sysregs.c (5806B)
1 /* 2 * Check emulated system register access for linux-user mode. 3 * 4 * See: https://www.kernel.org/doc/Documentation/arm64/cpu-feature-registers.txt 5 * 6 * Copyright (c) 2019 Linaro 7 * 8 * This work is licensed under the terms of the GNU GPL, version 2 or later. 9 * See the COPYING file in the top-level directory. 10 * 11 * SPDX-License-Identifier: GPL-2.0-or-later 12 */ 13 14 #include <asm/hwcap.h> 15 #include <stdio.h> 16 #include <sys/auxv.h> 17 #include <signal.h> 18 #include <string.h> 19 #include <stdbool.h> 20 21 #ifndef HWCAP_CPUID 22 #define HWCAP_CPUID (1 << 11) 23 #endif 24 25 int failed_bit_count; 26 27 /* Read and print system register `id' value */ 28 #define get_cpu_reg(id) ({ \ 29 unsigned long __val = 0xdeadbeef; \ 30 asm("mrs %0, "#id : "=r" (__val)); \ 31 printf("%-20s: 0x%016lx\n", #id, __val); \ 32 __val; \ 33 }) 34 35 /* As above but also check no bits outside of `mask' are set*/ 36 #define get_cpu_reg_check_mask(id, mask) ({ \ 37 unsigned long __cval = get_cpu_reg(id); \ 38 unsigned long __extra = __cval & ~mask; \ 39 if (__extra) { \ 40 printf("%-20s: 0x%016lx\n", " !!extra bits!!", __extra); \ 41 failed_bit_count++; \ 42 } \ 43 }) 44 45 /* As above but check RAZ */ 46 #define get_cpu_reg_check_zero(id) ({ \ 47 unsigned long __val = 0xdeadbeef; \ 48 asm("mrs %0, "#id : "=r" (__val)); \ 49 if (__val) { \ 50 printf("%-20s: 0x%016lx (not RAZ!)\n", #id, __val); \ 51 failed_bit_count++; \ 52 } \ 53 }) 54 55 /* Chunk up mask into 63:48, 47:32, 31:16, 15:0 to ease counting */ 56 #define _m(a, b, c, d) (0x ## a ## b ## c ## d ##ULL) 57 58 bool should_fail; 59 int should_fail_count; 60 int should_not_fail_count; 61 uintptr_t failed_pc[10]; 62 63 void sigill_handler(int signo, siginfo_t *si, void *data) 64 { 65 ucontext_t *uc = (ucontext_t *)data; 66 67 if (should_fail) { 68 should_fail_count++; 69 } else { 70 uintptr_t pc = (uintptr_t) uc->uc_mcontext.pc; 71 failed_pc[should_not_fail_count++] = pc; 72 } 73 uc->uc_mcontext.pc += 4; 74 } 75 76 int main(void) 77 { 78 struct sigaction sa; 79 80 /* Hook in a SIGILL handler */ 81 memset(&sa, 0, sizeof(struct sigaction)); 82 sa.sa_flags = SA_SIGINFO; 83 sa.sa_sigaction = &sigill_handler; 84 sigemptyset(&sa.sa_mask); 85 86 if (sigaction(SIGILL, &sa, 0) != 0) { 87 perror("sigaction"); 88 return 1; 89 } 90 91 /* Counter values have been exposed since Linux 4.12 */ 92 printf("Checking Counter registers\n"); 93 94 get_cpu_reg(ctr_el0); 95 get_cpu_reg(cntvct_el0); 96 get_cpu_reg(cntfrq_el0); 97 98 /* HWCAP_CPUID indicates we can read feature registers, since Linux 4.11 */ 99 if (!(getauxval(AT_HWCAP) & HWCAP_CPUID)) { 100 printf("CPUID registers unavailable\n"); 101 return 1; 102 } else { 103 printf("Checking CPUID registers\n"); 104 } 105 106 /* 107 * Some registers only expose some bits to user-space. Anything 108 * that is IMPDEF is exported as 0 to user-space. The _mask checks 109 * assert no extra bits are set. 110 * 111 * This check is *not* comprehensive as some fields are set to 112 * minimum valid fields - for the purposes of this check allowed 113 * to have non-zero values. 114 */ 115 get_cpu_reg_check_mask(id_aa64isar0_el1, _m(00ff,ffff,f0ff,fff0)); 116 get_cpu_reg_check_mask(id_aa64isar1_el1, _m(0000,00f0,ffff,ffff)); 117 /* TGran4 & TGran64 as pegged to -1 */ 118 get_cpu_reg_check_mask(id_aa64mmfr0_el1, _m(0000,0000,ff00,0000)); 119 get_cpu_reg_check_zero(id_aa64mmfr1_el1); 120 /* EL1/EL0 reported as AA64 only */ 121 get_cpu_reg_check_mask(id_aa64pfr0_el1, _m(000f,000f,00ff,0011)); 122 get_cpu_reg_check_mask(id_aa64pfr1_el1, _m(0000,0000,0000,00f0)); 123 /* all hidden, DebugVer fixed to 0x6 (ARMv8 debug architecture) */ 124 get_cpu_reg_check_mask(id_aa64dfr0_el1, _m(0000,0000,0000,0006)); 125 get_cpu_reg_check_zero(id_aa64dfr1_el1); 126 get_cpu_reg_check_zero(id_aa64zfr0_el1); 127 128 get_cpu_reg_check_zero(id_aa64afr0_el1); 129 get_cpu_reg_check_zero(id_aa64afr1_el1); 130 131 get_cpu_reg_check_mask(midr_el1, _m(0000,0000,ffff,ffff)); 132 /* mpidr sets bit 31, everything else hidden */ 133 get_cpu_reg_check_mask(mpidr_el1, _m(0000,0000,8000,0000)); 134 /* REVIDR is all IMPDEF so should be all zeros to user-space */ 135 get_cpu_reg_check_zero(revidr_el1); 136 137 /* 138 * There are a block of more registers that are RAZ in the rest of 139 * the Op0=3, Op1=0, CRn=0, CRm=0,4,5,6,7 space. However for 140 * brevity we don't check stuff that is currently un-allocated 141 * here. Feel free to add them ;-) 142 */ 143 144 printf("Remaining registers should fail\n"); 145 should_fail = true; 146 147 /* Unexposed register access causes SIGILL */ 148 get_cpu_reg(id_mmfr0_el1); 149 get_cpu_reg(id_mmfr1_el1); 150 get_cpu_reg(id_mmfr2_el1); 151 get_cpu_reg(id_mmfr3_el1); 152 153 get_cpu_reg(mvfr0_el1); 154 get_cpu_reg(mvfr1_el1); 155 156 if (should_not_fail_count > 0) { 157 int i; 158 for (i = 0; i < should_not_fail_count; i++) { 159 uintptr_t pc = failed_pc[i]; 160 uint32_t insn = *(uint32_t *) pc; 161 printf("insn %#x @ %#lx unexpected FAIL\n", insn, pc); 162 } 163 return 1; 164 } 165 166 if (failed_bit_count > 0) { 167 printf("Extra information leaked to user-space!\n"); 168 return 1; 169 } 170 171 return should_fail_count == 6 ? 0 : 1; 172 }