Re: [PATCH 0/8] unwind, arm64: add sframe unwinder for kernel

Josh Poimboeuf
2025-02-25T18:13:33Z

On Tue, Feb 25, 2025 at 01:02:24AM +0000, Weinan Liu wrote:
> On Mon, Feb 10, 2025 at 12:30 AM Weinan Liu <wnliu@google.com> wrote:
> > I already have a WIP patch to add sframe support to the kernel module.
> > However, it is not yet working. I had trouble unwinding frames for the
> > kernel module using the current algorithm.
> >
> > Indu has likely identified the issue and will be addressing it from the
> > toolchain side.
> >
> > https://sourceware.org/bugzilla/show_bug.cgi?id=32666
>
>
> I have a working in progress patch that adds sframe support for kernel
> module.
> https://github.com/heuza/linux/tree/sframe_unwinder.rfc
>
> According to the sframe table values I got during runtime testing, looks
> like the offsets are not correct .
>
> When unwind symbols init_module(0xffff80007b155048) from the kernel
> module(livepatch-sample.ko), the start_address of the FDE entries in the
> sframe table of the kernel modules appear incorrect.
> For instance, the first FDE's start_addr is reported as -20564. Adding
> this offset to the module's sframe section address (0xffff80007b15a040)
> yields 0xffff80007b154fec, which is not within the livepatch-sample.ko
> memory region(It should be larger than 0xffff80007b155000).

I assume kpatch create-diff-object needs to copy over a subset of the
.sframe section. Similar to what kpatch_regenerate_orc_sections() does.

--
Josh