arch/tile: Change struct sigcontext to be more useful

Rather than just using pt_regs, it now contains the actual saved
state explicitly, similar to pt_regs.  By doing it this way, we
provide a cleaner API for userspace (or equivalently, we avoid the
need for libc to provide its own definition of sigcontext).

While we're at it, move PT_FLAGS_xxx to where they are not visible
from userspace.  And always pass siginfo and mcontext to signal
handlers, even if they claim they don't need it, since sometimes
they actually try to use it anyway in practice.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
diff --git a/arch/tile/include/asm/ptrace.h b/arch/tile/include/asm/ptrace.h
index acdae81..4a02bb0 100644
--- a/arch/tile/include/asm/ptrace.h
+++ b/arch/tile/include/asm/ptrace.h
@@ -51,10 +51,7 @@
 
 /*
  * This struct defines the way the registers are stored on the stack during a
- * system call/exception.  It should be a multiple of 8 bytes to preserve
- * normal stack alignment rules.
- *
- * Must track <sys/ucontext.h> and <sys/procfs.h>
+ * system call or exception.  "struct sigcontext" has the same shape.
  */
 struct pt_regs {
 	/* Saved main processor registers; 56..63 are special. */
@@ -80,11 +77,6 @@
 
 #endif /* __ASSEMBLY__ */
 
-/* Flag bits in pt_regs.flags */
-#define PT_FLAGS_DISABLE_IRQ    1  /* on return to kernel, disable irqs */
-#define PT_FLAGS_CALLER_SAVES   2  /* caller-save registers are valid */
-#define PT_FLAGS_RESTORE_REGS   4  /* restore callee-save regs on return */
-
 #define PTRACE_GETREGS		12
 #define PTRACE_SETREGS		13
 #define PTRACE_GETFPREGS	14
@@ -101,6 +93,11 @@
 
 #ifdef __KERNEL__
 
+/* Flag bits in pt_regs.flags */
+#define PT_FLAGS_DISABLE_IRQ    1  /* on return to kernel, disable irqs */
+#define PT_FLAGS_CALLER_SAVES   2  /* caller-save registers are valid */
+#define PT_FLAGS_RESTORE_REGS   4  /* restore callee-save regs on return */
+
 #ifndef __ASSEMBLY__
 
 #define instruction_pointer(regs) ((regs)->pc)