// SPDX-License-Identifier: GPL-2.0
/*
* Copyright 2020, Sandipan Das, IBM Corp.
*
* Test if the signal information reports the correct memory protection
* key upon getting a key access violation fault for a page that was
* attempted to be protected by two different keys from two competing
* threads at the same time.
*/
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <unistd.h>
#include <pthread.h>
#include <sys/mman.h>
#include "pkeys.h"
#define PPC_INST_NOP 0x60000000
#define PPC_INST_BLR 0x4e800020
#define PROT_RWX (PROT_READ | PROT_WRITE | PROT_EXEC)
#define NUM_ITERATIONS 1000000
static volatile sig_atomic_t perm_pkey, rest_pkey;
static volatile sig_atomic_t rights, fault_count;
static volatile unsigned int *volatile fault_addr;
static pthread_barrier_t iteration_barrier;
static void segv_handler(int signum, siginfo_t *sinfo, void *ctx)
{
void *pgstart;
size_t pgsize;
int pkey;
pkey = siginfo_pkey(sinfo);
/* Check if this fault originated from a pkey access violation */
if (sinfo->si_code != SEGV_PKUERR) {
sigsafe_err("got a fault for an unexpected reason\n");
_exit(1);
}
/* Check if this fault originated from the expected address */
if (sinfo->si_addr != (void *) fault_addr) {
sigsafe_err("got a fault for an unexpected address\n");
_exit(1);
}
/* Check if this fault originated from the restrictive pkey */
if (pkey != rest_pkey) {
sigsafe_err("got a fault for an unexpected pkey\n");
_exit(1);
}
/* Check if too many faults have occurred for the same iteration */
if (fault_count > 0) {
sigsafe_err("got too many faults for the same address\n");
_exit(1);
}
pgsize = getpagesize();
pgstart = (void *) ((unsigned long) fault_addr & ~(pgsize - 1));
/*
* If the current fault occurred due to lack of execute rights,
* reassociate the page with the exec-only pkey since execute
* rights cannot be changed directly for the faulting pkey as
* IAMR is inaccessible from userspace.
*
* Otherwise, if the current fault occurred due to lack of
* read-write rights, change the AMR permission bits for the
* pkey.
*
* This will let the test continue.
*/
if (rights == PKEY_DISABLE_EXECUTE &&
mprotect(pgstart, pgsize, PROT_EXEC))
_exit(1);
else
pkey_set_rights(pkey, 0);
fault_count++;
}
struct region {
unsigned long rights;
unsigned int *base;
size_t size;
};
static void *protect(void *p)
{
unsigned long rights;
unsigned int *base;
size_t size;
int tid, i;
tid = gettid();
base = ((struct region *) p)->base;
size = ((struct region *) p)->size;
FAIL_IF_EXIT(!base);
/* No read, write and execute restrictions */
rights = 0;
printf("tid %d, pkey permissions are %s\n", tid, pkey_rights(rights));
/* Allocate the permissive pkey */
perm_pkey = sys_pkey_alloc(0, rights);
FAIL_IF_EXIT(perm_pkey < 0);
/*
* Repeatedly try to protect the common region with a permissive
* pkey
*/
for (i = 0; i < NUM_ITERATIONS; i++) {
/*
* Wait until the other thread has finished allocating the
* restrictive pkey or until the next iteration has begun
*/
pthread_barrier_wait(&iteration_barrier);
/* Try to associate the permissive pkey with the region */
FAIL_IF_EXIT(sys_pkey_mprotect(base, size, PROT_RWX,
perm_pkey));
}
/* Free the permissive pkey */
sys_pkey_free(perm_pkey);
return NULL;
}
static void *protect_access(void *p)
{
size_t size, numinsns;
unsigned int *base;
int tid, i;
tid = gettid();
base = ((struct region *) p)->base;
size = ((struct region *) p)->size;
rights = ((struct region *) p)->rights;
numinsns = size / sizeof(base[0]);
FAIL_IF_EXIT(!base);
/* Allocate the restrictive pkey */
rest_pkey = sys_pkey_alloc(0, rights);
FAIL_IF_EXIT(rest_pkey < 0);
printf("tid %d, pkey permissions are %s\n", tid, pkey_rights(rights));
printf("tid %d, %s randomly in range [%p, %p]\n", tid,
(rights == PKEY_DISABLE_EXECUTE) ? "execute" :
(rights == PKEY_DISABLE_WRITE) ? "write" : "read",
base, base + numinsns);
/*
* Repeatedly try to protect the common region with a restrictive
* pkey and read, write or execute from it
*/
for (i = 0; i < NUM_ITERATIONS; i++) {
/*
* Wait until the other thread has finished allocating the
* permissive pkey or until the next iteration has begun
*/
pthread_barrier_wait(&iteration_barrier);
/* Try to associate the restrictive pkey with the region */
FAIL_IF_EXIT(sys_pkey_mprotect(base, size, PROT_RWX,
rest_pkey));
/* Choose a random instruction word address from the region */
fault_addr = base + (rand() % numinsns);
