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

[David Hildenbrand]

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 <address@hidden>
> Signed-off-by: David Hildenbrand <address@hidden>
> ---
>  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"

-- 

Thanks,

David / dhildenb