* i386-tdep.c (i386_frameless_signal_p): New function.

(i386_frame_chain): Deal with frameless signals.
(i386_sigtramp_saved_sp): New function.
(i386_frame_saved_pc): Deal with frameless signals.
(i386_saved_pc_after_call): Make sure the correct value is
returned just after entry into a sigtramp.
* i386bsd-tdep.c (i386bsd_sc_sp_offset, i386nbsd_sc_sp_offset,
i386fbsd4_sc_sp_offset): New variables.
(i386bsd_init_abi, i386nbsd_init_abi, i386fbsd4_init_abi): Use
these variables to initialize tdep->sc_sp_offset.  * i386bsd-nat.c
(_initialize_i386bsd_nat): Add sanity check for sc_sp_offset
similiar to what we already did for sc_pc_offset.
* i386-sol2-tdep.c (i386_sol2_init_abi): Initialize
tdep->sc_sp_offset.

1 files changed, 56 insertions, 1 deletions

diff --git a/gdb/i386-tdep.c b/gdb/i386-tdep.c
index c45c2712dc7..59401467da4 100644
--- a/gdb/i386-tdep.c
+++ b/gdb/i386-tdep.c
@@ -452,6 +452,38 @@ i386_get_frame_setup (CORE_ADDR pc)
   return (-1);
 }
 
+/* Signal trampolines don't have a meaningful frame.  The frame
+   pointer value we use is actually the frame pointer of the calling
+   frame -- that is, the frame which was in progress when the signal
+   trampoline was entered.  GDB mostly treats this frame pointer value
+   as a magic cookie.  We detect the case of a signal trampoline by
+   looking at the SIGNAL_HANDLER_CALLER field, which is set based on
+   PC_IN_SIGTRAMP.
+
+   When a signal trampoline is invoked from a frameless function, we
+   essentially have two frameless functions in a row.  In this case,
+   we use the same magic cookie for three frames in a row.  We detect
+   this case by seeing whether the next frame has
+   SIGNAL_HANDLER_CALLER set, and, if it does, checking whether the
+   current frame is actually frameless.  In this case, we need to get
+   the PC by looking at the SP register value stored in the signal
+   context.
+
+   This should work in most cases except in horrible situations where
+   a signal occurs just as we enter a function but before the frame
+   has been set up.  */
+
+/* Return non-zero if we're dealing with a frameless signal, that is,
+   a signal trampoline invoked from a frameless function.  */
+
+static int
+i386_frameless_signal_p (struct frame_info *frame)
+{
+  return (frame->next
+	  && frame->next->signal_handler_caller
+	  && frameless_look_for_prologue);
+}
+
 /* Return the chain-pointer for FRAME.  In the case of the i386, the
    frame's nominal address is the address of a 4-byte word containing
    the calling frame's address.  */
@@ -459,7 +491,8 @@ i386_get_frame_setup (CORE_ADDR pc)
 static CORE_ADDR
 i386_frame_chain (struct frame_info *frame)
 {
-  if (frame->signal_handler_caller)
+  if (frame->signal_handler_caller
+      || i386_frameless_signal_p (frame))
     return frame->frame;
 
   if (! inside_entry_file (frame->pc))
@@ -494,6 +527,19 @@ i386_sigtramp_saved_pc (struct frame_info *frame)
   return read_memory_unsigned_integer (addr + tdep->sc_pc_offset, 4);
 }
 
+/* Assuming FRAME is for a sigtramp routine, return the saved stack
+   pointer.  */
+
+static CORE_ADDR
+i386_sigtramp_saved_sp (struct frame_info *frame)
+{
+  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);
+  CORE_ADDR addr;
+
+  addr = tdep->sigcontext_addr (frame);
+  return read_memory_unsigned_integer (addr + tdep->sc_sp_offset, 4);
+}
+
 /* Return the saved program counter for FRAME.  */
 
 static CORE_ADDR
@@ -502,6 +548,12 @@ i386_frame_saved_pc (struct frame_info *frame)
   if (frame->signal_handler_caller)
     return i386_sigtramp_saved_pc (frame);
 
+  if (i386_frameless_signal_p (frame))
+    {
+      CORE_ADDR sp = i386_sigtramp_saved_sp (frame->next);
+      return read_memory_unsigned_integer (sp, 4);
+    }
+
   return read_memory_unsigned_integer (frame->frame + 4, 4);
 }
 
@@ -510,6 +562,9 @@ i386_frame_saved_pc (struct frame_info *frame)
 static CORE_ADDR
 i386_saved_pc_after_call (struct frame_info *frame)
 {
+  if (frame->signal_handler_caller)
+    return i386_sigtramp_saved_pc (frame);
+
   return read_memory_unsigned_integer (read_register (SP_REGNUM), 4);
 }