From 1daf8ed47bf4aee6cef1697e810a5afd861be29e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20Lov=C3=A9n?= <thomasloven@gmail.com>
Date: Thu, 21 Dec 2017 16:15:55 +0100
Subject: [PATCH] PMM - alloc two pages

---
 src/kernel/memory/pmm.c  |  3 ++-
 src/kernel/memory/pmm.tt | 27 ++++++++++++++++++++++++++-
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/src/kernel/memory/pmm.c b/src/kernel/memory/pmm.c
index 70a8ef8..cfaf7c1 100644
--- a/src/kernel/memory/pmm.c
+++ b/src/kernel/memory/pmm.c
@@ -4,12 +4,13 @@ uintptr_t *first = 0;
 
 void pmm_free(void *c)
 {
+  *(uintptr_t *)c = (uintptr_t)first;
   first = c;
 }
 
 void *pmm_alloc()
 {
   void *c = first;
-  first = 0;
+  first = (uintptr_t *)(c?*(uintptr_t *)c:0);
   return c;
 }
diff --git a/src/kernel/memory/pmm.tt b/src/kernel/memory/pmm.tt
index 7ddca08..d724e7e 100644
--- a/src/kernel/memory/pmm.tt
+++ b/src/kernel/memory/pmm.tt
@@ -5,7 +5,7 @@
 
 struct {
   uint8_t data[PAGE_SIZE];
-}__attribute__((packed)) mem[4];
+}__attribute__((packed)) mem[2];
 
 TEST(alloc_returns_freed_page)
 {
@@ -25,3 +25,28 @@ TEST(alloc_zero_after_all_free_pages)
   void *a = pmm_alloc();
   ASSERT_EQ_PTR(a, 0);
 }
+
+TEST(alloc_two_pages___first_page_is_not_zero)
+{
+  pmm_free(&mem[0]);
+  pmm_free(&mem[1]);
+  void *a = pmm_alloc();
+  pmm_alloc();
+  ASSERT_NEQ_PTR(a, 0);
+}
+TEST(alloc_two_pages___second_page_is_not_zero)
+{
+  pmm_free(&mem[0]);
+  pmm_free(&mem[1]);
+  pmm_alloc();
+  void *a = pmm_alloc();
+  ASSERT_NEQ_PTR(a, 0);
+}
+TEST(alloc_two_pages___doesnt_return_same_page_twice)
+{
+  pmm_free(&mem[0]);
+  pmm_free(&mem[1]);
+  void *a = pmm_alloc();
+  void *b = pmm_alloc();
+  ASSERT_NEQ_PTR(a, b);
+}