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, 4 insertions, 4 deletions

diff --git a/src/dtables.rs b/src/dtables.rs
index a47d344..1aff96b 100644
--- a/src/dtables.rs
+++ b/src/dtables.rs
@@ -1,4 +1,4 @@
-/// Functions and data-structures to load descriptor tables.
+//! Functions and data-structures to load descriptor tables.
 
 /// A struct describing a pointer to a descriptor table (GDT / IDT).
 /// This is in a format suitable for giving to 'lgdt' or 'lidt'.
@@ -13,15 +13,15 @@ pub struct DescriptorTablePointer {
 
 /// Load GDT table.
 pub unsafe fn lgdt(gdt: &DescriptorTablePointer) {
-    asm!("lgdt ($0)" :: "r" (gdt));
+    asm!("lgdt ($0)" :: "r" (gdt) : "memory");
 }
 
 /// Load LDT table.
 pub unsafe fn lldt(ldt: &DescriptorTablePointer) {
-    asm!("lldt ($0)" :: "r" (ldt));
+    asm!("lldt ($0)" :: "r" (ldt) : "memory");
 }
 
 /// Load IDT table.
 pub unsafe fn lidt(idt: &DescriptorTablePointer) {
-    asm!("lidt ($0)" :: "r" (idt));
+    asm!("lidt ($0)" :: "r" (idt) : "memory");
 }
\ No newline at end of file