232 lines · c
1// SPDX-License-Identifier: GPL-2.02 3/*4 * Copyright 2022, Nicholas Miehlbradt, IBM Corporation5 * based on pkey_exec_prot.c6 *7 * Test if applying execute protection on pages works as expected.8 */9 10#define _GNU_SOURCE11#include <stdio.h>12#include <stdlib.h>13#include <string.h>14#include <signal.h>15 16#include <unistd.h>17#include <sys/mman.h>18 19#include "pkeys.h"20 21 22#define PPC_INST_NOP 0x6000000023#define PPC_INST_TRAP 0x7fe0000824#define PPC_INST_BLR 0x4e80002025 26static volatile sig_atomic_t fault_code;27static volatile sig_atomic_t remaining_faults;28static volatile unsigned int *fault_addr;29static unsigned long pgsize, numinsns;30static unsigned int *insns;31static bool pkeys_supported;32 33static bool is_fault_expected(int fault_code)34{35 if (fault_code == SEGV_ACCERR)36 return true;37 38 /* Assume any pkey error is fine since pkey_exec_prot test covers them */39 if (fault_code == SEGV_PKUERR && pkeys_supported)40 return true;41 42 return false;43}44 45static void trap_handler(int signum, siginfo_t *sinfo, void *ctx)46{47 /* Check if this fault originated from the expected address */48 if (sinfo->si_addr != (void *)fault_addr)49 sigsafe_err("got a fault for an unexpected address\n");50 51 _exit(1);52}53 54static void segv_handler(int signum, siginfo_t *sinfo, void *ctx)55{56 fault_code = sinfo->si_code;57 58 /* Check if this fault originated from the expected address */59 if (sinfo->si_addr != (void *)fault_addr) {60 sigsafe_err("got a fault for an unexpected address\n");61 _exit(1);62 }63 64 /* Check if too many faults have occurred for a single test case */65 if (!remaining_faults) {66 sigsafe_err("got too many faults for the same address\n");67 _exit(1);68 }69 70 71 /* Restore permissions in order to continue */72 if (is_fault_expected(fault_code)) {73 if (mprotect(insns, pgsize, PROT_READ | PROT_WRITE | PROT_EXEC)) {74 sigsafe_err("failed to set access permissions\n");75 _exit(1);76 }77 } else {78 sigsafe_err("got a fault with an unexpected code\n");79 _exit(1);80 }81 82 remaining_faults--;83}84 85static int check_exec_fault(int rights)86{87 /*88 * Jump to the executable region.89 *90 * The first iteration also checks if the overwrite of the91 * first instruction word from a trap to a no-op succeeded.92 */93 fault_code = -1;94 remaining_faults = 0;95 if (!(rights & PROT_EXEC))96 remaining_faults = 1;97 98 FAIL_IF(mprotect(insns, pgsize, rights) != 0);99 asm volatile("mtctr %0; bctrl" : : "r"(insns));100 101 FAIL_IF(remaining_faults != 0);102 if (!(rights & PROT_EXEC))103 FAIL_IF(!is_fault_expected(fault_code));104 105 return 0;106}107 108static int test(void)109{110 struct sigaction segv_act, trap_act;111 int i;112 113 /* Skip the test if the CPU doesn't support Radix */114 SKIP_IF(!have_hwcap2(PPC_FEATURE2_ARCH_3_00));115 116 /* Check if pkeys are supported */117 pkeys_supported = pkeys_unsupported() == 0;118 119 /* Setup SIGSEGV handler */120 segv_act.sa_handler = 0;121 segv_act.sa_sigaction = segv_handler;122 FAIL_IF(sigprocmask(SIG_SETMASK, 0, &segv_act.sa_mask) != 0);123 segv_act.sa_flags = SA_SIGINFO;124 segv_act.sa_restorer = 0;125 FAIL_IF(sigaction(SIGSEGV, &segv_act, NULL) != 0);126 127 /* Setup SIGTRAP handler */128 trap_act.sa_handler = 0;129 trap_act.sa_sigaction = trap_handler;130 FAIL_IF(sigprocmask(SIG_SETMASK, 0, &trap_act.sa_mask) != 0);131 trap_act.sa_flags = SA_SIGINFO;132 trap_act.sa_restorer = 0;133 FAIL_IF(sigaction(SIGTRAP, &trap_act, NULL) != 0);134 135 /* Setup executable region */136 pgsize = getpagesize();137 numinsns = pgsize / sizeof(unsigned int);138 insns = (unsigned int *)mmap(NULL, pgsize, PROT_READ | PROT_WRITE,139 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);140 FAIL_IF(insns == MAP_FAILED);141 142 /* Write the instruction words */143 for (i = 1; i < numinsns - 1; i++)144 insns[i] = PPC_INST_NOP;145 146 /*147 * Set the first instruction as an unconditional trap. If148 * the last write to this address succeeds, this should149 * get overwritten by a no-op.150 */151 insns[0] = PPC_INST_TRAP;152 153 /*154 * Later, to jump to the executable region, we use a branch155 * and link instruction (bctrl) which sets the return address156 * automatically in LR. Use that to return back.157 */158 insns[numinsns - 1] = PPC_INST_BLR;159 160 /*161 * Pick the first instruction's address from the executable162 * region.163 */164 fault_addr = insns;165 166 /*167 * Read an instruction word from the address when the page168 * is execute only. This should generate an access fault.169 */170 fault_code = -1;171 remaining_faults = 1;172 printf("Testing read on --x, should fault...");173 FAIL_IF(mprotect(insns, pgsize, PROT_EXEC) != 0);174 i = *fault_addr;175 FAIL_IF(remaining_faults != 0 || !is_fault_expected(fault_code));176 printf("ok!\n");177 178 /*179 * Write an instruction word to the address when the page180 * execute only. This should also generate an access fault.181 */182 fault_code = -1;183 remaining_faults = 1;184 printf("Testing write on --x, should fault...");185 FAIL_IF(mprotect(insns, pgsize, PROT_EXEC) != 0);186 *fault_addr = PPC_INST_NOP;187 FAIL_IF(remaining_faults != 0 || !is_fault_expected(fault_code));188 printf("ok!\n");189 190 printf("Testing exec on ---, should fault...");191 FAIL_IF(check_exec_fault(PROT_NONE));192 printf("ok!\n");193 194 printf("Testing exec on r--, should fault...");195 FAIL_IF(check_exec_fault(PROT_READ));196 printf("ok!\n");197 198 printf("Testing exec on -w-, should fault...");199 FAIL_IF(check_exec_fault(PROT_WRITE));200 printf("ok!\n");201 202 printf("Testing exec on rw-, should fault...");203 FAIL_IF(check_exec_fault(PROT_READ | PROT_WRITE));204 printf("ok!\n");205 206 printf("Testing exec on --x, should succeed...");207 FAIL_IF(check_exec_fault(PROT_EXEC));208 printf("ok!\n");209 210 printf("Testing exec on r-x, should succeed...");211 FAIL_IF(check_exec_fault(PROT_READ | PROT_EXEC));212 printf("ok!\n");213 214 printf("Testing exec on -wx, should succeed...");215 FAIL_IF(check_exec_fault(PROT_WRITE | PROT_EXEC));216 printf("ok!\n");217 218 printf("Testing exec on rwx, should succeed...");219 FAIL_IF(check_exec_fault(PROT_READ | PROT_WRITE | PROT_EXEC));220 printf("ok!\n");221 222 /* Cleanup */223 FAIL_IF(munmap((void *)insns, pgsize));224 225 return 0;226}227 228int main(void)229{230 return test_harness(test, "exec_prot");231}232