1f19fbd5eSMartin Schwidefsky // SPDX-License-Identifier: GPL-2.0 2f19fbd5eSMartin Schwidefsky #include <linux/module.h> 3*d424986fSMartin Schwidefsky #include <linux/device.h> 4f19fbd5eSMartin Schwidefsky #include <asm/nospec-branch.h> 5f19fbd5eSMartin Schwidefsky 6b2e2f43aSMartin Schwidefsky static int __init nobp_setup_early(char *str) 7b2e2f43aSMartin Schwidefsky { 8b2e2f43aSMartin Schwidefsky bool enabled; 9b2e2f43aSMartin Schwidefsky int rc; 10b2e2f43aSMartin Schwidefsky 11b2e2f43aSMartin Schwidefsky rc = kstrtobool(str, &enabled); 12b2e2f43aSMartin Schwidefsky if (rc) 13b2e2f43aSMartin Schwidefsky return rc; 146e179d64SMartin Schwidefsky if (enabled && test_facility(82)) { 156e179d64SMartin Schwidefsky /* 166e179d64SMartin Schwidefsky * The user explicitely requested nobp=1, enable it and 176e179d64SMartin Schwidefsky * disable the expoline support. 186e179d64SMartin Schwidefsky */ 19b2e2f43aSMartin Schwidefsky __set_facility(82, S390_lowcore.alt_stfle_fac_list); 206e179d64SMartin Schwidefsky if (IS_ENABLED(CONFIG_EXPOLINE)) 216e179d64SMartin Schwidefsky nospec_disable = 1; 226e179d64SMartin Schwidefsky } else { 23b2e2f43aSMartin Schwidefsky __clear_facility(82, S390_lowcore.alt_stfle_fac_list); 246e179d64SMartin Schwidefsky } 25b2e2f43aSMartin Schwidefsky return 0; 26b2e2f43aSMartin Schwidefsky } 27b2e2f43aSMartin Schwidefsky early_param("nobp", nobp_setup_early); 28b2e2f43aSMartin Schwidefsky 29b2e2f43aSMartin Schwidefsky static int __init nospec_setup_early(char *str) 30b2e2f43aSMartin Schwidefsky { 31b2e2f43aSMartin Schwidefsky __clear_facility(82, S390_lowcore.alt_stfle_fac_list); 32b2e2f43aSMartin Schwidefsky return 0; 33b2e2f43aSMartin Schwidefsky } 34b2e2f43aSMartin Schwidefsky early_param("nospec", nospec_setup_early); 35b2e2f43aSMartin Schwidefsky 36bc035599SMartin Schwidefsky static int __init nospec_report(void) 37bc035599SMartin Schwidefsky { 38bc035599SMartin Schwidefsky if (IS_ENABLED(CC_USING_EXPOLINE) && !nospec_disable) 39bc035599SMartin Schwidefsky pr_info("Spectre V2 mitigation: execute trampolines.\n"); 40bc035599SMartin Schwidefsky if (__test_facility(82, S390_lowcore.alt_stfle_fac_list)) 41bc035599SMartin Schwidefsky pr_info("Spectre V2 mitigation: limited branch prediction.\n"); 42bc035599SMartin Schwidefsky return 0; 43bc035599SMartin Schwidefsky } 44bc035599SMartin Schwidefsky arch_initcall(nospec_report); 45bc035599SMartin Schwidefsky 46*d424986fSMartin Schwidefsky #ifdef CONFIG_SYSFS 47*d424986fSMartin Schwidefsky ssize_t cpu_show_spectre_v1(struct device *dev, 48*d424986fSMartin Schwidefsky struct device_attribute *attr, char *buf) 49*d424986fSMartin Schwidefsky { 50*d424986fSMartin Schwidefsky return sprintf(buf, "Mitigation: __user pointer sanitization\n"); 51*d424986fSMartin Schwidefsky } 52*d424986fSMartin Schwidefsky 53*d424986fSMartin Schwidefsky ssize_t cpu_show_spectre_v2(struct device *dev, 54*d424986fSMartin Schwidefsky struct device_attribute *attr, char *buf) 55*d424986fSMartin Schwidefsky { 56*d424986fSMartin Schwidefsky if (IS_ENABLED(CC_USING_EXPOLINE) && !nospec_disable) 57*d424986fSMartin Schwidefsky return sprintf(buf, "Mitigation: execute trampolines\n"); 58*d424986fSMartin Schwidefsky if (__test_facility(82, S390_lowcore.alt_stfle_fac_list)) 59*d424986fSMartin Schwidefsky return sprintf(buf, "Mitigation: limited branch prediction.