <linux/pkeys.h>
#include <linux/ksm.h>
#include <linux/pkeys.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/cacheflush.h>
+#include <asm/mmu_context.h>
#include <asm/tlbflush.h>
#include "internal.h"
@@ -384,6 +386,14 @@ static int do_mprotect_pkey(unsigned lon
down_write(¤t->mm->mmap_sem);
+ /*
+ * If userspace did not allocate the pkey, do not let
+ * them use it here.
+ */
+ error = -EINVAL;
+ if ((pkey != -1) && !mm_pkey_is_allocated(current->mm, pkey))
+ goto out;
+
vma = find_vma(current->mm, start);
error = -ENOMEM;
if (!vma)
@@ -481,3 +491,48 @@ SYSCALL_DEFINE4(pkey_mprotect, unsigned
return do_mprotect_pkey(start, len, prot, pkey);
}
+
+SYSCALL_DEFINE2(pkey_alloc, unsigned long, flags, unsigned long, init_val)
+{
+ int pkey;
+ int ret;
+
+ /* No flags supported yet. */
+ if (flags)
+ return -EINVAL;
+ /* check for unsupported init values */
+ if (init_val & ~PKEY_ACCESS_MASK)
+ return -EINVAL;
+
+ down_write(¤t->mm->mmap_sem);
+ pkey = mm_pkey_alloc(current->mm);
+
+ ret = -ENOSPC;
+ if (pkey == -1)
+ goto out;
+
+ ret = arch_set_user_pkey_access(current, pkey, init_val);
+ if (ret) {
+ mm_pkey_free(current->mm, pkey);
+ goto out;
+ }
+ ret = pkey;
+out:
+ up_write(¤t->mm->mmap_sem);
+ return ret;
+}
+
+SYSCALL_DEFINE1(pkey_free, int, pkey)
+{
+ int ret;
+
+ down_write(¤t->mm->mmap_sem);
+ ret = mm_pkey_free(current->mm, pkey);
+ up_write(¤t->mm->mmap_sem);
+
+ /*
+ * We could provie warnings or errors if any VMA still
+ * has the pkey set here.
+ */
+ return ret;
+}
_
From: Dave Hansen <[email protected]>
This establishes two more system calls for protection key management:
unsigned long pkey_get(int pkey);
int pkey_set(int pkey, unsigned long access_rights);
The return value from pkey_get() and the 'access_rights' passed
to pkey_set() are the same format: a bitmask containing
PKEY_DENY_WRITE and/or PKEY_DENY_ACCESS, or nothing set at all.
These can replace userspace's direct use of the new rdpkru/wrpkru
instructions.
With current hardware, the kernel can not enforce that it has
control over a given key. But, this at least allows the kernel
to indicate to userspace that userspace does not control a given
protection key. This makes it more likely that situations like
using a pkey after sys_pkey_free() can be detected.
The kernel does _not_ enforce that this interface must be used for
changes to PKRU, whether or not a key has been "allocated".
This syscall interface could also theoretically be replaced with a
pair of vsyscalls. The vsyscalls would just call WRPKRU/RDPKRU
directly in situations where they are drop-in equivalents for
what the kernel would be doing.
