[USER] brk syscall

init/init.c

@@ -5,14 +5,18 @@ int main(int argc, char **argv)
 {
   (void) argc;
   (void) argv;
-  printf("Hello, world!\n");
-  printf("Some numbers:%d\n", 12345);
-  printf("And hex:%#x\n", 0xabcdef);
-  printf("And a string:%s\n", "Hello!");
 
-  printf("Arguments passed to init:\n");
-  for(int i=0; i < argc; i++)
-    printf("%d: %s\n", i, argv[i]);
+  char *a = malloc(0x100);
+  printf("Pointer: %p\n", a);
+  char *b = malloc(0x100);
+  printf("Pointer: %p\n", b);
+  char *c = malloc(0x10);
+  printf("Pointer: %p\n", c);
+  c[0] = 5;
+  free(a);
+  free(b);
+  free(c);
+
   for(;;);
   return 0;
 }

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);
   }
 
 }

libc/mem.c

@@ -0,0 +1,10 @@
+#include "syscalls.h"
+
+long kernel_syscall(int num, ...);
+
+SYSCALL_DEF(brk)
+{
+  SYSCALL_INIT(unsigned long, brk);
+
+  return kernel_syscall(SYS_BRK, brk);
+}

libc/syscall_num.h

@@ -1,4 +1,5 @@
 #pragma once
 
 #define SYS_WRITE 0x001
+#define SYS_BRK   0x002
 #define SYS_DEBUG 0x3FF