Re: PING: [PATCH 2/2] tests/tcg/s390x: Test unwinding from signal handlers

[Laurent Vivier <laurent@vivier.eu>]

Le 24/05/2022 à 11:56, Thomas Huth a écrit :
> On 19/05/2022 13.34, Ilya Leoshkevich wrote:
>> On Wed, 2022-05-04 at 00:51 +0200, Ilya Leoshkevich wrote:
>>> Add a small test to prevent regressions.
>>>
>>> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
>>> ---
>>>   tests/tcg/s390x/signals-s390x.c | 69 ++++++++++++++++++++++++++-----
>>> -- 
>>>   1 file changed, 55 insertions(+), 14 deletions(-)
>>>
>>> diff --git a/tests/tcg/s390x/signals-s390x.c
>>> b/tests/tcg/s390x/signals-s390x.c
>>> index dc2f8ee59a..48c3b6cdfd 100644
>>> --- a/tests/tcg/s390x/signals-s390x.c
>>> +++ b/tests/tcg/s390x/signals-s390x.c
>>> @@ -1,4 +1,5 @@
>>>   #include <assert.h>
>>> +#include <execinfo.h>
>>>   #include <signal.h>
>>>   #include <string.h>
>>>   #include <sys/mman.h>
>>> @@ -11,22 +12,28 @@
>>>    * inline asm is used instead.
>>>    */
>>> +#define DEFINE_ASM_FUNCTION(name, body) \
>>> +    asm(".globl " #name "\n" \
>>> +        #name ":\n" \
>>> +        ".cfi_startproc\n" \
>>> +        body "\n" \
>>> +        "br %r14\n" \
>>> +        ".cfi_endproc");
>>> +
>>>   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");
>>> +extern const char after_illegal_op;
>>> +DEFINE_ASM_FUNCTION(illegal_op,
>>> +    ".byte 0x00,0x00\n"
>>> +    ".globl after_illegal_op\n"
>>> +    "after_illegal_op:")
>>>   void stg(void *dst, unsigned long src);
>>> -asm(".globl\tstg\n"
>>> -    "stg:\tstg\t%r3,0(%r2)\n"
>>> -    "\tbr\t%r14");
>>> +DEFINE_ASM_FUNCTION(stg, "stg %r3,0(%r2)")
>>>   void mvc_8(void *dst, void *src);
>>> -asm(".globl\tmvc_8\n"
>>> -    "mvc_8:\tmvc\t0(8,%r2),0(%r3)\n"
>>> -    "\tbr\t%r14");
>>> +DEFINE_ASM_FUNCTION(mvc_8, "mvc 0(8,%r2),0(%r3)")
>>> +
>>> +extern const char return_from_main_1;
>>>   static void safe_puts(const char *s)
>>>   {
>>> @@ -49,8 +56,9 @@ static struct {
>>>   static void handle_signal(int sig, siginfo_t *info, void *ucontext)
>>>   {
>>> +    int err, i, n_frames;
>>> +    void *frames[16];
>>>       void *page;
>>> -    int err;
>>>       if (sig != expected.sig) {
>>>           safe_puts("[  FAILED  ] wrong signal");
>>> @@ -86,6 +94,17 @@ static void handle_signal(int sig, siginfo_t
>>> *info, void *ucontext)
>>>       default:
>>>           break;
>>>       }
>>> +
>>> +    n_frames = backtrace(frames, sizeof(frames) /
>>> sizeof(frames[0]));
>>> +    for (i = 0; i < n_frames; i++) {
>>> +        if (frames[i] == &return_from_main_1) {
>>> +            break;
>>> +        }
>>> +    }
>>> +    if (i == n_frames) {
>>> +        safe_puts("[  FAILED  ] backtrace() is broken");
>>> +        _exit(1);
>>> +    }
>>>   }
>>>   static void check_sigsegv(void *func, enum exception exception,
>>> @@ -122,7 +141,7 @@ static void check_sigsegv(void *func, enum
>>> exception exception,
>>>       assert(err == 0);
>>>   }
>>> -int main(void)
>>> +int main_1(void)
>>>   {
>>>       struct sigaction act;
>>>       int err;
>>> @@ -138,7 +157,7 @@ int main(void)
>>>       safe_puts("[ RUN      ] Operation exception");
>>>       expected.sig = SIGILL;
>>>       expected.addr = illegal_op;
>>> -    expected.psw_addr = (unsigned long)after_illegal_op;
>>> +    expected.psw_addr = (unsigned long)&after_illegal_op;
>>>       expected.exception = exception_operation;
>>>       illegal_op();
>>>       safe_puts("[       OK ]");
>>> @@ -163,3 +182,25 @@ int main(void)
>>>       _exit(0);
>>>   }
>>> +
>>> +/*
>>> + * Define main() in assembly in order to test that unwinding from
>>> signal
>>> + * handlers until main() works. This way we can define a specific
>>> point that
>>> + * the unwinder should reach. This is also better than defining
>>> main() in C
>>> + * and using inline assembly to call main_1(), since it's not easy
>>> to get all
>>> + * the clobbers right.
>>> + */
>>> +
>>> +DEFINE_ASM_FUNCTION(main,
>>> +    "stmg %r14,%r15,112(%r15)\n"
>>> +    ".cfi_offset 14,-48\n"
>>> +    ".cfi_offset 15,-40\n"
>>> +    "lay %r15,-160(%r15)\n"
>>> +    ".cfi_def_cfa_offset 320\n"
>>> +    "brasl %r14,main_1\n"
>>> +    ".globl return_from_main_1\n"
>>> +    "return_from_main_1:\n"
>>> +    "lmg %r14,%r15,272(%r15)\n"
>>> +    ".cfi_restore 15\n"
>>> +    ".cfi_restore 14\n"
>>> +    ".cfi_def_cfa_offset 160");
>>
>> Ping.
> 
> Acked-by: Thomas Huth <thuth@redhat.com>
> 
> Laurent, do you want to take these two patches through your linux-user branch, or shall I take them 
> via the s390x branch?

I will take both.

Thanks,
Laurent