Fixing volatile and memory attributes for assembly.

For volatile:
You can prevent an asm instruction from being deleted by writing the
keyword volatile after the asm. [...] The volatile keyword indicates
that the instruction has important side-effects. GCC will not
delete a volatile asm if it is reachable.
and
An asm instruction without any output operands will be treated
identically to a volatile asm instruction.

And for memory:
This will cause GCC to not keep memory values cached in
registers across the assembler instruction and not optimize
stores or loads to that memory.

See also:
https://gcc.gnu.org/onlinedocs/gcc-4.7.2/gcc/Extended-Asm.html
http://stackoverflow.com/questions/14449141/the-difference-between-asm-asm-volatile-and-clobbering-memory

1 files changed, 8 insertions, 6 deletions

diff --git a/src/io.rs b/src/io.rs
index 0f0e96a..eded102 100644
--- a/src/io.rs
+++ b/src/io.rs
@@ -1,35 +1,37 @@
+//! I/O port functionality.
+
 /// Write 8 bits to port
 pub unsafe fn outb(port: u16, val: u8) {
-	asm!("outb %al, %dx" : : "{dx}"(port), "{al}"(val));
+	asm!("outb %al, %dx" :: "{dx}"(port), "{al}"(val));
 }
 
 /// Read 8 bits from port
 pub unsafe fn inb(port: u16) -> u8 {
 	let ret : u8;
-	asm!("inb %dx, %al" : "={ax}"(ret) : "{dx}"(port));
+	asm!("inb %dx, %al" : "={ax}"(ret) : "{dx}"(port) :: "volatile");
 	return ret;
 }
 
 /// Write 16 bits to port
 pub unsafe fn outw(port: u16, val: u16) {
-	asm!("outw %ax, %dx" : : "{dx}"(port), "{al}"(val));
+	asm!("outw %ax, %dx" :: "{dx}"(port), "{al}"(val));
 }
 
 /// Read 16 bits from port
 pub unsafe fn inw(port: u16) -> u16 {
 	let ret : u16;
-	asm!("inw %dx, %ax" : "={ax}"(ret) : "{dx}"(port));
+	asm!("inw %dx, %ax" : "={ax}"(ret) : "{dx}"(port) :: "volatile");
 	return ret;
 }
 
 /// Write 32 bits to port
 pub unsafe fn outl(port: u16, val: u32) {
-	asm!("outl %eax, %dx" : : "{dx}"(port), "{al}"(val));
+	asm!("outl %eax, %dx" :: "{dx}"(port), "{al}"(val));
 }
 
 /// Read 32 bits from port
 pub unsafe fn inl(port: u16) -> u32 {
 	let ret : u32;
-	asm!("inl %dx, %eax" : "={ax}"(ret) : "{dx}"(port));
+	asm!("inl %dx, %eax" : "={ax}"(ret) : "{dx}"(port) :: "volatile");
 	return ret;
 }