On Wed, Mar 06, 2024 at 09:52:01AM +0000, Russell King (Oracle) wrote: > On Tue, Mar 05, 2024 at 09:58:46AM -0800, Josh Poimboeuf wrote: > > This is an off-by-one bug which is common in unwinders, due to the fact > > that the address on the stack points to the return address rather than > > the call address. > > > > So, for example, when the last instruction of a function is a function > > call (e.g., to a noreturn function), it can cause the unwinder to > > incorrectly try to unwind from the function *after* the callee. > > I suppose this can only happen in __noreturn functions because that > can be: > > foo: > ... > bl bar > ... end of function and thus next function ... > > which results in LR pointing into the next function. > > Would it make better sense to lookup the LR value winding it back by > one instruction like ORC on x86 does (as you mention) rather than > the patch you proposed which looks rather large and complicated? That patch *is* an attempt to make it match ORC's behavior. What specifically looks complicated about it? -- Josh
