Messages in this thread | | | Date | Wed, 1 Apr 2020 17:38:10 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH v2] objtool,ftrace: Implement UNWIND_HINT_RET_OFFSET |
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On Wed, Apr 01, 2020 at 09:39:16AM -0500, Josh Poimboeuf wrote: > On Wed, Apr 01, 2020 at 04:22:26PM +0200, Peter Zijlstra wrote:
> > > > @@ -366,6 +367,13 @@ create_trampoline(struct ftrace_ops *ops > > > > if (WARN_ON(ret < 0)) > > > > goto fail; > > > > > > > > + if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) { > > > > + ip = ftrace_regs_caller_ret; > > > > + ret = probe_kernel_read(ip, (void *)retq, RET_SIZE); > > > > + if (WARN_ON(ret < 0)) > > > > + goto fail; > > > > + } > > > > +
> Right, but 'ip' needs to point to the trampoline's version of > 'ftrace_regs_caller_ret', not the original ftrace_64 version.
Duh,
ip = trampline + (ftrace_regs_caller_ret - ftrace_regs_caller);
it is.
Luckily this would've triggerd a splat the first time I'd have actually booted this, because the regular text is RO, while the trampoline is still RW here. Still, good spotting.
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