diff options
Diffstat (limited to 'arch/s390/kernel/nospec-branch.c')
-rw-r--r-- | arch/s390/kernel/nospec-branch.c | 120 |
1 files changed, 96 insertions, 24 deletions
diff --git a/arch/s390/kernel/nospec-branch.c b/arch/s390/kernel/nospec-branch.c index 9aff72d3abda..14867ec5f726 100644 --- a/arch/s390/kernel/nospec-branch.c +++ b/arch/s390/kernel/nospec-branch.c @@ -1,32 +1,108 @@ // SPDX-License-Identifier: GPL-2.0 #include <linux/module.h> +#include <linux/device.h> #include <asm/nospec-branch.h> -int nospec_call_disable = IS_ENABLED(CONFIG_EXPOLINE_OFF); -int nospec_return_disable = !IS_ENABLED(CONFIG_EXPOLINE_FULL); +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 (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_SYSFS +ssize_t cpu_show_spectre_v1(struct device *dev, + struct device_attribute *attr, char *buf) +{ + return sprintf(buf, "Mitigation: __user pointer sanitization\n"); +} + +ssize_t cpu_show_spectre_v2(struct device *dev, + struct device_attribute *attr, char *buf) +{ + if (IS_ENABLED(CC_USING_EXPOLINE) && !nospec_disable) + return sprintf(buf, "Mitigation: execute trampolines\n"); + if (__test_facility(82, S390_lowcore.alt_stfle_fac_list)) + return sprintf(buf, "Mitigation: limited branch prediction.\n"); + return sprintf(buf, "Vulnerable\n"); +} +#endif + +#ifdef CONFIG_EXPOLINE + +int nospec_disable = IS_ENABLED(CONFIG_EXPOLINE_OFF); static int __init nospectre_v2_setup_early(char *str) { - nospec_call_disable = 1; - nospec_return_disable = 1; + nospec_disable = 1; return 0; } early_param("nospectre_v2", nospectre_v2_setup_early); +static int __init spectre_v2_auto_early(void) +{ + 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. + */ + return 0; +} +#ifdef CONFIG_EXPOLINE_AUTO +early_initcall(spectre_v2_auto_early); +#endif + static int __init spectre_v2_setup_early(char *str) { if (str && !strncmp(str, "on", 2)) { - nospec_call_disable = 0; - nospec_return_disable = 0; - } - if (str && !strncmp(str, "off", 3)) { - nospec_call_disable = 1; - nospec_return_disable = 1; - } - if (str && !strncmp(str, "auto", 4)) { - nospec_call_disable = 0; - nospec_return_disable = 1; + 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)) + spectre_v2_auto_early(); return 0; } early_param("spectre_v2", spectre_v2_setup_early); @@ -79,15 +155,9 @@ static void __init_or_module __nospec_revert(s32 *start, s32 *end) } } -void __init_or_module nospec_call_revert(s32 *start, s32 *end) -{ - if (nospec_call_disable) - __nospec_revert(start, end); -} - -void __init_or_module nospec_return_revert(s32 *start, s32 *end) +void __init_or_module nospec_revert(s32 *start, s32 *end) { - if (nospec_return_disable) + if (nospec_disable) __nospec_revert(start, end); } @@ -95,6 +165,8 @@ extern s32 __nospec_call_start[], __nospec_call_end[]; extern s32 __nospec_return_start[], __nospec_return_end[]; void __init nospec_init_branches(void) { - nospec_call_revert(__nospec_call_start, __nospec_call_end); - nospec_return_revert(__nospec_return_start, __nospec_return_end); + nospec_revert(__nospec_call_start, __nospec_call_end); + nospec_revert(__nospec_return_start, __nospec_return_end); } + +#endif /* CONFIG_EXPOLINE */ |