selftests/powerpc: Add ptrace tests for Protection Key registers

This test exercises read and write access to the AMR, IAMR and UAMOR.

Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
[mpe: Simplify make rule]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

tools/testing/selftests/powerpc/include/reg.h

@@ -54,6 +54,7 @@
 #define SPRN_DSCR_PRIV 0x11	/* Privilege State DSCR */
 #define SPRN_DSCR      0x03	/* Data Stream Control Register */
 #define SPRN_PPR       896	/* Program Priority Register */
+#define SPRN_AMR       13	/* Authority Mask Register - problem state */
 
 /* TEXASR register bits */
 #define TEXASR_FC	0xFE00000000000000

tools/testing/selftests/powerpc/ptrace/Makefile

@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 TEST_PROGS := ptrace-gpr ptrace-tm-gpr ptrace-tm-spd-gpr \
               ptrace-tar ptrace-tm-tar ptrace-tm-spd-tar ptrace-vsx ptrace-tm-vsx \
-              ptrace-tm-spd-vsx ptrace-tm-spr ptrace-hwbreak
+              ptrace-tm-spd-vsx ptrace-tm-spr ptrace-hwbreak ptrace-pkey
 
 include ../../lib.mk
 
@@ -9,6 +9,9 @@ all: $(TEST_PROGS)
 
 CFLAGS += -m64 -I../../../../../usr/include -I../tm -mhtm -fno-pie
 
+ptrace-pkey: child.h
+ptrace-pkey: LDLIBS += -pthread
+
 $(TEST_PROGS): ../harness.c ../utils.c ../lib/reg.S ptrace.h
 
 clean:

tools/testing/selftests/powerpc/ptrace/child.h

@@ -0,0 +1,139 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Helper functions to sync execution between parent and child processes.
+ *
+ * Copyright 2018, Thiago Jung Bauermann, IBM Corporation.
+ */
+#include <stdio.h>
+#include <stdbool.h>
+#include <semaphore.h>
+
+/*
+ * Information in a shared memory location for synchronization between child and
+ * parent.
+ */
+struct child_sync {
+	/* The parent waits on this semaphore. */
+	sem_t sem_parent;
+
+	/* If true, the child should give up as well. */
+	bool parent_gave_up;
+
+	/* The child waits on this semaphore. */
+	sem_t sem_child;
+
+	/* If true, the parent should give up as well. */
+	bool child_gave_up;
+};
+
+#define CHILD_FAIL_IF(x, sync)						\
+	do {								\
+		if (x) {						\
+			fprintf(stderr,					\
+				"[FAIL] Test FAILED on line %d\n", __LINE__); \
+			(sync)->child_gave_up = true;			\
+			prod_parent(sync);				\
+			return 1;					\
+		}							\
+	} while (0)
+
+#define PARENT_FAIL_IF(x, sync)						\
+	do {								\
+		if (x) {						\
+			fprintf(stderr,					\
+				"[FAIL] Test FAILED on line %d\n", __LINE__); \
+			(sync)->parent_gave_up = true;			\
+			prod_child(sync);				\
+			return 1;					\
+		}							\
+	} while (0)
+
+#define PARENT_SKIP_IF_UNSUPPORTED(x, sync)				\
+	do {								\
+		if ((x) == -1 && (errno == ENODEV || errno == EINVAL)) { \
+			(sync)->parent_gave_up = true;			\
+			prod_child(sync);				\
+			SKIP_IF(1);					\
+		}							\
+	} while (0)
+
+int init_child_sync(struct child_sync *sync)
+{
+	int ret;
+
+	ret = sem_init(&sync->sem_parent, 1, 0);
+	if (ret) {
+		perror("Semaphore initialization failed");
+		return 1;
+	}
+
+	ret = sem_init(&sync->sem_child, 1, 0);
+	if (ret) {
+		perror("Semaphore initialization failed");
+		return 1;
+	}
+
+	return 0;
+}
+
+void destroy_child_sync(struct child_sync *sync)
+{
+	sem_destroy(&sync->sem_parent);
+	sem_destroy(&sync->sem_child);
+}
+
+int wait_child(struct child_sync *sync)
+{
+	int ret;
+
+	/* Wait until the child prods us. */
+	ret = sem_wait(&sync->sem_parent);
+	if (ret) {
+		perror("Error waiting for child");
+		return 1;
+	}
+
+	return sync->child_gave_up;
+}
+
+int prod_child(struct child_sync *sync)
+{
+	int ret;
+
+	/* Unblock the child now. */
+	ret = sem_post(&sync->sem_child);
+	if (ret) {
+		perror("Error prodding child");
+		return 1;
+	}
+
+	return 0;
+}
+
+int wait_parent(struct child_sync *sync)
+{
+	int ret;
+
+	/* Wait until the parent prods us. */
+	ret = sem_wait(&sync->sem_child);
+	if (ret) {
+		perror("Error waiting for parent");
+		return 1;
+	}
+
+	return sync->parent_gave_up;
+}
+
+int prod_parent(struct child_sync *sync)
+{
+	int ret;
+
+	/* Unblock the parent now. */
+	ret = sem_post(&sync->sem_parent);
+	if (ret) {
+		perror("Error prodding parent");
+		return 1;
+	}
+
+	return 0;
+}

