On Mon, Jul 20, 2015 at 06:52:32PM +0200, Peter Zijlstra wrote: > On Mon, Jul 20, 2015 at 11:36:46AM -0500, Josh Poimboeuf wrote: > > If a function doesn't call any other functions, then it won't ever show > > up in a stack trace unless: > > > > a) the function itself walks the stack, in which case the frame pointer > > isn't necessary; or > > > > b) The function gets hit by an interrupt/exception, in which case frame > > pointers can't be 100% relied upon anyway. > > In case the interrupt happens whilst setting up the frame, right? Right. > > I've noticed that gcc *does* seem to create stack frames for leaf > > functions. But it's inconsistent, because the early exit path of some > > functions will skip the stack frame creation and go straight to the > > return. > > > > We could probably get a good performance boost with the > > -momit-leaf-frame-pointer flag. Though it would make stack traces less > > reliable when a leaf function gets interrupted. > > So the information we'd loose in that case would be the location in the > calling function, right? Right. > Which isn't a problem, if the current function (as obtained > through RIP) is only ever called once. However if there's multiple call > sites this might be a wee bit confusing. Agreed, though the stack dump code always prints '?' for any kernel address it finds on the stack. So there would still be a good clue. -- Josh -- To unsubscribe from this list: send the line "unsubscribe live-patching" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
