new

Author: FarWrong

Makefile

@@ -0,0 +1,14 @@
+ifneq ($(KERNELRELEASE),)
+   obj-m := gfn_to_pfn.o
+else
+
+KERNELDIR ?= /lib/modules/$(shell uname -r)/build
+
+PWD := $(shell pwd)
+
+default:
+	$(MAKE) -C $(KERNELDIR) M=$(PWD) modules
+
+clean:
+	$(MAKE) -C $(KERNELDIR) M=$(PWD) clean
+endif

gfn_to_pfn.c

@@ -0,0 +1,111 @@
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/kvm_host.h>
+#include <linux/kvm.h>
+#include <linux/mm.h>
+#include <linux/proc_fs.h>
+#include <linux/uaccess.h>
+static struct proc_dir_entry *proc_entry;
+#include <asm/pgtable.h>
+
+
+
+
+static long get_user_page_info(struct mm_struct *mm, unsigned long va)
+{
+	long ret;
+	int locked = 0;
+	struct page *pages[1] = { NULL };
+	ret = get_user_pages_remote(mm, va, 1, FOLL_GET, pages, NULL);
+	if (ret < 0) {
+        	pr_err("get_user_pages_remote failed with %ld\n", ret);
+		return ret;
+	}
+	if (ret == 0) {
+        	pr_err("No pages were returned for VA 0x%lx\n", va);
+        	return 0;
+	}
+	struct page *page = pages[0];
+	unsigned long pfn = page_to_pfn(page);
+	phys_addr_t phys = PFN_PHYS(pfn);
+	printk(KERN_INFO "Page Found for VA");
+	printk(KERN_INFO "Physical Address:0x%llx", (unsigned long long)phys);
+	printk(KERN_INFO "WARNING This is using PageTransHuge and PageHuge utilities to detect a hugepage i don't trust them");
+	//Note that if a page huge is declared it's probably a huge page. But I don't quite trust a non-huge page detection to detect if it isn't yet 
+	if (PageTransHuge(page)) {
+		printk(KERN_INFO "page is part of THP\n");
+	} else if (PageHuge(page)) {
+		printk(KERN_INFO "page is huge\n");
+	} else {
+		printk(KERN_INFO "page is not huge page\n");
+	}
+	put_page(page);
+	return ret;
+}
+
+
+
+static void print_gfn_to_hva(unsigned long gfn_val)
+{
+    	struct kvm *kvm;
+    	unsigned long hva;
+    	gfn_t gfn = (gfn_t)gfn_val;
+	//find first kvm - this needs expanding for variable # of kvms
+    	kvm = list_first_entry_or_null(&vm_list, struct kvm, vm_list);
+    	if (!kvm) {
+        	printk(KERN_ERR "No VMs found\n");
+        	return;
+    	}
+    	printk(KERN_INFO "Found VM\n");
+    	hva = gfn_to_hva(kvm, gfn);
+    	if (kvm_is_error_hva(hva)) {
+        	printk(KERN_ERR "Error getting HVA for GFN 0x%lx\n", gfn_val);
+        	return;
+    	}
+	printk(KERN_INFO "GFN 0x%lx maps to HVA 0x%lx\n", gfn_val, hva);
+	get_user_page_info(kvm->mm,hva);
+}
+
+
+static ssize_t gfn_write(struct file *file, const char __user *ubuf,
+                        size_t count, loff_t *ppos)
+{
+    //get gfn from buffer
+    char buf[32];
+    unsigned long gfn;
+    if (count > sizeof(buf) - 1)
+        return -EINVAL;
+    if (copy_from_user(buf, ubuf, count))
+        return -EFAULT;
+    buf[count] = '\0';
+    if (kstrtoul(buf, 0, &gfn))
+        return -EINVAL;
+    print_gfn_to_hva(gfn);
+    return count;
+}
+
+static const struct proc_ops gfn_fops = {
+    .proc_write = gfn_write,
+};
+
+static int __init gfn_module_init(void)
+{
+    proc_entry = proc_create("gfn_to_hva", 0666, NULL, &gfn_fops);
+    if (!proc_entry)
+        return -ENOMEM;
+    printk(KERN_INFO "GFN to HVA module loaded\n");
+    return 0;
+}
+
+static void __exit gfn_module_exit(void)
+{
+    proc_remove(proc_entry);
+    printk(KERN_INFO "GFN to HVA module unloaded\n");
+}
+
+module_init(gfn_module_init);
+module_exit(gfn_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Your Name");
+MODULE_DESCRIPTION("GFN to HVA translation module");