On Sat, 01 May 2021 00:24:06 +0100,
Ricardo Koller <ricarkol@xxxxxxxxxx> wrote:
>
> Add the infrastructure needed to enable exception handling in aarch64
> selftests. The exception handling defaults to an unhandled-exception
> handler which aborts the test, just like x86. These handlers can be
> overridden by calling vm_install_vector_handler(vector) or
> vm_install_exception_handler(vector, ec). The unhandled exception
> reporting from the guest is done using the ucall type introduced in a
> previous commit, UCALL_UNHANDLED.
>
> The exception handling code is heavily inspired on kvm-unit-tests.
>
> Signed-off-by: Ricardo Koller <ricarkol@xxxxxxxxxx>
> ---
> tools/testing/selftests/kvm/Makefile | 2 +-
> .../selftests/kvm/include/aarch64/processor.h | 78 +++++++++++
> .../selftests/kvm/lib/aarch64/handlers.S | 130 ++++++++++++++++++
> .../selftests/kvm/lib/aarch64/processor.c | 124 +++++++++++++++++
> 4 files changed, 333 insertions(+), 1 deletion(-)
> create mode 100644 tools/testing/selftests/kvm/lib/aarch64/handlers.S
>
> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> index 4e548d7ab0ab..618c5903f478 100644
> --- a/tools/testing/selftests/kvm/Makefile
> +++ b/tools/testing/selftests/kvm/Makefile
> @@ -35,7 +35,7 @@ endif
>
> LIBKVM = lib/assert.c lib/elf.c lib/io.c lib/kvm_util.c lib/sparsebit.c lib/test_util.c lib/guest_modes.c lib/perf_test_util.c
> LIBKVM_x86_64 = lib/x86_64/processor.c lib/x86_64/vmx.c lib/x86_64/svm.c lib/x86_64/ucall.c lib/x86_64/handlers.S
> -LIBKVM_aarch64 = lib/aarch64/processor.c lib/aarch64/ucall.c
> +LIBKVM_aarch64 = lib/aarch64/processor.c lib/aarch64/ucall.c lib/aarch64/handlers.S
> LIBKVM_s390x = lib/s390x/processor.c lib/s390x/ucall.c lib/s390x/diag318_test_handler.c
>
> TEST_GEN_PROGS_x86_64 = x86_64/cr4_cpuid_sync_test
> diff --git a/tools/testing/selftests/kvm/include/aarch64/processor.h b/tools/testing/selftests/kvm/include/aarch64/processor.h
> index b7fa0c8551db..40aae31b4afc 100644
> --- a/tools/testing/selftests/kvm/include/aarch64/processor.h
> +++ b/tools/testing/selftests/kvm/include/aarch64/processor.h
> @@ -8,6 +8,7 @@
> #define SELFTEST_KVM_PROCESSOR_H
>
> #include "kvm_util.h"
> +#include <linux/stringify.h>
>
>
> #define ARM64_CORE_REG(x) (KVM_REG_ARM64 | KVM_REG_SIZE_U64 | \
> @@ -18,6 +19,7 @@
> #define MAIR_EL1 3, 0, 10, 2, 0
> #define TTBR0_EL1 3, 0, 2, 0, 0
> #define SCTLR_EL1 3, 0, 1, 0, 0
> +#define VBAR_EL1 3, 0, 12, 0, 0
>
> /*
> * Default MAIR
> @@ -56,4 +58,80 @@ void aarch64_vcpu_setup(struct kvm_vm *vm, int vcpuid, struct kvm_vcpu_init *ini
> void aarch64_vcpu_add_default(struct kvm_vm *vm, uint32_t vcpuid,
> struct kvm_vcpu_init *init, void *guest_code);
>
> +struct ex_regs {
> + u64 regs[31];
> + u64 sp;
> + u64 pc;
> + u64 pstate;
> +};
> +
> +#define VECTOR_NUM 16
> +
> +enum {
> + VECTOR_SYNC_CURRENT_SP0,
> + VECTOR_IRQ_CURRENT_SP0,
> + VECTOR_FIQ_CURRENT_SP0,
> + VECTOR_ERROR_CURRENT_SP0,
> +
> + VECTOR_SYNC_CURRENT,
> + VECTOR_IRQ_CURRENT,
> + VECTOR_FIQ_CURRENT,
> + VECTOR_ERROR_CURRENT,
> +