\n"); 60*d424986fSMartin Schwidefsky return sprintf(buf, "Vulnerable\n"); 61*d424986fSMartin Schwidefsky } 62*d424986fSMartin Schwidefsky #endif 63*d424986fSMartin Schwidefsky 64b2e2f43aSMartin Schwidefsky #ifdef CONFIG_EXPOLINE 65b2e2f43aSMartin Schwidefsky 666e179d64SMartin Schwidefsky int nospec_disable = IS_ENABLED(CONFIG_EXPOLINE_OFF); 67f19fbd5eSMartin Schwidefsky 68f19fbd5eSMartin Schwidefsky static int __init nospectre_v2_setup_early(char *str) 69f19fbd5eSMartin Schwidefsky { 706e179d64SMartin Schwidefsky nospec_disable = 1; 71f19fbd5eSMartin Schwidefsky return 0; 72f19fbd5eSMartin Schwidefsky } 73f19fbd5eSMartin Schwidefsky early_param("nospectre_v2", nospectre_v2_setup_early); 74f19fbd5eSMartin Schwidefsky 756e179d64SMartin Schwidefsky static int __init spectre_v2_auto_early(void) 766e179d64SMartin Schwidefsky { 776e179d64SMartin Schwidefsky if (IS_ENABLED(CC_USING_EXPOLINE)) { 786e179d64SMartin Schwidefsky /* 796e179d64SMartin Schwidefsky * The kernel has been compiled with expolines. 806e179d64SMartin Schwidefsky * Keep expolines enabled and disable nobp. 816e179d64SMartin Schwidefsky */ 826e179d64SMartin Schwidefsky nospec_disable = 0; 836e179d64SMartin Schwidefsky __clear_facility(82, S390_lowcore.alt_stfle_fac_list); 846e179d64SMartin Schwidefsky } 856e179d64SMartin Schwidefsky /* 866e179d64SMartin Schwidefsky * If the kernel has not been compiled with expolines the 876e179d64SMartin Schwidefsky * nobp setting decides what is done, this depends on the 886e179d64SMartin Schwidefsky * CONFIG_KERNEL_NP option and the nobp/nospec parameters. 896e179d64SMartin Schwidefsky */ 906e179d64SMartin Schwidefsky return 0; 916e179d64SMartin Schwidefsky } 926e179d64SMartin Schwidefsky #ifdef CONFIG_EXPOLINE_AUTO 936e179d64SMartin Schwidefsky early_initcall(spectre_v2_auto_early); 946e179d64SMartin Schwidefsky #endif 956e179d64SMartin Schwidefsky 96f19fbd5eSMartin Schwidefsky static int __init spectre_v2_setup_early(char *str) 97f19fbd5eSMartin Schwidefsky { 98f19fbd5eSMartin Schwidefsky if (str && !strncmp(str, "on", 2)) { 996e179d64SMartin Schwidefsky nospec_disable = 0; 1006e179d64SMartin Schwidefsky __clear_facility(82, S390_lowcore.alt_stfle_fac_list); 101f19fbd5eSMartin Schwidefsky } 1026e179d64SMartin Schwidefsky if (str && !strncmp(str, "off", 3)) 1036e179d64SMartin Schwidefsky nospec_disable = 1; 1046e179d64SMartin Schwidefsky if (str && !strncmp(str, "auto", 4)) 1056e179d64SMartin Schwidefsky spectre_v2_auto_early(); 106f19fbd5eSMartin Schwidefsky return 0; 107f19fbd5eSMartin Schwidefsky } 108f19fbd5eSMartin Schwidefsky early_param("spectre_v2", spectre_v2_setup_early); 109f19fbd5eSMartin Schwidefsky 110f19fbd5eSMartin Schwidefsky static void __init_or_module __nospec_revert(s32 *start, s32 *end) 111f19fbd5eSMartin Schwidefsky { 112f19fbd5eSMartin Schwidefsky enum { BRCL_EXPOLINE, BRASL_EXPOLINE } type; 113f19fbd5eSMartin Schwidefsky u8 *instr, *thunk, *br; 114f19fbd5eSMartin Schwidefsky u8 insnbuf[6]; 115f19fbd5eSMartin Schwidefsky s32 *epo; 116f19fbd5eSMartin Schwidefsky 117f19fbd5eSMartin Schwidefsky /* Second part of the instruction replace is always a nop */ 118f19fbd5eSMartin Schwidefsky