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[PATCH] Fix NetBSD/amd64 sigtramp unwinder


The NetBSD folks have changed their implementation of the signal
trampolines on amd64.  This patch makes sure GDB catches up with that.
I've got some hope that this also works for older NetBSD/amd64
kernels, although it doesn't really matter; there hasn't been an
official release yet.

Unfortunately, it seems that there's a kernel bug with stepping out of
the signal trampoline now :-(.  Need to investigate that further.

Committed,

Mark


Index: ChangeLog
from  Mark Kettenis  <kettenis@gnu.org>
 
	* amd64nbsd-tdep.c (amd64nbsd_sigcontext_addr): Remove function.
	(amd64nbsd_mcontext_addr): New function.
	(amd64nbsd_init_abi): Initialize TDEP->sigcontext_addr as
	amd64nbsd_mcontext_addr.  Directly initialize TDEP->sc_reg_offset
	with amd64nbsd_r_reg_offset, instead of building it on the fly.

 
Index: amd64nbsd-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/amd64nbsd-tdep.c,v
retrieving revision 1.8
diff -u -p -r1.8 amd64nbsd-tdep.c
--- amd64nbsd-tdep.c 9 Apr 2004 23:26:18 -0000 1.8
+++ amd64nbsd-tdep.c 10 Apr 2004 11:31:04 -0000
@@ -47,18 +47,21 @@ amd64nbsd_sigtramp_p (struct frame_info 
   return nbsd_pc_in_sigtramp (pc, name);
 }
 
-/* Assuming NEXT_FRAME is for a frame following a BSD sigtramp
-   routine, return the address of the associated sigcontext structure.  */
+/* Assuming NEXT_FRAME is preceded by a frame corresponding to a
+   NetBSD sigtramp routine, return the address of the associated
+   mcontext structure.  */
 
 static CORE_ADDR
-amd64nbsd_sigcontext_addr (struct frame_info *next_frame)
+amd64nbsd_mcontext_addr (struct frame_info *next_frame)
 {
-  CORE_ADDR sp;
+  CORE_ADDR addr;
 
-  /* The stack pointer points at `struct sigcontext' upon entry of a
+  /* The register %r15 points at `struct ucontext' upon entry of a
      signal trampoline.  */
-  sp = frame_unwind_register_unsigned (next_frame, AMD64_RSP_REGNUM);
-  return sp;
+  addr = frame_unwind_register_unsigned (next_frame, AMD64_R15_REGNUM);
+
+  /* The mcontext structure lives as offset 56 in `struct ucontext'.  */
+  return addr + 56;
 }
 
 /* NetBSD 2.0 or later.  */
@@ -99,8 +102,6 @@ static void
 amd64nbsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 {
   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
-  int *sc_reg_offset;
-  int i;
 
   /* Initialize general-purpose register set details first.  */
   tdep->gregset_reg_offset = amd64nbsd_r_reg_offset;
@@ -113,21 +114,9 @@ amd64nbsd_init_abi (struct gdbarch_info 
 
   /* NetBSD has its own convention for signal trampolines.  */
   tdep->sigtramp_p = amd64nbsd_sigtramp_p;
-  tdep->sigcontext_addr = amd64nbsd_sigcontext_addr;
-
-  /* Initialize the array with register offsets in `struct
-     sigcontext'.  This `struct sigcontext' has an sc_mcontext member
-     at offset 32, and in <machine/reg.h> we have an explicit comment
-     saying that `struct reg' is the same as mcontext.__gregs.  */
+  tdep->sigcontext_addr = amd64nbsd_mcontext_addr;
+  tdep->sc_reg_offset = amd64nbsd_r_reg_offset;
   tdep->sc_num_regs = ARRAY_SIZE (amd64nbsd_r_reg_offset);
-  tdep->sc_reg_offset = XCALLOC (tdep->sc_num_regs, int);
-  for (i = 0; i < tdep->sc_num_regs; i++)
-    {
-      if (amd64nbsd_r_reg_offset[i] < 0)
-	tdep->sc_reg_offset[i] = -1;
-      else
-	tdep->sc_reg_offset[i] = 32 + amd64nbsd_r_reg_offset[i];
-    }
 
   /* NetBSD uses SVR4-style shared libraries.  */
   set_solib_svr4_fetch_link_map_offsets


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