> + VECTOR_SYNC_LOWER_64,
> + VECTOR_IRQ_LOWER_64,
> + VECTOR_FIQ_LOWER_64,
> + VECTOR_ERROR_LOWER_64,
> +
> + VECTOR_SYNC_LOWER_32,
> + VECTOR_IRQ_LOWER_32,
> + VECTOR_FIQ_LOWER_32,
> + VECTOR_ERROR_LOWER_32,
> +};
> +
> +#define VECTOR_IS_SYNC(v) ((v) == VECTOR_SYNC_CURRENT_SP0 || \
> + (v) == VECTOR_SYNC_CURRENT || \
> + (v) == VECTOR_SYNC_LOWER_64 || \
> + (v) == VECTOR_SYNC_LOWER_32)
> +
> +/* Some common EC (Exception classes) */
> +#define ESR_EC_ILLEGAL_INS 0x0e
> +#define ESR_EC_SVC64 0x15
> +#define ESR_EC_IABORT_CURRENT 0x21
> +#define ESR_EC_DABORT_CURRENT 0x25
> +#define ESR_EC_SERROR 0x2f
> +#define ESR_EC_HW_BP_CURRENT 0x31
> +#define ESR_EC_SSTEP_CURRENT 0x33
> +#define ESR_EC_WP_CURRENT 0x35
> +#define ESR_EC_BRK_INS 0x3C
> +
> +#define ESR_EC_NUM 64
> +
> +#define ESR_EC_SHIFT 26
> +#define ESR_EC_MASK (ESR_EC_NUM - 1)
> +
> +void vm_init_descriptor_tables(struct kvm_vm *vm);
> +void vcpu_init_descriptor_tables(struct kvm_vm *vm, uint32_t vcpuid);
> +
> +typedef void(*handler_fn)(struct ex_regs *);
> +void vm_install_exception_handler(struct kvm_vm *vm,
> + int vector, int ec, handler_fn handler);
> +void vm_install_vector_handler(struct kvm_vm *vm,
> + int vector, handler_fn handler);
> +
> +#define SPSR_D (1 << 9)
> +#define SPSR_SS (1 << 21)
> +
> +#define write_sysreg(reg, val) \
> +({ \
> + u64 __val = (u64)(val); \
> + asm volatile("msr " __stringify(reg) ", %x0" : : "rZ" (__val)); \
> +})
> +
> +#define read_sysreg(reg) \
> +({ u64 val; \
> + asm volatile("mrs %0, "__stringify(reg) : "=r"(val) : : "memory");\
> + val; \
> +})
> +
> #endif /* SELFTEST_KVM_PROCESSOR_H */
> diff --git a/tools/testing/selftests/kvm/lib/aarch64/handlers.S b/tools/testing/selftests/kvm/lib/aarch64/handlers.S
> new file mode 100644
> index 000000000000..8a560021892b
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/lib/aarch64/handlers.S
> @@ -0,0 +1,130 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +.macro save_registers, vector
> + add sp, sp, #-16 * 17
> +
> + stp x0, x1, [sp, #16 * 0]
> + stp x2, x3, [sp, #16 * 1]
> + stp x4, x5, [sp, #16 * 2]
> + stp x6, x7, [sp, #16 * 3]
> + stp x8, x9, [sp, #16 * 4]
> + stp x10, x11, [sp, #16 * 5]
> + stp x12, x13, [sp, #16 * 6]
> + stp x14, x15, [sp, #16 * 7]
> + stp x16, x17, [sp, #16 * 8]
> + stp x18, x19, [sp, #16 * 9]
> + stp x20, x21, [sp, #16 * 10]
> + stp x22, x23, [sp, #16 * 11]
> + stp x24, x25, [sp, #16 * 12]
> + stp x26, x27, [sp, #16 * 13]
> + stp x28, x29, [sp, #16 * 14]
> +
> + .if \vector >= 8
> + mrs x1, sp_el0
I'm still a bit perplexed by this. SP_EL0 is never changed, since you
always run in handler mode. Therefore, saving/restoring it is only
overhead. If an exception handler wants to introspect it, it is
already available in the relevant system register.
Or did you have something else in mind for it?
> + .else
> + /*
> + * This stores sp_el1 into ex_regs.sp so exception handlers can
> + * "look" at it. It will _not_ be used to restore the sp_el1 on
> + * return from the exception so handlers can not update it.
