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debug: Avoid underflow when scanning for landing pad bytes #2866

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Merged
alexcrichton merged 1 commit into from
May 3, 2021
Merged

debug: Avoid underflow when scanning for landing pad bytes #2866

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28 changes: 16 additions & 12 deletions crates/debug/src/transform/expression.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -512,24 +512,28 @@ where
}
};
}

// Find all landing pads by scanning bytes, do not care about
// false location at this moment.
// Looks hacky but it is fast; does not need to be really exact.
for i in 0..buf.len() - 2 {
let op = buf[i];
if op == gimli::constants::DW_OP_bra.0 || op == gimli::constants::DW_OP_skip.0 {
// TODO fix for big-endian
let offset = i16::from_le_bytes([buf[i + 1], buf[i + 2]]);
let origin = i + 3;
// Discarding out-of-bounds jumps (also some of falsely detected ops)
if (offset >= 0 && offset as usize + origin <= buf.len())
|| (offset < 0 && -offset as usize <= origin)
{
let target = buf.len() as isize - origin as isize - offset as isize;
jump_targets.insert(target as u64, JumpTargetMarker::new());
if buf.len() > 2 {
for i in 0..buf.len() - 2 {
let op = buf[i];
if op == gimli::constants::DW_OP_bra.0 || op == gimli::constants::DW_OP_skip.0 {
// TODO fix for big-endian
let offset = i16::from_le_bytes([buf[i + 1], buf[i + 2]]);
let origin = i + 3;
// Discarding out-of-bounds jumps (also some of falsely detected ops)
if (offset >= 0 && offset as usize + origin <= buf.len())
|| (offset < 0 && -offset as usize <= origin)
{
let target = buf.len() as isize - origin as isize - offset as isize;
jump_targets.insert(target as u64, JumpTargetMarker::new());
}
}
}
}

while !pc.is_empty() {
let unread_bytes = pc.len().into_u64();
if let Some(marker) = jump_targets.get(&unread_bytes) {
Expand Down