1 files changed, 70 insertions, 2 deletions
diff --git a/gdb/config/i386/tm-linux.h b/gdb/config/i386/tm-linux.h
index e39dc04..0767bd9 100644
--- a/gdb/config/i386/tm-linux.h
+++ b/gdb/config/i386/tm-linux.h
@@ -26,8 +26,14 @@
 
 #include "i386/tm-i386.h"
 
-/* Offset to saved PC in sigcontext, from <linux/signal.h>.  */
-#define SIGCONTEXT_PC_OFFSET 38
+/* Size of sigcontext, from <asm/sigcontext.h>.  */
+#define LINUX_SIGCONTEXT_SIZE (88)
+
+/* Offset to saved PC in sigcontext, from <asm/sigcontext.h>.  */
+#define LINUX_SIGCONTEXT_PC_OFFSET (56)
+
+/* Offset to saved SP in sigcontext, from <asm/sigcontext.h>.  */
+#define LINUX_SIGCONTEXT_SP_OFFSET (28)
 
 /* We need this file for the SOLIB_TRAMPOLINE stuff. */
 
@@ -36,4 +42,66 @@
 /* The following works around a problem with /usr/include/sys/procfs.h  */
 #define sys_quotactl 1
 
+/* When the i386 Linux kernel calls a signal handler, the return
+   address points to a bit of code on the stack.  These definitions
+   are used to identify this bit of code as a signal trampoline in
+   order to support backtracing through calls to signal handlers.  */
+
+#define I386_LINUX_SIGTRAMP
+#define IN_SIGTRAMP(pc, name) ((name) == NULL && i386_linux_sigtramp (pc))
+
+extern int i386_linux_sigtramp PARAMS ((CORE_ADDR));
+
+/* We need our own version of sigtramp_saved_pc to get the saved PC in
+   a sigtramp routine.  */
+
+#define sigtramp_saved_pc i386_linux_sigtramp_saved_pc
+extern CORE_ADDR i386_linux_sigtramp_saved_pc PARAMS ((struct frame_info *));
+
+/* Signal trampolines don't have a meaningful frame.  As in tm-i386.h,
+   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 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.  */
+
+#define FRAMELESS_SIGNAL(FRAME)					\
+  ((FRAME)->next != NULL					\
+   && (FRAME)->next->signal_handler_caller			\
+   && frameless_look_for_prologue (FRAME))
+
+#undef FRAME_CHAIN
+#define FRAME_CHAIN(FRAME)					\
+  ((FRAME)->signal_handler_caller				\
+   ? (FRAME)->frame						\
+    : (FRAMELESS_SIGNAL (FRAME)					\
+       ? (FRAME)->frame						\
+       : (!inside_entry_file ((FRAME)->pc)			\
+	  ? read_memory_integer ((FRAME)->frame, 4)		\
+	  : 0)))
+
+#undef FRAME_SAVED_PC
+#define FRAME_SAVED_PC(FRAME)					\
+  ((FRAME)->signal_handler_caller				\
+   ? sigtramp_saved_pc (FRAME)					\
+   : (FRAMELESS_SIGNAL (FRAME)					\
+      ? read_memory_integer (i386_linux_sigtramp_saved_sp ((FRAME)->next), 4) \
+      : read_memory_integer ((FRAME)->frame + 4, 4)))
+
+extern CORE_ADDR i386_linux_sigtramp_saved_sp PARAMS ((struct frame_info *));
+
 #endif /* #ifndef TM_LINUX_H */