Re: [PATCH v1 20/28] tests/tcg/aarch64: userspace system register test

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

Philippe Mathieu-Daudé <philmd@redhat.com> writes:

> On 3/16/20 6:21 PM, Alex Bennée wrote:
>> This tests a bunch of registers that the kernel allows userspace to
>> read including the CPUID registers. We need a SVE aware compiler as we
>> are testing the id_aa64zfr0_el1 register in the set.
>> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
>> Message-Id: <20190205190224.2198-7-alex.bennee@linaro.org>
>> ---
>> vgdbstub
>>    - don't build unless using docker or CROSS_CC_HAS_SVE
>> ---
>>   tests/tcg/aarch64/sysregs.c       | 172 ++++++++++++++++++++++++++++++
>>   tests/tcg/aarch64/Makefile.target |   6 ++
>>   2 files changed, 178 insertions(+)
>>   create mode 100644 tests/tcg/aarch64/sysregs.c
>> diff --git a/tests/tcg/aarch64/sysregs.c
>> b/tests/tcg/aarch64/sysregs.c
>> new file mode 100644
>> index 00000000000..40cf8d2877e
>> --- /dev/null
>> +++ b/tests/tcg/aarch64/sysregs.c
>> @@ -0,0 +1,172 @@
>> +/*
>> + * Check emulated system register access for linux-user mode.
>> + *
>> + * See: https://www.kernel.org/doc/Documentation/arm64/cpu-feature-registers.txt
>> + *
>> + * Copyright (c) 2019 Linaro
>> + *
>> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
>> + * See the COPYING file in the top-level directory.
>> + *
>> + * SPDX-License-Identifier: GPL-2.0-or-later
>> + */
>> +
>> +#include <asm/hwcap.h>
>> +#include <stdio.h>
>> +#include <sys/auxv.h>
>> +#include <signal.h>
>> +#include <string.h>
>> +#include <stdbool.h>
>> +
>> +#ifndef HWCAP_CPUID
>> +#define HWCAP_CPUID (1 << 11)
>> +#endif
>> +
>> +int failed_bit_count;
>> +
>> +/* Read and print system register `id' value */
>> +#define get_cpu_reg(id) ({                                      \
>> +            unsigned long __val = 0xdeadbeef;                   \
>> +            asm("mrs %0, "#id : "=r" (__val));                  \
>> +            printf("%-20s: 0x%016lx\n", #id, __val);            \
>> +            __val;                                               \
>> +        })
>> +
>> +/* As above but also check no bits outside of `mask' are set*/
>> +#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_bit_count++;                            \
>> +            }                                                   \
>> +})
>> +
>> +/* As above but check RAZ */
>> +#define get_cpu_reg_check_zero(id) ({                           \
>> +            unsigned long __val = 0xdeadbeef;                   \
>> +            asm("mrs %0, "#id : "=r" (__val));                  \
>> +            if (__val) {                                        \
>> +                printf("%-20s: 0x%016lx (not RAZ!)\n", #id, __val);        \
>> +                failed_bit_count++;                            \
>> +            }                                                   \
>> +})
>> +
>> +/* Chunk up mask into 63:48, 47:32, 31:16, 15:0 to ease counting */
>> +#define _m(a, b, c, d) (0x ## a ## b ## c ## d ##ULL)
>> +
>> +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;
>> +    }
>> +
>> +    /* Counter values have been exposed since Linux 4.12 */
>> +    printf("Checking Counter registers\n");
>> +
>> +    get_cpu_reg(ctr_el0);
>> +    get_cpu_reg(cntvct_el0);
>> +    get_cpu_reg(cntfrq_el0);
>> +