Signed-off-by: Dave Hansen <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
---
b/arch/x86/entry/syscalls/syscall_32.tbl | 2 +
b/arch/x86/entry/syscalls/syscall_64.tbl | 2 +
b/arch/x86/include/asm/pkeys.h | 4 +-
b/arch/x86/kernel/fpu/xstate.c | 55 +++++++++++++++++++++++++++++--
b/include/linux/pkeys.h | 8 ++++
b/mm/mprotect.c | 41 +++++++++++++++++++++++
6 files changed, 109 insertions(+), 3 deletions(-)
diff -puN arch/x86/entry/syscalls/syscall_32.tbl~pkeys-118-syscalls-set-get arch/x86/entry/syscalls/syscall_32.tbl
--- a/arch/x86/entry/syscalls/syscall_32.tbl~pkeys-118-syscalls-set-get 2016-04-11 08:38:42.988346496 -0700
+++ b/arch/x86/entry/syscalls/syscall_32.tbl 2016-04-11 08:38:43.000347039 -0700
@@ -389,3 +389,5 @@
380 i386 pkey_mprotect sys_pkey_mprotect
381 i386 pkey_alloc sys_pkey_alloc
382 i386 pkey_free sys_pkey_free
+383 i386 pkey_get sys_pkey_get
+384 i386 pkey_set sys_pkey_set
diff -puN arch/x86/entry/syscalls/syscall_64.tbl~pkeys-118-syscalls-set-get arch/x86/entry/syscalls/syscall_64.tbl
--- a/arch/x86/entry/syscalls/syscall_64.tbl~pkeys-118-syscalls-set-get 2016-04-11 08:38:42.990346586 -0700
+++ b/arch/x86/entry/syscalls/syscall_64.tbl 2016-04-11 08:38:43.000347039 -0700
@@ -338,6 +338,8 @@
329 common pkey_mprotect sys_pkey_mprotect
330 common pkey_alloc sys_pkey_alloc
331 common pkey_free sys_pkey_free
+332 common pkey_get sys_pkey_get
+333 common pkey_set sys_pkey_set
#
# x32-specific system call numbers start at 512 to avoid cache impact
diff -puN arch/x86/include/asm/pkeys.h~pkeys-118-syscalls-set-get arch/x86/include/asm/pkeys.h
--- a/arch/x86/include/asm/pkeys.h~pkeys-118-syscalls-set-get 2016-04-11 08:38:42.992346677 -0700
+++ b/arch/x86/include/asm/pkeys.h 2016-04-11 08:38:43.000347039 -0700
@@ -57,7 +57,7 @@ static inline bool validate_pkey(int pke
}
static inline
-bool mm_pkey_is_allocated(struct mm_struct *mm, unsigned long pkey)
+bool mm_pkey_is_allocated(struct mm_struct *mm, int pkey)
{
if (!validate_pkey(pkey))
return true;
@@ -108,4 +108,6 @@ extern int arch_set_user_pkey_access(str
extern int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
unsigned long init_val);
+extern unsigned long arch_get_user_pkey_access(struct task_struct *tsk,
+ int pkey);
#endif /*_ASM_X86_PKEYS_H */
diff -puN arch/x86/kernel/fpu/xstate.c~pkeys-118-syscalls-set-get arch/x86/kernel/fpu/xstate.c
--- a/arch/x86/kernel/fpu/xstate.c~pkeys-118-syscalls-set-get 2016-04-11 08:38:42.993346722 -0700
+++ b/arch/x86/kernel/fpu/xstate.c 2016-04-11 08:38:43.001347084 -0700
@@ -690,7 +690,7 @@ void fpu__resume_cpu(void)
*
* Note: does not work for compacted buffers.
*/
-void *__raw_xsave_addr(struct xregs_state *xsave, int xstate_feature_mask)
+static void *__raw_xsave_addr(struct xregs_state *xsave, int xstate_feature_mask)
{
int feature_nr = fls64(xstate_feature_mask) - 1;
@@ -864,6 +864,7 @@ out:
#define NR_VALID_PKRU_BITS (CONFIG_NR_PROTECTION_KEYS * 2)
#define PKRU_VALID_MASK (NR_VALID_PKRU_BITS - 1)
+#define PKRU_INIT_STATE 0
/*
* This will go out and modify the XSAVE buffer so that PKRU is
@@ -882,6 +883,9 @@ int __arch_set_user_pkey_access(struct t
int pkey_shift = (pkey * PKRU_BITS_PER_PKEY);
u32 new_pkru_bits = 0;
+ /* Only support manipulating current task for now */
+ if (tsk != current)
+ return -EINVAL;
/*
* This check implies XSAVE support. OSPKE only gets
* set if we enable XSAVE and we enable PKU in XCR0.
@@ -907,7 +911,7 @@ int __arch_set_user_pkey_access(struct t
* state.
*/
if (!old_pkru_state)
- new_pkru_state.pkru = 0;
+ new_pkru_state.pkru = PKRU_INIT_STATE;
else
new_pkru_state.pkru = old_pkru_state->pkru;
@@ -945,4 +949,51 @@ int arch_set_user_pkey_access(struct tas
return -EINVAL;
return __arch_set_user_pkey_access(tsk, pkey, init_val);
}
+
+/*
+ * Figures out what the rights are currently for 'pkey'.
