Author | Tokens | Token Proportion | Commits | Commit Proportion |
---|---|---|---|---|
Martin Schwidefsky | 922 | 99.89% | 9 | 90.00% |
Eugeniu Rosca | 1 | 0.11% | 1 | 10.00% |
Total | 923 | 10 |
// SPDX-License-Identifier: GPL-2.0 #include <linux/module.h> #include <linux/device.h> #include <asm/nospec-branch.h> static int __init nobp_setup_early(char *str) { bool enabled; int rc; rc = kstrtobool(str, &enabled); if (rc) return rc; if (enabled && test_facility(82)) { /* * The user explicitely requested nobp=1, enable it and * disable the expoline support. */ __set_facility(82, S390_lowcore.alt_stfle_fac_list); if (IS_ENABLED(CONFIG_EXPOLINE)) nospec_disable = 1; } else { __clear_facility(82, S390_lowcore.alt_stfle_fac_list); } return 0; } early_param("nobp", nobp_setup_early); static int __init nospec_setup_early(char *str) { __clear_facility(82, S390_lowcore.alt_stfle_fac_list); return 0; } early_param("nospec", nospec_setup_early); static int __init nospec_report(void) { if (test_facility(156)) pr_info("Spectre V2 mitigation: etokens\n"); if (IS_ENABLED(CC_USING_EXPOLINE) && !nospec_disable) pr_info("Spectre V2 mitigation: execute trampolines\n"); if (__test_facility(82, S390_lowcore.alt_stfle_fac_list)) pr_info("Spectre V2 mitigation: limited branch prediction\n"); return 0; } arch_initcall(nospec_report); #ifdef CONFIG_EXPOLINE int nospec_disable = IS_ENABLED(CONFIG_EXPOLINE_OFF); static int __init nospectre_v2_setup_early(char *str) { nospec_disable = 1; return 0; } early_param("nospectre_v2", nospectre_v2_setup_early); void __init nospec_auto_detect(void) { if (test_facility(156)) { /* * The machine supports etokens. * Disable expolines and disable nobp. */ if (IS_ENABLED(CC_USING_EXPOLINE)) nospec_disable = 1; __clear_facility(82, S390_lowcore.alt_stfle_fac_list); } else if (IS_ENABLED(CC_USING_EXPOLINE)) { /* * The kernel has been compiled with expolines. * Keep expolines enabled and disable nobp. */ nospec_disable = 0; __clear_facility(82, S390_lowcore.alt_stfle_fac_list); } /* * If the kernel has not been compiled with expolines the * nobp setting decides what is done, this depends on the * CONFIG_KERNEL_NP option and the nobp/nospec parameters. */ } static int __init spectre_v2_setup_early(char *str) { if (str && !strncmp(str, "on", 2)) { nospec_disable = 0; __clear_facility(82, S390_lowcore.alt_stfle_fac_list); } if (str && !strncmp(str, "off", 3)) nospec_disable = 1; if (str && !strncmp(str, "auto", 4)) nospec_auto_detect(); return 0; } early_param("spectre_v2", spectre_v2_setup_early); static void __init_or_module __nospec_revert(s32 *start, s32 *end) { enum { BRCL_EXPOLINE, BRASL_EXPOLINE } type; u8 *instr, *thunk, *br; u8 insnbuf[6]; s32 *epo; /* Second part of the instruction replace is always a nop */ for (epo = start; epo < end; epo++) { instr = (u8 *) epo + *epo; if (instr[0] == 0xc0 && (instr[1] & 0x0f) == 0x04) type = BRCL_EXPOLINE; /* brcl instruction */ else if (instr[0] == 0xc0 && (instr[1] & 0x0f) == 0x05) type = BRASL_EXPOLINE; /* brasl instruction */ else continue; thunk = instr + (*(int *)(instr + 2)) * 2; if (thunk[0] == 0xc6 && thunk[1] == 0x00) /* exrl %r0,<target-br> */ br = thunk + (*(int *)(thunk + 2)) * 2; else if (thunk[0] == 0xc0 && (thunk[1] & 0x0f) == 0x00 && thunk[6] == 0x44 && thunk[7] == 0x00 && (thunk[8] & 0x0f) == 0x00 && thunk[9] == 0x00 && (thunk[1] & 0xf0) == (thunk[8] & 0xf0)) /* larl %rx,<target br> + ex %r0,0(%rx) */ br = thunk + (*(int *)(thunk + 2)) * 2; else continue; /* Check for unconditional branch 0x07f? or 0x47f???? */ if ((br[0] & 0xbf) != 0x07 || (br[1] & 0xf0) != 0xf0) continue; memcpy(insnbuf + 2, (char[]) { 0x47, 0x00, 0x07, 0x00 }, 4); switch (type) { case BRCL_EXPOLINE: insnbuf[0] = br[0]; insnbuf[1] = (instr[1] & 0xf0) | (br[1] & 0x0f); if (br[0] == 0x47) { /* brcl to b, replace with bc + nopr */ insnbuf[2] = br[2]; insnbuf[3] = br[3]; } else { /* brcl to br, replace with bcr + nop */ } break; case BRASL_EXPOLINE: insnbuf[1] = (instr[1] & 0xf0) | (br[1] & 0x0f); if (br[0] == 0x47) { /* brasl to b, replace with bas + nopr */ insnbuf[0] = 0x4d; insnbuf[2] = br[2]; insnbuf[3] = br[3]; } else { /* brasl to br, replace with basr + nop */ insnbuf[0] = 0x0d; } break; } s390_kernel_write(instr, insnbuf, 6); } } void __init_or_module nospec_revert(s32 *start, s32 *end) { if (nospec_disable) __nospec_revert(start, end); } extern s32 __nospec_call_start[], __nospec_call_end[]; extern s32 __nospec_return_start[], __nospec_return_end[]; void __init nospec_init_branches(void) { nospec_revert(__nospec_call_start, __nospec_call_end); nospec_revert(__nospec_return_start, __nospec_return_end); } #endif /* CONFIG_EXPOLINE */
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