memcpy(insnbuf + 2, (char[]) { 0x47, 0x00, 0x00, 0x00 }, 4); 119f19fbd5eSMartin Schwidefsky for (epo = start; epo < end; epo++) { 120f19fbd5eSMartin Schwidefsky instr = (u8 *) epo + *epo; 121f19fbd5eSMartin Schwidefsky if (instr[0] == 0xc0 && (instr[1] & 0x0f) == 0x04) 122f19fbd5eSMartin Schwidefsky type = BRCL_EXPOLINE; /* brcl instruction */ 123f19fbd5eSMartin Schwidefsky else if (instr[0] == 0xc0 && (instr[1] & 0x0f) == 0x05) 124f19fbd5eSMartin Schwidefsky type = BRASL_EXPOLINE; /* brasl instruction */ 125f19fbd5eSMartin Schwidefsky else 126f19fbd5eSMartin Schwidefsky continue; 127f19fbd5eSMartin Schwidefsky thunk = instr + (*(int *)(instr + 2)) * 2; 128f19fbd5eSMartin Schwidefsky if (thunk[0] == 0xc6 && thunk[1] == 0x00) 129f19fbd5eSMartin Schwidefsky /* exrl %r0,<target-br> */ 130f19fbd5eSMartin Schwidefsky br = thunk + (*(int *)(thunk + 2)) * 2; 131f19fbd5eSMartin Schwidefsky else if (thunk[0] == 0xc0 && (thunk[1] & 0x0f) == 0x00 && 132f19fbd5eSMartin Schwidefsky thunk[6] == 0x44 && thunk[7] == 0x00 && 133f19fbd5eSMartin Schwidefsky (thunk[8] & 0x0f) == 0x00 && thunk[9] == 0x00 && 134f19fbd5eSMartin Schwidefsky (thunk[1] & 0xf0) == (thunk[8] & 0xf0)) 135f19fbd5eSMartin Schwidefsky /* larl %rx,<target br> + ex %r0,0(%rx) */ 136f19fbd5eSMartin Schwidefsky br = thunk + (*(int *)(thunk + 2)) * 2; 137f19fbd5eSMartin Schwidefsky else 138f19fbd5eSMartin Schwidefsky continue; 139f19fbd5eSMartin Schwidefsky if (br[0] != 0x07 || (br[1] & 0xf0) != 0xf0) 140f19fbd5eSMartin Schwidefsky continue; 141f19fbd5eSMartin Schwidefsky switch (type) { 142f19fbd5eSMartin Schwidefsky case BRCL_EXPOLINE: 143f19fbd5eSMartin Schwidefsky /* brcl to thunk, replace with br + nop */ 144f19fbd5eSMartin Schwidefsky insnbuf[0] = br[0]; 145f19fbd5eSMartin Schwidefsky insnbuf[1] = (instr[1] & 0xf0) | (br[1] & 0x0f); 146f19fbd5eSMartin Schwidefsky break; 147f19fbd5eSMartin Schwidefsky case BRASL_EXPOLINE: 148f19fbd5eSMartin Schwidefsky /* brasl to thunk, replace with basr + nop */ 149f19fbd5eSMartin Schwidefsky insnbuf[0] = 0x0d; 150f19fbd5eSMartin Schwidefsky insnbuf[1] = (instr[1] & 0xf0) | (br[1] & 0x0f); 151f19fbd5eSMartin Schwidefsky break; 152f19fbd5eSMartin Schwidefsky } 153f19fbd5eSMartin Schwidefsky 154f19fbd5eSMartin Schwidefsky s390_kernel_write(instr, insnbuf, 6); 155f19fbd5eSMartin Schwidefsky } 156f19fbd5eSMartin Schwidefsky } 157f19fbd5eSMartin Schwidefsky 1586e179d64SMartin Schwidefsky void __init_or_module nospec_revert(s32 *start, s32 *end) 159f19fbd5eSMartin Schwidefsky { 1606e179d64SMartin Schwidefsky if (nospec_disable) 161f19fbd5eSMartin Schwidefsky __nospec_revert(start, end); 162f19fbd5eSMartin Schwidefsky } 163f19fbd5eSMartin Schwidefsky 164f19fbd5eSMartin Schwidefsky extern s32 __nospec_call_start[], __nospec_call_end[]; 165f19fbd5eSMartin Schwidefsky extern s32 __nospec_return_start[], __nospec_return_end[]; 166f19fbd5eSMartin Schwidefsky void __init nospec_init_branches(void) 167f19fbd5eSMartin Schwidefsky { 1686e179d64SMartin Schwidefsky nospec_revert(__nospec_call_start, __nospec_call_end); 1696e179d64SMartin Schwidefsky nospec_revert(__nospec_return_start, __nospec_return_end); 170f19fbd5eSMartin Schwidefsky } 171b2e2f43aSMartin Schwidefsky 172b2e2f43aSMartin Schwidefsky #endif /* CONFIG_EXPOLINE */ 173