From patchwork Wed May 27 03:03:42 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sandipan Das X-Patchwork-Id: 208467 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9BAD7C433E0 for ; Wed, 27 May 2020 03:04:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6F8DC207D3 for ; Wed, 27 May 2020 03:04:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728177AbgE0DEE (ORCPT ); Tue, 26 May 2020 23:04:04 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:41738 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725893AbgE0DED (ORCPT ); Tue, 26 May 2020 23:04:03 -0400 Received: from pps.filterd (m0098394.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 04R32xoN165476; Tue, 26 May 2020 23:03:51 -0400 Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com with ESMTP id 3170b8ruxr-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 26 May 2020 23:03:50 -0400 Received: from m0098394.ppops.net (m0098394.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.36/8.16.0.36) with SMTP id 04R330xu165563; Tue, 26 May 2020 23:03:50 -0400 Received: from ppma04ams.nl.ibm.com (63.31.33a9.ip4.static.sl-reverse.com [169.51.49.99]) by mx0a-001b2d01.pphosted.com with ESMTP id 3170b8ruwk-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 26 May 2020 23:03:49 -0400 Received: from pps.filterd (ppma04ams.nl.ibm.com [127.0.0.1]) by ppma04ams.nl.ibm.com (8.16.0.42/8.16.0.42) with SMTP id 04R31JOW002507; Wed, 27 May 2020 03:03:47 GMT Received: from b06avi18626390.portsmouth.uk.ibm.com (b06avi18626390.portsmouth.uk.ibm.com [9.149.26.192]) by ppma04ams.nl.ibm.com with ESMTP id 316uf8y1es-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 27 May 2020 03:03:47 +0000 Received: from d06av25.portsmouth.uk.ibm.com (d06av25.portsmouth.uk.ibm.com [9.149.105.61]) by b06avi18626390.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 04R32UYt66191632 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 27 May 2020 03:02:30 GMT Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4C6F111C052; Wed, 27 May 2020 03:03:44 +0000 (GMT) Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B2CD611C04A; Wed, 27 May 2020 03:03:42 +0000 (GMT) Received: from fir03.in.ibm.com (unknown [9.121.59.65]) by d06av25.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 27 May 2020 03:03:42 +0000 (GMT) From: Sandipan Das To: mpe@ellerman.id.au Cc: linux-kselftest@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, linuxram@us.ibm.com, aneesh.kumar@linux.ibm.com, bauerman@linux.ibm.com, fweimer@redhat.com, ruscur@russell.cc Subject: [PATCH v2] selftests: powerpc: Add test for execute-disabled pkeys Date: Wed, 27 May 2020 08:33:42 +0530 Message-Id: <20200527030342.13712-1-sandipan@linux.ibm.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.216, 18.0.687 definitions=2020-05-26_04:2020-05-26,2020-05-26 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 cotscore=-2147483648 malwarescore=0 priorityscore=1501 clxscore=1015 impostorscore=0 mlxlogscore=999 spamscore=0 adultscore=0 mlxscore=0 phishscore=0 bulkscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2005270021 Sender: linux-kselftest-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org Apart from read and write access, memory protection keys can also be used for restricting execute permission of pages on powerpc. This adds a test to verify if the feature works as expected. Signed-off-by: