From 19d58ec71da2fd05f0bbfc21bdc6375f75bb7b0f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20Lov=C3=A9n?= <thomasloven@gmail.com>
Date: Wed, 28 Feb 2018 22:02:20 +0100
Subject: [PATCH] Functions for copying stuff between kernel and user space

---
 src/kernel/boot/kmain.c     |  5 ++--
 src/kernel/include/memory.h |  2 ++
 src/kernel/memory/vmm.c     | 46 +++++++++++++++++++++++++++++++++++++
 3 files changed, 50 insertions(+), 3 deletions(-)

diff --git a/src/kernel/boot/kmain.c b/src/kernel/boot/kmain.c
index bbd10a8..0b7f20e 100644
--- a/src/kernel/boot/kmain.c
+++ b/src/kernel/boot/kmain.c
@@ -29,9 +29,8 @@ void kmain(uint64_t multiboot_magic, void *multiboot_data)
   cpu_init();
 
   struct process *p1 = new_process((void (*)(void))0x10000);
-  uint64_t page = pmm_alloc();
-  vmm_set_page(p1->P4, 0x10000, page, PAGE_WRITE | PAGE_PRESENT | PAGE_USER);
-  memcpy(P2V(page), (void *)(uintptr_t)thread_function, PAGE_SIZE);
+  vmm_set_page(p1->P4, 0x10000, pmm_calloc(), PAGE_WRITE | PAGE_PRESENT | PAGE_USER);
+  memcpy_k2u(p1->P4, (void *)0x10000, (void *)(uintptr_t)thread_function, 100);
 
   ready(p1);
 
diff --git a/src/kernel/include/memory.h b/src/kernel/include/memory.h
index 13e8035..849cd9f 100644
--- a/src/kernel/include/memory.h
+++ b/src/kernel/include/memory.h
@@ -45,6 +45,8 @@ uint64_t vmm_get_page(uint64_t P4, uint64_t addr);
 #define PAGE_EXIST(p) ((p) != (uint64_t)-1)
 int vmm_set_page(uint64_t P4, uint64_t addr, uint64_t page, uint16_t flags);
 void vmm_clear_page(uint64_t P4, uint64_t addr, int free);
+size_t memcpy_k2u(uint64_t P4, void *dst, void *src, size_t n);
+size_t memcpy_u2k(void *dst, uint64_t P4, void *src, size_t n);
 
 extern union PTE BootP4;
 extern int kernel_start, kernel_end;
diff --git a/src/kernel/memory/vmm.c b/src/kernel/memory/vmm.c
index eae6c17..b13abd1 100644
--- a/src/kernel/memory/vmm.c
+++ b/src/kernel/memory/vmm.c
@@ -1,4 +1,5 @@
 #include <memory.h>
+#include <debug.h>
 
 #define FLAGS_MASK (PAGE_SIZE-1)
 #define MASK_FLAGS(addr) ((uint64_t)addr & ~FLAGS_MASK)
@@ -101,3 +102,48 @@ void vmm_clear_page(uint64_t P4, uint64_t addr, int free)
   pmm_free(MASK_FLAGS(P4E));
   P4E = 0;
 }
+
+#define min(a,b) (((a) < (b))?(a):(b))
+#define offset(p) ((uintptr_t)(p) % PAGE_SIZE)
+#define remaining(p) (PAGE_SIZE - offset(p))
+size_t memcpy_k2u(uint64_t P4, void *dst, void *src, size_t n)
+{
+  size_t copied = 0;
+  while(n)
+  {
+    size_t bytes = min(remaining(dst), n);
+    uintptr_t page = vmm_get_page(P4, (uintptr_t)dst);
+    if(!PAGE_EXIST(page))
+      return copied;
+
+    void *to = P2V(MASK_FLAGS(page) + offset(dst));
+    memcpy(to, src, bytes);
+
+    copied += bytes;
+    n -= bytes;
+    dst = incptr(dst, bytes);
+    src = incptr(src, bytes);
+  }
+  return copied;
+}
+
+size_t memcpy_u2k(void *dst, uint64_t P4, void *src, size_t n)
+{
+  size_t copied = 0;
+  while(n)
+  {
+    size_t bytes = min(remaining(src), n);
+    uintptr_t page = vmm_get_page(P4, (uintptr_t)src);
+    if(!PAGE_EXIST(page))
+      return copied;
+
+    void *from = P2V(MASK_FLAGS(page) + offset(src));
+    memcpy(dst, from, bytes);
+
+    copied += bytes;
+    n -= bytes;
+    dst = incptr(dst, bytes);
+    src = incptr(src, bytes);
+  }
+  return copied;
+}