Messages in this thread Patch in this message | | | Date | Tue, 31 Mar 2020 23:07:20 +0200 | From | Peter Zijlstra <> | Subject | Re: [RFC][PATCH] objtool,ftrace: Implement UNWIND_HINT_RET_OFFSET |
| |
On Tue, Mar 31, 2020 at 10:40:47PM +0200, Peter Zijlstra wrote: > On Tue, Mar 31, 2020 at 03:23:15PM -0500, Josh Poimboeuf wrote:
> > I now understand what you're trying to do with the RET_TAIL thing, and I > > guess it's ok for the ftrace case. But I'd rather an UNWIND_HINT_IGNORE > > before the tail cail, which would tell objtool to just silence the tail > > call warning. It's simpler for the user to understand, it's simpler > > logic in objtool, and I think an "ignore warnings for the next insn" > > hint would be more generally applicable anyway. > > I like how this is specific on how far the stack can be off, as opposed > so say 'ignore any warning on this instruction'. > > Because by saying this RET should be +8, we'll still get a warning when > this is not the case (and in fact I should strengthen the patch to > implement that).
Like this; I'm confused on what cfa.offset is vs stack_size though.
But this way we're strict and always warn when the unexpected happens.
--- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -1423,8 +1423,7 @@ static bool has_modified_stack_frame(str !(ret_offset && state->cfa.offset == initial_func_cfi.cfa.offset + ret_offset)) return true; - if (state->stack_size != initial_func_cfi.cfa.offset && - !(ret_offset && state->stack_size == initial_func_cfi.cfa.offset + ret_offset)) + if (state->stack_size != initial_func_cfi.cfa.offset + ret_offset) return true; for (i = 0; i < CFI_NUM_REGS; i++) {
| |