tools/testing/selftests/powerpc/ptrace/ptrace-pkey.c

@@ -0,0 +1,327 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Ptrace test for Memory Protection Key registers
+ *
+ * Copyright (C) 2015 Anshuman Khandual, IBM Corporation.
+ * Copyright (C) 2018 IBM Corporation.
+ */
+#include "ptrace.h"
+#include "child.h"
+
+#ifndef __NR_pkey_alloc
+#define __NR_pkey_alloc		384
+#endif
+
+#ifndef __NR_pkey_free
+#define __NR_pkey_free		385
+#endif
+
+#ifndef NT_PPC_PKEY
+#define NT_PPC_PKEY		0x110
+#endif
+
+#ifndef PKEY_DISABLE_EXECUTE
+#define PKEY_DISABLE_EXECUTE	0x4
+#endif
+
+#define AMR_BITS_PER_PKEY 2
+#define PKEY_REG_BITS (sizeof(u64) * 8)
+#define pkeyshift(pkey) (PKEY_REG_BITS - ((pkey + 1) * AMR_BITS_PER_PKEY))
+
+static const char user_read[] = "[User Read (Running)]";
+static const char user_write[] = "[User Write (Running)]";
+static const char ptrace_read_running[] = "[Ptrace Read (Running)]";
+static const char ptrace_write_running[] = "[Ptrace Write (Running)]";
+
+/* Information shared between the parent and the child. */
+struct shared_info {
+	struct child_sync child_sync;
+
+	/* AMR value the parent expects to read from the child. */
+	unsigned long amr1;
+
+	/* AMR value the parent is expected to write to the child. */
+	unsigned long amr2;
+
+	/* AMR value that ptrace should refuse to write to the child. */
+	unsigned long amr3;
+
+	/* IAMR value the parent expects to read from the child. */
+	unsigned long expected_iamr;
+
+	/* UAMOR value the parent expects to read from the child. */
+	unsigned long expected_uamor;
+
+	/*
+	 * IAMR and UAMOR values that ptrace should refuse to write to the child
+	 * (even though they're valid ones) because userspace doesn't have
+	 * access to those registers.
+	 */
+	unsigned long new_iamr;
+	unsigned long new_uamor;
+};
+
+static int sys_pkey_alloc(unsigned long flags, unsigned long init_access_rights)
+{
+	return syscall(__NR_pkey_alloc, flags, init_access_rights);
+}
+
+static int sys_pkey_free(int pkey)
+{
+	return syscall(__NR_pkey_free, pkey);
+}
+
+static int child(struct shared_info *info)
+{
+	unsigned long reg;
+	bool disable_execute = true;
+	int pkey1, pkey2, pkey3;
+	int ret;
+
+	/* Wait until parent fills out the initial register values. */
+	ret = wait_parent(&info->child_sync);
+	if (ret)
+		return ret;
+
+	/* Get some pkeys so that we can change their bits in the AMR. */
+	pkey1 = sys_pkey_alloc(0, PKEY_DISABLE_EXECUTE);
+	if (pkey1 < 0) {
+		pkey1 = sys_pkey_alloc(0, 0);
+		CHILD_FAIL_IF(pkey1 < 0, &info->child_sync);
+
+		disable_execute = false;
+	}
+
+	pkey2 = sys_pkey_alloc(0, 0);
+	CHILD_FAIL_IF(pkey2 < 0, &info->child_sync);
+
+	pkey3 = sys_pkey_alloc(0, 0);
+	CHILD_FAIL_IF(pkey3 < 0, &info->child_sync);
+
+	info->amr1 |= 3ul << pkeyshift(pkey1);
+	info->amr2 |= 3ul << pkeyshift(pkey2);
+	info->amr3 |= info->amr2 | 3ul << pkeyshift(pkey3);
+
+	if (disable_execute)
+		info->expected_iamr |= 1ul << pkeyshift(pkey1);
+
+	info->expected_uamor |= 3ul << pkeyshift(pkey1) |
+				3ul << pkeyshift(pkey2);
+	info->new_iamr |= 1ul << pkeyshift(pkey1) | 1ul << pkeyshift(pkey2);
+	info->new_uamor |= 3ul << pkeyshift(pkey1);
+
+	/*
+	 * We won't use pkey3. We just want a plausible but invalid key to test
+	 * whether ptrace will let us write to AMR bits we are not supposed to.
+	 *
+	 * This also tests whether the kernel restores the UAMOR permissions
+	 * after a key is freed.
+	 */
+	sys_pkey_free(pkey3);
+
+	printf("%-30s AMR: %016lx pkey1: %d pkey2: %d pkey3: %d\n",
+	       user_write, info->amr1, pkey1, pkey2, pkey3);
+
+	mtspr(SPRN_AMR, info->amr1);
+
+	/* Wait for parent to read our AMR value and write a new one. */
+	ret = prod_parent(&info->child_sync);
+	CHILD_FAIL_IF(ret, &info->child_sync);
+
+	ret = wait_parent(&info->child_sync);
+	if (ret)
+		return ret;
+
+	reg = mfspr(SPRN_AMR);
+
+	printf("%-30s AMR: %016lx\n", user_read, reg);
+
+	CHILD_FAIL_IF(reg != info->amr2, &info->child_sync);
+
+	/*
+	 * Wait for parent to try to write an invalid AMR value.
+	 */
+	ret = prod_parent(&info->child_sync);
+	CHILD_FAIL_IF(ret, &info->child_sync);
+
+	ret = wait_parent(&info->child_sync);
+	if (ret)
+		return ret;
+
+	reg = mfspr(SPRN_AMR);
+
+	printf("%-30s AMR: %016lx\n", user_read, reg);
+
+	CHILD_FAIL_IF(reg != info->amr2, &info->child_sync);
+
+	/*
+	 * Wait for parent to try to write an IAMR and a UAMOR value. We can't
+	 * verify them, but we can verify that the AMR didn't change.
+	 */
+	ret = prod_parent(&info->child_sync);
+	CHILD_FAIL_IF(ret, &info->child_sync);
+
