From 4ecec1eec682a9b39eba26bdd1c35b3f9542bd8b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20Lov=C3=A9n?= <thomasloven@gmail.com>
Date: Thu, 1 Mar 2018 15:12:35 +0100
Subject: [PATCH] Stupidly simple process memory manager with brk()

---
 src/kernel/boot/kmain.c      |  4 ++--
 src/kernel/include/memory.h  |  4 ++--
 src/kernel/include/process.h |  7 ++++++-
 src/kernel/memory/vmm.c      |  4 ++--
 src/kernel/proc/process.c    |  8 +++++---
 src/kernel/proc/procmm.c     | 24 ++++++++++++++++++++++++
 6 files changed, 41 insertions(+), 10 deletions(-)
 create mode 100644 src/kernel/proc/procmm.c

diff --git a/src/kernel/boot/kmain.c b/src/kernel/boot/kmain.c
index 0b7f20e..4fdbc94 100644
--- a/src/kernel/boot/kmain.c
+++ b/src/kernel/boot/kmain.c
@@ -29,8 +29,8 @@ void kmain(uint64_t multiboot_magic, void *multiboot_data)
   cpu_init();
 
   struct process *p1 = new_process((void (*)(void))0x10000);
-  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);
+  procmm_brk(p1, (void *)0x10010);
+  memcpy_to_p4(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 849cd9f..671f3f8 100644
--- a/src/kernel/include/memory.h
+++ b/src/kernel/include/memory.h
@@ -45,8 +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);
+size_t memcpy_to_p4(uint64_t P4, void *dst, void *src, size_t n);
+size_t memcpy_from_p4(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/include/process.h b/src/kernel/include/process.h
index 5473bb6..3b63546 100644
--- a/src/kernel/include/process.h
+++ b/src/kernel/include/process.h
@@ -3,15 +3,18 @@
 #include <scheduler.h>
 #include <stdint.h>
 #include <interrupts.h>
+#include <stddef.h>
 
 struct process
 {
   uint64_t pid;
   void *stack_ptr;
   uint64_t state;
+
   uint64_t P4;
+  uint64_t brk;
+  uint64_t stack;
   QUEUE_SPOT(runQ);
-  uint8_t stack[];
 };
 
 struct process *process();
@@ -21,3 +24,5 @@ void yield();
 void start_scheduler();
 
 void switch_stack(void *old_ptr, void *new_ptr);
+
+uint64_t procmm_brk(struct process *p, void *addr);
diff --git a/src/kernel/memory/vmm.c b/src/kernel/memory/vmm.c
index b13abd1..96099a9 100644
--- a/src/kernel/memory/vmm.c
+++ b/src/kernel/memory/vmm.c
@@ -106,7 +106,7 @@ void vmm_clear_page(uint64_t P4, uint64_t addr, int free)
 #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 memcpy_to_p4(uint64_t P4, void *dst, void *src, size_t n)
 {
   size_t copied = 0;
   while(n)
@@ -127,7 +127,7 @@ size_t memcpy_k2u(uint64_t P4, void *dst, void *src, size_t n)
   return copied;
 }
 
-size_t memcpy_u2k(void *dst, uint64_t P4, void *src, size_t n)
+size_t memcpy_from_p4(void *dst, uint64_t P4, void *src, size_t n)
 {
   size_t copied = 0;
   while(n)
diff --git a/src/kernel/proc/process.c b/src/kernel/proc/process.c
index 9dee224..9e6b4ca 100644
--- a/src/kernel/proc/process.c
+++ b/src/kernel/proc/process.c
@@ -20,13 +20,15 @@ struct swtch_stack
 struct process *sched_proc = 0;
 struct process *_proc = 0;
 
+void procmm_init(struct process *p);
+
 uint64_t next_pid = 1;
 struct process *new_process(void (*function)(void))
 {
   struct process *proc = P2V(pmm_calloc());
   proc->pid = next_pid++;
   proc->stack_ptr = incptr(proc, PAGE_SIZE - sizeof(struct swtch_stack));
-  proc->P4 = new_P4();
+  procmm_init(proc);
 
   struct swtch_stack *stk = proc->stack_ptr;
   stk->RBP = (uint64_t)&stk->RBP2;
@@ -38,7 +40,7 @@ struct process *new_process(void (*function)(void))
   stk->r.cs = 0x10 | 3;
   stk->r.ss = 0x18 | 3;
   stk->r.rflags = 3<<12;
-  stk->r.rsp = 0x10FFF;
+  stk->r.rsp = KERNEL_OFFSET;
 
   return proc;
 }
@@ -62,7 +64,7 @@ void scheduler()
 
     _proc = new;
     write_cr3(new->P4);
-    interrupt_stack(new + PAGE_SIZE);
+    interrupt_stack(incptr(new, PAGE_SIZE));
     switch_stack(&sched_proc->stack_ptr, &new->stack_ptr);
 
     ready(_proc);
diff --git a/src/kernel/proc/procmm.c b/src/kernel/proc/procmm.c
new file mode 100644
index 0000000..0c8c9f3
--- /dev/null
+++ b/src/kernel/proc/procmm.c
@@ -0,0 +1,24 @@
+#include <process.h>
+#include <memory.h>
+#include <stdint.h>
+#include <stddef.h>
+#include <debug.h>
+#include <memory.h>
+
+void procmm_init(struct process *p)
+{
+  p->P4 = new_P4();
+  p->brk = 0;
+  p->stack = KERNEL_OFFSET;
+
+}
+
+uint64_t procmm_brk(struct process *p, void *addr)
+{
+  while((uint64_t)addr > p->brk)
+  {
+    vmm_set_page(p->P4, p->brk, pmm_alloc(), PAGE_USER | PAGE_WRITE | PAGE_PRESENT);
+    p->brk += PAGE_SIZE;
+  }
+  return p->brk;
+}