Re: [PATCH v2 09/11] KVM: arm64: Type-check hypercall arguments at the caller
Marc Zyngier <[email protected]>
| Newsgroups | gmane.linux.kernel,gmane.linux.ports.arm.kernel |
|---|---|
| Message-ID | <[email protected]> |
On Mon, 03 Aug 2026 13:42:18 +0100, Fuad Tabba <[email protected]> wrote: > > kvm_call_hyp_nvhe() reduces its target to an SMCCC function number, so > the compiler never sees a callable: arguments that are wrong in number, > type or order are silently marshalled into registers. The kvm_call_hyp() > wrappers only catch this on the VHE branch, and the pKVM-only hypercalls > have no such branch. > > Declare each hypercall's signature once in kvm_hcall.h and generate a > typed stub from it, in the mold of the syscall wrappers. Make > kvm_call_hyp_nvhe() resolve to the stub so every caller is checked > against the declared signature; a stale or mistyped call now fails to > compile. The stubs inline to the same SMCCC call the untyped macro used > to make: the compiled callers are unchanged, apart from hypercall > returns now being tested at their declared width. > > The stage-2 protection arguments are declared u64 rather than > enum kvm_pgtable_prot, as kvm_pgtable.h includes linux/kvm_host.h and > the enum cannot be completed here. > > Assisted-by: Antigravity:gemini-3.1-pro > Signed-off-by: Fuad Tabba <[email protected]> > --- > arch/arm64/include/asm/kvm_hcall.h | 168 ++++++++++++++++++++++++++++- > arch/arm64/kvm/hyp_trace.c | 2 +- > 2 files changed, 168 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/include/asm/kvm_hcall.h b/arch/arm64/include/asm/kvm_hcall.h > index d925b2c28a3d8..1c9c182ddcd1b 100644 > --- a/arch/arm64/include/asm/kvm_hcall.h > +++ b/arch/arm64/include/asm/kvm_hcall.h > @@ -9,6 +9,7 @@ > #ifndef __ARM64_KVM_HCALL_H__ > #define __ARM64_KVM_HCALL_H__ > > +#include <linux/args.h> > #include <linux/arm-smccc.h> > #include <linux/bug.h> > #include <linux/errno.h> > @@ -16,12 +17,37 @@ > > #include <asm/barrier.h> > #include <asm/kvm_asm.h> > +#include <asm/spectre.h> > #include <asm/virt.h> > > typedef u16 pkvm_handle_t; > > +struct kvm; > +struct kvm_s2_mmu; > +struct kvm_vcpu; > +struct vgic_v3_cpu_if; > +struct vgic_v5_cpu_if; > + > +/* > + * Hypercall signatures are declared as (type, name) argument pairs. > + * __KVM_HCALL_MAP() applies a macro to each pair, in the mold of __MAP() > + * in <linux/syscalls.h>. The ladder is indexed by list entries, two per > + * argument; __KVM_HCALL_MAP_N() takes that count explicitly. > + */ > +#define __KVM_HCALL_MAP2(m, t, a, ...) m(t, a) > +#define __KVM_HCALL_MAP4(m, t, a, ...) m(t, a), __KVM_HCALL_MAP2(m, __VA_ARGS__) > +#define __KVM_HCALL_MAP6(m, t, a, ...) m(t, a), __KVM_HCALL_MAP4(m, __VA_ARGS__) > +#define __KVM_HCALL_MAP8(m, t, a, ...) m(t, a), __KVM_HCALL_MAP6(m, __VA_ARGS__) > +#define __KVM_HCALL_MAP10(m, t, a, ...) m(t, a), __KVM_HCALL_MAP8(m, __VA_ARGS__) > +#define __KVM_HCALL_MAP12(m, t, a, ...) m(t, a), __KVM_HCALL_MAP10(m, __VA_ARGS__) > +#define __KVM_HCALL_MAP_N(n, m, ...) CONCATENATE(__KVM_HCALL_MAP, n)(m, __VA_ARGS__) > +#define __KVM_HCALL_MAP(m, ...) __KVM_HCALL_MAP_N(COUNT_ARGS(__VA_ARGS__), m, __VA_ARGS__) > + > +#define __KVM_HCALL_DECL(t, a) t a > +#define __KVM_HCALL_ARGS(t, a) a > + > #ifndef __KVM_NVHE_HYPERVISOR__ > -#define kvm_call_hyp_nvhe(f, ...) \ > +#define __kvm_call_hyp_nvhe(f, ...) \ > ({ \ > struct arm_smccc_res res; \ > \ > @@ -33,6 +59,43 @@ typedef u16 pkvm_handle_t; > res.a1; \ > }) > > +/* > + * Generate a typed stub for each declared hypercall. kvm_call_hyp_nvhe() > + * resolves to the stub, so a call with the wrong argument count or types > + * fails to compile instead of being silently truncated to an SMCCC function > + * number and a pile of registers. The stub inlines to the same SMCCC call > + * the untyped macro used to make. > + */ > +#define DECLARE_KVM_HOST_HCALL(ret, name, ...) \ > + static __always_inline \ > + ret nvhe_hvc_##name(__KVM_HCALL_MAP(__KVM_HCALL_DECL, __VA_ARGS__)) \ > + { \ > + return (ret)__kvm_call_hyp_nvhe(name, \ > + __KVM_HCALL_MAP(__KVM_HCALL_ARGS, __VA_ARGS__));\ > + } > + > +#define DECLARE_KVM_HOST_HCALL_VOID(name, ...) \ > + static __always_inline \ > + void nvhe_hvc_##name(__KVM_HCALL_MAP(__KVM_HCALL_DECL, __VA_ARGS__)) \ > + { \ > + __kvm_call_hyp_nvhe(name, \ > + __KVM_HCALL_MAP(__KVM_HCALL_ARGS, __VA_ARGS__));\ > + } I'll bite! ;-) void is a type, not the absence of a type. And returning void is perfectly valid. So with this in mind, I got rid of the *_VOID() helpers altogether, see below. Thanks, M. diff --git a/arch/arm64/include/asm/kvm_hcall.h b/arch/arm64/include/asm/kvm_hcall.h index 3958396a83345..0b1b10d4212da 100644 --- a/arch/arm64/include/asm/kvm_hcall.h +++ b/arch/arm64/include/asm/kvm_hcall.h @@ -88,26 +88,12 @@ struct vgic_v5_cpu_if; __KVM_HCALL_MAP(__KVM_HCALL_ARGS, __VA_ARGS__));\ } -#define DECLARE_KVM_HOST_HCALL_VOID(name, ...) \ - static __always_inline \ - void nvhe_hvc_##name(__KVM_HCALL_MAP(__KVM_HCALL_DECL, __VA_ARGS__)) \ - { \ - __kvm_call_hyp_nvhe(name, \ - __KVM_HCALL_MAP(__KVM_HCALL_ARGS, __VA_ARGS__));\ - } - #define DECLARE_KVM_HOST_HCALL0(ret, name) \ static __always_inline ret nvhe_hvc_##name(void) \ { \ return (ret)__kvm_call_hyp_nvhe(name); \ } -#define DECLARE_KVM_HOST_HCALL0_VOID(name) \ - static __always_inline void nvhe_hvc_##name(void) \ - { \ - __kvm_call_hyp_nvhe(name); \ - } - #define kvm_call_hyp_nvhe(f, ...) nvhe_hvc_##f(__VA_ARGS__) /* @@ -148,12 +134,8 @@ struct vgic_v5_cpu_if; */ #define DECLARE_KVM_HOST_HCALL(ret, name, ...) \ typedef ret kvm_host_hcall_sig_##name(__KVM_HCALL_MAP(__KVM_HCALL_DECL, __VA_ARGS__)); -#define DECLARE_KVM_HOST_HCALL_VOID(name, ...) \ - typedef void kvm_host_hcall_sig_##name(__KVM_HCALL_MAP(__KVM_HCALL_DECL, __VA_ARGS__)); #define DECLARE_KVM_HOST_HCALL0(ret, name) \ typedef ret kvm_host_hcall_sig_##name(void); -#define DECLARE_KVM_HOST_HCALL0_VOID(name) \ - typedef void kvm_host_hcall_sig_##name(void); #endif /* __KVM_NVHE_HYPERVISOR__ */ /* Hypercalls that are unavailable once pKVM has finalised. */ @@ -164,52 +146,52 @@ DECLARE_KVM_HOST_HCALL(unsigned long, __pkvm_create_private_mapping, phys_addr_t, phys, size_t, size, u64, prot) DECLARE_KVM_HOST_HCALL(int, __pkvm_cpu_set_vector, enum arm64_hyp_spectre_vector, slot) -DECLARE_KVM_HOST_HCALL0_VOID(__kvm_enable_ssbs) -DECLARE_KVM_HOST_HCALL0_VOID(__vgic_v3_init_lrs) +DECLARE_KVM_HOST_HCALL0(void, __kvm_enable_ssbs) +DECLARE_KVM_HOST_HCALL0(void, __vgic_v3_init_lrs) DECLARE_KVM_HOST_HCALL0(u64, __vgic_v3_get_gic_config) DECLARE_KVM_HOST_HCALL0(int, __pkvm_prot_finalize) /* Hypercalls that are always available and common to [nh]VHE/pKVM. */ -DECLARE_KVM_HOST_HCALL_VOID(__kvm_adjust_pc, +DECLARE_KVM_HOST_HCALL(void, __kvm_adjust_pc, struct kvm_vcpu __kern *, vcpu) DECLARE_KVM_HOST_HCALL(int, __kvm_vcpu_run, struct kvm_vcpu __kern *, vcpu) -DECLARE_KVM_HOST_HCALL0_VOID(__kvm_flush_vm_context) -DECLARE_KVM_HOST_HCALL_VOID(__kvm_tlb_flush_vmid_ipa, +DECLARE_KVM_HOST_HCALL0(void, __kvm_flush_vm_context) +DECLARE_KVM_HOST_HCALL(void, __kvm_tlb_flush_vmid_ipa, struct kvm_s2_mmu __kern *, mmu, phys_addr_t, ipa, int, level) -DECLARE_KVM_HOST_HCALL_VOID(__kvm_tlb_flush_vmid_ipa_nsh, +DECLARE_KVM_HOST_HCALL(void, __kvm_tlb_flush_vmid_ipa_nsh, struct kvm_s2_mmu __kern *, mmu, phys_addr_t, ipa, int, level) -DECLARE_KVM_HOST_HCALL_VOID(__kvm_tlb_flush_vmid, +DECLARE_KVM_HOST_HCALL(void, __kvm_tlb_flush_vmid, struct kvm_s2_mmu __kern *, mmu) -DECLARE_KVM_HOST_HCALL_VOID(__kvm_tlb_flush_vmid_range, +DECLARE_KVM_HOST_HCALL(void, __kvm_tlb_flush_vmid_range, struct kvm_s2_mmu __kern *, mmu, phys_addr_t, start, unsigned long, pages) -DECLARE_KVM_HOST_HCALL_VOID(__kvm_flush_cpu_context, +DECLARE_KVM_HOST_HCALL(void, __kvm_flush_cpu_context, struct kvm_s2_mmu __kern *, mmu) -DECLARE_KVM_HOST_HCALL_VOID(__kvm_timer_set_cntvoff, +DECLARE_KVM_HOST_HCALL(void, __kvm_timer_set_cntvoff, u64, cntvoff) DECLARE_KVM_HOST_HCALL(int, __tracing_load, void __kern *, desc_hva, size_t, desc_size) -DECLARE_KVM_HOST_HCALL0_VOID(__tracing_unload) +DECLARE_KVM_HOST_HCALL0(void, __tracing_unload) DECLARE_KVM_HOST_HCALL(int, __tracing_enable, bool, enable) DECLARE_KVM_HOST_HCALL(int, __tracing_swap_reader, unsigned int, cpu) -DECLARE_KVM_HOST_HCALL_VOID(__tracing_update_clock, +DECLARE_KVM_HOST_HCALL(void, __tracing_update_clock, u32, mult, u32, shift, u64, epoch_ns, u64, epoch_cyc) DECLARE_KVM_HOST_HCALL(int, __tracing_reset, unsigned int, cpu) DECLARE_KVM_HOST_HCALL(int, __tracing_enable_event, unsigned short, id, bool, enable) -DECLARE_KVM_HOST_HCALL_VOID(__tracing_write_event, +DECLARE_KVM_HOST_HCALL(void, __tracing_write_event, u64, id) -DECLARE_KVM_HOST_HCALL_VOID(__vgic_v3_save_aprs, +DECLARE_KVM_HOST_HCALL(void, __vgic_v3_save_aprs, struct vgic_v3_cpu_if __kern *, cpu_if) -DECLARE_KVM_HOST_HCALL_VOID(__vgic_v3_restore_vmcr_aprs, +DECLARE_KVM_HOST_HCALL(void, __vgic_v3_restore_vmcr_aprs, struct vgic_v3_cpu_if __kern *, cpu_if) -DECLARE_KVM_HOST_HCALL_VOID(__vgic_v5_save_apr, +DECLARE_KVM_HOST_HCALL(void, __vgic_v5_save_apr, struct vgic_v5_cpu_if __kern *, cpu_if) -DECLARE_KVM_HOST_HCALL_VOID(__vgic_v5_restore_vmcr_apr, +DECLARE_KVM_HOST_HCALL(void, __vgic_v5_restore_vmcr_apr, struct vgic_v5_cpu_if __kern *, cpu_if) /* Hypercalls that are available only when pKVM has finalised. */ @@ -232,7 +214,7 @@ DECLARE_KVM_HOST_HCALL(int, __pkvm_host_test_clear_young_guest, DECLARE_KVM_HOST_HCALL(int, __pkvm_host_mkyoung_guest, u64, gfn) DECLARE_KVM_HOST_HCALL0(int, __pkvm_reserve_vm) -DECLARE_KVM_HOST_HCALL_VOID(__pkvm_unreserve_vm, +DECLARE_KVM_HOST_HCALL(void, __pkvm_unreserve_vm, pkvm_handle_t, handle) DECLARE_KVM_HOST_HCALL(int, __pkvm_init_vm, struct kvm __kern *, host_kvm, void __kern *, vm_hva, @@ -249,10 +231,10 @@ DECLARE_KVM_HOST_HCALL(int, __pkvm_start_teardown_vm, pkvm_handle_t, handle) DECLARE_KVM_HOST_HCALL(int, __pkvm_finalize_teardown_vm, pkvm_handle_t, handle) -DECLARE_KVM_HOST_HCALL_VOID(__pkvm_vcpu_load, +DECLARE_KVM_HOST_HCALL(void, __pkvm_vcpu_load, pkvm_handle_t, handle, unsigned int, vcpu_idx, u64, hcr_el2) -DECLARE_KVM_HOST_HCALL0_VOID(__pkvm_vcpu_put) -DECLARE_KVM_HOST_HCALL_VOID(__pkvm_tlb_flush_vmid, +DECLARE_KVM_HOST_HCALL0(void, __pkvm_vcpu_put) +DECLARE_KVM_HOST_HCALL(void, __pkvm_tlb_flush_vmid, pkvm_handle_t, handle) #endif /* __ARM64_KVM_HCALL_H__ */ -- Without deviation from the norm, progress is not possible.