+	ret = wait_parent(&info->child_sync);
+	if (ret)
+		return ret;
+
+	reg = mfspr(SPRN_AMR);
+
+	printf("%-30s AMR: %016lx\n", user_read, reg);
+
+	CHILD_FAIL_IF(reg != info->amr2, &info->child_sync);
+
+	/* Now let parent now that we are finished. */
+
+	ret = prod_parent(&info->child_sync);
+	CHILD_FAIL_IF(ret, &info->child_sync);
+
+	return TEST_PASS;
+}
+
+static int parent(struct shared_info *info, pid_t pid)
+{
+	unsigned long regs[3];
+	int ret, status;
+
+	/*
+	 * Get the initial values for AMR, IAMR and UAMOR and communicate them
+	 * to the child.
+	 */
+	ret = ptrace_read_regs(pid, NT_PPC_PKEY, regs, 3);
+	PARENT_SKIP_IF_UNSUPPORTED(ret, &info->child_sync);
+	PARENT_FAIL_IF(ret, &info->child_sync);
+
+	info->amr1 = info->amr2 = info->amr3 = regs[0];
+	info->expected_iamr = info->new_iamr = regs[1];
+	info->expected_uamor = info->new_uamor = regs[2];
+
+	/* Wake up child so that it can set itself up. */
+	ret = prod_child(&info->child_sync);
+	PARENT_FAIL_IF(ret, &info->child_sync);
+
+	ret = wait_child(&info->child_sync);
+	if (ret)
+		return ret;
+
+	/* Verify that we can read the pkey registers from the child. */
+	ret = ptrace_read_regs(pid, NT_PPC_PKEY, regs, 3);
+	PARENT_FAIL_IF(ret, &info->child_sync);
+
+	printf("%-30s AMR: %016lx IAMR: %016lx UAMOR: %016lx\n",
+	       ptrace_read_running, regs[0], regs[1], regs[2]);
+
+	PARENT_FAIL_IF(regs[0] != info->amr1, &info->child_sync);
+	PARENT_FAIL_IF(regs[1] != info->expected_iamr, &info->child_sync);
+	PARENT_FAIL_IF(regs[2] != info->expected_uamor, &info->child_sync);
+
+	/* Write valid AMR value in child. */
+	ret = ptrace_write_regs(pid, NT_PPC_PKEY, &info->amr2, 1);
+	PARENT_FAIL_IF(ret, &info->child_sync);
+
+	printf("%-30s AMR: %016lx\n", ptrace_write_running, info->amr2);
+
+	/* Wake up child so that it can verify it changed. */
+	ret = prod_child(&info->child_sync);
+	PARENT_FAIL_IF(ret, &info->child_sync);
+
+	ret = wait_child(&info->child_sync);
+	if (ret)
+		return ret;
+
+	/* Write invalid AMR value in child. */
+	ret = ptrace_write_regs(pid, NT_PPC_PKEY, &info->amr3, 1);
+	PARENT_FAIL_IF(ret, &info->child_sync);
+
+	printf("%-30s AMR: %016lx\n", ptrace_write_running, info->amr3);
+
+	/* Wake up child so that it can verify it didn't change. */
+	ret = prod_child(&info->child_sync);
+	PARENT_FAIL_IF(ret, &info->child_sync);
+
+	ret = wait_child(&info->child_sync);
+	if (ret)
+		return ret;
+
+	/* Try to write to IAMR. */
+	regs[0] = info->amr1;
+	regs[1] = info->new_iamr;
+	ret = ptrace_write_regs(pid, NT_PPC_PKEY, regs, 2);
+	PARENT_FAIL_IF(!ret, &info->child_sync);
+
+	printf("%-30s AMR: %016lx IAMR: %016lx\n",
+	       ptrace_write_running, regs[0], regs[1]);
+
+	/* Try to write to IAMR and UAMOR. */
+	regs[2] = info->new_uamor;
+	ret = ptrace_write_regs(pid, NT_PPC_PKEY, regs, 3);
+	PARENT_FAIL_IF(!ret, &info->child_sync);
+
+	printf("%-30s AMR: %016lx IAMR: %016lx UAMOR: %016lx\n",
+	       ptrace_write_running, regs[0], regs[1], regs[2]);
+
+	/* Verify that all registers still have their expected values. */
+	ret = ptrace_read_regs(pid, NT_PPC_PKEY, regs, 3);
+	PARENT_FAIL_IF(ret, &info->child_sync);
+
+	printf("%-30s AMR: %016lx IAMR: %016lx UAMOR: %016lx\n",
+	       ptrace_read_running, regs[0], regs[1], regs[2]);
+
+	PARENT_FAIL_IF(regs[0] != info->amr2, &info->child_sync);
+	PARENT_FAIL_IF(regs[1] != info->expected_iamr, &info->child_sync);
+	PARENT_FAIL_IF(regs[2] != info->expected_uamor, &info->child_sync);
+
+	/* Wake up child so that it can verify AMR didn't change and wrap up. */
+	ret = prod_child(&info->child_sync);
+	PARENT_FAIL_IF(ret, &info->child_sync);
+
+	ret = wait(&status);
+	if (ret != pid) {
+		printf("Child's exit status not captured\n");
+		ret = TEST_PASS;
+	} else if (!WIFEXITED(status)) {
+		printf("Child exited abnormally\n");
+		ret = TEST_FAIL;
+	} else
+		ret = WEXITSTATUS(status) ? TEST_FAIL : TEST_PASS;
+
+	return ret;
+}
+
+static int ptrace_pkey(void)
+{
+	struct shared_info *info;
+	int shm_id;
+	int ret;
+	pid_t pid;
+
+	shm_id = shmget(IPC_PRIVATE, sizeof(*info), 0777 | IPC_CREAT);
+	info = shmat(shm_id, NULL, 0);
+
+	ret = init_child_sync(&info->child_sync);
+	if (ret)
+		return ret;
+
+	pid = fork();
+	if (pid < 0) {
+		perror("fork() failed");
+		ret = TEST_FAIL;
+	} else if (pid == 0)
+		ret = child(info);
+	else
+		ret = parent(info, pid);
+
+	shmdt(info);
+
+	if (pid) {
+		destroy_child_sync(&info->child_sync);
+		shmctl(shm_id, IPC_RMID, NULL);
+	}
+
+	return ret;
+}
+
+int main(int argc, char *argv[])
+{
+	return test_harness(ptrace_pkey, "ptrace_pkey");
+}

