2 files changed, 20 insertions, 2 deletions

diff --git a/arch/sparc64/kernel/etrap.S b/arch/sparc64/kernel/etrap.S
index 4b2bf9eb447a..b49d3b60bc0c 100644
--- a/arch/sparc64/kernel/etrap.S
+++ b/arch/sparc64/kernel/etrap.S
@@ -53,7 +53,11 @@ etrap_irq:
                 stx     %g3, [%g2 + STACKFRAME_SZ + PT_V9_TPC]
                 rd      %y, %g3
                 stx     %g1, [%g2 + STACKFRAME_SZ + PT_V9_TNPC]
+                rdpr    %tt, %g1
                 st      %g3, [%g2 + STACKFRAME_SZ + PT_V9_Y]
+                sethi   %hi(PT_REGS_MAGIC), %g3
+                or      %g3, %g1, %g1
+                st      %g1, [%g2 + STACKFRAME_SZ + PT_V9_MAGIC]
 
                 rdpr    %cansave, %g1
                 brnz,pt %g1, etrap_save
diff --git a/include/asm-sparc64/ptrace.h b/include/asm-sparc64/ptrace.h
index 6da197803efc..b4b951d570bb 100644
--- a/include/asm-sparc64/ptrace.h
+++ b/include/asm-sparc64/ptrace.h
@@ -8,6 +8,8 @@
  * stack during a system call and basically all traps.
  */
 
+#define PT_REGS_MAGIC 0x57ac6c00
+
 #ifndef __ASSEMBLY__
 
 struct pt_regs {
@@ -16,7 +18,19 @@ struct pt_regs {
         unsigned long tpc;
         unsigned long tnpc;
         unsigned int y;
-        unsigned int fprs;
+
+        /* We encode a magic number, PT_REGS_MAGIC, along
+         * with the %tt (trap type) register value at trap
+         * entry time.  The magic number allows us to identify
+         * accurately a trap stack frame in the stack
+         * unwinder, and the %tt value allows us to test
+         * things like "in a system call" etc. for an arbitray
+         * process.
+         *
+         * The PT_REGS_MAGIC is choosen such that it can be
+         * loaded completely using just a sethi instruction.
+         */
+        unsigned int magic;
 };
 
 struct pt_regs32 {
@@ -147,7 +161,7 @@ extern void __show_regs(struct pt_regs *);
 #define PT_V9_TPC    0x88
 #define PT_V9_TNPC   0x90
 #define PT_V9_Y      0x98
-#define PT_V9_FPRS   0x9c
+#define PT_V9_MAGIC  0x9c
 #define PT_TSTATE       PT_V9_TSTATE
 #define PT_TPC          PT_V9_TPC
 #define PT_TNPC         PT_V9_TNPC