fault_count = 0;
switch (rights) {
/* Read protection test */
case PKEY_DISABLE_ACCESS:
/*
* Read an instruction word from the region and
* verify if it has not been overwritten to
* something unexpected
*/
FAIL_IF_EXIT(*fault_addr != PPC_INST_NOP &&
*fault_addr != PPC_INST_BLR);
break;
/* Write protection test */
case PKEY_DISABLE_WRITE:
/*
* Write an instruction word to the region and
* verify if the overwrite has succeeded
*/
*fault_addr = PPC_INST_BLR;
FAIL_IF_EXIT(*fault_addr != PPC_INST_BLR);
break;
/* Execute protection test */
case PKEY_DISABLE_EXECUTE:
/* Jump to the region and execute instructions */
asm volatile(
"mtctr %0; bctrl"
: : "r"(fault_addr) : "ctr", "lr");
break;
}
/*
* Restore the restrictions originally imposed by the
* restrictive pkey as the signal handler would have
* cleared out the corresponding AMR bits
*/
pkey_set_rights(rest_pkey, rights);
}
/* Free restrictive pkey */
sys_pkey_free(rest_pkey);
return NULL;
}
static void reset_pkeys(unsigned long rights)
{
int pkeys[NR_PKEYS], i;
/* Exhaustively allocate all available pkeys */
for (i = 0; i < NR_PKEYS; i++)
pkeys[i] = sys_pkey_alloc(0, rights);
/* Free all allocated pkeys */
for (i = 0; i < NR_PKEYS; i++)
sys_pkey_free(pkeys[i]);
}
static int test(void)
{
pthread_t prot_thread, pacc_thread;
struct sigaction act;
pthread_attr_t attr;
size_t numinsns;
struct region r;
int ret, i;
srand(time(NULL));
ret = pkeys_unsupported();
if (ret)
return ret;
/* Allocate the region */
r.size = getpagesize();
r.base = mmap(NULL, r.size, PROT_RWX,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
FAIL_IF(r.base == MAP_FAILED);
/*
* Fill the region with no-ops with a branch at the end
* for returning to the caller
*/
numinsns = r.size / sizeof(r.base[0]);
for (i = 0; i < numinsns - 1; i++)
r.base[i] = PPC_INST_NOP;
r.base[i] = PPC_INST_BLR;
/* Setup SIGSEGV handler */
act.sa_handler = 0;
act.sa_sigaction = segv_handler;
FAIL_IF(sigprocmask(SIG_SETMASK, 0, &act.sa_mask) != 0);
act.sa_flags = SA_SIGINFO;
act.sa_restorer = 0;
FAIL_IF(sigaction(SIGSEGV, &act, NULL) != 0);
/*
* For these tests, the parent process should clear all bits of
* AMR and IAMR, i.e. impose no restrictions, for all available
* pkeys. This will be the base for the initial AMR and IAMR
* values for all the test thread pairs.
*
* If the AMR and IAMR bits of all available pkeys are cleared
* before running the tests and a fault is generated when
* attempting to read, write or execute instructions from a
* pkey protected region, the pkey responsible for this must be
* the one from the protect-and-access thread since the other
* one is fully permissive. Despite that, if the pkey reported
* by siginfo is not the restrictive pkey, then there must be a
* kernel bug.
*/
reset_pkeys(0);
/* Setup barrier for protect and protect-and-access threads */
FAIL_IF(pthread_attr_init(&attr) != 0);
FAIL_IF(pthread_barrier_init(&iteration_barrier, NULL, 2) != 0);
/* Setup and start protect and protect-and-read threads */
puts("starting thread pair (protect, protect-and-read)");
r.rights = PKEY_DISABLE_ACCESS;
FAIL_IF(pthread_create(&prot_thread, &attr, &protect, &r) != 0);
FAIL_IF(pthread_create(&pacc_thread, &attr, &protect_access, &r) != 0);
FAIL_IF(pthread_join(prot_thread, NULL) != 0);
FAIL_IF(pthread_join(pacc_thread, NULL) != 0);
/* Setup and start protect and protect-and-write threads */
puts("starting thread pair (protect, protect-and-write)");
r.rights = PKEY_DISABLE_WRITE;
FAIL_IF(pthread_create(&prot_thread, &attr, &protect, &r) != 0);
FAIL_IF(pthread_create(&pacc_thread, &attr, &protect_access, &r) != 0);
FAIL_IF(pthread_join(prot_thread, NULL) != 0);
FAIL_IF(pthread_join(pacc_thread, NULL) != 0);
/* Setup and start protect and protect-and-execute threads */
puts("starting thread pair (protect, protect-and-execute)");
r.rights = PKEY_DISABLE_EXECUTE;
FAIL_IF(pthread_create(&prot_thread, &attr, &protect, &r) != 0);
FAIL_IF(pthread_create(&pacc_thread, &attr, &protect_access, &r) != 0);
FAIL_IF(pthread_join(prot_thread, NULL) != 0);
FAIL_IF(pthread_join(pacc_thread, NULL) != 0);
/* Cleanup */
FAIL_IF(pthread_attr_destroy(&attr) != 0);
FAIL_IF(pthread_barrier_destroy(&iteration_barrier) != 0);
munmap(r.base, r.size);
return 0;
}
int main(void)
{
return test_harness(test, "pkey_siginfo");
}
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