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, 11 insertions, 27 deletions

diff --git a/sys/ia64/include/ucontext.h b/sys/ia64/include/ucontext.h
index e8660a5..fc32b76 100644
--- a/sys/ia64/include/ucontext.h
+++ b/sys/ia64/include/ucontext.h
@@ -31,35 +31,19 @@
 #ifndef _MACHINE_UCONTEXT_H_
 #define	_MACHINE_UCONTEXT_H_
 
-#define IA64_MC_FLAG_ONSTACK		0
-#define IA64_MC_FLAG_IN_SYSCALL		1
-#define IA64_MC_FLAG_FPH_VALID		2
+#include <machine/_regset.h>
 
 typedef struct __mcontext {
-	/*
-	 * These fields must match the definition
-	 * of struct sigcontext. That way we can support
-	 * struct sigcontext and ucontext_t at the same
-	 * time.
-	 */
-	long	mc_onstack;		/* XXX - sigcontext compat. */
-	unsigned long	mc_flags;
-	unsigned long	mc_nat;
-	unsigned long	mc_sp;
-	unsigned long	mc_ip;
-	unsigned long	mc_cfm;
-	unsigned long	mc_um;
-	unsigned long	mc_ar_rsc;
-	unsigned long	mc_ar_bsp;
-	unsigned long	mc_ar_rnat;
-	unsigned long	mc_ar_ccv;
-	unsigned long	mc_ar_unat;
-	unsigned long	mc_ar_fpsr;
-	unsigned long	mc_ar_pfs;
-	unsigned long	mc_pr;
-	unsigned long	mc_br[8];
-	unsigned long	mc_gr[32];
-	struct ia64_fpreg mc_fr[128];
+	uint64_t		mc_flags;
+#define	IA64_MC_FLAGS_SCRATCH_VALID	1
+#define	IA64_MC_FLAGS_HIGHFP_VALID	2
+	uint64_t		_reserved_;
+	struct _special		mc_special;
+	struct _callee_saved	mc_preserved;
+	struct _callee_saved_fp	mc_preserved_fp;
+	struct _caller_saved	mc_scratch;
+	struct _caller_saved_fp	mc_scratch_fp;
+	struct _high_fp		mc_high_fp;
 } mcontext_t;
 
 #endif /* !_MACHINE_UCONTEXT_H_ */