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 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

(limited to 'sys/arch/amd64')

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)
 {
-- 
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