Add stack-heap collision check to BrkSyscall execution

src/syscall/control.h

@@ -56,8 +56,19 @@ class BrkSyscall : public BaseSyscall {
 
   void execute() {
     // Nothing to do - at the moment we allow infinite growth of the heap.
-    // @todo: Add checks to ensure that the heap doesn't grow into the stack
-    // segment...!
+
+    // Retrieves the argument of the brk syscall, the new program break
+    uint64_t newBreak = BaseSyscall::getArg(BaseSyscall::REG_FILE, 0);
+    // Retrieve the current stack pointer from the processor handler
+    uint64_t stackPointer =
+        ProcessorHandler::getProcessor()->getRegister(BaseSyscall::REG_FILE, 2);
+    if (newBreak >= stackPointer) {
+      SystemIO::printString(
+          "Error: Attempted to allocate memory overlapping stack segment\n");
+      BaseSyscall::setRet(BaseSyscall::REG_FILE, 0, -1); // Syscall error code
+      return;
+    }
+
     BaseSyscall::setRet(BaseSyscall::REG_FILE, 0, 0);
   }
 };

test/riscv-tests-64/brk_syscall.S

@@ -0,0 +1,35 @@
+.text
+ .globl _start
+ _start: nop
+
+#-------------------------------------------------------------
+# Stack-Heap Collision brk syscall Test
+#-------------------------------------------------------------
+
+test_0: # Test Ecall Return Value
+    mv a0, sp # Assign the ecall parameter to the stack pointer value 
+  	lw a7, BRK # Load the brk syscall immediate value
+    ecall
+
+    # If the return value of the ecall is zero, then the ecall
+    # was executed successfully and therefore the test failed
+    beqz a0, fail
+
+  bne x0, gp, pass
+
+pass: 
+ li a0, 42
+ li a7, 93
+ ecall
+
+
+fail: 
+ li a0, 0
+ li a7, 93
+ ecall
+
+.data
+.align 4
+
+# Syscall immediate value
+BRK: .word 214

test/riscv-tests/brk_syscall.s

@@ -0,0 +1,27 @@
+.text
+
+#-------------------------------------------------------------
+# Stack-Heap Collision brk syscall Test
+#-------------------------------------------------------------
+
+test_0: # Test Ecall Return Value
+    mv a0, sp # Assign the ecall parameter to the stack pointer value 
+  	li a7, 214 # Load the brk syscall immediate value
+    ecall
+
+    # If the return value of the ecall is zero, then the ecall
+    # was executed successfully and therefore the test failed
+    beqz a0, fail
+
+  bne x0, gp, pass
+
+pass: 
+ li a0, 42
+ li a7, 93
+ ecall
+
+
+fail: 
+ li a0, 0
+ li a7, 93
+ ecall