Sandipan Das --- Previous versions can be found at v1: https://lore.kernel.org/linuxppc-dev/20200508162332.65316-1-sandipan@linux.ibm.com/ Changes in v2: - Added .gitignore entry for test binary. - Fixed builds for older distros where siginfo_t might not have si_pkey as a formal member based on discussion with Michael. --- tools/testing/selftests/powerpc/mm/.gitignore | 1 + tools/testing/selftests/powerpc/mm/Makefile | 3 +- .../selftests/powerpc/mm/pkey_exec_prot.c | 336 ++++++++++++++++++ 3 files changed, 339 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/powerpc/mm/pkey_exec_prot.c diff --git a/tools/testing/selftests/powerpc/mm/.gitignore b/tools/testing/selftests/powerpc/mm/.gitignore index 2ca523255b1b..8f841f925baa 100644 --- a/tools/testing/selftests/powerpc/mm/.gitignore +++ b/tools/testing/selftests/powerpc/mm/.gitignore @@ -8,3 +8,4 @@ wild_bctr large_vm_fork_separation bad_accesses tlbie_test +pkey_exec_prot diff --git a/tools/testing/selftests/powerpc/mm/Makefile b/tools/testing/selftests/powerpc/mm/Makefile index b9103c4bb414..2816229f648b 100644 --- a/tools/testing/selftests/powerpc/mm/Makefile +++ b/tools/testing/selftests/powerpc/mm/Makefile @@ -3,7 +3,7 @@ noarg: $(MAKE) -C ../ TEST_GEN_PROGS := hugetlb_vs_thp_test subpage_prot prot_sao segv_errors wild_bctr \ - large_vm_fork_separation bad_accesses + large_vm_fork_separation bad_accesses pkey_exec_prot TEST_GEN_PROGS_EXTENDED := tlbie_test TEST_GEN_FILES := tempfile @@ -17,6 +17,7 @@ $(OUTPUT)/prot_sao: ../utils.c $(OUTPUT)/wild_bctr: CFLAGS += -m64 $(OUTPUT)/large_vm_fork_separation: CFLAGS += -m64 $(OUTPUT)/bad_accesses: CFLAGS += -m64 +$(OUTPUT)/pkey_exec_prot: CFLAGS += -m64 $(OUTPUT)/tempfile: dd if=/dev/zero of=$@ bs=64k count=1 diff --git a/tools/testing/selftests/powerpc/mm/pkey_exec_prot.c b/tools/testing/selftests/powerpc/mm/pkey_exec_prot.c new file mode 100644 index 000000000000..147fb9ed47d5 --- /dev/null +++ b/tools/testing/selftests/powerpc/mm/pkey_exec_prot.c @@ -0,0 +1,336 @@ +// SPDX-License-Identifier: GPL-2.0+ + +/* + * Copyright 2020, Sandipan Das, IBM Corp. + * + * Test if applying execute protection on pages using memory + * protection keys works as expected. + */ + +#define _GNU_SOURCE +#include +#include +#include +#include + +#include +#include +#include + +#include "utils.h" + +/* Override definitions as they might be inconsistent */ +#undef PKEY_DISABLE_ACCESS +#define PKEY_DISABLE_ACCESS 0x3 + +#undef PKEY_DISABLE_WRITE +#define PKEY_DISABLE_WRITE 0x2 + +#undef PKEY_DISABLE_EXECUTE +#define PKEY_DISABLE_EXECUTE 0x4 + +/* Older distros might not define this */ +#ifndef SEGV_PKUERR +#define SEGV_PKUERR 4 +#endif + +#define SI_PKEY_OFFSET 0x20 + +#define SYS_pkey_mprotect 386 +#define SYS_pkey_alloc 384 +#define SYS_pkey_free 385 + +#define PKEY_BITS_PER_PKEY 2 +#define NR_PKEYS 32 + +#define PKEY_BITS_MASK ((1UL << PKEY_BITS_PER_PKEY) - 1) + +static unsigned long pkeyreg_get(void) +{ + unsigned long uamr; + + asm volatile("mfspr %0, 0xd" : "=r"(uamr)); + return uamr; +} + +static void pkeyreg_set(unsigned long uamr) +{ + asm volatile("isync; mtspr 0xd, %0; isync;" : : "r"(uamr)); +} + +static void pkey_set_rights(int pkey, unsigned long rights) +{ + unsigned long uamr, shift; + + shift = (NR_PKEYS - pkey - 1) * PKEY_BITS_PER_PKEY; + uamr = pkeyreg_get(); + uamr &= ~(PKEY_BITS_MASK << shift); + uamr |= (rights & PKEY_BITS_MASK) << shift; + pkeyreg_set(uamr); +} + +static int sys_pkey_mprotect(void *addr, size_t len, int prot, int pkey) +{ + return syscall(SYS_pkey_mprotect, addr, len, prot, pkey); +} + +static int sys_pkey_alloc(unsigned long flags, unsigned long rights) +{ + return syscall(SYS_pkey_alloc, flags, rights); +} + +static int sys_pkey_free(int pkey) +{ + return syscall(SYS_pkey_free, pkey); +} + +static volatile int fpkey, fcode, ftype, faults; +static unsigned long pgsize, numinsns; +static volatile unsigned int *faddr; +static unsigned int *insns; + +static void segv_handler(int signum, siginfo_t *sinfo, void *ctx) +{ + int pkey; + +#ifdef si_pkey + pkey = sinfo->si_pkey; +#else + pkey = *((int *)(((char *) sinfo) + SI_PKEY_OFFSET)); +#endif + + /* Check if this fault originated because of the expected reasons */ + if (sinfo->si_code != SEGV_ACCERR && sinfo->si_code != SEGV_PKUERR) { + printf("got an unexpected fault, code = %d\n", + sinfo->si_code); + goto fail; + } + + /* Check if this fault originated from the expected address */ + if (sinfo->si_addr != (void *) faddr) { + printf("got an unexpected fault, addr = %p\n", + sinfo->si_addr); + goto fail; + } + + /* Check if the expected number of faults has been exceeded */ + if (faults == 0) + goto fail; + + fcode = sinfo->si_code; + + /* Restore permissions in order to continue */ + switch (fcode) { + case SEGV_ACCERR: + if (mprotect(insns, pgsize, PROT_READ | PROT_WRITE)) { + perror("mprotect"); + goto fail; + } + break; + case SEGV_PKUERR: + if (pkey != fpkey) + goto fail; + + if (ftype == PKEY_DISABLE_ACCESS) { + pkey_set_rights(fpkey, 0); + } else if (ftype == PKEY_DISABLE_EXECUTE) { + /* + * Reassociate the exec-only pkey with the region + * to be able to continue. Unlike AMR, we cannot + * set IAMR directly from userspace to restore the + * permissions. + */ + if (mprotect(insns, pgsize, PROT_EXEC)) { + perror("mprotect"); + goto fail; + } + } else { + goto fail; + } + break; + } + + faults--; + return; + +fail: + /* Restore all page permissions to avoid repetitive faults */ + if (mprotect(insns, pgsize, PROT_READ | PROT_WRITE | PROT_EXEC)) + perror("mprotect"); + if (sinfo->si_code == SEGV_PKUERR) + pkey_set_rights(pkey, 0); + faults = -1; /* Something unexpected happened */ +} + +static int pkeys_unsupported(void) +{ + bool using_hash = false; + char line[128]; + int pkey; + FILE *f; + + f = fopen("/proc/cpuinfo", "r"); + FAIL_IF(!f); + + /* Protection keys are currently supported on Hash MMU only */ + while (fgets(line, sizeof(line), f)) { + if (strcmp(line, "MMU : Hash\n") == 0) { + using_hash = true; + break; + } + } + + fclose(f); + SKIP_IF(!using_hash); + + /* Check if the system call is supported */ + pkey = sys_pkey_alloc(0, 0); + SKIP_IF(pkey < 0); + sys_pkey_free(pkey); + + return 0; +} + +static int test(void) +{ + struct sigaction act; + int pkey, ret, i; + + ret = pkeys_unsupported(); + if (ret) + return ret; + + /* Setup signal 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); + + /* Setup executable region */ + pgsize = sysconf(_SC_PAGESIZE); + numinsns = pgsize / sizeof(unsigned int); + insns = (unsigned int *) mmap(NULL, pgsize, PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); + FAIL_IF(insns == MAP_FAILED); + + /* Write the instruction words */ + for (i = 0; i < numinsns - 1; i++) + insns[i] = 0x60000000; /* nop */ + + /* + * Later, to jump