Add filesystem syscall 70 wrapper and fs_demo example

examples/fs_demo.rs

@@ -0,0 +1,25 @@
+#![no_std]
+#![no_main]
+
+use kos::fs::{FileInfo, fs_read};
+
+static FILENAME: &[u8] = b"/rd/1/readme.txt\0";
+static mut BUFFER: [u8; 256] = [0u8; 256];
+
+#[no_mangle]
+pub extern "C" fn _start() -> ! {
+    unsafe {
+        let info = FileInfo {
+            func:   0,
+            param1: 0,
+            param2: 0,
+            param3: 256,
+            buf:    BUFFER.as_mut_ptr(),
+            name:   FILENAME.as_ptr(),
+        };
+
+        let (_result, _bytes_read) = fs_read(&info as *const FileInfo);
+    }
+
+    loop {}
+}

src/fs.rs

@@ -0,0 +1,31 @@
+use core::arch::asm;
+
+/// KolibriOS Function 70 — filesystem operations
+/// Passes a pointer to a FileInfo structure via ebx
+/// int 0x40 with eax=70 is the KolibriOS FS syscall
+
+#[repr(C, packed)]
+pub struct FileInfo {
+    pub func:       u32,   // 0 = read, 1 = read folder, 2 = create/write
+    pub param1:     u32,   // offset (low)
+    pub param2:     u32,   // offset (high) or flags
+    pub param3:     u32,   // bytes to read/write
+    pub buf:        *mut u8, // pointer to buffer
+    pub name:       *const u8, // pointer to filename (ASCIIZ)
+}
+
+/// Opens/reads a file on KolibriOS using syscall eax=70
+/// Returns (eax_result, ebx_bytes_read)
+pub unsafe fn fs_read(info: *const FileInfo) -> (u32, u32) {
+    let eax_out: u32;
+    let ebx_out: u32;
+    unsafe {
+        asm!(
+            "int 0x40",
+            inlateout("eax") 70u32 => eax_out,
+            inlateout("ebx") info as u32 => ebx_out,
+            options(nostack)
+        );
+    }
+    (eax_out, ebx_out)
+}