+ * Converts from PKRU's format to the user-visible PKEY_DISABLE_*
+ * format.
+ */
+unsigned long arch_get_user_pkey_access(struct task_struct *tsk, int pkey)
+{
+ struct fpu *fpu = ¤t->thread.fpu;
+ u32 pkru_reg;
+ int ret = 0;
+
+ /* Only support manipulating current task for now */
+ if (tsk != current)
+ return -1;
+ if (!boot_cpu_has(X86_FEATURE_OSPKE))
+ return -1;
+ /*
+ * The contents of PKRU itself are invalid. Consult the
+ * task's XSAVE buffer for PKRU contents. This is much
+ * more expensive than reading PKRU directly, but should
+ * be rare or impossible with eagerfpu mode.
+ */
+ if (!fpu->fpregs_active) {
+ struct xregs_state *xsave = &fpu->state.xsave;
+ struct pkru_state *pkru_state =
+ get_xsave_addr(xsave, XFEATURE_MASK_PKRU);
+ /*
+ * PKRU is in its init state and not present in
+ * the buffer in a saved form.
+ */
+ if (!pkru_state)
+ return PKRU_INIT_STATE;
+
+ return pkru_state->pkru;
+ }
+ /*
+ * Consult the user register directly.
+ */
+ pkru_reg = read_pkru();
+ if (!__pkru_allows_read(pkru_reg, pkey))
+ ret |= PKEY_DISABLE_ACCESS;
+ if (!__pkru_allows_write(pkru_reg, pkey))
+ ret |= PKEY_DISABLE_WRITE;
+
+ return ret;
+}
#endif /* CONFIG_ARCH_HAS_PKEYS */
diff -puN include/linux/pkeys.h~pkeys-118-syscalls-set-get include/linux/pkeys.h
--- a/include/linux/pkeys.h~pkeys-118-syscalls-set-get 2016-04-11 08:38:42.995346813 -0700
+++ b/include/linux/pkeys.h 2016-04-11 08:38:43.001347084 -0700
@@ -44,6 +44,14 @@ static inline int mm_pkey_free(struct mm
static inline int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
unsigned long init_val)
{
+ return -EINVAL;
+}
+
+static inline
+unsigned long arch_get_user_pkey_access(struct task_struct *tsk, int pkey)
+{
+ if (pkey)
+ return -1;
return 0;
}
diff -puN mm/mprotect.c~pkeys-118-syscalls-set-get mm/mprotect.c
--- a/mm/mprotect.c~pkeys-118-syscalls-set-get 2016-04-11 08:38:42.997346903 -0700
+++ b/mm/mprotect.c 2016-04-11 08:38:43.002347129 -0700
@@ -536,3 +536,44 @@ SYSCALL_DEFINE1(pkey_free, int, pkey)
*/
return ret;
}
+
+SYSCALL_DEFINE2(pkey_get, int, pkey, unsigned long, flags)
+{
+ unsigned long ret = 0;
+
+ if (flags)
+ return -EINVAL;
+
+ down_write(¤t->mm->mmap_sem);
+ if (!mm_pkey_is_allocated(current->mm, pkey))
+ ret = -EBADF;
+ up_write(¤t->mm->mmap_sem);
+
+ if (ret)
+ return ret;
+
+ ret = arch_get_user_pkey_access(current, pkey);
+
+ return ret;
+}
+
+SYSCALL_DEFINE3(pkey_set, int, pkey, unsigned long, access_rights,
+ unsigned long, flags)
+{
+ unsigned long ret = 0;
+
+ if (flags)
+ return -EINVAL;
+
+ down_write(¤t->mm->mmap_sem);
+ if (!mm_pkey_is_allocated(current->mm, pkey))
+ ret = -EBADF;
+ up_write(¤t->mm->mmap_sem);
+
+ if (ret)
+ return ret;
+
+ ret = arch_set_user_pkey_access(current, pkey, access_rights);
+
+ return ret;
+}
_
From: Dave Hansen <[email protected]>
This spells out all of the pkey-related system calls that we have
and provides some example code fragments to demonstrate how we
expect them to be used.
