Add ist() method for DescriptorBuilder.

2 files changed, 20 insertions, 3 deletions

diff --git a/src/bits64/segmentation.rs b/src/bits64/segmentation.rs
index d246f0f..6d58a80 100644
--- a/src/bits64/segmentation.rs
+++ b/src/bits64/segmentation.rs
@@ -59,9 +59,10 @@ impl Descriptor64 {
 
 impl GateDescriptorBuilder<u64> for DescriptorBuilder {
     fn tss_descriptor(base: u64, limit: u64, available: bool) -> DescriptorBuilder {
-        let typ = match available {
-            true => DescriptorType::System64(SystemDescriptorTypes64::TssAvailable),
-            false => DescriptorType::System64(SystemDescriptorTypes64::TssBusy),
+        let typ = if available {
+            DescriptorType::System64(SystemDescriptorTypes64::TssAvailable)
+        } else {
+            DescriptorType::System64(SystemDescriptorTypes64::TssBusy)
         };
 
         DescriptorBuilder::with_base_limit(base, limit).set_type(typ)
@@ -105,6 +106,11 @@ impl BuildDescriptor<Descriptor64> for DescriptorBuilder {
                 {
                     assert!(!self.db);
                 }
+
+                if typ == SystemDescriptorTypes64::InterruptGate {
+                    desc.set_ist(self.ist);
+                }
+
                 typ as u8
             }
             Some(DescriptorType::System32(_typ)) => {
diff --git a/src/segmentation.rs b/src/segmentation.rs
index a9cc684..c58403e 100644
--- a/src/segmentation.rs
+++ b/src/segmentation.rs
@@ -239,6 +239,8 @@ pub struct DescriptorBuilder {
     pub(crate) limit_granularity_4k: bool,
     /// 64-bit code segment (IA-32e mode only)
     pub(crate) l: bool,
+    /// Interrupt stack table (IST) selector (IA-32e mode only)
+    pub(crate) ist: u8,
 }
 
 impl DescriptorBuilder {
@@ -254,6 +256,7 @@ impl DescriptorBuilder {
             db: false,
             limit_granularity_4k: false,
             l: false,
+            ist: 0,
         }
     }
 
@@ -272,6 +275,7 @@ impl DescriptorBuilder {
             db: false,
             limit_granularity_4k: false,
             l: false,
+            ist: 0,
         }
     }
 
@@ -317,6 +321,13 @@ impl DescriptorBuilder {
         self.l = true;
         self
     }
+
+    /// Set a the interrupt stack table index (only if this ends up being a 64-bit interrupt descriptor).
+    pub fn ist(mut self, index: u8) -> DescriptorBuilder {
+        debug_assert!(index <= 7);
+        self.ist = index;
+        self
+    }
 }
 
 impl GateDescriptorBuilder<u32> for DescriptorBuilder {