A better fix for handling different FPU initial control words for different

ABIs:
- Store the FPU initial control word in the pcb for each thread.
- When first using the FPU, load the initial control word after restoring
  the clean state if it is not the standard control word.
- Provide a correct control word for Linux/i386 binaries under
  FreeBSD/amd64.
- Adjust the control word returned for fpugetregs()/npxgetregs() when a
  thread hasn't used the FPU yet to reflect the real initial control
  word for the current ABI.
- The Linux/i386 ABI for FreeBSD/i386 now properly sets the right control
  word instead of trashing whatever the current state of the FPU is.

Reviewed by:	bde

1 files changed, 3 insertions, 7 deletions

diff --git a/sys/i386/linux/linux_sysvec.c b/sys/i386/linux/linux_sysvec.c
index c98fe14..4efd496 100644
--- a/sys/i386/linux/linux_sysvec.c
+++ b/sys/i386/linux/linux_sysvec.c
@@ -89,9 +89,6 @@ MALLOC_DEFINE(M_LINUX, "linux", "Linux mode structures");
 #define	LINUX_SYS_linux_rt_sendsig	0
 #define	LINUX_SYS_linux_sendsig		0
 
-#define	fldcw(addr)		__asm("fldcw %0" : : "m" (*(addr)))
-#define	__LINUX_NPXCW__		0x37f
-
 extern char linux_sigcode[];
 extern int linux_szsigcode;
 
@@ -930,16 +927,15 @@ static void
 exec_linux_setregs(struct thread *td, u_long entry,
 		   u_long stack, u_long ps_strings)
 {
-	static const u_short control = __LINUX_NPXCW__;
 	struct pcb *pcb = td->td_pcb;
 
 	exec_setregs(td, entry, stack, ps_strings);
 
 	/* Linux sets %gs to 0, we default to _udatasel */
-	pcb->pcb_gs = 0; load_gs(0);
+	pcb->pcb_gs = 0;
+	load_gs(0);
 
-	/* Linux sets the i387 to extended precision. */
-	fldcw(&control);
+	pcb->pcb_initial_npxcw = __LINUX_NPXCW__;
 }
 
 static void