Re: [PATCH v1] tests/tcg: target/s390x: Test MVC

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

David Hildenbrand <david@redhat.com> writes:

> On 19.09.19 11:28, David Hildenbrand wrote:
>> Let's add a test that especially verifies that no data will be touched
>> in case we cross page boundaries and one page access triggers a fault.
>>
>> Before the fault-safe handling fixes, the test failes with:
>>       TEST    mvc on s390x
>>     data modified during a fault
>>     make[2]: *** [../Makefile.target:116: run-mvc] Error 1
>>
>> Cc: Alex Bennée <alex.bennee@linaro.org>
>> Signed-off-by: David Hildenbrand <david@redhat.com>
>> ---
>>  tests/tcg/s390x/Makefile.target |   1 +
>>  tests/tcg/s390x/mvc.c           | 109 ++++++++++++++++++++++++++++++++
>>  2 files changed, 110 insertions(+)
>>  create mode 100644 tests/tcg/s390x/mvc.c
>>
>> diff --git a/tests/tcg/s390x/Makefile.target b/tests/tcg/s390x/Makefile.target
>> index 6a3bfa8b29..241ef28f61 100644
>> --- a/tests/tcg/s390x/Makefile.target
>> +++ b/tests/tcg/s390x/Makefile.target
>> @@ -7,3 +7,4 @@ TESTS+=exrl-trt
>>  TESTS+=exrl-trtr
>>  TESTS+=pack
>>  TESTS+=mvo
>> +TESTS+=mvc
>> diff --git a/tests/tcg/s390x/mvc.c b/tests/tcg/s390x/mvc.c
>> new file mode 100644
>> index 0000000000..aa552d52e5
>> --- /dev/null
>> +++ b/tests/tcg/s390x/mvc.c
>> @@ -0,0 +1,109 @@
>> +#include <stdint.h>
>> +#include <stdlib.h>
>> +#include <stdio.h>
>> +#include <string.h>
>> +#include <sys/mman.h>
>> +#include <signal.h>
>> +#include <setjmp.h>
>> +
>> +jmp_buf jmp_env;
>> +
>> +static void handle_sigsegv(int sig)
>> +{
>> +    siglongjmp(jmp_env, 1);
>> +}
>> +
>> +#define ALLOC_SIZE (2 * 4096)
>> +
>> +static inline void mvc_256(const char *dst, const char *src)
>> +{
>> +    asm volatile (
>> +        "    mvc 0(256,%[dst]),0(%[src])\n"
>> +        :
>> +        : [dst] "d" (dst),
>> +          [src] "d" (src)
>> +        : "memory");
>> +}
>> +
>> +int main(void)
>> +{
>> +    char *src, *dst;
>> +    int i;
>> +
>> +    /* register the SIGSEGV handler */
>> +    if (signal(SIGSEGV, handle_sigsegv) == SIG_ERR) {
>> +        fprintf(stderr, "SIGSEGV not registered\n");
>> +        return 1;
>> +    }
>> +
>> +    /* prepare the buffers - two consecutive pages */
>> +    src = valloc(ALLOC_SIZE);
>> +    dst = valloc(ALLOC_SIZE);
>> +    memset(src, 0xff, ALLOC_SIZE);
>> +    memset(dst, 0x0, ALLOC_SIZE);
>> +
>> +    /* protect the second pages */
>> +    if (mprotect(src + 4096, 4096, PROT_NONE) ||
>> +        mprotect(dst + 4096, 4096, PROT_NONE)) {
>> +        fprintf(stderr, "mprotect failed\n");
>> +        return 1;
>> +    }
>> +
>> +    /* fault on second destination page */
>> +    if (sigsetjmp(jmp_env, 1) == 0) {
>> +        mvc_256(dst + 4096 - 128, src);
>> +        fprintf(stderr, "fault not triggered\n");
>> +        return 1;
>> +    }
>> +
>> +    /* fault on second source page */
>> +    if (sigsetjmp(jmp_env, 1) == 0) {
>> +        mvc_256(dst, src + 4096 - 128);
>> +        fprintf(stderr, "fault not triggered\n");
>> +        return 1;
>> +    }
>> +
>> +    /* fault on second source and second destination page */
>> +    if (sigsetjmp(jmp_env, 1) == 0) {
>> +        mvc_256(dst + 4096 - 128, src + 4096 - 128);
>> +        fprintf(stderr, "fault not triggered\n");
>> +        return 1;
>> +    }
>> +
>> +    /* restore permissions */
>> +    if (mprotect(src + 4096, 4096, PROT_READ | PROT_WRITE) ||
>> +        mprotect(dst + 4096, 4096, PROT_READ | PROT_WRITE)) {
>> +        fprintf(stderr, "mprotect failed\n");
>> +        return 1;
>> +    }
>> +
>> +    /* no data must be touched during the faults */
>> +    for (i = 0; i < ALLOC_SIZE; i++) {
>> +        if (src[i] != 0xff || dst[i]) {
>> +            fprintf(stderr, "data modified during a fault\n");
>> +            return 1;
>> +        }
>> +    }
>> +
>> +    /* test if MVC works now correctly accross page boundaries */
>> +    mvc_256(dst + 4096 - 128, src + 4096 - 128);
>> +    for (i = 0; i < ALLOC_SIZE; i++) {
>> +        if (src[i] != 0xff) {
>> +            fprintf(stderr, "src modified\n");
>> +            return 1;
>> +        }
>> +        if (i < 4096 - 128 || i >= 4096 + 128) {
>> +            if (dst[i]) {
>> +                fprintf(stderr, "wrong dst modified\n");
>> +                return 1;
>> +            }
>> +        } else {
>> +            if (dst[i] != 0xff) {
>> +                fprintf(stderr, "wrong data moved\n");
>> +                return 1;
>> +            }
>> +        }
>> +    }
>> +
>> +    return 0;
>> +}
>>
>
> I'll send this along with the updated pull request of
>
> "[PULL SUBSYSTEM s390x 00/29] s390x/tcg: mem_helper: Fault-safe
> handling"

Acked-by: Alex Bennée <alex.bennee@linaro.org>


--
Alex Bennée