* config/m68k/tm-m68k.h (SIG_PC_FP_OFFSET, SIG_SP_FP_OFFSET):

	Define for correct handling of bachtraces through _sigtramp.

1 files changed, 19 insertions, 0 deletions

diff --git a/gdb/config/m68k/tm-sun3.h b/gdb/config/m68k/tm-sun3.h
index 69d1055..103abfc 100644
--- a/gdb/config/m68k/tm-sun3.h
+++ b/gdb/config/m68k/tm-sun3.h
@@ -71,3 +71,22 @@ extern CORE_ADDR m68k_saved_pc_after_call PARAMS ((struct frame_info *));
 
 /* The code which tries to deal with this bug is never harmful on a sun3.  */
 #define SUN_FIXED_LBRAC_BUG (0)
+
+/* On the sun3 the kernel pushes a sigcontext on the user stack and then
+   `calls' _sigtramp in user code. _sigtramp saves the floating point status
+   on the stack and calls the signal handler function. The stack does not
+   contain enough information to allow a normal backtrace, but sigcontext
+   contains the saved user pc/sp. FRAME_CHAIN and friends in tm-m68k.h and
+   m68k_find_saved_regs deal with this situation by manufacturing a fake frame
+   for _sigtramp.
+   SIG_PC_FP_OFFSET is the offset from the signal handler frame to the
+   saved pc in sigcontext.
+   SIG_SP_FP_OFFSET is the offset from the signal handler frame to the end
+   of sigcontext which is identical to the saved sp at SIG_PC_FP_OFFSET - 4.
+
+   Please note that it is impossible to correctly backtrace from a breakpoint
+   in _sigtramp as _sigtramp modifies the stack pointer a few times.  */
+
+#undef SIG_PC_FP_OFFSET
+#define SIG_PC_FP_OFFSET 324
+#define SIG_SP_FP_OFFSET 332