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

From: Thiago Jung Bauermann
Date: Tue Mar 27 2018 - 13:36:18 EST

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Ram Pai <linuxram@xxxxxxxxxx> writes:

> On Fri, Feb 23, 2018 at 03:33:43PM -0300, Thiago Jung Bauermann wrote:
>> This test exercises read and write access to the AMR, IAMR and UAMOR.
>>
>
> Tested-by: Ram Pai <linuxram@xxxxxxxxxx>
> Acked-by: Ram Pai <linuxram@xxxxxxxxxx>

Ping? Can this and patch 2/2 go in v4.17?

>> Signed-off-by: Thiago Jung Bauermann <bauerman@xxxxxxxxxxxxxxxxxx>
>> ---
>> tools/testing/selftests/powerpc/include/reg.h | 1 +
>> tools/testing/selftests/powerpc/ptrace/Makefile | 5 +-
>> tools/testing/selftests/powerpc/ptrace/child.h | 130 ++++++++
>> .../testing/selftests/powerpc/ptrace/ptrace-pkey.c | 326 +++++++++++++++++++++
>> tools/testing/selftests/powerpc/ptrace/ptrace.h | 37 +++
>> 5 files changed, 498 insertions(+), 1 deletion(-)
>> create mode 100644 tools/testing/selftests/powerpc/ptrace/child.h
>> create mode 100644 tools/testing/selftests/powerpc/ptrace/ptrace-pkey.c
>>
>> 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..40c1a6d92111
>> --- /dev/null
>> +++ b/tools/testing/selftests/powerpc/ptrace/child.h
>> @@ -0,0 +1,130 @@
>> +// 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)
>> +
>> +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..8332b9338d39
>> --- /dev/null
>> +++ b/tools/testing/selftests/powerpc/ptrace/ptrace-pkey.c
>> @@ -0,0 +1,326 @@
>> +// 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_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..d2c9c4c2b5ee 100644
>> --- a/tools/testing/selftests/powerpc/ptrace/ptrace.h
>> +++ b/tools/testing/selftests/powerpc/ptrace/ptrace.h
>> @@ -102,6 +102,43 @@ 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);
>> + FAIL_IF(ret != 0);
>> +
>> + 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)
>> {

--
Thiago Jung Bauermann
IBM Linux Technology Center

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