From fc9c7bab5bb64dd2242e9e9dff98060d64af2a32 Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Wed, 13 Mar 2024 21:27:39 -0400
Subject: kernel/amd64: machdep: Add pcb init code

This commit adds a processor specific routine which sets up the
Process Control Block for a thread

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 sys/arch/amd64/amd64/machdep.c | 25 +++++++++++++++++++++++++
 sys/include/sys/machdep.h      |  2 ++
 sys/kern/kern_sched.c          |  2 ++
 3 files changed, 29 insertions(+)

diff --git a/sys/arch/amd64/amd64/machdep.c b/sys/arch/amd64/amd64/machdep.c
index 809e395..0789f5a 100644
--- a/sys/arch/amd64/amd64/machdep.c
+++ b/sys/arch/amd64/amd64/machdep.c
@@ -154,6 +154,31 @@ intr_unmask(void)
     __ASMV("sti");
 }
 
+int
+processor_init_pcb(struct proc *proc)
+{
+    struct pcb *pcb = &proc->pcb;
+    const uint16_t FPU_FCW = 0x33F;
+    const uint32_t SSE_MXCSR = 0x1F80;
+
+    /* Allocate FPU save area, aligned on a 16 byte boundary */
+    pcb->fpu_state = PHYS_TO_VIRT(vm_alloc_pageframe(1));
+    if (pcb->fpu_state == 0) {
+        return -1;
+    }
+
+    /*
+     * Setup x87 FPU control word and SSE MXCSR bits
+     * as per the sysv ABI
+     */
+    __ASMV("fldcw %0\n"
+           "ldmxcsr %1"
+           :: "m" (FPU_FCW),
+              "m" (SSE_MXCSR) : "memory");
+
+    amd64_fxsave(pcb->fpu_state);
+    return 0;
+}
 void
 processor_init(void)
 {
diff --git a/sys/include/sys/machdep.h b/sys/include/sys/machdep.h
index 713b7db..151d5f8 100644
--- a/sys/include/sys/machdep.h
+++ b/sys/include/sys/machdep.h
@@ -32,11 +32,13 @@
 
 #include <sys/types.h>
 #include <sys/cdefs.h>
+#include <sys/proc.h>
 
 #if defined(_KERNEL)
 
 #define MAXCPUS 32
 
+int processor_init_pcb(struct proc *proc);
 void processor_init(void);
 void processor_halt(void);
 void intr_mask(void);
diff --git a/sys/kern/kern_sched.c b/sys/kern/kern_sched.c
index 7be8241..f8f09c4 100644
--- a/sys/kern/kern_sched.c
+++ b/sys/kern/kern_sched.c
@@ -36,6 +36,7 @@
 #include <sys/spinlock.h>
 #include <sys/loader.h>
 #include <sys/panic.h>
+#include <sys/machdep.h>
 #include <fs/initramfs.h>
 #include <vm/dynalloc.h>
 #include <vm/physseg.h>
@@ -264,6 +265,7 @@ sched_create_td(uintptr_t rip, char *argvp[], char *envp[], struct auxval auxv,
     td->cpu = NULL;     /* Not yet assigned a core */
     td->tf = tf;
     td->addrsp = vas;
+    processor_init_pcb(td);
 
     /* Setup trapframe */
     if (!is_user) {
-- 
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