fuzz: add bitmap_allocator harness.

Signed-off-by: Vasant Karasulli <vkarasulli@suse.de>

fuzz/Cargo.toml

@@ -56,3 +56,9 @@ name = "insn"
 path = "fuzz_targets/insn.rs"
 test = false
 doc = false
+
+[[bin]]
+name = "bitmap_allocator"
+path = "fuzz_targets/bitmap_allocator.rs"
+test = false
+doc = false

fuzz/fuzz_targets/bitmap_allocator.rs

@@ -0,0 +1,192 @@
+// SPDX-License-Identifier: MIT OR Apache-2.0
+//
+// Copyright (c) 2023 SUSE LLC
+//
+// Author: Vasant Karasulli <vkarasulli@suse.de>
+
+#![no_main]
+use arbitrary::Arbitrary;
+use libfuzzer_sys::fuzz_target;
+use svsm::utils::bitmap_allocator::{BitmapAllocator, BitmapAllocator1024, BitmapAllocator64};
+
+#[derive(Arbitrary, Debug)]
+enum BmaAction {
+    Alloc(usize, usize),
+    Free(usize, usize),
+    Set(usize, usize, bool),
+    NextFree(usize),
+}
+
+pub trait TestBitmapAllocator: BitmapAllocator {
+    fn prune_alloc_params(&self, entries: usize, align: usize) -> (usize, usize) {
+        let align_p = align % (self.max_align() + 1);
+        let entries_limit = self.capacity() - (1 << align_p);
+        let entries_p = (entries % entries_limit) + 1;
+        (entries_p, align_p)
+    }
+
+    fn prune_set_params(&self, start: usize, entries: usize) -> (usize, usize) {
+        let start_p = start % self.capacity();
+        let entries_limit = self.capacity() - start_p;
+        let entries_p = (entries % entries_limit) + 1;
+        (start_p, entries_p)
+    }
+
+    fn test_alloc(&self, bma_before: &Self, entries: usize, align: usize, offset: Option<usize>) {
+        match offset {
+            Some(offset) => {
+                assert_eq!(offset % (1 << align), 0);
+                self.test_set(bma_before, offset, entries, true);
+            }
+            None => {
+                for i in (0..=(self.capacity() - entries)).step_by(1 << align) {
+                    let mut flag = false;
+                    for j in 0..entries {
+                        if self.get(i + j) {
+                            flag = true;
+                            break;
+                        }
+                    }
+                    assert!(flag);
+                }
+            }
+        }
+    }
+    fn test_set(&self, bma: &Self, start: usize, entries: usize, val: bool);
+    fn test_nextfree(&self, start: usize, res: Option<usize>);
+}
+
+impl TestBitmapAllocator for BitmapAllocator64 {
+    fn test_set(&self, bma64_before: &Self, start: usize, entries: usize, val: bool) {
+        let start_mask = !((1 << start) - 1);
+        let end_mask = (((1 << (start + entries - 1)) - 1) << 1) + 1;
+        let mask = start_mask & end_mask;
+        if val {
+            assert_eq!(bma64_before.get_bits() | mask, self.get_bits());
+        } else {
+            assert_eq!(bma64_before.get_bits() & !mask, self.get_bits());
+        }
+    }
+
+    fn test_nextfree(&self, start: usize, res: Option<usize>) {
+        match res {
+            Some(res) => {
+                assert!(res >= start);
+                assert!(!self.get(res));
+                if res > start {
+                    let mask: u64 = ((1 << (res - start)) - 1) << start;
+                    assert_eq!(self.get_bits() & mask, mask);
+                }
+            }
+            None => {
+                let mask: u64 = (1 << start) - 1;
+                assert_eq!(
+                    (self.get_bits() | mask).trailing_ones(),
+                    self.capacity() as u32
+                );
+            }
+        }
+    }
+}
+
+impl TestBitmapAllocator for BitmapAllocator1024 {
+    fn test_set(&self, bma1024_before: &Self, start: usize, entries: usize, val: bool) {
+        let capacity = self.get_child(0).capacity();
+        let first = start / capacity;
+        let last = (start + entries - 1) / capacity;
+        let mut off = start % capacity;
+        let mut remain = entries;
+        let mut size;
+        for i in 0..16 {
+            let bma64 = self.get_child(i);
+            let bma64_before = bma1024_before.get_child(i);
+            if i >= first && i <= last {
+                size = if (off + remain) > capacity {
+                    capacity - off
+                } else {
+                    remain
+                };
+                bma64.test_set(&bma64_before, off, size, val);
+                remain -= size;
+                if remain == 0 {
+                    continue;
+                }
+                off = 0;
+            } else {
+                assert_eq!(bma64.get_bits(), bma64_before.get_bits());
+            }
+        }
+    }
+
+    fn test_nextfree(&self, start: usize, res: Option<usize>) {
+        let capacity = self.get_child(0).capacity();
+        match res {
+            Some(res) => {
+                let first = start / capacity;
+                let last = res / capacity;
+                let mut off_start = start % capacity;
+                let off_last = res % capacity;
+                for i in first..last {
+                    assert_eq!(self.get_child(i).next_free(off_start), None);
+                    off_start = 0;
+                }
+                let bma64_last = self.get_child(last);
+                assert!(!bma64_last.get(off_last));
+                assert_eq!(bma64_last.next_free(off_start), Some(off_last));
+            }
+            None => {
+                let first = start / capacity;
+                let mut off_start = start % capacity;
+                for i in first..16 {
+                    assert_eq!(self.get_child(i).next_free(off_start), None);
+                    off_start = 0;
+                }
+            }
+        }
+    }
+}
+
+fuzz_target!(|actions: Vec<BmaAction>| {
+    let mut bma64 = BitmapAllocator64::new();
+    let mut bma1024 = BitmapAllocator1024::new();
+    for action in actions.iter() {
+        let bma64_before = bma64;
+        let bma1024_before = bma1024.clone();
+        match action {
+            BmaAction::Alloc(entries, align) => {
+                let (entries_p, align_p) = bma64.prune_alloc_params(*entries, *align);
+                let offset = bma64.alloc(entries_p, align_p);
+                bma64.test_alloc(&bma64_before, entries_p, align_p, offset);
+
+                let (entries_p, align_p) = bma1024.prune_alloc_params(*entries, *align);
+                let offset = bma1024.alloc(entries_p, align_p);
+                bma1024.test_alloc(&bma1024_before, entries_p, align_p, offset);
+            }
+            BmaAction::Free(start, entries) => {
+                let (start_p, entries_p) = bma64.prune_set_params(*start, *entries);
+                bma64.free(start_p, entries_p);
+                bma64.test_set(&bma64_before, start_p, entries_p, false);
+
+                let (start_p, entries_p) = bma1024.prune_set_params(*start, *entries);
+                bma1024.free(start_p, entries_p);
+                bma1024.test_set(&bma1024_before, start_p, entries_p, false);
+            }
+            BmaAction::Set(start, entries, value) => {
+                let (start_p, entries_p) = bma64.prune_set_params(*start, *entries);
+                bma64.set(start_p, entries_p, *value);
+                bma64.test_set(&bma64_before, start_p, entries_p, *value);
+
+                let (start_p, entries_p) = bma1024.prune_set_params(*start, *entries);
+                bma1024.set(start_p, entries_p, *value);
+                bma1024.test_set(&bma1024_before, start_p, entries_p, *value);
+            }
+            BmaAction::NextFree(start) => {
+                let res = bma64.next_free(start % bma64.capacity());
+                bma64.test_nextfree(start % bma64.capacity(), res);
+
+                let res = bma1024.next_free(start % bma1024.capacity());
+                bma1024.test_nextfree(start % bma1024.capacity(), res);
+            }
+        }
+    }
+});

