fix: use syscalls.S FFI pattern for fs syscall, pub fn kol_main

examples/fs_demo.rs

@@ -1,12 +1,10 @@
 #![no_std]
 #![no_main]
 
-use kos::fs::fs_read;
+use kos::fs::read_file;
 
 #[no_mangle]
-pub extern "C" fn _start() -> ! {
-    let path = c"/rd/1/readme.txt";
-    let mut buf = [0u8; 512];
-    let (_status, _bytes) = fs_read(path, &mut buf);
-    loop {}
+pub fn kol_main() {
+    let mut buf = [0u8; 256];
+    let _ = read_file(c"/rd/1/readme.txt", &mut buf);
 }

src/fs.rs

@@ -1,14 +1,16 @@
 use core::ffi::CStr;
-use crate::sys::{syscall_fs, FileSystemRequest};
+use crate::sys::{fs_read, FsInfo};
 
-pub fn fs_read(path: &CStr, buf: &mut [u8]) -> (u32, u32) {
-    let req = FileSystemRequest {
-        operation:   0,
-        offset_low:  0,
-        offset_high: 0,
-        byte_count:  buf.len() as u32,
-        buffer:      buf.as_mut_ptr() as u32,
-        path:        path.as_ptr() as u32,
+pub fn read_file(path: &CStr, buf: &mut [u8]) -> Result<(), u32> {
+    let info = FsInfo {
+        operation:  0,
+        offset:     0,
+        offset_hi:  0,
+        byte_count: buf.len() as u32,
+        buffer:     buf.as_mut_ptr(),
+        reserved:   0,
+        path:       path.as_ptr() as *const u8,
     };
-    unsafe { syscall_fs(&req) }
+    let result = unsafe { fs_read(&info) };
+    if result == 0 { Ok(()) } else { Err(result) }
 }

src/sys.rs

@@ -67,27 +67,19 @@ extern "C" {
     // 68.19
     #[link_name = "_load_dll"]
     pub fn load_dll(name: *const u8) -> *const u32;
+
+    // 70
+    #[link_name = "_fs_read"]
+    pub fn fs_read(info: *const FsInfo) -> u32;
 }
 
 #[repr(C)]
-pub struct FileSystemRequest {
-    pub operation:    u32,
-    pub offset_low:   u32,
-    pub offset_high:  u32,
-    pub byte_count:   u32,
-    pub buffer:       u32,
-    pub path:         u32,
-}
-
-pub unsafe fn syscall_fs(req: *const FileSystemRequest) -> (u32, u32) {
-    let eax_result: u32;
-    let ebx_result: u32;
-    core::arch::asm!(
-        "int 0x40",
-        inout("eax") 70u32 => eax_result,
-        in("ebx") req,
-        out("ebx") ebx_result,
-        options(nostack)
-    );
-    (eax_result, ebx_result)
+pub struct FsInfo {
+    pub operation:  u32,
+    pub offset:     u32,
+    pub offset_hi:  u32,
+    pub byte_count: u32,
+    pub buffer:     *mut u8,
+    pub reserved:   u8,
+    pub path:       *const u8,
 }

src/syscalls.S

@@ -20,6 +20,7 @@ section '.text'
     public _get_lang
     public _load_dll
     public _set_event_mask
+    public _fs_read
 
 _exit:
     mov eax, SF_TERMINATE_PROCESS
@@ -143,3 +144,10 @@ _set_event_mask:
     int 0x40
     ret
 
+_fs_read:
+    push ebx
+    mov eax, 70
+    mov ebx, [esp + 4 * 2]
+    int 0x40
+    pop ebx
+    ret