Re: [PATCH v1 4/4] tests/tcg/aarch64: userspace system register test

["Alex Bennée" <alex.bennee@linaro.org>]

Alex Bennée <alex.bennee@linaro.org> writes:

> This tests a bunch of registers that the kernel allows userspace to
> read including the CPUID registers.
>
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

I'll also merge the following fix:

modified   tests/tcg/aarch64/sysregs.c
@@ -11,6 +11,10 @@
 #include <string.h>
 #include <stdbool.h>

+#ifndef HWCAP_CPUID
+#define HWCAP_CPUID (1 << 11)
+#endif
+
 int failed_mask_count;

 #define get_cpu_reg(id) ({                                      \


>
> ---
> v4
>   - also test for extra bits that shouldn't be exposed
> ---
>  tests/tcg/aarch64/Makefile.target |   2 +-
>  tests/tcg/aarch64/sysregs.c       | 120 ++++++++++++++++++++++++++++++
>  2 files changed, 121 insertions(+), 1 deletion(-)
>  create mode 100644 tests/tcg/aarch64/sysregs.c
>
> diff --git a/tests/tcg/aarch64/Makefile.target b/tests/tcg/aarch64/Makefile.target
> index 08c45b8470..cc1a7eb486 100644
> --- a/tests/tcg/aarch64/Makefile.target
> +++ b/tests/tcg/aarch64/Makefile.target
> @@ -7,7 +7,7 @@ VPATH 		+= $(AARCH64_SRC)
>
>  # we don't build any of the ARM tests
>  AARCH64_TESTS=$(filter-out $(ARM_TESTS), $(TESTS))
> -AARCH64_TESTS+=fcvt
> +AARCH64_TESTS+=fcvt sysregs
>  TESTS:=$(AARCH64_TESTS)
>
>  fcvt: LDFLAGS+=-lm
> diff --git a/tests/tcg/aarch64/sysregs.c b/tests/tcg/aarch64/sysregs.c
> new file mode 100644
> index 0000000000..8e11288ee3
> --- /dev/null
> +++ b/tests/tcg/aarch64/sysregs.c
> @@ -0,0 +1,120 @@
> +/*
> + * Check emulated system register access for linux-user mode.
> + *
> + * See: https://www.kernel.org/doc/Documentation/arm64/cpu-feature-registers.txt
> + */
> +
> +#include <asm/hwcap.h>
> +#include <stdio.h>
> +#include <sys/auxv.h>
> +#include <signal.h>
> +#include <string.h>
> +#include <stdbool.h>
> +
> +int failed_mask_count;
> +
> +#define get_cpu_reg(id) ({                                      \
> +            unsigned long __val = 0xdeadbeef;                   \
> +            asm("mrs %0, "#id : "=r" (__val));                  \
> +            printf("%-20s: 0x%016lx\n", #id, __val);            \
> +            __val;                                               \
> +        })
> +
> +#define get_cpu_reg_check_mask(id, mask) ({                     \
> +            unsigned long __cval = get_cpu_reg(id);             \
> +            unsigned long __extra = __cval & ~mask;             \
> +            if (__extra) {                                      \
> +                printf("%-20s: 0x%016lx\n", "  !!extra bits!!", __extra);   \
> +                failed_mask_count++;                            \
> +            }                                                   \
> +})
> +
> +bool should_fail;
> +int should_fail_count;
> +int should_not_fail_count;
> +uintptr_t failed_pc[10];
> +
> +void sigill_handler(int signo, siginfo_t *si, void *data)
> +{
> +    ucontext_t *uc = (ucontext_t *)data;
> +
> +    if (should_fail) {
> +        should_fail_count++;
> +    } else {
> +        uintptr_t pc = (uintptr_t) uc->uc_mcontext.pc;
> +        failed_pc[should_not_fail_count++] =  pc;
> +    }
> +    uc->uc_mcontext.pc += 4;
> +}
> +
> +int main(void)
> +{
> +    struct sigaction sa;
> +
> +    /* Hook in a SIGILL handler */
> +    memset(&sa, 0, sizeof(struct sigaction));
> +    sa.sa_flags = SA_SIGINFO;
> +    sa.sa_sigaction = &sigill_handler;
> +    sigemptyset(&sa.sa_mask);
> +
> +    if (sigaction(SIGILL, &sa, 0) != 0) {
> +        perror("sigaction");
> +        return 1;
> +    }
> +
> +    /* since 4.12 */
> +    printf("Checking CNT registers\n");
> +
> +    get_cpu_reg(ctr_el0);
> +    get_cpu_reg(cntvct_el0);
> +    get_cpu_reg(cntfrq_el0);
> +
> +    /* when (getauxval(AT_HWCAP) & HWCAP_CPUID), since 4.11*/
> +    if (!(getauxval(AT_HWCAP) & HWCAP_CPUID)) {
> +        printf("CPUID registers unavailable\n");
> +        return 1;
> +    } else {
> +        printf("Checking CPUID registers\n");
> +    }
> +
> +    /*
> +     * Some registers only expose some bits to user-space. Anything
> +     * that is IMDEF is exported as 0 to user-space.
> +     */
> +    get_cpu_reg_check_mask(id_aa64isar0_el1, 0x000fffffff0ffff0ULL);
> +    get_cpu_reg_check_mask(id_aa64isar1_el1, 0x00000000ffffffffULL);
> +    get_cpu_reg(id_aa64mmfr0_el1);
> +    get_cpu_reg(id_aa64mmfr1_el1);
> +    get_cpu_reg_check_mask(id_aa64pfr0_el1, 0x000f000f0ff0000ULL);
> +    get_cpu_reg(id_aa64pfr1_el1);
> +    get_cpu_reg(id_aa64dfr0_el1);
> +    get_cpu_reg(id_aa64dfr1_el1);
> +
> +    get_cpu_reg_check_mask(midr_el1, 0x00000000ffffffffULL);
> +    get_cpu_reg(mpidr_el1);
> +    /* REVIDR is all IMPDEF so should be all zeros to user-space */
> +    get_cpu_reg_check_mask(revidr_el1, 0x0);
> +
> +    printf("Remaining registers should fail\n");
> +    should_fail = true;
> +
> +    /* Unexposed register access causes SIGILL */
> +    get_cpu_reg(id_mmfr0_el1);
> +
> +    if (should_not_fail_count > 0) {
> +        int i;
> +        for (i = 0; i < should_not_fail_count; i++) {
> +            uintptr_t pc = failed_pc[i];
> +            uint32_t insn = *(uint32_t *) pc;
> +            printf("insn %#x @ %#lx unexpected FAIL\n", insn, pc);
> +        }
> +        return 1;
> +    }
> +
> +    if (failed_mask_count > 0) {
> +        printf("Extra information leaked to user-space!\n");
> +        return 1;
> +    }
> +
> +    return should_fail_count == 1 ? 0 : 1;
> +}


--
Alex Bennée