| Message ID | 20190125180711.1970973-8-jeremy.linton@arm.com |
|---|---|
| State | New |
| Headers | show |
| Series | arm64: add system vulnerability sysfs entries | expand |
Hi Jeremy, On 25/01/2019 18:07, Jeremy Linton wrote: > Display the mitigation status if active, otherwise > assume the cpu is safe unless it doesn't have CSV3 > and isn't in our whitelist. > > Signed-off-by: Jeremy Linton <jeremy.linton@arm.com> > --- > arch/arm64/kernel/cpufeature.c | 33 +++++++++++++++++++++++++++------ > 1 file changed, 27 insertions(+), 6 deletions(-) > > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > index a9e18b9cdc1e..624dfe0b5cdd 100644 > --- a/arch/arm64/kernel/cpufeature.c > +++ b/arch/arm64/kernel/cpufeature.c > @@ -944,6 +944,8 @@ has_useable_cnp(const struct arm64_cpu_capabilities *entry, int scope) > return has_cpuid_feature(entry, scope); > } > > +/* default value is invalid until unmap_kernel_at_el0() runs */ > +static bool __meltdown_safe = true; > static int __kpti_forced; /* 0: not forced, >0: forced on, <0: forced off */ > > static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, > @@ -962,6 +964,16 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, > { /* sentinel */ } > }; > char const *str = "command line option"; > + bool meltdown_safe; > + > + meltdown_safe = is_midr_in_range_list(read_cpuid_id(), kpti_safe_list); > + > + /* Defer to CPU feature registers */ > + if (has_cpuid_feature(entry, scope)) > + meltdown_safe = true; Do we need to check the cpuid registers if the CPU is in the known safe list? Otherwise: Reviewed-by: Julien Thierry <julien.thierry@arm.com> > + > + if (!meltdown_safe) > + __meltdown_safe = false; > > /* > * For reasons that aren't entirely clear, enabling KPTI on Cavium > @@ -984,12 +996,7 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, > if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) > return kaslr_offset() > 0; > > - /* Don't force KPTI for CPUs that are not vulnerable */ > - if (is_midr_in_range_list(read_cpuid_id(), kpti_safe_list)) > - return false; > - > - /* Defer to CPU feature registers */ > - return !has_cpuid_feature(entry, scope); > + return !meltdown_safe; > } > > static void > @@ -2055,3 +2062,17 @@ static int __init enable_mrs_emulation(void) > } > > core_initcall(enable_mrs_emulation); > + > +#ifdef CONFIG_GENERIC_CPU_VULNERABILITIES > +ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, > + char *buf) > +{ > + if (arm64_kernel_unmapped_at_el0()) > + return sprintf(buf, "Mitigation: KPTI\n"); > + > + if (__meltdown_safe) > + return sprintf(buf, "Not affected\n"); > + > + return sprintf(buf, "Vulnerable\n"); > +} > +#endif > -- Julien Thierry
On Fri, 25 Jan 2019 12:07:06 -0600 Jeremy Linton <jeremy.linton@arm.com> wrote: Hi, > Display the mitigation status if active, otherwise > assume the cpu is safe unless it doesn't have CSV3 > and isn't in our whitelist. > > Signed-off-by: Jeremy Linton <jeremy.linton@arm.com> > --- > arch/arm64/kernel/cpufeature.c | 33 +++++++++++++++++++++++++++------ > 1 file changed, 27 insertions(+), 6 deletions(-) > > diff --git a/arch/arm64/kernel/cpufeature.c > b/arch/arm64/kernel/cpufeature.c > index a9e18b9cdc1e..624dfe0b5cdd 100644 > --- a/arch/arm64/kernel/cpufeature.c > +++ b/arch/arm64/kernel/cpufeature.c > @@ -944,6 +944,8 @@ has_useable_cnp(const struct arm64_cpu_capabilities *entry, int scope) > return has_cpuid_feature(entry, scope); > } > > +/* default value is invalid until unmap_kernel_at_el0() runs */ Shall we somehow enforce this? For instance by making __meltdown_safe an enum, initialised to UNKNOWN? Then bail out with a BUG_ON or WARN_ON in the sysfs code? I just want to avoid to accidentally report "safe" when we actually aren't. > +static bool __meltdown_safe = true; > static int __kpti_forced; /* 0: not forced, >0: forced on, <0: forced off */ > static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, > @@ -962,6 +964,16 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, > { /* sentinel */ } > }; > char const *str = "command line option"; > + bool meltdown_safe; > + > + meltdown_safe = is_midr_in_range_list(read_cpuid_id(), kpti_safe_list); > + > + /* Defer to CPU feature registers */ > + if (has_cpuid_feature(entry, scope)) > + meltdown_safe = true; > + > + if (!meltdown_safe) > + __meltdown_safe = false; > > /* > * For reasons that aren't entirely clear, enabling KPTI on Cavium > @@ -984,12 +996,7 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, > if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) > return