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Therefore, the kCFI handler must be able to parse the contents of the register file at the point where the exception was triggered. To achieve this, introduce a new hypervisor panic path that first stores the CPU context in the per-CPU kvm_hyp_ctxt before calling (directly or indirectly) hyp_panic() and execute it from all EL2 synchronous exception handlers i.e. - call it directly in host_el2_sync_vect (__kvm_hyp_host_vector, EL2t&h) - call it directly in el2t_sync_invalid (__kvm_hyp_vector, EL2t) - set ELR_EL2 to it in el2_sync (__kvm_hyp_vector, EL2h), which ERETs Teach hyp_panic() to decode the kCFI ESR and extract the target and type from the saved CPU context. In VHE, use that information to panic() with a specialized error message. In nVHE, only report it if the host (EL1) has access to the saved CPU context i.e. iff CONFIG_NVHE_EL2_DEBUG=y, which aligns with the behavior of CONFIG_PROTECTED_NVHE_STACKTRACE. Signed-off-by: Pierre-Clément Tosi --- arch/arm64/kvm/handle_exit.c | 30 +++++++++++++++++++++++-- arch/arm64/kvm/hyp/entry.S | 24 +++++++++++++++++++- arch/arm64/kvm/hyp/hyp-entry.S | 2 +- arch/arm64/kvm/hyp/include/hyp/switch.h | 4 ++-- arch/arm64/kvm/hyp/nvhe/host.S | 2 +- arch/arm64/kvm/hyp/vhe/switch.c | 26 +++++++++++++++++++-- 6 files changed, 79 insertions(+), 9 deletions(-) diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c index 69b08ac7322d..2fac3be3db00 100644 --- a/arch/arm64/kvm/handle_exit.c +++ b/arch/arm64/kvm/handle_exit.c @@ -26,6 +26,8 @@ #define CREATE_TRACE_POINTS #include "trace_handle_exit.h" +DECLARE_KVM_NVHE_PER_CPU(struct kvm_cpu_context, kvm_hyp_ctxt); + typedef int (*exit_handle_fn)(struct kvm_vcpu *); static void kvm_handle_guest_serror(struct kvm_vcpu *vcpu, u64 esr) @@ -417,10 +419,34 @@ static void print_nvhe_hyp_panic(const char *name, u64 panic_addr) (void *)(panic_addr + kaslr_offset())); } -static void kvm_nvhe_report_cfi_failure(u64 panic_addr) +static void kvm_nvhe_report_cfi_target(struct user_pt_regs *regs, u64 esr, + u64 hyp_offset) +{ + u64 va_mask = GENMASK_ULL(vabits_actual - 1, 0); + u8 type_idx = FIELD_GET(CFI_BRK_IMM_TYPE, esr); + u8 target_idx = FIELD_GET(CFI_BRK_IMM_TARGET, esr); + u32 expected_type = (u32)regs->regs[type_idx]; + u64 target_addr = (regs->regs[target_idx] & va_mask) + hyp_offset; + + kvm_err(" (target: [<%016llx>] %ps, expected type: 0x%08x)\n", + target_addr, (void *)(target_addr + kaslr_offset()), + expected_type); +} + +static void kvm_nvhe_report_cfi_failure(u64 panic_addr, u64 esr, u64 hyp_offset) { + struct user_pt_regs *regs = NULL; + print_nvhe_hyp_panic("CFI failure", panic_addr); + if (IS_ENABLED(CONFIG_NVHE_EL2_DEBUG) || !is_protected_kvm_enabled()) + regs = &this_cpu_ptr_nvhe_sym(kvm_hyp_ctxt)->regs; + + if (regs) + kvm_nvhe_report_cfi_target(regs, esr, hyp_offset); + else + kvm_err(" (no target information: !CONFIG_NVHE_EL2_DEBUG)\n"); + if (IS_ENABLED(CONFIG_CFI_PERMISSIVE)) kvm_err(" (CONFIG_CFI_PERMISSIVE ignored for hyp failures)\n"); } @@ -455,7 +481,7 @@ void __noreturn __cold nvhe_hyp_panic_handler(u64 esr, u64 spsr, else print_nvhe_hyp_panic("BUG", panic_addr); } else if (IS_ENABLED(CONFIG_CFI_CLANG) && esr_is_cfi_brk(esr)) { - kvm_nvhe_report_cfi_failure(panic_addr); + kvm_nvhe_report_cfi_failure(panic_addr, esr, hyp_offset); } else { print_nvhe_hyp_panic("panic", panic_addr); } diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S index 343851c17373..8965dbc75972 100644 --- a/arch/arm64/kvm/hyp/entry.S +++ b/arch/arm64/kvm/hyp/entry.S @@ -83,7 +83,7 @@ alternative_else_nop_endif eret sb -SYM_INNER_LABEL(__hyp_restore_elr_and_panic, SYM_L_GLOBAL) +SYM_INNER_LABEL(__hyp_restore_elr_save_context_and_panic, SYM_L_GLOBAL) // x2-x29,lr: vcpu regs // vcpu x0-x1 on the stack @@ -91,6 +91,28 @@ SYM_INNER_LABEL(__hyp_restore_elr_and_panic, SYM_L_GLOBAL) ldr x0, [x0, #CPU_ELR_EL2] msr elr_el2, x0 +SYM_INNER_LABEL(__hyp_save_context_and_panic, SYM_L_GLOBAL) + // x0-x29,lr: hyp regs + + stp x0, x1, [sp, #-16]! + + adr_this_cpu x0, kvm_hyp_ctxt, x1 + + stp x2, x3, [x0, #CPU_XREG_OFFSET(2)] + + ldp x2, x3, [sp], #16 + + stp x2, x3, [x0, #CPU_XREG_OFFSET(0)] + stp x4, x5, [x0, #CPU_XREG_OFFSET(4)] + stp x6, x7, [x0, #CPU_XREG_OFFSET(6)] + stp x8, x9, [x0, #CPU_XREG_OFFSET(8)] + stp x10, x11, [x0, #CPU_XREG_OFFSET(10)] + stp x12, x13, [x0, #CPU_XREG_OFFSET(12)] + stp x14, x15, [x0, #CPU_XREG_OFFSET(14)] + stp x16, x17, [x0, #CPU_XREG_OFFSET(16)] + + save_callee_saved_regs x0 + SYM_INNER_LABEL(__hyp_panic, SYM_L_GLOBAL) // x2-x29,lr: vcpu regs // vcpu x0-x1 on the stack diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S index 7e65ef738ec9..d0d90d598338 100644 --- a/arch/arm64/kvm/hyp/hyp-entry.S +++ b/arch/arm64/kvm/hyp/hyp-entry.S @@ -130,7 +130,7 @@ SYM_CODE_END(\label) .endm /* None of these should ever happen */ - invalid_vector el2t_sync_invalid + invalid_vector el2t_sync_invalid, __hyp_save_context_and_panic invalid_vector el2t_irq_invalid invalid_vector el2t_fiq_invalid invalid_vector el2t_error_invalid diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h index d9931abf14c2..77783dbc1833 100644 --- a/arch/arm64/kvm/hyp/include/hyp/switch.h +++ b/arch/arm64/kvm/hyp/include/hyp/switch.h @@ -689,7 +689,7 @@ static inline bool fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code) static inline void __kvm_unexpected_el2_exception(void) { - extern char __hyp_restore_elr_and_panic[]; + extern char __hyp_restore_elr_save_context_and_panic[]; unsigned long