> + */
> + mov x1, sp
> + .endif
> + stp x30, x1, [sp, #16 * 15] /* x30, SP */
> +
> + mrs x1, elr_el1
> + mrs x2, spsr_el1
> + stp x1, x2, [sp, #16 * 16] /* PC, PSTATE */
> +.endm
> +
> +.macro restore_registers, vector
> + ldp x1, x2, [sp, #16 * 16] /* PC, PSTATE */
> + msr elr_el1, x1
> + msr spsr_el1, x2
> +
> + ldp x30, x1, [sp, #16 * 15] /* x30, SP */
> + .if \vector >= 8
> + msr sp_el0, x1
> + .endif
> +
> + ldp x28, x29, [sp, #16 * 14]
> + ldp x26, x27, [sp, #16 * 13]
> + ldp x24, x25, [sp, #16 * 12]
> + ldp x22, x23, [sp, #16 * 11]
> + ldp x20, x21, [sp, #16 * 10]
> + ldp x18, x19, [sp, #16 * 9]
> + ldp x16, x17, [sp, #16 * 8]
> + ldp x14, x15, [sp, #16 * 7]
> + ldp x12, x13, [sp, #16 * 6]
> + ldp x10, x11, [sp, #16 * 5]
> + ldp x8, x9, [sp, #16 * 4]
> + ldp x6, x7, [sp, #16 * 3]
> + ldp x4, x5, [sp, #16 * 2]
> + ldp x2, x3, [sp, #16 * 1]
> + ldp x0, x1, [sp, #16 * 0]
> +
> + add sp, sp, #16 * 17
> +
> + eret
> +.endm
> +
> +.pushsection ".entry.text", "ax"
> +.balign 0x800
> +.global vectors
> +vectors:
> +.popsection
> +
> +.set vector, 0
> +
> +/*
> + * Build an exception handler for vector and append a jump to it into
> + * vectors (while making sure that it's 0x80 aligned).
> + */
> +.macro HANDLER, label
> +handler_\()\label:
> + save_registers vector
> + mov x0, sp
> + mov x1, #vector
> + bl route_exception
> + restore_registers vector
> +
> +.pushsection ".entry.text", "ax"
> +.balign 0x80
> + b handler_\()\label
> +.popsection
> +
> +.set vector, vector + 1
> +.endm
> +
> +.macro HANDLER_INVALID
> +.pushsection ".entry.text", "ax"
> +.balign 0x80
> +/* This will abort so no need to save and restore registers. */
> + mov x0, #vector
> + b kvm_exit_unexpected_vector
> +.popsection
> +
> +.set vector, vector + 1
> +.endm
> +
> +/*
> + * Caution: be sure to not add anything between the declaration of vectors
> + * above and these macro calls that will build the vectors table below it.
> + */
> + HANDLER_INVALID // Synchronous EL1t
> + HANDLER_INVALID // IRQ EL1t
> + HANDLER_INVALID // FIQ EL1t
> + HANDLER_INVALID // Error EL1t
> +
> + HANDLER el1h_sync // Synchronous EL1h
> + HANDLER el1h_irq // IRQ EL1h
> + HANDLER el1h_fiq // FIQ EL1h
> + HANDLER el1h_error // Error EL1h
> +
> + HANDLER el0_sync_64 // Synchronous 64-bit EL0
> + HANDLER el0_irq_64 // IRQ 64-bit EL0
> + HANDLER el0_fiq_64 // FIQ 64-bit EL0
> + HANDLER el0_error_64 // Error 64-bit EL0
> +
> + HANDLER el0_sync_32 // Synchronous 32-bit EL0
> + HANDLER el0_irq_32 // IRQ 32-bit EL0
> + HANDLER el0_fiq_32 // FIQ 32-bit EL0
> + HANDLER el0_error_32 // Error 32-bit EL0
> diff --git a/tools/testing/selftests/kvm/lib/aarch64/processor.c b/tools/testing/selftests/kvm/lib/aarch64/processor.c
> index cee92d477dc0..25be71ec88be 100644
> --- a/tools/testing/selftests/kvm/lib/aarch64/processor.c
> +++ b/tools/testing/selftests/kvm/lib/aarch64/processor.c
> @@ -6,6 +6,7 @@
> */
>
> #include <linux/compiler.h>
> +#include <assert.h>
>
> #include "kvm_util.h"
> #include "../kvm_util_internal.h"
> @@ -14,6 +15,8 @@
> #define KVM_GUEST_PAGE_TABLE_MIN_PADDR 0x180000
> #define DEFAULT_ARM64_GUEST_STACK_VADDR_MIN 0xac0000
>
> +vm_vaddr_t exception_handlers;
> +
> static uint64_t page_align(struct kvm_vm *vm, uint64_t v)
> {
> return (v + vm->page_size) & ~(vm->page_size - 1);
> @@ -334,6 +337,127 @@ void vcpu_args_set(struct kvm_vm *vm, uint32_t vcpuid, unsigned int num, ...)