to the executable region, we use a linked + * branch which sets the return address automatically in LR. + * Use that to return back. + */ + insns[numinsns - 1] = 0x4e800020; /* blr */ + + /* Allocate a pkey that restricts execution */ + pkey = sys_pkey_alloc(0, PKEY_DISABLE_EXECUTE); + FAIL_IF(pkey < 0); + + /* + * Pick a random instruction address from the executable + * region. + */ + srand(time(NULL)); + faddr = &insns[rand() % (numinsns - 1)]; + + /* The following two cases will avoid SEGV_PKUERR */ + ftype = -1; + fpkey = -1; + + /* + * Read an instruction word from the address when AMR bits + * are not set. + * + * This should not generate a fault as having PROT_EXEC + * implicitly allows reads. The pkey currently restricts + * execution only based on the IAMR bits. The AMR bits are + * cleared. + */ + faults = 0; + FAIL_IF(sys_pkey_mprotect(insns, pgsize, PROT_EXEC, pkey) != 0); + printf("read from %p, pkey is execute-disabled\n", (void *) faddr); + i = *faddr; + FAIL_IF(faults != 0); + + /* + * Write an instruction word to the address when AMR bits + * are not set. + * + * This should generate an access fault as having just + * PROT_EXEC also restricts writes. The pkey currently + * restricts execution only based on the IAMR bits. The + * AMR bits are cleared. + */ + faults = 1; + FAIL_IF(sys_pkey_mprotect(insns, pgsize, PROT_EXEC, pkey) != 0); + printf("write to %p, pkey is execute-disabled\n", (void *) faddr); + *faddr = 0x60000000; /* nop */ + FAIL_IF(faults != 0 || fcode != SEGV_ACCERR); + + /* The following three cases will generate SEGV_PKUERR */ + ftype = PKEY_DISABLE_ACCESS; + fpkey = pkey; + + /* + * Read an instruction word from the address when AMR bits + * are set. + * + * This should generate a pkey fault based on AMR bits only + * as having PROT_EXEC implicitly allows reads. + */ + faults = 1; + FAIL_IF(sys_pkey_mprotect(insns, pgsize, PROT_EXEC, pkey) != 0); + printf("read from %p, pkey is execute-disabled, access-disabled\n", + (void *) faddr); + pkey_set_rights(pkey, PKEY_DISABLE_ACCESS); + i = *faddr; + FAIL_IF(faults != 0 || fcode != SEGV_PKUERR); + + /* + * Write an instruction word to the address when AMR bits + * are set. + * + * This should generate two faults. First, a pkey fault based + * on AMR bits and then an access fault based on PROT_EXEC. + */ + faults = 2; + FAIL_IF(sys_pkey_mprotect(insns, pgsize, PROT_EXEC, pkey) != 0); + printf("write to %p, pkey is execute-disabled, access-disabled\n", + (void *) faddr); + pkey_set_rights(pkey, PKEY_DISABLE_ACCESS); + *faddr = 0x60000000; /* nop */ + FAIL_IF(faults != 0 || fcode != SEGV_ACCERR); + + /* + * Jump to the executable region. This should generate a pkey + * fault based on IAMR bits. AMR bits will not affect execution. + */ + faddr = insns; + ftype = PKEY_DISABLE_EXECUTE; + fpkey = pkey; + faults = 1; + FAIL_IF(sys_pkey_mprotect(insns, pgsize, PROT_EXEC, pkey) != 0); + pkey_set_rights(pkey, PKEY_DISABLE_ACCESS); + printf("execute at %p, ", (void *) faddr); + printf("pkey is execute-disabled, access-disabled\n"); + + /* Branch into the executable region */ + asm volatile("mtctr %0" : : "r"((unsigned long) insns)); + asm volatile("bctrl"); + FAIL_IF(faults != 0 || fcode != SEGV_PKUERR); + + /* Cleanup */ + munmap((void *) insns, pgsize); + sys_pkey_free(pkey); + + return 0; +} + +int main(void) +{ + test_harness(test, "pkey_exec_prot"); +}