Fix a problem in tracing across fork on PPC64

In order to avoid single-stepping through large portions of the
dynamic linker, ltrace remembers at which address the instruction that
resolved a PLT slot is.  It then puts a breakpoint to this address so
that it can fast-forward to that address next time it needs to catch a
PLT slot being resolved.

When a process is cloned, the pointer to this breakpoint is simply
copied over to the new process, instead of being looked up in the new
process structures.  This patches fixes this.

diff --git a/sysdeps/linux-gnu/ppc/plt.c b/sysdeps/linux-gnu/ppc/plt.c
index 3ec1397..8715da6 100644 (file)
--- a/sysdeps/linux-gnu/ppc/plt.c
+++ b/sysdeps/linux-gnu/ppc/plt.c
@@ -1,6 +1,6 @@
 /*
  * This file is part of ltrace.
- * Copyright (C) 2012,2013 Petr Machata, Red Hat Inc.
+ * Copyright (C) 2012,2013,2014 Petr Machata, Red Hat Inc.
  * Copyright (C) 2004,2008,2009 Juan Cespedes
  * Copyright (C) 2006 Paul Gilliam
  *
@@ -1157,6 +1157,18 @@ int
 arch_process_clone(struct process *retp, struct process *proc)
 {
        retp->arch = proc->arch;
+
+       if (retp->arch.dl_plt_update_bp != NULL) {
+               /* Point it to the corresponding breakpoint in RETP.
+                * It must be there, this part of PROC has already
+                * been cloned to RETP.  */
+               retp->arch.dl_plt_update_bp
+                       = address2bpstruct(retp,
+                                          retp->arch.dl_plt_update_bp->addr);
+
+               assert(retp->arch.dl_plt_update_bp != NULL);
+       }
+
        return 0;
 }