>> +    /* HWCAP_CPUID indicates we can read feature registers, since Linux 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 IMPDEF is exported as 0 to user-space. The _mask checks
>> +     * assert no extra bits are set.
>> +     *
>> +     * This check is *not* comprehensive as some fields are set to
>> +     * minimum valid fields - for the purposes of this check allowed
>> +     * to have non-zero values.
>> +     */
>> +    get_cpu_reg_check_mask(id_aa64isar0_el1, _m(00ff,ffff,f0ff,fff0));
>> +    get_cpu_reg_check_mask(id_aa64isar1_el1, _m(0000,00f0,ffff,ffff));
>> +    /* TGran4 & TGran64 as pegged to -1 */
>> +    get_cpu_reg_check_mask(id_aa64mmfr0_el1, _m(0000,0000,ff00,0000));
>> +    get_cpu_reg_check_zero(id_aa64mmfr1_el1);
>> +    /* EL1/EL0 reported as AA64 only */
>> +    get_cpu_reg_check_mask(id_aa64pfr0_el1,  _m(000f,000f,00ff,0011));
>> +    get_cpu_reg_check_mask(id_aa64pfr1_el1,  _m(0000,0000,0000,00f0));
>> +    /* all hidden, DebugVer fixed to 0x6 (ARMv8 debug architecture) */
>> +    get_cpu_reg_check_mask(id_aa64dfr0_el1,  _m(0000,0000,0000,0006));
>> +    get_cpu_reg_check_zero(id_aa64dfr1_el1);
>> +    get_cpu_reg_check_zero(id_aa64zfr0_el1);
>> +
>> +    get_cpu_reg_check_zero(id_aa64afr0_el1);
>> +    get_cpu_reg_check_zero(id_aa64afr1_el1);
>> +
>> +    get_cpu_reg_check_mask(midr_el1,         _m(0000,0000,ffff,ffff));
>> +    /* mpidr sets bit 31, everything else hidden */
>> +    get_cpu_reg_check_mask(mpidr_el1,        _m(0000,0000,8000,0000));
>> +    /* REVIDR is all IMPDEF so should be all zeros to user-space */
>> +    get_cpu_reg_check_zero(revidr_el1);
>> +
>> +    /*
>> +     * There are a block of more registers that are RAZ in the rest of
>> +     * the Op0=3, Op1=0, CRn=0, CRm=0,4,5,6,7 space. However for
>> +     * brevity we don't check stuff that is currently un-allocated
>> +     * here. Feel free to add them ;-)
>> +     */
>> +
>> +    printf("Remaining registers should fail\n");
>> +    should_fail = true;
>> +
>> +    /* Unexposed register access causes SIGILL */
>> +    get_cpu_reg(id_mmfr0_el1);
>> +    get_cpu_reg(id_mmfr1_el1);
>> +    get_cpu_reg(id_mmfr2_el1);
>> +    get_cpu_reg(id_mmfr3_el1);
>> +
>> +    get_cpu_reg(mvfr0_el1);
>> +    get_cpu_reg(mvfr1_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_bit_count > 0) {
>> +        printf("Extra information leaked to user-space!\n");
>> +        return 1;
>> +    }
>> +
>> +    return should_fail_count == 6 ? 0 : 1;
>> +}
>> diff --git a/tests/tcg/aarch64/Makefile.target b/tests/tcg/aarch64/Makefile.target
>> index 8ed477d0d51..a25afc071cc 100644
>> --- a/tests/tcg/aarch64/Makefile.target
>> +++ b/tests/tcg/aarch64/Makefile.target
>> @@ -42,4 +42,10 @@ run-semiconsole: semiconsole
>>   run-plugin-semiconsole-with-%:
>>   	$(call skip-test, $<, "MANUAL ONLY")
>>   +ifneq ($(DOCKER_IMAGE)$(CROSS_CC_HAS_SVE),)
>> +# System Registers Tests
>> +AARCH64_TESTS += sysregs
>> +sysregs: CFLAGS+=-march=armv8.1-a+sve
>> +endif
>> +
>>   TESTS += $(AARCH64_TESTS)
>> 
>
> warning: while parsing target description (at line 47): Vector
> "vq128hf" references undefined type "ieee_half"
> warning: Could not load XML target description; ignoring
> *** stack smashing detected ***: <unknown> terminated

How? That test doesn't even use the gdbstub.

>
> (GCC 9.2.1, Fedora 30)


-- 
Alex Bennée