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

[Thomas Huth]

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?

 Thomas