src/utils/bitmap_allocator.rs

@@ -18,6 +18,10 @@ pub trait BitmapAllocator {
     fn empty(&self) -> bool;
     fn capacity(&self) -> usize;
     fn used(&self) -> usize;
+    #[cfg(fuzzing)]
+    fn max_align(&self) -> usize {
+        (<Self as BitmapAllocator>::CAPACITY.ilog2() - 1) as usize
+    }
 }
 
 pub type BitmapAllocator1024 = BitmapAllocatorTree<BitmapAllocator64>;
@@ -31,6 +35,11 @@ impl BitmapAllocator64 {
     pub const fn new() -> Self {
         Self { bits: u64::MAX }
     }
+
+    #[cfg(fuzzing)]
+    pub fn get_bits(&self) -> u64 {
+        self.bits
+    }
 }
 
 impl BitmapAllocator for BitmapAllocator64 {
@@ -45,6 +54,7 @@ impl BitmapAllocator for BitmapAllocator64 {
     }
 
     fn set(&mut self, start: usize, entries: usize, value: bool) {
+        assert!(entries > 0);
         assert!((start + entries) <= BitmapAllocator64::CAPACITY);
         // Create a mask for changing the bitmap
         let start_mask = !((1 << start) - 1);
@@ -84,7 +94,7 @@ impl BitmapAllocator for BitmapAllocator64 {
     }
 }
 
-#[derive(Debug, Default)]
+#[derive(Debug, Default, Clone)]
 pub struct BitmapAllocatorTree<T: BitmapAllocator + Debug> {
     bits: u16,
     child: [T; 16],
@@ -97,6 +107,11 @@ impl BitmapAllocatorTree<BitmapAllocator64> {
             child: [BitmapAllocator64::new(); 16],
         }
     }
+
+    #[cfg(fuzzing)]
+    pub fn get_child(&self, index: usize) -> BitmapAllocator64 {
+        self.child[index]
+    }
 }
 
 impl<T: BitmapAllocator + Debug> BitmapAllocator for BitmapAllocatorTree<T> {
@@ -171,6 +186,7 @@ impl<T: BitmapAllocator + Debug> BitmapAllocator for BitmapAllocatorTree<T> {
 fn alloc_aligned(ba: &mut impl BitmapAllocator, entries: usize, align: usize) -> Option<usize> {
     // Iterate through the bitmap checking on each alignment boundary
     // for a free range of the requested size
+    assert!((align as u32) < ba.capacity().ilog2());
     let align_mask = (1 << align) - 1;
     let mut offset = 0;
     while (offset + entries) <= ba.capacity() {