diff options
Diffstat (limited to 'arch/s390/kernel/nospec-branch.c')
| -rw-r--r-- | arch/s390/kernel/nospec-branch.c | 56 |
1 files changed, 19 insertions, 37 deletions
diff --git a/arch/s390/kernel/nospec-branch.c b/arch/s390/kernel/nospec-branch.c index 29e511f5bf06..e11ec15960a1 100644 --- a/arch/s390/kernel/nospec-branch.c +++ b/arch/s390/kernel/nospec-branch.c @@ -4,6 +4,8 @@ #include <linux/cpu.h> #include <asm/nospec-branch.h> +int nobp = IS_ENABLED(CONFIG_KERNEL_NOBP); + static int __init nobp_setup_early(char *str) { bool enabled; @@ -14,14 +16,14 @@ static int __init nobp_setup_early(char *str) return rc; if (enabled && test_facility(82)) { /* - * The user explicitely requested nobp=1, enable it and + * The user explicitly requested nobp=1, enable it and * disable the expoline support. */ - __set_facility(82, S390_lowcore.alt_stfle_fac_list); + nobp = 1; if (IS_ENABLED(CONFIG_EXPOLINE)) nospec_disable = 1; } else { - __clear_facility(82, S390_lowcore.alt_stfle_fac_list); + nobp = 0; } return 0; } @@ -29,7 +31,7 @@ early_param("nobp", nobp_setup_early); static int __init nospec_setup_early(char *str) { - __clear_facility(82, S390_lowcore.alt_stfle_fac_list); + nobp = 0; return 0; } early_param("nospec", nospec_setup_early); @@ -38,9 +40,9 @@ static int __init nospec_report(void) { if (test_facility(156)) pr_info("Spectre V2 mitigation: etokens\n"); - if (__is_defined(CC_USING_EXPOLINE) && !nospec_disable) + if (nospec_uses_trampoline()) pr_info("Spectre V2 mitigation: execute trampolines\n"); - if (__test_facility(82, S390_lowcore.alt_stfle_fac_list)) + if (nobp_enabled()) pr_info("Spectre V2 mitigation: limited branch prediction\n"); return 0; } @@ -66,14 +68,14 @@ void __init nospec_auto_detect(void) */ if (__is_defined(CC_USING_EXPOLINE)) nospec_disable = 1; - __clear_facility(82, S390_lowcore.alt_stfle_fac_list); + nobp = 0; } else if (__is_defined(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); + nobp = 0; } /* * If the kernel has not been compiled with expolines the @@ -86,7 +88,7 @@ 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); + nobp = 0; } if (str && !strncmp(str, "off", 3)) nospec_disable = 1; @@ -99,11 +101,13 @@ 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; + static const u8 branch[] = { 0x47, 0x00, 0x07, 0x00 }; u8 *instr, *thunk, *br; u8 insnbuf[6]; s32 *epo; /* Second part of the instruction replace is always a nop */ + memcpy(insnbuf + 2, branch, sizeof(branch)); for (epo = start; epo < end; epo++) { instr = (u8 *) epo + *epo; if (instr[0] == 0xc0 && (instr[1] & 0x0f) == 0x04) @@ -112,46 +116,24 @@ static void __init_or_module __nospec_revert(s32 *start, s32 *end) type = BRASL_EXPOLINE; /* brasl instruction */ else continue; - thunk = instr + (*(int *)(instr + 2)) * 2; + thunk = instr + (long)(*(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; + br = thunk + (long)(*(int *)(thunk + 2)) * 2; else continue; - /* Check for unconditional branch 0x07f? or 0x47f???? */ - if ((br[0] & 0xbf) != 0x07 || (br[1] & 0xf0) != 0xf0) + if (br[0] != 0x07 || (br[1] & 0xf0) != 0xf0) continue; - - memcpy(insnbuf + 2, (char[]) { 0x47, 0x00, 0x07, 0x00 }, 4); switch (type) { case BRCL_EXPOLINE: + /* brcl to thunk, replace with br + nop */ 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: + /* brasl to thunk, replace with basr + nop */ + insnbuf[0] = 0x0d; 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; } |