forked from OSchip/llvm-project
a8b284eeec
Summary: Windows unwinding is weird. The unwind rules do not (always) describe the precise layout of the stack, but rather expect the debugger to scan the stack for something which looks like a plausible return address, and the unwind based on that. The reason this works somewhat reliably is because the the unwinder also has access to the frame sizes of the functions on the stack. This allows it (in most cases) to skip function pointers in local variables or function arguments, which could otherwise be mistaken for return addresses. Implementing this kind of unwind mechanism in lldb was a bit challenging because we expect to be able to statically describe (in the UnwindPlan) structure, the layout of the stack for any given instruction. Giving a precise desription of this is not possible, because it requires correlating information from two functions -- the pushed arguments to a function are considered a part of the callers stack frame, and their size needs to be considered when unwinding the caller, but they are only present in the unwind entry of the callee. The callee may end up being in a completely different module, or it may not even be possible to determine it statically (indirect calls). This patch implements this functionality by introducing a couple of new APIs: SymbolFile::GetParameterStackSize - return the amount of stack space taken up by parameters of this function. SymbolFile::GetOwnFrameSize - the size of this function's frame. This excludes the parameters, but includes stuff like local variables and spilled registers. These functions are then used by the unwinder to compute the estimated location of the return address. This address is not always exact, because the stack may contain some additional values -- for instance, if we're getting ready to call a function then the stack will also contain partially set up arguments, but we will not know their size because we haven't called the function yet. For this reason the unwinder will crawl up the stack from the return address position, and look for something that looks like a possible return address. Currently, we assume that something is a valid return address if it ends up pointing to an executable section. All of this logic kicks in when the UnwindPlan sets the value of CFA as "isHeuristicallyDetected", which is also the final new API here. Right now, only SymbolFileBreakpad implements these APIs, but in the future SymbolFilePDB will use them too. Differential Revision: https://reviews.llvm.org/D66638 llvm-svn: 373072 |
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| .. | ||
| Inputs | ||
| line-table-discontinuous-file-ids.test | ||
| line-table-edgecases.test | ||
| line-table-missing-file.test | ||
| line-table-mixed-path-styles.test | ||
| line-table.test | ||
| stack-cfi-parsing.test | ||
| symtab-macho.test | ||
| symtab.test | ||
| unwind-via-raSearch.test | ||
| unwind-via-stack-cfi.test | ||
| unwind-via-stack-win.test | ||