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

// 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 <limits.h>
#include <linux/kernel.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <fcntl.h>
#include <unistd.h>
#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))

#define CORE_FILE_LIMIT	(5 * 1024 * 1024)	/* 5 MB should be enough */

static const char core_pattern_file[] = "/proc/sys/kernel/core_pattern";

static const char user_write[] = "[User Write (Running)]";
static const char core_read_running[] = "[Core Read (Running)]";

/* Information shared between the parent and the child. */
struct shared_info {
	struct child_sync child_sync;

	/* AMR value the parent expects to read in the core file. */
	unsigned long amr;

	/* IAMR value the parent expects to read in the core file. */
	unsigned long iamr;

	/* UAMOR value the parent expects to read in the core file. */
	unsigned long uamor;

	/* When the child crashed. */
	time_t core_time;
};

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 increase_core_file_limit(void)
{
	struct rlimit rlim;
	int ret;

	ret = getrlimit(RLIMIT_CORE, &rlim);
	FAIL_IF(ret);

	if (rlim.rlim_cur != RLIM_INFINITY && rlim.rlim_cur < CORE_FILE_LIMIT) {
		rlim.rlim_cur = CORE_FILE_LIMIT;

		if (rlim.rlim_max != RLIM_INFINITY &&
		    rlim.rlim_max < CORE_FILE_LIMIT)
			rlim.rlim_max = CORE_FILE_LIMIT;

		ret = setrlimit(RLIMIT_CORE, &rlim);
		FAIL_IF(ret);
	}

	ret = getrlimit(RLIMIT_FSIZE, &rlim);
	FAIL_IF(ret);

	if (rlim.rlim_cur != RLIM_INFINITY && rlim.rlim_cur < CORE_FILE_LIMIT) {
		rlim.rlim_cur = CORE_FILE_LIMIT;

		if (rlim.rlim_max != RLIM_INFINITY &&
		    rlim.rlim_max < CORE_FILE_LIMIT)
			rlim.rlim_max = CORE_FILE_LIMIT;

		ret = setrlimit(RLIMIT_FSIZE, &rlim);
		FAIL_IF(ret);
	}

	return TEST_PASS;
}

static int child(struct shared_info *info)
{
	bool disable_execute = true;
	int pkey1, pkey2, pkey3;
	int *ptr, ret;

	/* Wait until parent fills out the initial register values. */
	ret = wait_parent(&info->child_sync);
	if (ret)
		return ret;

	ret = increase_core_file_limit();
	FAIL_IF(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);
		FAIL_IF(pkey1 < 0);

		disable_execute = false;
	}

	pkey2 = sys_pkey_alloc(0, 0);
	FAIL_IF(pkey2 < 0);

	pkey3 = sys_pkey_alloc(0, 0);
	FAIL_IF(pkey3 < 0);

	info->amr |= 3ul << pkeyshift(pkey1) | 2ul << pkeyshift(pkey2);

	if (disable_execute)
		info->iamr |= 1ul << pkeyshift(pkey1);
	else
		info->iamr &= ~(1ul << pkeyshift(pkey1));

	info->iamr &= ~(1ul << pkeyshift(pkey2) | 1ul << pkeyshift(pkey3));

	info->uamor |= 3ul << pkeyshift(pkey1) | 3ul << pkeyshift(pkey2);

	printf("%-30s AMR: %016lx pkey1: %d pkey2: %d pkey3: %d\n",
	       user_write, info->amr, pkey1, pkey2, pkey3);

	set_amr(info->amr);

	/*
	 * We won't use pkey3. This tests whether the kernel restores the UAMOR
	 * permissions after a key is freed.
	 */
	sys_pkey_free(pkey3);

	info->core_time = time(NULL);

	/* Crash. */
	ptr = 0;
	*ptr = 1;

	/* Shouldn't get here. */
	FAIL_IF(true);

	return TEST_FAIL;
}

/* Return file size if filename exists and pass sanity check, or zero if not. */
static off_t try_core_file(const char *filename, struct shared_info *info,
			   pid_t pid)
{
	struct stat buf;
	int ret;

	ret = stat(filename, &buf);
	if (ret == -1)
		return TEST_FAIL;

	/* Make sure we're not using a stale core file. */
	return buf.st_mtime >= info->core_time ? buf.st_size : TEST_FAIL;
}

static Elf64_Nhdr *next_note(Elf64_Nhdr *nhdr)
{
	return (void *) nhdr + sizeof(*nhdr) +
		__ALIGN_KERNEL(nhdr->n_namesz, 4) +
		__ALIGN_KERNEL(nhdr->n_descsz, 4);
}

static int check_core_file(struct shared_info *info, Elf64_Ehdr *ehdr,
			   off_t core_size)
{
	unsigned long *regs;
	Elf64_Phdr *phdr;
	Elf64_Nhdr *nhdr;
	size_t phdr_size;
	void *p = ehdr, *note;
	int ret;

	ret = memcmp(ehdr->e_ident, ELFMAG, SELFMAG);
	FAIL_IF(ret);

	FAIL_IF(ehdr->e_type != ET_CORE);
	FAIL_IF(ehdr->e_machine != EM_PPC64);
	FAIL_IF(ehdr->e_phoff == 0 || ehdr->e_phnum == 0);

	/*
	 * e_phnum is at most 65535 so calculating the size of the
	 * program header cannot overflow.
	 */
	phdr_size = sizeof(*phdr) * ehdr->e_phnum;

	/* Sanity check the program header table location. */
	FAIL_IF(ehdr->e_phoff + phdr_size < ehdr->e_phoff);
	FAIL_IF(ehdr->e_phoff + phdr_size > core_size);

