[Bug 1737444] Re: gccgo setcontext conftest crashes qemu-sh4

[Thomas Huth]

The QEMU project is currently considering to move its bug tracking to
another system. For this we need to know which bugs are still valid
and which could be closed already. Thus we are setting older bugs to
"Incomplete" now.

If you still think this bug report here is valid, then please switch
the state back to "New" within the next 60 days, otherwise this report
will be marked as "Expired". Or please mark it as "Fix Released" if
the problem has been solved with a newer version of QEMU already.

Thank you and sorry for the inconvenience.

** Changed in: qemu
       Status: New => Incomplete

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https://bugs.launchpad.net/bugs/1737444

Title:
  gccgo setcontext conftest crashes qemu-sh4

Status in QEMU:
  Incomplete

Bug description:
  While testing gccgo on sh4 to add SH platform definitions to libgo, I
  discovered that the following conftest program which is part of the
  libgo configure script crashes on qemu-sh4:

  (sid-sh4-sbuild)root@z6:/# cat setcontext.c
  #include <pthread.h>                                                          
                                                                                
                                                                                
                                 
  #include <stdlib.h>                                                           
                                                                                
                                                                                
                                 
  #include <ucontext.h>                                                         
                                                                                
                                                                                
                                 
  #include <unistd.h>                                                           
                                                                                
                                                                                
                                 

  __thread int tls;

  static char stack[10 * 1024 * 1024];
  static ucontext_t c;

  /* Called via makecontext/setcontext.  */

  static void
  cfn (void)
  {
    exit (tls);
  }

  /* Called via pthread_create.  */

  static void *
  tfn (void *dummy)
  {
    /* The thread should still see this value after calling
       setcontext.  */
    tls = 0;

    setcontext (&c);

    /* The call to setcontext should not return.  */
    abort ();
  }

  int
  main ()
  {
    pthread_t tid;

    /* The thread should not see this value.  */
    tls = 1;

    if (getcontext (&c) < 0)
      abort ();

    c.uc_stack.ss_sp = stack;
  #ifdef MAKECONTEXT_STACK_TOP                                                  
                                                                                
                                                                                
                                 
    c.uc_stack.ss_sp += sizeof stack;
  #endif                                                                        
                                                                                
                                                                                
                                 
    c.uc_stack.ss_flags = 0;
    c.uc_stack.ss_size = sizeof stack;
    c.uc_link = NULL;
    makecontext (&c, cfn, 0);

    if (pthread_create (&tid, NULL, tfn, NULL) != 0)
      abort ();

    if (pthread_join (tid, NULL) != 0)
      abort ();

    /* The thread should have called exit.  */
    abort ();
  }

  (sid-sh4-sbuild)root@z6:/# gcc -o setcontext -lpthread setcontext.c
  (sid-sh4-sbuild)root@z6:/# ./setcontext 
  Unhandled trap: 0x180
  pc=0x7f69235e sr=0x00000000 pr=0x00400710 fpscr=0x00080000
  spc=0x00000000 ssr=0x00000000 gbr=0x7f658478 vbr=0x00000000
  sgr=0x00000000 dbr=0x00000000 delayed_pc=0x7f692320 fpul=0x00000000
  r0=0x00e11158 r1=0x00000000 r2=0x00000001 r3=0x7ffff2e0
  r4=0x00e11068 r5=0x7ffff314 r6=0x7ffff31c r7=0x00000000
  r8=0x004007b0 r9=0x00000000 r10=0x00000000 r11=0x00000000
  r12=0x7f79ac54 r13=0x00000000 r14=0x7ffff288 r15=0x7ffff288
  r16=0x00000000 r17=0x00000000 r18=0x00000000 r19=0x00000000
  r20=0x00000000 r21=0x00000000 r22=0x00000000 r23=0x00000000
  (sid-sh4-sbuild)root@z6:/#

  The same code works fine on my Renesas SH7785LCR evaluation board:

  root@tirpitz:~> uname -a
  Linux tirpitz 3.16.7-ckt7 #8 PREEMPT Fri Oct 21 18:47:41 CEST 2016 sh4a 
GNU/Linux
  root@tirpitz:~> gcc -o setcontext setcontext.c  -lpthread
  root@tirpitz:~> ./setcontext 
  root@tirpitz:~> echo $?
  0
  root@tirpitz:~>

  Due to this bug, it is not possible to compile gcc-7 with the Go
  frontend enabled on qemu-sh4.

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