Revamp of the syscall path, exception and context handling. The

prime objectives are:
o  Implement a syscall path based on the epc inststruction (see
   sys/ia64/ia64/syscall.s).
o  Revisit the places were we need to save and restore registers
   and define those contexts in terms of the register sets (see
   sys/ia64/include/_regset.h).

Secundairy objectives:
o  Remove the requirement to use contigmalloc for kernel stacks.
o  Better handling of the high FP registers for SMP systems.
o  Switch to the new cpu_switch() and cpu_throw() semantics.
o  Add a good unwinder to reconstruct contexts for the rare
   cases we need to (see sys/contrib/ia64/libuwx)

Many files are affected by this change. Functionally it boils
down to:
o  The EPC syscall doesn't preserve registers it does not need
   to preserve and places the arguments differently on the stack.
   This affects libc and truss.
o  The address of the kernel page directory (kptdir) had to
   be unstaticized for use by the nested TLB fault handler.
   The name has been changed to ia64_kptdir to avoid conflicts.
   The renaming affects libkvm.
o  The trapframe only contains the special registers and the
   scratch registers. For syscalls using the EPC syscall path
   no scratch registers are saved. This affects all places where
   the trapframe is accessed. Most notably the unaligned access
   handler, the signal delivery code and the debugger.
o  Context switching only partly saves the special registers
   and the preserved registers. This affects cpu_switch() and
   triggered the move to the new semantics, which additionally
   affects cpu_throw().
o  The high FP registers are either in the PCB or on some
   CPU. context switching for them is done lazily. This affects
   trap().
o  The mcontext has room for all registers, but not all of them
   have to be defined in all cases. This mostly affects signal
   delivery code now. The *context syscalls are as of yet still
   unimplemented.

Many details went into the removal of the requirement to use
contigmalloc for kernel stacks. The details are mostly CPU
specific and limited to exception_save() and exception_restore().
The few places where we create, destroy or switch stacks were
mostly simplified by not having to construct physical addresses
and additionally saving the virtual addresses for later use.

Besides more efficient context saving and restoring, which of
course yields a noticable speedup, this also fixes the dreaded
SMP bootup problem as a side-effect. The details of which are
still not fully understood.

This change includes all the necessary backward compatibility
code to have it handle older userland binaries that use the
break instruction for syscalls. Support for break-based syscalls
has been pessimized in favor of a clean implementation. Due to
the overall better performance of the kernel, this will still
be notived as an improvement if it's noticed at all.

Approved by: re@ (jhb)

1 files changed, 12 insertions, 39 deletions

diff --git a/sys/ia64/include/signal.h b/sys/ia64/include/signal.h
index 1a20e01..025b979 100644
--- a/sys/ia64/include/signal.h
+++ b/sys/ia64/include/signal.h
@@ -51,62 +51,35 @@ typedef long	sig_atomic_t;
 #endif
 
 #if __XSI_VISIBLE
-/*
- * Minimum signal stack size. The current signal frame
- * for IA-64 is 2656 bytes large.
- */
+/* Minimum signal stack size. */
 #define MINSIGSTKSZ     (3072 * 4)
 #endif
 
-#if __BSD_VISIBLE
-#ifndef _IA64_FPREG_DEFINED
-
-struct ia64_fpreg {
-	unsigned long	fpr_bits[2];
-} __aligned(16);
-
-#define _IA64_FPREG_DEFINED
-
-#endif
-#endif
-
-
 /*
  * Information pushed on stack when a signal is delivered.
  * This is used by the kernel to restore state following
  * execution of the signal handler.  It is also made available
  * to the handler to allow it to restore state properly if
  * a non-standard exit is performed.
- *
- * Note that sc_regs[] and sc_fpregs[]+sc_fpcr are inline
- * representations of 'struct reg' and 'struct fpreg', respectively.
  */
 
 #if __BSD_VISIBLE
+#include <machine/_regset.h>
+
 /*
  * The sequence of the fields should match those in
  * mcontext_t. Keep them in sync!
  */
 struct sigcontext {
-	struct __sigset	sc_mask;		/* signal mask to restore */
-	unsigned long	sc_onstack;
-	unsigned long	sc_flags;
-	unsigned long	sc_nat;
-	unsigned long	sc_sp;
-	unsigned long	sc_ip;
-	unsigned long	sc_cfm;
-	unsigned long	sc_um;
-	unsigned long	sc_ar_rsc;
-	unsigned long	sc_ar_bsp;
-	unsigned long	sc_ar_rnat;
-	unsigned long	sc_ar_ccv;
-	unsigned long	sc_ar_unat;
-	unsigned long	sc_ar_fpsr;
-	unsigned long	sc_ar_pfs;
-	unsigned long	sc_pr;
-	unsigned long	sc_br[8];
-	unsigned long	sc_gr[32];
-	struct ia64_fpreg sc_fr[128];
+	struct __sigset		sc_mask;	/* signal mask to restore */
+	unsigned long		sc_onstack;
+	unsigned long		sc_flags;
+	struct _special		sc_special;
+	struct _callee_saved	sc_preserved;
+	struct _callee_saved_fp	sc_preserved_fp;
+	struct _caller_saved	sc_scratch;
+	struct _caller_saved_fp	sc_scratch_fp;
+	struct _high_fp		sc_high_fp;
 };
 #endif /* __BSD_VISIBLE */