> va_end(ap);
> }
>
> +void kvm_exit_unexpected_vector(int vector)
> +{
> + ucall(UCALL_UNHANDLED, 3, vector, 0, false /* !valid_ec */);
> +}
> +
> +void kvm_exit_unexpected_exception(int vector, uint64_t ec)
> +{
> + ucall(UCALL_UNHANDLED, 3, vector, ec, true /* valid_ec */);
> +}
> +
> void assert_on_unhandled_exception(struct kvm_vm *vm, uint32_t vcpuid)
> {
> + struct ucall uc;
> +
> + if (get_ucall(vm, vcpuid, &uc) != UCALL_UNHANDLED)
> + return;
> +
> + if (uc.args[2]) /* valid_ec */ {
> + assert(VECTOR_IS_SYNC(uc.args[0]));
> + TEST_ASSERT(false,
> + "Unexpected exception (vector:0x%lx, ec:0x%lx)",
> + uc.args[0], uc.args[1]);
> + } else {
> + assert(!VECTOR_IS_SYNC(uc.args[0]));
> + TEST_ASSERT(false,
> + "Unexpected exception (vector:0x%lx)",
> + uc.args[0]);
> + }
> +}
> +
> +/*
> + * This exception handling code was heavily inspired on kvm-unit-tests. There
> + * is a set of default vector handlers stored in vector_handlers. These default
> + * vector handlers call user-installed handlers stored in exception_handlers.
> + * Synchronous handlers are indexed by (vector, ec), and irq handlers by
> + * (vector, ec=0).
> + */
> +
> +typedef void(*vector_fn)(struct ex_regs *, int vector);
> +
> +struct handlers {
> + vector_fn vector_handlers[VECTOR_NUM];
> + handler_fn exception_handlers[VECTOR_NUM][ESR_EC_NUM];
> +};
> +
> +void vcpu_init_descriptor_tables(struct kvm_vm *vm, uint32_t vcpuid)
> +{
> + extern char vectors;
> +
> + set_reg(vm, vcpuid, ARM64_SYS_REG(VBAR_EL1), (uint64_t)&vectors);
> +}
> +
> +void default_sync_handler(struct ex_regs *regs, int vector)
> +{
> + struct handlers *handlers = (struct handlers *)exception_handlers;
> + uint64_t esr = read_sysreg(esr_el1);
> + uint64_t ec = (esr >> ESR_EC_SHIFT) & ESR_EC_MASK;
> +
> + GUEST_ASSERT(VECTOR_IS_SYNC(vector));
> +
> + if (handlers && handlers->exception_handlers[vector][ec])
> + handlers->exception_handlers[vector][ec](regs);
> + else
> + kvm_exit_unexpected_exception(vector, ec);
> +}
> +
> +void default_irq_handler(struct ex_regs *regs, int vector)
> +{
> + struct handlers *handlers = (struct handlers *)exception_handlers;
> +
> + GUEST_ASSERT(!VECTOR_IS_SYNC(vector));
> +
> + if (handlers && handlers->exception_handlers[vector][0])
> + handlers->exception_handlers[vector][0](regs);
> + else
> + kvm_exit_unexpected_vector(vector);
> +}
> +
> +void route_exception(struct ex_regs *regs, int vector)
> +{
> + struct handlers *handlers = (struct handlers *)exception_handlers;
> +
> + if (handlers && handlers->vector_handlers[vector])
> + handlers->vector_handlers[vector](regs, vector);
> + else
> + kvm_exit_unexpected_vector(vector);
> +}
> +
> +void vm_init_descriptor_tables(struct kvm_vm *vm)
> +{
> + struct handlers *handlers;
> +
> + vm->handlers = vm_vaddr_alloc(vm, sizeof(struct handlers),
> + vm->page_size, 0, 0);
> +
> + handlers = (struct handlers *)addr_gva2hva(vm, vm->handlers);
> + handlers->vector_handlers[VECTOR_SYNC_CURRENT] = default_sync_handler;
> + handlers->vector_handlers[VECTOR_IRQ_CURRENT] = default_irq_handler;
> + handlers->vector_handlers[VECTOR_SYNC_LOWER_64] = default_sync_handler;
> + handlers->vector_handlers[VECTOR_IRQ_LOWER_64] = default_irq_handler;
How about FIQ, Error? Although they are unlikely, they are valid
exceptions.
> +
> + *(vm_vaddr_t *)addr_gva2hva(vm, (vm_vaddr_t)(&exception_handlers)) = vm->handlers;
> +}
> +
> +void vm_install_exception_handler(struct kvm_vm *vm, int vector, int ec,
> + void (*handler)(struct ex_regs *))
> +{
> + struct handlers *handlers = (struct handlers *)addr_gva2hva(vm, vm->handlers);
> +
> + assert(VECTOR_IS_SYNC(vector));
> + assert(vector < VECTOR_NUM);
> + assert(ec < ESR_EC_NUM);
> + handlers->exception_handlers[vector][ec] = handler;
> +}
> +
> +void vm_install_vector_handler(struct kvm_vm *vm, int vector,
> + void (*handler)(struct ex_regs *))
> +{
> + struct handlers *handlers = (struct handlers *)addr_gva2hva(vm, vm->handlers);
> +
> + assert(!VECTOR_IS_SYNC(vector));
> + assert(vector < VECTOR_NUM);
> + handlers->exception_handlers[vector][0] = handler;
> }
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
