regs: set up mxcsr properly; arch_regs_firsttimesetup()

src/arch/x86_64/include/arch/regs.h

@@ -9,6 +9,7 @@ typedef uint64_t arch_reg;
 typedef struct{
 	uint64_t gsbase, fsbase;
 	uint8_t  fx[512];
+	uint32_t mxcsr;
 } arch_extraregs;
 
 typedef struct{
@@ -16,6 +17,9 @@ typedef struct{
 } arch_regs;
 void arch_regs_saveextra(arch_extraregs* regs);
 void arch_regs_setupextra(arch_extraregs* regs);
+
+void arch_regs_firsttimesetup(arch_regs* regs, arch_extraregs* xregs);
+
 void arch_regs_setupkernel(arch_regs* regs, void* ip, void* stack, bool interrupts);
 void arch_regs_setupuser(arch_regs* regs, void* ip, void* stack, bool interrupts);
 

src/arch/x86_64/regs.c

@@ -1,12 +1,16 @@
 #include <arch/regs.h>
 #include <arch/msr.h>
 
+void arch_regs_firsttimesetup(arch_regs* regs, arch_extraregs* xregs){
+	xregs->mxcsr = 0x1F80; // all exceptions masked
+}
+
 void arch_regs_saveextra(arch_extraregs* regs){
 	// user gs was swapped
 	regs->gsbase = rdmsr(MSR_KERNELGSBASE);
 	regs->fsbase = rdmsr(MSR_FSBASE);	
 	asm("fxsave (%%rax)" : : "a"(&regs->fx[0]));
-
+	asm("stmxcsr (%%rax)" : : "a"(&regs->mxcsr));
 }
 
 void arch_regs_setupextra(arch_extraregs* regs){
@@ -14,6 +18,7 @@ void arch_regs_setupextra(arch_extraregs* regs){
 	wrmsr(MSR_KERNELGSBASE, regs->gsbase);
 	wrmsr(MSR_FSBASE, regs->fsbase);
 	asm("fxrstor (%%rax)" : : "a"(&regs->fx[0]));
+	asm("ldmxcsr (%%rax)" : : "a"(&regs->mxcsr));
 }
 
 void arch_regs_setupkernel(arch_regs* regs, void* ip, void* stack, bool interrupts){

src/sys/sched/scheduler.c

@@ -98,6 +98,8 @@ static thread_t* allocthread(proc_t* proc, state_t state, pid_t tid, size_t ksta
 	thread->kernelstack = thread->kernelstackbase + kstacksize;
 	thread->stacksize = kstacksize;
 	
+	arch_regs_firsttimesetup(thread->regs, &thread->extraregs);
+
 	return thread;
 
 }