	/* Find the PT_NOTE segment. */
	for (phdr = p + ehdr->e_phoff;
	     (void *) phdr < p + ehdr->e_phoff + phdr_size;
	     phdr += ehdr->e_phentsize)
		if (phdr->p_type == PT_NOTE)
			break;

	FAIL_IF((void *) phdr >= p + ehdr->e_phoff + phdr_size);

	/* Find the NT_PPC_PKEY note. */
	for (nhdr = p + phdr->p_offset;
	     (void *) nhdr < p + phdr->p_offset + phdr->p_filesz;
	     nhdr = next_note(nhdr))
		if (nhdr->n_type == NT_PPC_PKEY)
			break;

	FAIL_IF((void *) nhdr >= p + phdr->p_offset + phdr->p_filesz);
	FAIL_IF(nhdr->n_descsz == 0);

	p = nhdr;
	note = p + sizeof(*nhdr) + __ALIGN_KERNEL(nhdr->n_namesz, 4);

	regs = (unsigned long *) note;

	printf("%-30s AMR: %016lx IAMR: %016lx UAMOR: %016lx\n",
	       core_read_running, regs[0], regs[1], regs[2]);

	FAIL_IF(regs[0] != info->amr);
	FAIL_IF(regs[1] != info->iamr);
	FAIL_IF(regs[2] != info->uamor);

	return TEST_PASS;
}

static int parent(struct shared_info *info, pid_t pid)
{
	char *filenames, *filename[3];
	int fd, i, ret, status;
	unsigned long regs[3];
	off_t core_size;
	void *core;

	/*
	 * 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->amr = regs[0];
	info->iamr = regs[1];
	info->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(&status);
	if (ret != pid) {
		printf("Child's exit status not captured\n");
		return TEST_FAIL;
	} else if (!WIFSIGNALED(status) || !WCOREDUMP(status)) {
		printf("Child didn't dump core\n");
		return TEST_FAIL;
	}

	/* Construct array of core file names to try. */

	filename[0] = filenames = malloc(PATH_MAX);
	if (!filenames) {
		perror("Error allocating memory");
		return TEST_FAIL;
	}

	ret = snprintf(filename[0], PATH_MAX, "core-pkey.%d", pid);
	if (ret < 0 || ret >= PATH_MAX) {
		ret = TEST_FAIL;
		goto out;
	}

	filename[1] = filename[0] + ret + 1;
	ret = snprintf(filename[1], PATH_MAX - ret - 1, "core.%d", pid);
	if (ret < 0 || ret >= PATH_MAX - ret - 1) {
		ret = TEST_FAIL;
		goto out;
	}
	filename[2] = "core";

	for (i = 0; i < 3; i++) {
		core_size = try_core_file(filename[i], info, pid);
		if (core_size != TEST_FAIL)
			break;
	}

	if (i == 3) {
		printf("Couldn't find core file\n");
		ret = TEST_FAIL;
		goto out;
	}

	fd = open(filename[i], O_RDONLY);
	if (fd == -1) {
		perror("Error opening core file");
		ret = TEST_FAIL;
		goto out;
	}

	core = mmap(NULL, core_size, PROT_READ, MAP_PRIVATE, fd, 0);
	if (core == (void *) -1) {
		perror("Error mmaping core file");
		ret = TEST_FAIL;
		goto out;
	}

	ret = check_core_file(info, core, core_size);

	munmap(core, core_size);
	close(fd);
	unlink(filename[i]);

 out:
	free(filenames);

	return ret;
}

static int write_core_pattern(const char *core_pattern)
{
	size_t len = strlen(core_pattern), ret;
	FILE *f;

	f = fopen(core_pattern_file, "w");
	SKIP_IF_MSG(!f, "Try with root privileges");

	ret = fwrite(core_pattern, 1, len, f);
	fclose(f);
	if (ret != len) {
		perror("Error writing to core_pattern file");
		return TEST_FAIL;
	}

	return TEST_PASS;
}

static int setup_core_pattern(char **core_pattern_, bool *changed_)
{
	FILE *f;
	char *core_pattern;
	int ret;

	core_pattern = malloc(PATH_MAX);
	if (!core_pattern) {
		perror("Error allocating memory");
		return TEST_FAIL;
	}

	f = fopen(core_pattern_file, "r");
	if (!f) {
		perror("Error opening core_pattern file");
		ret = TEST_FAIL;
		goto out;
	}

	ret = fread(core_pattern, 1, PATH_MAX, f);
	fclose(f);
	if (!ret) {
		perror("Error reading core_pattern file");
		ret = TEST_FAIL;
		goto out;
	}

	/* Check whether we can predict the name of the core file. */
	if (!strcmp(core_pattern, "core") || !strcmp(core_pattern, "core.%p"))
		*changed_ = false;
	else {
		ret = write_core_pattern("core-pkey.%p");
		if (ret)
			goto out;

		*changed_ = true;
	}

	*core_pattern_ = core_pattern;
	ret = TEST_PASS;

 out:
	if (ret)
		free(core_pattern);

	return ret;
}

static int core_pkey(void)
{
	char *core_pattern;
	bool changed_core_pattern;
	struct shared_info *info;
	int shm_id;
	int ret;
	pid_t pid;

	ret = setup_core_pattern(&core_pattern, &changed_core_pattern);
	if (ret)
		return ret;

	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);

		if (changed_core_pattern)
			write_core_pattern(core_pattern);
	}

	free(core_pattern);

	return ret;
}

int main(int argc, char *argv[])
{
	return test_harness(core_pkey, "core_pkey");
}