Signed-off-by: Dave Hansen <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
---
b/Documentation/x86/protection-keys.txt | 63 ++++++++++++++++++++++++++++++++
1 file changed, 63 insertions(+)
diff -puN Documentation/x86/protection-keys.txt~pkeys-120-syscall-docs Documentation/x86/protection-keys.txt
--- a/Documentation/x86/protection-keys.txt~pkeys-120-syscall-docs 2016-04-11 08:38:43.515370350 -0700
+++ b/Documentation/x86/protection-keys.txt 2016-04-11 08:38:43.518370485 -0700
@@ -18,6 +18,69 @@ even though there is theoretically space
permissions are enforced on data access only and have no effect on
instruction fetches.
+=========================== Syscalls ===========================
+
+There are 5 system calls which directly interact with pkeys:
+
+ int pkey_alloc(unsigned long flags, unsigned long init_access_rights)
+ int pkey_free(int pkey);
+ int sys_pkey_mprotect(unsigned long start, size_t len,
+ unsigned long prot, int pkey);
+ unsigned long pkey_get(int pkey);
+ int pkey_set(int pkey, unsigned long access_rights);
+
+Before a pkey can be used, it must first be allocated with
+pkey_alloc(). An application may either call pkey_set() or the
+WRPKRU instruction directly in order to change access permissions
+to memory covered with a key.
+
+ int real_prot = PROT_READ|PROT_WRITE;
+ pkey = pkey_alloc(0, PKEY_DENY_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_DENY_WRITE
+ *ptr = foo; // assign something
+ pkey_set(pkey, PKEY_DENY_WRITE); // set PKEY_DENY_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);
+
+=========================== 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:
+
+ sys_pkey_alloc(0, PKEY_DISABLE_WRITE | PKEY_DISABLE_READ);
+ sys_pkey_mprotect(ptr, size, PROT_READ|PROT_WRITE);
+ 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.
+
=========================== Config Option ===========================
This config option adds approximately 1.5kb of text. and 50 bytes of
_
From: Dave Hansen <[email protected]>
pkey_mprotect() is just like mprotect, except it also takes a
protection key as an argument. On systems that do not support
protection keys, it still works, but requires that key=0.
Otherwise it does exactly what mprotect does.
I expect it to get used like this, if you want to guarantee that
any mapping you create can *never* be accessed without the right
protection keys set up.
int real_prot = PROT_READ|PROT_WRITE;
pkey = pkey_alloc(0, PKEY_DENY_ACCESS);
ptr = mmap(NULL, PAGE_SIZE, PROT_NONE, MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
ret = pkey_mprotect(ptr, PAGE_SIZE, real_prot, pkey);
This way, there is *no* window where the mapping is accessible
since it was always either PROT_NONE or had a protection key set.
We settled on 'unsigned long' for the type of the key here. We
only need 4 bits on x86 today, but I figured that other
architectures might need some more space.
Semantically, we have a bit of a problem if we combine this
syscall with our previously-introduced execute-only support:
What do we do when we mix execute-only pkey use with
pkey_mprotect() use? For instance:
pkey_mprotect(ptr, PAGE_SIZE, PROT_WRITE, 6); // set pkey=6
mprotect(ptr, PAGE_SIZE, PROT_EXEC); // set pkey=X_ONLY_PKEY?
mprotect(ptr, PAGE_SIZE, PROT_WRITE); // is pkey=6 again?
To solve that, we make the plain-mprotect()-initiated execute-only
support only apply to VMAs that have the default protection key (0)
set on them.
Proposed semantics:
1. protection key 0 is special and represents the default,
unassigned protection key. It is always allocated.
2. mprotect() never affects a mapping's pkey_mprotect()-assigned
protection key. A protection key of 0 (even if set explicitly)
represents an unassigned protection key.
2a. mprotect(PROT_EXEC) on a mapping with an assigned protection
key may or may not result in a mapping with execute-only
properties. pkey_mprotect() plus pkey_set() on all threads
should be used to _guarantee_ execute-only semantics.