kaslr_offset() > 0; > > - /* Don't force KPTI for CPUs that are not vulnerable */ > - if (is_midr_in_range_list(read_cpuid_id(), kpti_safe_list)) > - return false; > - > - /* Defer to CPU feature registers */ > - return !has_cpuid_feature(entry, scope); > + return !meltdown_safe; > } > > static void > @@ -2055,3 +2062,17 @@ static int __init enable_mrs_emulation(void) > } > > core_initcall(enable_mrs_emulation); > + > +#ifdef CONFIG_GENERIC_CPU_VULNERABILITIES > +ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, > + char *buf) w/s issue. Cheers, Andre. > +{ > + if (arm64_kernel_unmapped_at_el0()) > + return sprintf(buf, "Mitigation: KPTI\n"); > + > + if (__meltdown_safe) > + return sprintf(buf, "Not affected\n"); > + > + return sprintf(buf, "Vulnerable\n"); > +} > +#endif
Hi, On 01/31/2019 03:28 AM, Julien Thierry wrote: > Hi Jeremy, > > On 25/01/2019 18:07, Jeremy Linton wrote: >> Display the mitigation status if active, otherwise >> assume the cpu is safe unless it doesn't have CSV3 >> and isn't in our whitelist. >> >> Signed-off-by: Jeremy Linton <jeremy.linton@arm.com> >> --- >> arch/arm64/kernel/cpufeature.c | 33 +++++++++++++++++++++++++++------ >> 1 file changed, 27 insertions(+), 6 deletions(-) >> >> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c >> index a9e18b9cdc1e..624dfe0b5cdd 100644 >> --- a/arch/arm64/kernel/cpufeature.c >> +++ b/arch/arm64/kernel/cpufeature.c >> @@ -944,6 +944,8 @@ has_useable_cnp(const struct arm64_cpu_capabilities *entry, int scope) >> return has_cpuid_feature(entry, scope); >> } >> >> +/* default value is invalid until unmap_kernel_at_el0() runs */ >> +static bool __meltdown_safe = true; >> static int __kpti_forced; /* 0: not forced, >0: forced on, <0: forced off */ >> >> static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, >> @@ -962,6 +964,16 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, >> { /* sentinel */ } >> }; >> char const *str = "command line option"; >> + bool meltdown_safe; >> + >> + meltdown_safe = is_midr_in_range_list(read_cpuid_id(), kpti_safe_list); >> + >> + /* Defer to CPU feature registers */ >> + if (has_cpuid_feature(entry, scope)) >> + meltdown_safe = true; > > Do we need to check the cpuid registers if the CPU is in the known safe > list? I don't believe so. In the previous patch where this was broken out these checks were just or'ed together. In this path it just seemed a little cleaner than adding the additional check/or'ing the results here/whatever as we only want to set it safe (never the other way around). AKA, i'm running out of horizontal space, and I want to keep the 'defer to registers' comment. > > Otherwise: > > Reviewed-by: Julien Thierry <julien.thierry@arm.com> > >> + >> + if (!meltdown_safe) >> + __meltdown_safe = false; >> >> /* >> * For reasons that aren't entirely clear, enabling KPTI on Cavium >> @@ -984,12 +996,7 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, >> if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) >> return kaslr_offset() > 0; >> >> - /* Don't force KPTI for CPUs that are not vulnerable */ >> - if (is_midr_in_range_list(read_cpuid_id(), kpti_safe_list)) >> - return false; >> - >> - /* Defer to CPU feature registers */ >> - return !has_cpuid_feature(entry, scope); >> + return !meltdown_safe; >> } >> >> static void >> @@ -2055,3 +2062,17 @@ static int __init enable_mrs_emulation(void) >> } >> >> core_initcall(enable_mrs_emulation); >> + >> +#ifdef CONFIG_GENERIC_CPU_VULNERABILITIES >> +ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, >> + char *buf) >> +{ >> + if (arm64_kernel_unmapped_at_el0()) >> + return sprintf(buf, "Mitigation: KPTI\n"); >> + >> + if (__meltdown_safe) >> + return sprintf(buf, "Not affected\n"); >> + >> + return sprintf(buf, "Vulnerable\n"); >> +} >> +#endif >> >
Hi, On 01/31/2019 11:54 AM, Andre Przywara wrote: > On Fri, 25 Jan 2019 12:07:06 -0600 > Jeremy Linton <jeremy.linton@arm.com> wrote: > > Hi, > >> Display the mitigation status if active, otherwise >> assume the cpu is safe unless it doesn't have CSV3 >> and isn't in our whitelist. >> >> Signed-off-by: Jeremy Linton <jeremy.linton@arm.com> >> --- >> arch/arm64/kernel/cpufeature.c | 33 +++++++++++++++++++++++++++------ >> 1 file changed, 27 insertions(+), 6 deletions(-) >> >> diff --git a/arch/arm64/kernel/cpufeature.c >> b/arch/arm64/kernel/cpufeature.c >> index a9e18b9cdc1e..624dfe0b5cdd 100644 >> --- a/arch/arm64/kernel/cpufeature.c >> +++ b/arch/arm64/kernel/cpufeature.c >> @@ -944,6 +944,8 @@ has_useable_cnp(const struct arm64_cpu_capabilities *entry, int scope) >> return has_cpuid_feature(entry, scope); >> } >> >> +/* default value is invalid until unmap_kernel_at_el0() runs */ > > Shall we somehow enforce this? For instance by making __meltdown_safe > an enum, initialised to UNKNOWN? Hehe, well I think people complained about my "UNKNOWN" enum. But, in the end this version is trying to make it clear we shouldn't have any unknown states remaining. > Then bail out with a BUG_ON or WARN_ON in the sysfs code? AFAIK, it shouldn't be possible to actually run the sysfs code before this gets initialized. So, the comment is just making it clear/forcing the understanding of that. > > I just want to avoid to accidentally report "safe" when we actually > aren't. > >> +static bool __meltdown_safe = true; >> static int __kpti_forced; /* 0: not forced, >0: forced on, <0: forced off */ >> static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, >> @@ -962,6 +964,16 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, >> { /* sentinel */ } >> }; >> char const *str = "command line option"; >> + bool meltdown_safe; >> + >> + meltdown_safe = is_midr_in_range_list(read_cpuid_id(), kpti_safe_list); >> + >> + /* Defer to CPU feature registers */ >> + if (has_cpuid_feature(entry, scope)) >> + meltdown_safe = true; >> + >> + if (!meltdown_safe) >> + __meltdown_safe = false; >> >> /* >> * For reasons that aren't entirely clear, enabling KPTI on Cavium >> @@ -984,12 +996,7 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, >> if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) >> return kaslr_offset() > 0; >> >> - /* Don't force KPTI for CPUs that are not vulnerable */ >> - if (is_midr_in_range_list(read_cpuid_id(), kpti_safe_list)) >> - return false; >> - >> - /* Defer to CPU feature registers */ >> - return !has_cpuid_feature(entry, scope); >> + return !meltdown_safe; >> } >> >> static void >> @@ -2055,3 +2062,17 @@ static int __init enable_mrs_emulation(void) >> } >> >> core_initcall(enable_mrs_emulation); >> + >> +#ifdef CONFIG_GENERIC_CPU_VULNERABILITIES >> +ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, >> + char *buf) > > w/s issue. > > Cheers, > Andre. > >> +{ >> + if (arm64_kernel_unmapped_at_el0()) >> + return sprintf(buf, "Mitigation: KPTI\n"); >> + >> + if (__meltdown_safe) >> + return sprintf(buf, "Not affected\n"); >> + >> + return sprintf(buf, "Vulnerable\n"); >> +} >> +#endif >
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index a9e18b9cdc1e..624dfe0b5cdd 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -944,6 +944,8 @@ has_useable_cnp(const struct arm64_cpu_capabilities *entry, int scope) return has_cpuid_feature(entry, scope); } +/* default value is invalid until unmap_kernel_at_el0() runs */ +static bool __meltdown_safe = true; static int __kpti_forced; /* 0: not forced, >0: forced on, <0: forced off */ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, @@ -962,6 +964,16 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, { /* sentinel */ } }; char const *str = "command line option"; + bool meltdown_safe; + + meltdown_safe = is_midr_in_range_list(read_cpuid_id(), kpti_safe_list); + + /* Defer to CPU feature registers */ + if (has_cpuid_feature(entry, scope)) + meltdown_safe = true; + + if (!meltdown_safe) + __meltdown_safe = false; /* * For reasons that aren't entirely clear, enabling KPTI on Cavium @@ -984,12 +996,7 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) return kaslr_offset() > 0; - /* Don't force KPTI for CPUs that are not vulnerable */ - if (is_midr_in_range_list(read_cpuid_id(), kpti_safe_list)) - return false; - - /* Defer to CPU feature registers */ - return !has_cpuid_feature(entry, scope); + return !meltdown_safe; } static void @@ -2055,3 +2062,17 @@ static int __init enable_mrs_emulation(void) } core_initcall(enable_mrs_emulation); + +#ifdef CONFIG_GENERIC_CPU_VULNERABILITIES +ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, + char *buf) +{ + if (arm64_kernel_unmapped_at_el0()) + return sprintf(buf, "Mitigation: KPTI\n"); + + if (__meltdown_safe) + return sprintf(buf, "Not affected\n"); + + return sprintf(buf, "Vulnerable\n"); +} +#endif
Display the mitigation status if active, otherwise assume the cpu is safe unless it doesn't have CSV3 and isn't in our whitelist. Signed-off-by: Jeremy Linton <jeremy.linton@arm.com> --- arch/arm64/kernel/cpufeature.c | 33 +++++++++++++++++++++++++++------ 1 file changed, 27 insertions(+), 6 deletions(-) -- 2.17.2