Support other SigStackFlags

kernel/src/process/signal/sig_stack.rs

@@ -18,6 +18,8 @@ pub struct SigStack {
 
 bitflags! {
     pub struct SigStackFlags: u32 {
+        const SS_ONSTACK = 1 << 0;
+        const SS_DISABLE = 1 << 1;
         const SS_AUTODISARM = 1 << 31;
     }
 }
@@ -57,16 +59,16 @@ impl SigStack {
     }
 
     pub fn status(&self) -> SigStackStatus {
-        if self.handler_counter == 0 {
-            return SigStackStatus::SS_INACTIVE;
-        }
-
         // Learning From [sigaltstack doc](https://man7.org/linux/man-pages/man2/sigaltstack.2.html):
         // If the stack is currently executed on,
         // 1. If the stack was established with flag SS_AUTODISARM, the stack status is DISABLE,
         // 2. otherwise, the stack status is ONSTACK
-        if self.flags.contains(SigStackFlags::SS_AUTODISARM) {
-            SigStackStatus::SS_DISABLE
+        if self.handler_counter == 0 {
+            if self.flags.contains(SigStackFlags::SS_AUTODISARM) {
+                SigStackStatus::SS_DISABLE
+            } else {
+                SigStackStatus::SS_INACTIVE
+            }
         } else {
             SigStackStatus::SS_ONSTACK
         }
@@ -85,11 +87,13 @@ impl SigStack {
 
     /// Determines whether the stack is executed on by any signal handler
     pub fn is_active(&self) -> bool {
-        // FIXME: can DISABLE stack be used?
-        self.handler_counter != 0 && !self.flags.contains(SigStackFlags::SS_AUTODISARM)
+        (self.handler_counter > 0)
+            && !(self.flags.intersects(SigStackFlags::SS_AUTODISARM)
+                || self.flags.intersects(SigStackFlags::SS_DISABLE))
     }
 
     pub fn is_disabled(&self) -> bool {
-        self.handler_counter != 0 && self.flags.contains(SigStackFlags::SS_AUTODISARM)
+        self.flags.contains(SigStackFlags::SS_DISABLE)
+            || (self.handler_counter > 0 && self.flags.contains(SigStackFlags::SS_AUTODISARM))
     }
 }

kernel/src/syscall/sigaltstack.rs

@@ -36,14 +36,23 @@ fn get_old_stack(
         return Ok(());
     }
 
-    let Some(old_stack) = old_stack else {
-        return Ok(());
-    };
+    if let Some(old_stack) = old_stack {
+        debug!("old stack = {:?}", old_stack);
 
-    debug!("old stack = {:?}", old_stack);
+        let stack = stack_t::from(old_stack.clone());
+        ctx.get_user_space()
+            .write_val::<stack_t>(old_sig_stack_addr, &stack)?;
+    } else {
+        let stack = stack_t {
+            sp: 0,
+            flags: SigStackFlags::SS_DISABLE.bits() as i32,
+            size: 0,
+        };
+        ctx.get_user_space()
+            .write_val::<stack_t>(old_sig_stack_addr, &stack)?;
+    }
 
-    let stack = stack_t::from(old_stack.clone());
-    ctx.get_user_space().write_val(old_sig_stack_addr, &stack)
+    Ok(())
 }
 
 fn set_new_stack(sig_stack_addr: Vaddr, old_stack: Option<&SigStack>, ctx: &Context) -> Result<()> {
@@ -88,13 +97,20 @@ impl TryFrom<stack_t> for SigStack {
             return_errno_with_message!(Errno::EINVAL, "negative flags");
         }
 
-        let flags = SigStackFlags::from_bits(stack.flags as u32)
+        let mut flags = SigStackFlags::from_bits(stack.flags as u32)
             .ok_or_else(|| Error::with_message(Errno::EINVAL, "invalid flags"))?;
 
+        if flags.contains(SigStackFlags::SS_DISABLE) {
+            return Ok(Self::new(0, flags, 0));
+        }
         if stack.size < MINSTKSZ {
             return_errno_with_message!(Errno::ENOMEM, "stack size is less than MINSTKSZ");
         }
 
+        if flags.is_empty() {
+            flags.insert(SigStackFlags::SS_ONSTACK);
+        }
+
         Ok(Self::new(stack.sp, flags, stack.size))
     }
 }
@@ -102,6 +118,7 @@ impl TryFrom<stack_t> for SigStack {
 impl From<SigStack> for stack_t {
     fn from(stack: SigStack) -> Self {
         let flags = stack.flags().bits() as i32 | stack.status() as i32;
+
         Self {
             sp: stack.base(),
             flags,

test/syscall_test/Makefile

@@ -40,6 +40,7 @@ TESTS ?= \
 	rename_test \
 	semaphore_test \
 	sendfile_test \
+	sigaltstack_test \
 	stat_test \
 	stat_times_test \
 	statfs_test \

test/syscall_test/blocklists/sigaltstack_test

@@ -0,0 +1,3 @@
+SigaltstackTest.ResetByExecve
+SigaltstackTest.WalksOffBottom
+SigaltstackTest.SetCurrentStack