From: Kristina Martsenko kristina.martsenko@arm.com
mainline inclusion from v5.7-rc1 commit deeaac5175a5 category: feature bugzilla: 27615 CVE: NA
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Each system capability can be of either boot, local, or system scope, depending on when the state of the capability is finalized. When we detect a conflict on a late CPU, we either offline the CPU or panic the system. We currently always panic if the conflict is caused by a boot scope capability, and offline the CPU if the conflict is caused by a local or system scope capability.
We're going to want to add a new capability (for pointer authentication) which needs to be boot scope but doesn't need to panic the system when a conflict is detected. So add a new flag to specify whether the capability requires the system to panic or not. Current boot scope capabilities are updated to set the flag, so there should be no functional change as a result of this patch.
Signed-off-by: Amit Daniel Kachhap amit.kachhap@arm.com Signed-off-by: Kristina Martsenko kristina.martsenko@arm.com Reviewed-by: Vincenzo Frascino vincenzo.frascino@arm.com Reviewed-by: Suzuki K Poulose suzuki.poulose@arm.com Reviewed-by: Kees Cook keescook@chromium.org Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com Reviewed-by: Hanjun Guo guohanjun@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- arch/arm64/include/asm/cpufeature.h | 12 ++++++++++-- arch/arm64/kernel/cpufeature.c | 29 +++++++++++++++-------------- 2 files changed, 25 insertions(+), 16 deletions(-)
diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h index 2c7fb746f2c86..a845640c41b4c 100644 --- a/arch/arm64/include/asm/cpufeature.h +++ b/arch/arm64/include/asm/cpufeature.h @@ -220,6 +220,10 @@ int arm64_cpu_ftr_regs_traverse(int (*op)(u32, u64, void *), void *argp); * In some non-typical cases either both (a) and (b), or neither, * should be permitted. This can be described by including neither * or both flags in the capability's type field. + * + * In case of a conflict, the CPU is prevented from booting. If the + * ARM64_CPUCAP_PANIC_ON_CONFLICT flag is specified for the capability, + * then a kernel panic is triggered. */
@@ -252,6 +256,8 @@ int arm64_cpu_ftr_regs_traverse(int (*op)(u32, u64, void *), void *argp); #define ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU ((u16)BIT(4)) /* Is it safe for a late CPU to miss this capability when system has it */ #define ARM64_CPUCAP_OPTIONAL_FOR_LATE_CPU ((u16)BIT(5)) +/* Panic when a conflict is detected */ +#define ARM64_CPUCAP_PANIC_ON_CONFLICT ((u16)BIT(6))
/* * CPU errata workarounds that need to be enabled at boot time if one or @@ -291,9 +297,11 @@ int arm64_cpu_ftr_regs_traverse(int (*op)(u32, u64, void *), void *argp);
/* * CPU feature used early in the boot based on the boot CPU. All secondary - * CPUs must match the state of the capability as detected by the boot CPU. + * CPUs must match the state of the capability as detected by the boot CPU. In + * case of a conflict, a kernel panic is triggered. */ -#define ARM64_CPUCAP_STRICT_BOOT_CPU_FEATURE ARM64_CPUCAP_SCOPE_BOOT_CPU +#define ARM64_CPUCAP_STRICT_BOOT_CPU_FEATURE \ + (ARM64_CPUCAP_SCOPE_BOOT_CPU | ARM64_CPUCAP_PANIC_ON_CONFLICT)
struct arm64_cpu_capabilities { const char *desc; diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index ebe1f4a9825d9..66bb94dca935d 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -1349,6 +1349,12 @@ cpucap_late_cpu_permitted(const struct arm64_cpu_capabilities *cap) return !!(cap->type & ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU); }
+static bool +cpucap_panic_on_conflict(const struct arm64_cpu_capabilities *cap) +{ + return !!(cap->type & ARM64_CPUCAP_PANIC_ON_CONFLICT); +} + static const struct arm64_cpu_capabilities arm64_features[] = { { .desc = "GIC system register CPU interface", @@ -1944,10 +1950,8 @@ static void __init enable_cpu_capabilities(u16 scope_mask) * Run through the list of capabilities to check for conflicts. * If the system has already detected a capability, take necessary * action on this CPU. - * - * Returns "false" on conflicts. */ -static bool verify_local_cpu_caps(u16 scope_mask) +static void verify_local_cpu_caps(u16 scope_mask) { int i; bool cpu_has_cap, system_has_cap; @@ -1992,10 +1996,12 @@ static bool verify_local_cpu_caps(u16 scope_mask) pr_crit("CPU%d: Detected conflict for capability %d (%s), System: %d, CPU: %d\n", smp_processor_id(), caps->capability, caps->desc, system_has_cap, cpu_has_cap); - return false; - }
- return true; + if (cpucap_panic_on_conflict(caps)) + cpu_panic_kernel(); + else + cpu_die_early(); + } }
/* @@ -2005,12 +2011,8 @@ static bool verify_local_cpu_caps(u16 scope_mask) static void check_early_cpu_features(void) { verify_cpu_asid_bits(); - /* - * Early features are used by the kernel already. If there - * is a conflict, we cannot proceed further. - */ - if (!verify_local_cpu_caps(SCOPE_BOOT_CPU)) - cpu_panic_kernel(); + + verify_local_cpu_caps(SCOPE_BOOT_CPU); }
static void @@ -2058,8 +2060,7 @@ static void verify_local_cpu_capabilities(void) * check_early_cpu_features(), as they need to be verified * on all secondary CPUs. */ - if (!verify_local_cpu_caps(SCOPE_ALL & ~SCOPE_BOOT_CPU)) - cpu_die_early(); + verify_local_cpu_caps(SCOPE_ALL & ~SCOPE_BOOT_CPU);
verify_local_elf_hwcaps(arm64_elf_hwcaps);