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

[John Paul Adrian Glaubitz]

This still reproduces on git master:

(sid-sh4-sbuild)address@hidden:/# gcc setcontext.c -o setcontext -lpthread
(sid-sh4-sbuild)address@hidden:/# ./setcontext 
Unhandled trap: 0x180
pc=0x7f68e99e sr=0x00000000 pr=0x00400750 fpscr=0x00080000
spc=0x00000000 ssr=0x00000000 gbr=0x7f7a2de8 vbr=0x00000000
sgr=0x00000000 dbr=0x00000000 delayed_pc=0x7f68e960 fpul=0x00000000
r0=0x00e11158 r1=0x00000000 r2=0x00000001 r3=0x7ffff590
r4=0x00e11068 r5=0x7ffff5c4 r6=0x7ffff5cc r7=0x00000000
r8=0x004007f0 r9=0x00000000 r10=0x00000000 r11=0x00000000
r12=0x7f79ec64 r13=0x00000000 r14=0x7ffff538 r15=0x7ffff538
r16=0x00000000 r17=0x00000000 r18=0x00000000 r19=0x00000000
r20=0x00000000 r21=0x00000000 r22=0x00000000 r23=0x00000000
(sid-sh4-sbuild)address@hidden:/#

And it is fixed by reverting 61dedf2af7

(sid-sh4-sbuild)address@hidden:/# ./setcontext 
(sid-sh4-sbuild)address@hidden:/# echo $?
0
(sid-sh4-sbuild)address@hidden:/#

So it's presumably the same bug as
https://bugs.launchpad.net/qemu/+bug/1796520

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

Title:
  gccgo setcontext conftest crashes qemu-sh4

Status in QEMU:
  New

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)address@hidden:/# 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)address@hidden:/# gcc -o setcontext -lpthread setcontext.c
  (sid-sh4-sbuild)address@hidden:/# ./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)address@hidden:/#

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

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

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

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