Re: [PATCH v6 2/2] tests/tcg/s390x: Test SIGILL and SIGSEGV handling

[Ilya Leoshkevich]

On Mon, 2021-07-05 at 23:04 +0200, Ilya Leoshkevich wrote:
> Verify that s390x-specific uc_mcontext.psw.addr is reported correctly
> and that signal handling interacts properly with debugging.
> 
> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
> ---
>  tests/tcg/s390x/Makefile.target               |  18 +-
>  tests/tcg/s390x/gdbstub/test-signals-s390x.py |  76 ++++++++
>  tests/tcg/s390x/signals-s390x.c               | 165
> ++++++++++++++++++
>  3 files changed, 258 insertions(+), 1 deletion(-)
>  create mode 100644 tests/tcg/s390x/gdbstub/test-signals-s390x.py
>  create mode 100644 tests/tcg/s390x/signals-s390x.c
> 
> diff --git a/tests/tcg/s390x/Makefile.target
> b/tests/tcg/s390x/Makefile.target
> index 0036b8a505..0a5b25c156 100644
> --- a/tests/tcg/s390x/Makefile.target
> +++ b/tests/tcg/s390x/Makefile.target
> @@ -1,4 +1,5 @@
> -VPATH+=$(SRC_PATH)/tests/tcg/s390x
> +S390X_SRC=$(SRC_PATH)/tests/tcg/s390x
> +VPATH+=$(S390X_SRC)
>  CFLAGS+=-march=zEC12 -m64
>  TESTS+=hello-s390x
>  TESTS+=csst
> @@ -12,3 +13,18 @@ TESTS+=mvc
>  # This triggers failures on s390x hosts about 4% of the time
>  run-signals: signals
>         $(call skip-test, $<, "BROKEN awaiting sigframe clean-ups")
> +
> +TESTS+=signals-s390x
> +
> +ifneq ($(HAVE_GDB_BIN),)
> +GDB_SCRIPT=$(SRC_PATH)/tests/guest-debug/run-test.py
> +
> +run-gdbstub-signals-s390x: signals-s390x
> +       $(call run-test, $@, $(GDB_SCRIPT) \
> +               --gdb $(HAVE_GDB_BIN) \
> +               --qemu $(QEMU) --qargs "$(QEMU_OPTS)" \
> +               --bin $< --test $(S390X_SRC)/gdbstub/test-signals-
> s390x.py, \
> +       "mixing signals and debugging on s390x")
> +
> +EXTRA_RUNS += run-gdbstub-signals-s390x
> +endif
> diff --git a/tests/tcg/s390x/gdbstub/test-signals-s390x.py
> b/tests/tcg/s390x/gdbstub/test-signals-s390x.py
> new file mode 100644
> index 0000000000..80a284b475
> --- /dev/null
> +++ b/tests/tcg/s390x/gdbstub/test-signals-s390x.py
> @@ -0,0 +1,76 @@
> +from __future__ import print_function
> +
> +#
> +# Test that signals and debugging mix well together on s390x.
> +#
> +# This is launched via tests/guest-debug/run-test.py
> +#
> +
> +import gdb
> +import sys
> +
> +failcount = 0
> +
> +
> +def report(cond, msg):
> +    """Report success/fail of test"""
> +    if cond:
> +        print("PASS: %s" % (msg))
> +    else:
> +        print("FAIL: %s" % (msg))
> +        global failcount
> +        failcount += 1
> +
> +
> +def run_test():
> +    """Run through the tests one by one"""
> +    illegal_op = gdb.Breakpoint("illegal_op")
> +    stg = gdb.Breakpoint("stg")
> +    mvc_8 = gdb.Breakpoint("mvc_8")
> +
> +    # Expect the following events:
> +    # 1x illegal_op breakpoint
> +    # 2x stg breakpoint, segv, breakpoint
> +    # 2x mvc_8 breakpoint, segv, breakpoint
> +    for _ in range(14):
> +        gdb.execute("c")
> +    report(illegal_op.hit_count == 1, "illegal_op.hit_count == 1")
> +    report(stg.hit_count == 4, "stg.hit_count == 4")
> +    report(mvc_8.hit_count == 4, "mvc_8.hit_count == 4")
> +
> +    # The test must succeed.
> +    gdb.Breakpoint("_exit")
> +    gdb.execute("c")
> +    status = int(gdb.parse_and_eval("$r2"))
> +    report(status == 0, "status == 0");
> +
> +
> +#
> +# This runs as the script it sourced (via -x, via run-test.py)
> +#
> +try:
> +    inferior = gdb.selected_inferior()
> +    arch = inferior.architecture()
> +    print("ATTACHED: %s" % arch.name())
> +except (gdb.error, AttributeError):
> +    print("SKIPPING (not connected)", file=sys.stderr)
> +    exit(0)
> +
> +if gdb.parse_and_eval("$pc") == 0:
> +    print("SKIP: PC not set")
> +    exit(0)
> +
> +try:
> +    # These are not very useful in scripts
> +    gdb.execute("set pagination off")
> +    gdb.execute("set confirm off")
> +
> +    # Run the actual tests
> +    run_test()
> +except (gdb.error):
> +    print("GDB Exception: %s" % (sys.exc_info()[0]))
> +    failcount += 1
> +    pass
> +
> +print("All tests complete: %d failures" % failcount)
> +exit(failcount)
> diff --git a/tests/tcg/s390x/signals-s390x.c
> b/tests/tcg/s390x/signals-s390x.c
> new file mode 100644
> index 0000000000..dc2f8ee59a
> --- /dev/null
> +++ b/tests/tcg/s390x/signals-s390x.c
> @@ -0,0 +1,165 @@
> +#include <assert.h>
> +#include <signal.h>
> +#include <string.h>
> +#include <sys/mman.h>
> +#include <ucontext.h>
> +#include <unistd.h>
> +
> +/*
> + * Various instructions that generate SIGILL and SIGSEGV. They could
> have been
> + * defined in a separate .s file, but this would complicate the
