[USER] brk syscall

kernel/include/process.h

@@ -62,5 +62,6 @@ void procmm_free_map(process_t *proc);
 void procmm_print_map(procmm_mmap_t *map);
 procmm_area_t *procmm_map(procmm_mmap_t *map, uintptr_t start, uintptr_t end, uint64_t flags);
 void procmm_unmap(procmm_area_t *a);
+size_t procmm_resize(process_t *p, procmm_area_t *a, size_t len);
 int procmm_setup(process_t *proc, size_t brk_size);
 registers_t *procmm_page_fault(registers_t *r);

kernel/include/syscall.h

@@ -41,3 +41,4 @@ typedef long (*syscall_handler_t)(long num, long, long, long, long, long, long);
 #define SYSCALL_REGISTER(name, num) syscall_handlers[num] = syscall_##name
 
 SYSCALL_DECL(write);
+SYSCALL_DECL(brk);

kernel/proc/procmm.c

@@ -103,6 +103,35 @@ void procmm_unmap(procmm_area_t *a)
   kfree(a);
 }
 
+size_t procmm_resize(process_t *p, procmm_area_t *a, size_t len)
+{
+  procmm_mmap_t *map = p->mmap;
+  size_t old_len = a->end - a->start;
+  size_t old_end = a->end;
+  if(old_len < len)
+  {
+    procmm_area_t *next = a->areas.next;
+    uintptr_t max = next->start;
+    max = (max < a->start)?KERNEL_OFFSET:max;
+    if((a->start + len) > max)
+      len = max - a->start;
+
+    a->end = a->start + len;
+
+    uintptr_t page = (old_end + PAGE_SIZE) & ~(PAGE_SIZE-1);
+    while(page < a->end)
+    {
+      vmm_set_page(map->P4, page, pmm_alloc(), PAGE_PRESENT | PAGE_WRITE | PAGE_USER);
+      page += PAGE_SIZE;
+    }
+
+  } else {
+    debug_error("Decreasing memory area size is not implemented yet\n");
+    for(;;);
+  }
+  return len;
+}
+
 int procmm_setup(process_t *proc, size_t brk_size)
 {
   procmm_mmap_t *map = proc->mmap;

kernel/syscall/sys_mem.c

@@ -0,0 +1,19 @@
+#include <syscall.h>
+#include <scheduler.h>
+#include <debug.h>
+
+
+SYSCALL_DEF(brk)
+{
+  SYSCALL_INIT(uint64_t, addr);
+  procmm_area_t *brk = get_current_process()->mmap->brk;
+
+  if(addr)
+  {
+    size_t len = addr - brk->start;
+    procmm_resize(get_current_process(), brk, len);
+    return brk->end;
+  } else {
+    return brk->end;
+  }
+}

kernel/syscall/syscall.c

@@ -57,6 +57,7 @@ void syscall_init()
 
     SYSCALL_REGISTER(debug, SYS_DEBUG);
     SYSCALL_REGISTER(write, SYS_WRITE);
+    SYSCALL_REGISTER(brk, SYS_BRK);
   }
 
 }