From 2bdafab229439dcd9968114ab232ed0a3a218bfb Mon Sep 17 00:00:00 2001
From: Tianhao Wang <wth@riseup.net>
Date: Thu, 1 Feb 2024 04:16:43 +0100
Subject: use inline asm for x86 IO instr

---
 src/arch/x86_64/asm/io_port.s | 71 -------------------------------------------
 src/arch/x86_64/io_port.rs    | 44 +++++++++++++++++----------
 2 files changed, 28 insertions(+), 87 deletions(-)
 delete mode 100644 src/arch/x86_64/asm/io_port.s

(limited to 'src/arch')

diff --git a/src/arch/x86_64/asm/io_port.s b/src/arch/x86_64/asm/io_port.s
deleted file mode 100644
index 3aec69d..0000000
--- a/src/arch/x86_64/asm/io_port.s
+++ /dev/null
@@ -1,71 +0,0 @@
-;***************************************************************************
-;* Operating-System Construction                                             *
-;*---------------------------------------------------------------------------*
-;*                                                                           *
-;*                             I O _ P O R T                                 *
-;*                                                                           *
-;*---------------------------------------------------------------------------*
-;* The functions defined here encapsulate the machine instructions 'in' and  *
-;* 'out' for class IO_Port.                                                  *
-;*****************************************************************************
-
-; EXPORTED FUNCTIONS
-
-[GLOBAL _outb]
-[GLOBAL _outw]
-[GLOBAL _inb]
-[GLOBAL _inw]
-
-; FUNCTION IMPLEMENTATIONS
-
-[SECTION .text]
-
-; OUTB: Byte-wise output via an I/O port.
-;
-;       C prototype: void outb (int port, int value);
-
-_outb:
-	push   rbp
-	mov    rbp, rsp
-	mov    rdx, rdi
-	mov    rax, rsi
-	out    dx, al
-	pop    rbp
-	ret
-
-; OUTW: Word-wise output via an I/O port.
-;
-;       C prototype: void outw (int port, int value);
-
-_outw:
-	push   rbp
-	mov    rbp, rsp
-	mov    rdx, rdi
-	mov    rax, rsi
-	out    dx, ax
-	pop    rbp
-	ret
-
-; INB: Byte-wise input via an I/O port.
-;
-;      C prototype: unsigned char inb (int port);
-
-_inb:
-	push   rbp
-	mov    rbp, rsp
-	mov    rdx, rdi
-	in     al, dx
-	pop    rbp
-	ret
-
-; INW: Word-wise input via an I/O port.
-;
-;      C prototype: unsigned short inw (int port);
-
-_inw:
-	push   rbp
-	mov    rbp, rsp
-	mov    rdx, rdi
-	in     ax, dx
-	pop    rbp
-	ret
diff --git a/src/arch/x86_64/io_port.rs b/src/arch/x86_64/io_port.rs
index f5755f4..7b37989 100644
--- a/src/arch/x86_64/io_port.rs
+++ b/src/arch/x86_64/io_port.rs
@@ -1,29 +1,41 @@
-extern "C" {
-	fn _inb(port: u16) -> u8;
-	fn _inw(port: u16) -> u16;
-	fn _outb(port: u16, val: u8);
-	fn _outw(port: u16, val: u16);
-}
-
-// The port addr is 16-bit wide.
-// wrappers for in/out[b,w]
-// Also I don't feel necessary to have a IO_Port Class give how
-// trivial it is
-// TODO perhaps use inline asm, because the code is short
+use core::arch::asm;
 
 pub fn inw(p: u16) -> u16 {
-	unsafe { _inw(p) }
+	let result: u16;
+	unsafe {
+		asm!("in ax, dx",
+			in("dx") p,
+			out("ax") result
+		)
+	}
+	result
 }
 
 pub fn inb(p: u16) -> u8 {
-	unsafe { _inb(p) }
+	let result: u8;
+	unsafe {
+		asm!("in al, dx",
+			in("dx") p,
+			out("al") result
+		)
+	}
+	result
 }
+
 pub fn outb(p: u16, val: u8) {
 	unsafe {
-		_outb(p, val);
+		asm!("out dx, al",
+			in("dx") p,
+			in("al") val,
+		)
 	}
 }
 
 pub fn outw(p: u16, val: u16) {
-	unsafe { _outw(p, val) }
+	unsafe {
+		asm!("out dx, ax",
+			in("dx") p,
+			in("ax") val,
+		)
+	}
 }
-- 
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