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Refactor debugger breakpoint handling #790
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ranweiler
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Apr 13, 2021
| fn module_from_address(&mut self, address: u64) -> &mut Module { | ||
| let module_base = self | ||
| .module_base_from_address(address) | ||
| .unwrap_or(unsafe { NonZeroU64::new_unchecked(module::UNKNOWN_MODULE_BASE_ADDRESS) }); |
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How about avoiding unsafe and doing:
Suggested change
| .unwrap_or(unsafe { NonZeroU64::new_unchecked(module::UNKNOWN_MODULE_BASE_ADDRESS) }); | |
| .unwrap_or(NonZeroU64::new(module::UNKNOWN_MODULE_BASE_ADDRESS).unwrap()); |
Alternately, it looks like new_unchecked() is a const fn, so maybe we could just make the exported constant a NonZeroU64.
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We have too many unwrap calls already and I started replacing them with expect or adding proper error handling.
Unfortunately const fn doesn't alleviate the need to use unsafe, and you can't use unwrap or expect on a const.
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Ah, darn. Maybe someday soon: rust-lang/rust#51999 (comment)
ranweiler
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Apr 19, 2021
ranweiler
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Apr 19, 2021
ghost
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There is a bunch of refactoring in the PR but also a couple of important fixes.
Breakpoints are now cleared after
ContinueDebugEventreturns and restored just before callingContinueDebugEventagain. This ensures that debugger clients can read process memory and not see the breakpoints.Additionally, the original code byte for a breakpoint is reread to correctly handle the rare case of self modifying code.
Note that with this change, debug event processing is now significantly slower than before this PR. For infrequent events it might not be a big deal, but single stepping performance is much worse.
I may look at adding a way to simulate process reads to account for our breakpoints to improve performance, but I think this refactoring is worth taking as is because it is more correct and also I think cleans up breakpoints in general.