fixesHEADhelloworldmaster

1 files changed, 56 insertions, 0 deletions

diff --git a/programs/libc/unistd/sbrk.c b/programs/libc/unistd/sbrk.c
new file mode 100644
index 0000000..7e32118
--- /dev/null
+++ b/programs/libc/unistd/sbrk.c
@@ -0,0 +1,56 @@
+/*
+ * wnix, a Unix-like operating system for WebAssembly applications.
+ * Copyright (C) 2025  Xavier Del Campo Romero
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <errno.h>
+#include <unistd.h>
+#include <stddef.h>
+#include <stdint.h>
+
+void *sbrk(const intptr_t increment)
+{
+    const unsigned pagesize = 64 << 10;
+    extern char __heap_base[];
+    static char *cur = __heap_base, *end;
+
+    if (increment < 0)
+    {
+        errno = EINVAL;
+        return NULL;
+    }
+    else if (!end)
+        end = cur + __builtin_wasm_memory_size(0) * pagesize;
+
+    if (increment >= (intptr_t)end || cur >= end - increment)
+    {
+        const unsigned long pages = (uintptr_t)increment / pagesize,
+            new_end = __builtin_wasm_memory_grow(0, pages);
+
+        if (!new_end)
+        {
+            errno = ENOMEM;
+            return NULL;
+        }
+
+        end = (void *)new_end;
+    }
+
+    void *ret = cur;
+
+    cur += increment;
+    return ret;
+}