[PATCH v2 1/2] selftests/powerpc: Add ptrace tests for Protection Key registers

Thiago Jung Bauermann
2018-05-25T02:12:22Z

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

Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
---
tools/testing/selftests/powerpc/include/reg.h | 1 +
tools/testing/selftests/powerpc/ptrace/Makefile | 5 +-
tools/testing/selftests/powerpc/ptrace/child.h | 139 +++++++++
.../testing/selftests/powerpc/ptrace/ptrace-pkey.c | 327 +++++++++++++++++++++
tools/testing/selftests/powerpc/ptrace/ptrace.h | 38 +++
5 files changed, 509 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/powerpc/ptrace/child.h
create mode 100644 tools/testing/selftests/powerpc/ptrace/ptrace-pkey.c

Changes in v2:
- Added PARENT_SKIP_IF_UNSUPPORTED macro in child.h and use it in first
call to ptrace_read_regs(NT_PPC_PKEY). (Suggested by Michael Ellerman)
- Changed ptrace_read_regs() to simply return the ptrace error value in
case of error and avoid calling fprintf() so that errno is preserved.

diff --git a/tools/testing/selftests/powerpc/include/reg.h b/tools/testing/selftests/powerpc/include/reg.h
index 4afdebcce4cd..7f348c059bc2 100644
--- a/tools/testing/selftests/powerpc/include/reg.h
+++ b/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
diff --git a/tools/testing/selftests/powerpc/ptrace/Makefile b/tools/testing/selftests/powerpc/ptrace/Makefile
index 480305266504..707ba734faf2 100644
--- a/tools/testing/selftests/powerpc/ptrace/Makefile
+++ b/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-tm-spd-vsx ptrace-tm-spr ptrace-pkey

include ../../lib.mk

@@ -9,6 +9,9 @@ all: $(TEST_PROGS)

CFLAGS += -m64 -I../../../../../usr/include -I../tm -mhtm -fno-pie

+ptrace-pkey: ../harness.c ../utils.c ../lib/reg.S ptrace.h child.h ptrace-pkey.c
+ $(LINK.c) $^ $(LDLIBS) -pthread -o $@
+
$(TEST_PROGS): ../harness.c ../utils.c ../lib/reg.S ptrace.h

clean:
diff --git a/tools/testing/selftests/powerpc/ptrace/child.h b/tools/testing/selftests/powerpc/ptrace/child.h
new file mode 100644
index 000000000000..d7275b7b33dc
--- /dev/null
+++ b/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;
+}
diff --git a/tools/testing/selftests/powerpc/ptrace/ptrace-pkey.c b/tools/testing/selftests/powerpc/ptrace/ptrace-pkey.c
new file mode 100644
index 000000000000..5cf631f792cc
--- /dev/null
+++ b/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");
+}
diff --git a/tools/testing/selftests/powerpc/ptrace/ptrace.h b/tools/testing/selftests/powerpc/ptrace/ptrace.h
index 19fb825270a1..34201cfa8335 100644
--- a/tools/testing/selftests/powerpc/ptrace/ptrace.h
+++ b/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)
{