3. mprotect(PROT_EXEC) may result in an "execute-only" mapping. The
kernel will internally attempt to allocate and dedicate a
protection key for the purpose of execute-only mappings. This
may not be possible in cases where there are no free protection
keys available.
Signed-off-by: Dave Hansen <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
---
b/arch/x86/include/asm/mmu_context.h | 15 ++++++++++-----
b/arch/x86/include/asm/pkeys.h | 11 +++++++++--
b/arch/x86/kernel/fpu/xstate.c | 15 ++++++++++++++-
b/arch/x86/mm/pkeys.c | 2 +-
b/mm/mprotect.c | 27 +++++++++++++++++++++++----
5 files changed, 57 insertions(+), 13 deletions(-)
diff -puN arch/x86/include/asm/mmu_context.h~pkeys-110-syscalls-mprotect_pkey arch/x86/include/asm/mmu_context.h
--- a/arch/x86/include/asm/mmu_context.h~pkeys-110-syscalls-mprotect_pkey 2016-04-11 08:38:40.875250853 -0700
+++ b/arch/x86/include/asm/mmu_context.h 2016-04-11 08:38:40.885251305 -0700
@@ -4,6 +4,7 @@
#include <asm/desc.h>
#include <linux/atomic.h>
#include <linux/mm_types.h>
+#include <linux/pkeys.h>
#include <trace/events/tlb.h>
@@ -286,16 +287,20 @@ static inline void arch_unmap(struct mm_
mpx_notify_unmap(mm, vma, start, end);
}
+#ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
static inline int vma_pkey(struct vm_area_struct *vma)
{
- u16 pkey = 0;
-#ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
unsigned long vma_pkey_mask = VM_PKEY_BIT0 | VM_PKEY_BIT1 |
VM_PKEY_BIT2 | VM_PKEY_BIT3;
- pkey = (vma->vm_flags & vma_pkey_mask) >> VM_PKEY_SHIFT;
-#endif
- return pkey;
+
+ return (vma->vm_flags & vma_pkey_mask) >> VM_PKEY_SHIFT;
+}
+#else
+static inline int vma_pkey(struct vm_area_struct *vma)
+{
+ return 0;
}
+#endif
static inline bool __pkru_allows_pkey(u16 pkey, bool write)
{
diff -puN arch/x86/include/asm/pkeys.h~pkeys-110-syscalls-mprotect_pkey arch/x86/include/asm/pkeys.h
--- a/arch/x86/include/asm/pkeys.h~pkeys-110-syscalls-mprotect_pkey 2016-04-11 08:38:40.877250943 -0700
+++ b/arch/x86/include/asm/pkeys.h 2016-04-11 08:38:40.885251305 -0700
@@ -1,7 +1,12 @@
#ifndef _ASM_X86_PKEYS_H
#define _ASM_X86_PKEYS_H
-#define arch_max_pkey() (boot_cpu_has(X86_FEATURE_OSPKE) ? 16 : 1)
+#define PKEY_DEDICATED_EXECUTE_ONLY 15
+/*
+ * Consider the PKEY_DEDICATED_EXECUTE_ONLY key unavailable.
+ */
+#define arch_max_pkey() (boot_cpu_has(X86_FEATURE_OSPKE) ? \
+ PKEY_DEDICATED_EXECUTE_ONLY : 1)
extern int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
unsigned long init_val);
@@ -10,7 +15,6 @@ extern int arch_set_user_pkey_access(str
* Try to dedicate one of the protection keys to be used as an
* execute-only protection key.
*/
-#define PKEY_DEDICATED_EXECUTE_ONLY 15
extern int __execute_only_pkey(struct mm_struct *mm);
static inline int execute_only_pkey(struct mm_struct *mm)
{
@@ -31,4 +35,7 @@ static inline int arch_override_mprotect
return __arch_override_mprotect_pkey(vma, prot, pkey);
}
+extern int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
+ unsigned long init_val);
+
#endif /*_ASM_X86_PKEYS_H */
diff -puN arch/x86/kernel/fpu/xstate.c~pkeys-110-syscalls-mprotect_pkey arch/x86/kernel/fpu/xstate.c
--- a/arch/x86/kernel/fpu/xstate.c~pkeys-110-syscalls-mprotect_pkey 2016-04-11 08:38:40.878250989 -0700
+++ b/arch/x86/kernel/fpu/xstate.c 2016-04-11 08:38:40.886251351 -0700
@@ -871,7 +871,7 @@ out:
* not modfiy PKRU *itself* here, only the XSAVE state that will
* be restored in to PKRU when we return back to userspace.