addr, fixup; struct kvm_exception_table_entry *entry, *end; unsigned long elr_el2 = read_sysreg(elr_el2); @@ -712,7 +712,7 @@ static inline void __kvm_unexpected_el2_exception(void) /* Trigger a panic after restoring the hyp context. */ this_cpu_ptr(&kvm_hyp_ctxt)->sys_regs[ELR_EL2] = elr_el2; - write_sysreg(__hyp_restore_elr_and_panic, elr_el2); + write_sysreg(__hyp_restore_elr_save_context_and_panic, elr_el2); } #endif /* __ARM64_KVM_HYP_SWITCH_H__ */ diff --git a/arch/arm64/kvm/hyp/nvhe/host.S b/arch/arm64/kvm/hyp/nvhe/host.S index a7db40a51e4a..9343160f5357 100644 --- a/arch/arm64/kvm/hyp/nvhe/host.S +++ b/arch/arm64/kvm/hyp/nvhe/host.S @@ -214,7 +214,7 @@ SYM_FUNC_END(__host_hvc) .endm .macro host_el2_sync_vect - __host_el2_vect __hyp_panic + __host_el2_vect __hyp_save_context_and_panic .endm .macro invalid_host_el1_vect diff --git a/arch/arm64/kvm/hyp/vhe/switch.c b/arch/arm64/kvm/hyp/vhe/switch.c index 0550b9f6317f..6c64783c3e00 100644 --- a/arch/arm64/kvm/hyp/vhe/switch.c +++ b/arch/arm64/kvm/hyp/vhe/switch.c @@ -17,6 +17,7 @@ #include #include +#include #include #include #include @@ -384,7 +385,24 @@ int __kvm_vcpu_run(struct kvm_vcpu *vcpu) return ret; } -static void __noreturn __hyp_call_panic(u64 spsr, u64 elr, u64 par) +static void __noreturn __hyp_call_panic_for_cfi(u64 elr, u64 esr) +{ + struct user_pt_regs *regs = &this_cpu_ptr(&kvm_hyp_ctxt)->regs; + u8 type_idx = FIELD_GET(CFI_BRK_IMM_TYPE, esr); + u8 target_idx = FIELD_GET(CFI_BRK_IMM_TARGET, esr); + u32 expected_type = (u32)regs->regs[type_idx]; + u64 target = regs->regs[target_idx]; + + panic("VHE hyp CFI failure at: [<%016llx>] %pB (target: [<%016llx>] %ps, expected type: 0x%08x)\n" +#ifdef CONFIG_CFI_PERMISSIVE + " (CONFIG_CFI_PERMISSIVE ignored for hyp failures)\n" +#endif + , + elr, (void *)elr, target, (void *)target, expected_type); +} +NOKPROBE_SYMBOL(__hyp_call_panic_for_cfi); + +static void __noreturn __hyp_call_panic(u64 spsr, u64 elr, u64 par, u64 esr) { struct kvm_cpu_context *host_ctxt; struct kvm_vcpu *vcpu; @@ -395,6 +413,9 @@ static void __noreturn __hyp_call_panic(u64 spsr, u64 elr, u64 par) __deactivate_traps(vcpu); sysreg_restore_host_state_vhe(host_ctxt); + if (IS_ENABLED(CONFIG_CFI_CLANG) && esr_is_cfi_brk(esr)) + __hyp_call_panic_for_cfi(elr, esr); + panic("HYP panic:\nPS:%08llx PC:%016llx ESR:%08llx\nFAR:%016llx HPFAR:%016llx PAR:%016llx\nVCPU:%p\n", spsr, elr, read_sysreg_el2(SYS_ESR), read_sysreg_el2(SYS_FAR), @@ -407,8 +428,9 @@ void __noreturn hyp_panic(void) u64 spsr = read_sysreg_el2(SYS_SPSR); u64 elr = read_sysreg_el2(SYS_ELR); u64 par = read_sysreg_par(); + u64 esr = read_sysreg_el2(SYS_ESR); - __hyp_call_panic(spsr, elr, par); + __hyp_call_panic(spsr, elr, par, esr); } asmlinkage void kvm_unexpected_el2_exception(void)