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Various QEMU SnapshotModule fixes #3542

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Various QEMU SnapshotModule fixes #3542

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c31305b
Clear dirty pages on snapshot in SnapshotModule
wfdewith Nov 22, 2025
0f4e15c
Use log statement for memory map in SnapshotModule
wfdewith Nov 22, 2025
b00e45c
Fix SnapshotModule filter bugs
wfdewith Nov 22, 2025
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15 changes: 8 additions & 7 deletions crates/libafl_qemu/src/modules/usermode/snapshot.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -238,14 +238,15 @@ impl SnapshotModule {
self.initial_brk = qemu.get_initial_brk();
self.mmap_start = qemu.get_mmap_start();
self.pages.clear();
for acc in &mut self.accesses {
unsafe { (*acc.get()).clear() };
}
for map in qemu.mappings() {
println!("mapping: {map:?}");
log::debug!("mapping: {map:}");

let mut addr = map.start();
while addr < map.end() {
let zero = self.interval_filter.to_zero(addr);
let skip = self.interval_filter.to_skip(addr);
if let Some(range) = zero.or(skip) {
if let Some(range) = self.interval_filter.to_skip(addr) {
addr = range.end;
continue;
}
Expand All @@ -255,7 +256,7 @@ impl SnapshotModule {
private: map.is_priv(),
data: None,
};
if map.flags().readable() {
if map.flags().readable() && self.interval_filter.to_zero(addr).is_none() {
// TODO not just for R pages
unsafe {
info.data = Some(Box::new(core::mem::zeroed()));
Expand Down Expand Up @@ -478,7 +479,7 @@ impl SnapshotModule {
for acc in &mut self.accesses {
unsafe { &mut (*acc.get()) }.dirty.retain(|page| {
if let Some(info) = self.pages.get_mut(page) {
if self.interval_filter.to_skip(*page as u64).is_some() {
if self.interval_filter.to_zero(*page as u64).is_some() {
if !Self::modify_mapping(qemu, new_maps, *page) {
return true; // Restore later
}
Expand Down Expand Up @@ -523,7 +524,7 @@ impl SnapshotModule {
}
}

if self.interval_filter.to_skip(*page as u64).is_some() {
if self.interval_filter.to_zero(*page as u64).is_some() {
unsafe { qemu.write_mem_unchecked(*page, &SNAPSHOT_PAGE_ZEROES) };
} else if let Some(info) = self.pages.get_mut(page) {
// TODO avoid duplicated memcpy
Expand Down
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