*/
-int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
+int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
unsigned long init_val)
{
struct xregs_state *xsave = &tsk->thread.fpu.state.xsave;
@@ -930,3 +930,16 @@ int arch_set_user_pkey_access(struct tas
return 0;
}
+
+/*
+ * When setting a userspace-provided value, we need to ensure
+ * that it is valid. The __ version can get used by
+ * kernel-internal uses like the execute-only support.
+ */
+int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
+ unsigned long init_val)
+{
+ if (!validate_pkey(pkey))
+ return -EINVAL;
+ return __arch_set_user_pkey_access(tsk, pkey, init_val);
+}
diff -puN arch/x86/mm/pkeys.c~pkeys-110-syscalls-mprotect_pkey arch/x86/mm/pkeys.c
--- a/arch/x86/mm/pkeys.c~pkeys-110-syscalls-mprotect_pkey 2016-04-11 08:38:40.880251079 -0700
+++ b/arch/x86/mm/pkeys.c 2016-04-11 08:38:40.886251351 -0700
@@ -38,7 +38,7 @@ int __execute_only_pkey(struct mm_struct
return PKEY_DEDICATED_EXECUTE_ONLY;
}
preempt_enable();
- ret = arch_set_user_pkey_access(current, PKEY_DEDICATED_EXECUTE_ONLY,
+ ret = __arch_set_user_pkey_access(current, PKEY_DEDICATED_EXECUTE_ONLY,
PKEY_DISABLE_ACCESS);
/*
* If the PKRU-set operation failed somehow, just return
diff -puN mm/mprotect.c~pkeys-110-syscalls-mprotect_pkey mm/mprotect.c
--- a/mm/mprotect.c~pkeys-110-syscalls-mprotect_pkey 2016-04-11 08:38:40.881251124 -0700
+++ b/mm/mprotect.c 2016-04-11 08:38:40.886251351 -0700
@@ -352,8 +352,11 @@ fail:
return error;
}
-SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len,
- unsigned long, prot)
+/*
+ * pkey==-1 when doing a legacy mprotect()
+ */
+static int do_mprotect_pkey(unsigned long start, size_t len,
+ unsigned long prot, int pkey)
{
unsigned long nstart, end, tmp, reqprot;
struct vm_area_struct *vma, *prev;
@@ -408,7 +411,7 @@ SYSCALL_DEFINE3(mprotect, unsigned long,
for (nstart = start ; ; ) {
unsigned long newflags;
- int pkey = arch_override_mprotect_pkey(vma, prot, -1);
+ int vma_pkey;
/* Here we know that vma->vm_start <= nstart < vma->vm_end. */
@@ -416,7 +419,8 @@ SYSCALL_DEFINE3(mprotect, unsigned long,
if (rier && (vma->vm_flags & VM_MAYEXEC))
prot |= PROT_EXEC;
- newflags = calc_vm_prot_bits(prot, pkey);
+ vma_pkey = arch_override_mprotect_pkey(vma, prot, pkey);
+ newflags = calc_vm_prot_bits(prot, vma_pkey);
newflags |= (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC));
/* newflags >> 4 shift VM_MAY% in place of VM_% */
@@ -453,3 +457,18 @@ out:
up_write(¤t->mm->mmap_sem);
return error;
}
+
+SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len,
+ unsigned long, prot)
+{
+ return do_mprotect_pkey(start, len, prot, -1);
+}
+
+SYSCALL_DEFINE4(pkey_mprotect, unsigned long, start, size_t, len,
+ unsigned long, prot, int, pkey)
+{
+ if (!validate_pkey(pkey))
+ return -EINVAL;
+
+ return do_mprotect_pkey(start, len, prot, pkey);
+}
_
From: Dave Hansen <[email protected]>
Today, mprotect() takes 4 bits of data: PROT_READ/WRITE/EXEC/NONE.