> build, so the
> + * inline asm is used instead.
> + */
> +
> +void illegal_op(void);
> +void after_illegal_op(void);
> +asm(".globl\tillegal_op\n"
> +    "illegal_op:\t.byte\t0x00,0x00\n"
> +    "\t.globl\tafter_illegal_op\n"
> +    "after_illegal_op:\tbr\t%r14");
> +
> +void stg(void *dst, unsigned long src);
> +asm(".globl\tstg\n"
> +    "stg:\tstg\t%r3,0(%r2)\n"
> +    "\tbr\t%r14");
> +
> +void mvc_8(void *dst, void *src);
> +asm(".globl\tmvc_8\n"
> +    "mvc_8:\tmvc\t0(8,%r2),0(%r3)\n"
> +    "\tbr\t%r14");
> +
> +static void safe_puts(const char *s)
> +{
> +    write(0, s, strlen(s));
> +    write(0, "\n", 1);
> +}
> +
> +enum exception {
> +    exception_operation,
> +    exception_translation,
> +    exception_protection,
> +};
> +
> +static struct {
> +    int sig;
> +    void *addr;
> +    unsigned long psw_addr;
> +    enum exception exception;
> +} expected;
> +
> +static void handle_signal(int sig, siginfo_t *info, void *ucontext)
> +{
> +    void *page;
> +    int err;
> +
> +    if (sig != expected.sig) {
> +        safe_puts("[  FAILED  ] wrong signal");
> +        _exit(1);
> +    }
> +
> +    if (info->si_addr != expected.addr) {
> +        safe_puts("[  FAILED  ] wrong si_addr");
> +        _exit(1);
> +    }
> +
> +    if (((ucontext_t *)ucontext)->uc_mcontext.psw.addr !=
> expected.psw_addr) {
> +        safe_puts("[  FAILED  ] wrong psw.addr");
> +        _exit(1);
> +    }
> +
> +    switch (expected.exception) {
> +    case exception_translation:
> +        page = mmap(expected.addr, 4096, PROT_READ | PROT_WRITE,
> +                    MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0);
> +        if (page != expected.addr) {
> +            safe_puts("[  FAILED  ] mmap() failed");
> +            _exit(1);
> +        }
> +        break;
> +    case exception_protection:
> +        err = mprotect(expected.addr, 4096, PROT_READ | PROT_WRITE);
> +        if (err != 0) {
> +            safe_puts("[  FAILED  ] mprotect() failed");
> +            _exit(1);
> +        }
> +        break;
> +    default:
> +        break;
> +    }
> +}
> +
> +static void check_sigsegv(void *func, enum exception exception,
> +                          unsigned long val)
> +{
> +    int prot;
> +    unsigned long *page;
> +    unsigned long *addr;
> +    int err;
> +
> +    prot = exception == exception_translation ? PROT_NONE :
> PROT_READ;
> +    page = mmap(NULL, 4096, prot, MAP_PRIVATE | MAP_ANONYMOUS, -1,
> 0);
> +    assert(page != MAP_FAILED);
> +    if (exception == exception_translation) {
> +        /* Hopefully nothing will be mapped at this address. */
> +        err = munmap(page, 4096);
> +        assert(err == 0);
> +    }
> +    addr = page + (val & 0x1ff);
> +
> +    expected.sig = SIGSEGV;
> +    expected.addr = page;
> +    expected.psw_addr = (unsigned long)func;
> +    expected.exception = exception;
> +    if (func == stg) {
> +        stg(addr, val);
> +    } else {
> +        assert(func == mvc_8);
> +        mvc_8(addr, &val);
> +    }
> +    assert(*addr == val);
> +
> +    err = munmap(page, 4096);
> +    assert(err == 0);
> +}
> +
> +int main(void)
> +{
> +    struct sigaction act;
> +    int err;
> +
> +    memset(&act, 0, sizeof(act));
> +    act.sa_sigaction = handle_signal;
> +    act.sa_flags = SA_SIGINFO;
> +    err = sigaction(SIGILL, &act, NULL);
> +    assert(err == 0);
> +    err = sigaction(SIGSEGV, &act, NULL);
> +    assert(err == 0);
> +
> +    safe_puts("[ RUN      ] Operation exception");
> +    expected.sig = SIGILL;
> +    expected.addr = illegal_op;
> +    expected.psw_addr = (unsigned long)after_illegal_op;
> +    expected.exception = exception_operation;
> +    illegal_op();
> +    safe_puts("[       OK ]");
> +
> +    safe_puts("[ RUN      ] Translation exception from stg");
> +    check_sigsegv(stg, exception_translation, 42);
> +    safe_puts("[       OK ]");
> +
> +    safe_puts("[ RUN      ] Translation exception from mvc");
> +    check_sigsegv(mvc_8, exception_translation, 4242);
> +    safe_puts("[       OK ]");
> +
> +    safe_puts("[ RUN      ] Protection exception from stg");
> +    check_sigsegv(stg, exception_protection, 424242);
> +    safe_puts("[       OK ]");
> +
> +    safe_puts("[ RUN      ] Protection exception from mvc");
> +    check_sigsegv(mvc_8, exception_protection, 42424242);
> +    safe_puts("[       OK ]");
> +
> +    safe_puts("[  PASSED  ]");
> +
> +    _exit(0);
> +}

Another ping - could somebody please have a look at this patch?

Also, could the fix patch be picked separately? David has already
reviewed it a while ago.

Best regards,
Ilya