basic process support and some syscalls

[lunaix-os.git] / lunaix-os / kernel / mm / cow.c

diff --git a/lunaix-os/kernel/mm/cow.c b/lunaix-os/kernel/mm/cow.c
new file mode 100644 (file)
index 0000000..30cead9
--- /dev/null
+++ b/lunaix-os/kernel/mm/cow.c
@@ -0,0 +1,16 @@
+#include <lunaix/mm/vmm.h>
+
+void* vmm_dup_page(void* va) {    
+    void* new_ppg = pmm_alloc_page(KERNEL_PID, 0);
+    vmm_fmap_page(KERNEL_PID, PG_MOUNT_3, new_ppg, PG_PREM_RW);
+
+    asm volatile (
+        "movl %1, %%edi\n"
+        "rep movsl\n"
+        :: "c"(1024), "r"(PG_MOUNT_3), "S"((uintptr_t)va)
+        : "memory", "%edi");
+
+    vmm_unset_mapping(PG_MOUNT_3);
+
+    return new_ppg;
+}
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