Re: [PATCH 3/3] tests/tcg/s390x: Test BRASL and BRCL with large negative offsets

[David Hildenbrand]

On 11.03.22 19:49, Ilya Leoshkevich wrote:
> Add a small test in order to prevent regressions.
> 
> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
> ---
>  tests/tcg/s390x/Makefile.target        |  1 +
>  tests/tcg/s390x/branch-relative-long.c | 29 ++++++++++++++++++++++++++
>  2 files changed, 30 insertions(+)
>  create mode 100644 tests/tcg/s390x/branch-relative-long.c
> 
> diff --git a/tests/tcg/s390x/Makefile.target b/tests/tcg/s390x/Makefile.target
> index 257c568c58..fd34b130f7 100644
> --- a/tests/tcg/s390x/Makefile.target
> +++ b/tests/tcg/s390x/Makefile.target
> @@ -15,6 +15,7 @@ TESTS+=mvc
>  TESTS+=shift
>  TESTS+=trap
>  TESTS+=signals-s390x
> +TESTS+=branch-relative-long
>  
>  ifneq ($(HAVE_GDB_BIN),)
>  GDB_SCRIPT=$(SRC_PATH)/tests/guest-debug/run-test.py
> diff --git a/tests/tcg/s390x/branch-relative-long.c 
> b/tests/tcg/s390x/branch-relative-long.c
> new file mode 100644
> index 0000000000..b9fcee9873
> --- /dev/null
> +++ b/tests/tcg/s390x/branch-relative-long.c
> @@ -0,0 +1,29 @@
> +#include <assert.h>
> +#include <stddef.h>
> +#include <sys/mman.h>
> +
> +int main(void)
> +{
> +    const unsigned short opcodes[] = {
> +        0xc005,  /* brasl %r0 */
> +        0xc0f4,  /* brcl 0xf */
> +    };
> +    size_t length = 0x100000006;
> +    unsigned char *buf;
> +    int i;
> +
> +    buf = mmap(NULL, length, PROT_READ | PROT_WRITE | PROT_EXEC,
> +               MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
> +    assert(buf != MAP_FAILED);
> +
> +    *(unsigned short *)&buf[0] = 0x07fe;  /* br %r14 */
> +    *(unsigned int *)&buf[0x100000002] = 0x80000000;
> +    for (i = 0; i < sizeof(opcodes) / sizeof(opcodes[0]); i++) {
> +        *(unsigned short *)&buf[0x100000000] = opcodes[i];
> +        ((void (*)(void))&buf[0x100000000])();
> +    }

Hmmm, can't we write some "nice" inline asm instead?


-- 
Thanks,

David / dhildenb