tools/testing/selftests/powerpc/ptrace/ptrace.h

@@ -102,6 +102,44 @@ int cont_trace(pid_t child)
 	return TEST_PASS;
 }
 
+int ptrace_read_regs(pid_t child, unsigned long type, unsigned long regs[],
+		     int n)
+{
+	struct iovec iov;
+	long ret;
+
+	FAIL_IF(start_trace(child));
+
+	iov.iov_base = regs;
+	iov.iov_len = n * sizeof(unsigned long);
+
+	ret = ptrace(PTRACE_GETREGSET, child, type, &iov);
+	if (ret)
+		return ret;
+
+	FAIL_IF(stop_trace(child));
+
+	return TEST_PASS;
+}
+
+long ptrace_write_regs(pid_t child, unsigned long type, unsigned long regs[],
+		       int n)
+{
+	struct iovec iov;
+	long ret;
+
+	FAIL_IF(start_trace(child));
+
+	iov.iov_base = regs;
+	iov.iov_len = n * sizeof(unsigned long);
+
+	ret = ptrace(PTRACE_SETREGSET, child, type, &iov);
+
+	FAIL_IF(stop_trace(child));
+
+	return ret;
+}
+
 /* TAR, PPR, DSCR */
 int show_tar_registers(pid_t child, unsigned long *out)
 {