On Fri, 22 Jan 2021 at 18:44, Mark Brown <broonie@xxxxxxxxxx> wrote: > > On Thu, Jan 21, 2021 at 12:54:52PM -0600, Josh Poimboeuf wrote: > > > 2) The shadow stack idea sounds promising -- how hard would it be to > > make a prototype reliable unwinder? > > In theory it doesn't look too hard and I can't see a particular reason > not to try doing this - there's going to be edge cases but hopefully for > reliable stack trace they're all in areas where we would be happy to > just decide the stack isn't reliable anyway, things like nesting which > allocates separate shadow stacks for each nested level for example. > I'll take a look. This reminds me - a while ago, I had a stab at writing a rudimentary GCC plugin that pushes/pops return addresses to a shadow call stack pointed to by x18 [0] I am by no means suggesting that we should rely on a GCC plugin for this, only that it does seem rather straight-forward for the compiler to manage a stack with return addresses like that (although the devil is probably in the details, as usual) [0] https://git.kernel.org/pub/scm/linux/kernel/git/ardb/linux.git/log/?h=arm64-scs-gcc