Three of those bits: READ/WRITE/EXEC get translated directly in to
vma->vm_flags by calc_vm_prot_bits(). If a bit is unset in
mprotect()'s 'prot' argument then it must be cleared in vma->vm_flags
during the mprotect() call.
We do this clearing today by first calculating the VMA flags we
want set, then clearing the ones we do not want to inherit from
the original VMA:
vm_flags = calc_vm_prot_bits(prot, key);
...
newflags = vm_flags;
newflags |= (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC));
However, we *also* want to mask off the original VMA's vm_flags in
which we store the protection key.
To do that, this patch adds a new macro:
ARCH_VM_PKEY_FLAGS
which allows the architecture to specify additional bits that it would
like cleared. We use that to ensure that the VM_PKEY_BIT* bits get
cleared.
Signed-off-by: Dave Hansen <[email protected]>
Reviewed-by: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
---
b/arch/x86/include/asm/pkeys.h | 2 ++
b/include/linux/pkeys.h | 1 +
b/mm/mprotect.c | 11 ++++++++++-
3 files changed, 13 insertions(+), 1 deletion(-)
diff -puN arch/x86/include/asm/pkeys.h~pkeys-112-mask-off-correct-vm_flags arch/x86/include/asm/pkeys.h
--- a/arch/x86/include/asm/pkeys.h~pkeys-112-mask-off-correct-vm_flags 2016-04-11 08:38:41.373273394 -0700
+++ b/arch/x86/include/asm/pkeys.h 2016-04-11 08:38:41.380273711 -0700
@@ -38,4 +38,6 @@ static inline int arch_override_mprotect
extern int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
unsigned long init_val);
+#define ARCH_VM_PKEY_FLAGS (VM_PKEY_BIT0 | VM_PKEY_BIT1 | VM_PKEY_BIT2 | VM_PKEY_BIT3)
+
#endif /*_ASM_X86_PKEYS_H */
diff -puN include/linux/pkeys.h~pkeys-112-mask-off-correct-vm_flags include/linux/pkeys.h
--- a/include/linux/pkeys.h~pkeys-112-mask-off-correct-vm_flags 2016-04-11 08:38:41.375273485 -0700
+++ b/include/linux/pkeys.h 2016-04-11 08:38:41.381273757 -0700
@@ -16,6 +16,7 @@
#define execute_only_pkey(mm) (0)
#define arch_override_mprotect_pkey(vma, prot, pkey) (0)
#define PKEY_DEDICATED_EXECUTE_ONLY 0
+#define ARCH_VM_PKEY_FLAGS 0
#endif /* ! CONFIG_ARCH_HAS_PKEYS */
/*
diff -puN mm/mprotect.c~pkeys-112-mask-off-correct-vm_flags mm/mprotect.c
--- a/mm/mprotect.c~pkeys-112-mask-off-correct-vm_flags 2016-04-11 08:38:41.377273575 -0700
+++ b/mm/mprotect.c 2016-04-11 08:38:41.381273757 -0700
@@ -410,6 +410,7 @@ static int do_mprotect_pkey(unsigned lon
prev = vma;
for (nstart = start ; ; ) {
+ unsigned long mask_off_old_flags;
unsigned long newflags;
int vma_pkey;
@@ -419,9 +420,17 @@ static int do_mprotect_pkey(unsigned lon
if (rier && (vma->vm_flags & VM_MAYEXEC))
prot |= PROT_EXEC;
+ /*
+ * Each mprotect() call explicitly passes r/w/x permissions.
+ * If a permission is not passed to mprotect(), it must be
+ * cleared from the VMA.
+ */
+ mask_off_old_flags = VM_READ | VM_WRITE | VM_EXEC |
+ ARCH_VM_PKEY_FLAGS;
+
vma_pkey = arch_override_mprotect_pkey(vma, prot, pkey);
newflags = calc_vm_prot_bits(prot, vma_pkey);
- newflags |= (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC));
+ newflags |= (vma->vm_flags & ~mask_off_old_flags);
/* newflags >> 4 shift VM_MAY% in place of VM_% */
if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) {
_