[Guile-commits] 04/07: ia64: Fix crash in thread context switch.

[Ludovic Courtès]

civodul pushed a commit to branch stable-2.2
in repository guile.

commit f92888853439a8ded221f3423865c78de2a96a14
Author: Sergei Trofimovich <address@hidden>
Date:   Sun Nov 5 09:30:45 2017 +0000

    ia64: Fix crash in thread context switch.
    
    Fixes <https://bugs.gnu.org/29151> and <https://bugs.gentoo.org/613986>.
    
    Backtrace looks like that:
    
      Program terminated with signal SIGSEGV, Segmentation fault.
      #0  0x200000000014a5c0 in scm_ia64_longjmp (JB=0x6000000000817020, VAL=1) 
at continuations.c:372
      372                   t->pending_rbs_continuation->backing_store,
      [Current thread is 1 (Thread 0x2000000000049340 (LWP 8190))]
      (gdb) bt
      #0  0x200000000014a5c0 in scm_ia64_longjmp (JB=0x6000000000817020, VAL=1) 
at continuations.c:372
      #1  0x2000000000148e00 in scm_c_abort (vm=0x60000000000edea0, 
tag=0x6000000000795ba0, n=0, argv=0x60000fffff7f0ce0, cookie=-1) at 
control.c:239
      #2  0x2000000000149070 in scm_at_abort (tag=0x6000000000795ba0, 
args=0x304) at control.c:258
      (gdb) print t
      $2 = (scm_i_thread *) 0x6000000000068000
      (gdb) print t->pending_rbs_continuation
      $3 = (scm_t_contregs *) 0xffeb
    
    The problem here is the value of 't->pending_rbs_continuation' pointer.
    It's supposed to poin to a register stack pointer or be NULL if not yet
    backed up.
    
    The problem is it is never initialized to NULL at creation time and
    contained garbage on stack. Sometimes people are lucky and have zeros
    on stack and guile works. But sometimes there is something and guile
    crashes.
    
    The fix is trivial: initialize 'pending_rbs_continuation = NULL'
    at thread registration time (the same way other threads are registered).
    
    Reported-by: Matt Turner
    
    * libguile/threads.c (guilify_self_1): Initialize pending_rbs_continuation
    to avoid crash on ia64.
    
    Signed-off-by: Sergei Trofimovich <address@hidden>
    Signed-off-by: Ludovic Courtès <address@hidden>
---
 libguile/threads.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/libguile/threads.c b/libguile/threads.c
index 9ceb5b8..770f62c 100644
--- a/libguile/threads.c
+++ b/libguile/threads.c
@@ -395,6 +395,7 @@ guilify_self_1 (struct GC_stack_base *base, int 
needs_unregister)
   t.base = base->mem_base;
 #ifdef __ia64__
   t.register_backing_store_base = base->reg_base;
+  t.pending_rbs_continuation = 0;
 #endif
   t.continuation_root = SCM_EOL;
   t.continuation_base = t.base;