powerpc: Allow emulating optional FPU instructions on CPUs with an FPU

The e5500 has an FPU, but lacks the optional fsqrt instruction.  This
instruction gets emulated in the kernel, but the emulation uses stale data,
from the last switch out, and does not return the result of the operation
immediately.  Fix both of these conditions by saving and restoring the FPRs
around the emulation point.

MFC after:	1 week
MFC with:	r345829

3 files changed, 10 insertions, 5 deletions

diff --git a/sys/powerpc/include/trap.h b/sys/powerpc/include/trap.h
index fc927419db68..5017a7535d29 100644
--- a/sys/powerpc/include/trap.h
+++ b/sys/powerpc/include/trap.h
@@ -152,10 +152,10 @@
 
 #ifndef LOCORE
 struct	trapframe;
-struct	pcb;
+struct	thread;
 extern int	(*hmi_handler)(struct trapframe *);
 void    trap(struct trapframe *);
-int	ppc_instr_emulate(struct trapframe *, struct pcb *);
+int	ppc_instr_emulate(struct trapframe *, struct thread *);
 #endif
 
 #endif	/* _POWERPC_TRAP_H_ */
diff --git a/sys/powerpc/powerpc/exec_machdep.c b/sys/powerpc/powerpc/exec_machdep.c
index 3ae1640b2642..0ce6f0e26869 100644
--- a/sys/powerpc/powerpc/exec_machdep.c
+++ b/sys/powerpc/powerpc/exec_machdep.c
@@ -1081,8 +1081,9 @@ emulate_mtspr(int spr, int reg, struct trapframe *frame){
 
 #define XFX 0xFC0007FF
 int
-ppc_instr_emulate(struct trapframe *frame, struct pcb *pcb)
+ppc_instr_emulate(struct trapframe *frame, struct thread *td)
 {
+	struct pcb *pcb;
 	uint32_t instr;
 	int reg, sig;
 	int rs, spr;
@@ -1109,12 +1110,16 @@ ppc_instr_emulate(struct trapframe *frame, struct pcb *pcb)
 		return (0);
 	}
 
+	pcb = td->td_pcb;
 #ifdef FPU_EMU
 	if (!(pcb->pcb_flags & PCB_FPREGS)) {
 		bzero(&pcb->pcb_fpu, sizeof(pcb->pcb_fpu));
 		pcb->pcb_flags |= PCB_FPREGS;
-	}
+	} else if (pcb->pcb_flags & PCB_FPU)
+		save_fpu(td);
 	sig = fpu_emulate(frame, &pcb->pcb_fpu);
+	if ((sig == 0 || sig == SIGFPE) && pcb->pcb_flags & PCB_FPU)
+		enable_fpu(td);
 #endif
 	if (sig == SIGILL) {
 		if (pcb->pcb_lastill != frame->srr0) {
diff --git a/sys/powerpc/powerpc/trap.c b/sys/powerpc/powerpc/trap.c
index 111e69a7b32e..2a63f47b71a1 100644
--- a/sys/powerpc/powerpc/trap.c
+++ b/sys/powerpc/powerpc/trap.c
@@ -363,7 +363,7 @@ trap(struct trapframe *frame)
  				sig = SIGTRAP;
 				ucode = TRAP_BRKPT;
 			} else {
-				sig = ppc_instr_emulate(frame, td->td_pcb);
+				sig = ppc_instr_emulate(frame, td);
 				if (sig == SIGILL) {
 					if (frame->srr1 & EXC_PGM_PRIV)
 						ucode = ILL_PRVOPC;