[PATCH v2 0/3] powerpc/ftrace: Fix livepatch module OOL ftrace corruption

[Naveen N Rao]

On Fri, Sep 12, 2025 at 10:27:37AM -0400, Joe Lawrence wrote:
> This patch series fixes a couple of bugs in the powerpc64 out-of-line
> (OOL) ftrace support for modules, and follows up with a patch to
> simplify the module .stubs allocation code. An analysis of the module
> stub area corruption that prompted this work can be found in the v1
> thread [1].
> 
> The first two patches fix bugs introduced by commit eec37961a56a
> ("powerpc64/ftrace: Move ftrace sequence out of line"). The first,
> suggested by Naveen, ensures that a NOP'd ftrace call site has its
> ftrace_ops record updated correctly. The second patch corrects a loop in
> setup_ftrace_ool_stubs() to ensure all required stubs are reserved, not
> just the first. Together, these bugs lead to potential corruption of the
> OOL ftrace stubs area for livepatch modules.
> 
> The final patch replaces the sentinel-based allocation in the module
> .stubs section with an explicit counter. This improves clarity and helps
> prevent similar problems in the future.
> 
> Changes since v1: https://lore.kernel.org/live-patching/df7taxdxpbo4qfn7lniggj5o4ili6kweg4nytyb2fwwwgmnyo4@halp5gf244nn/T/
> 
> - Split into parts: bug fix x2, code cleanup
> - Call ftrace_rec_set_nop_ops() from ftrace_init_nop() [Naveen]
> - Update commit msg on cleanup patch [Naveen]
> 
> Joe Lawrence (3):
>   powerpc/ftrace: ensure ftrace record ops are always set for NOPs
>   powerpc64/modules: correctly iterate over stubs in
>     setup_ftrace_ool_stubs
>   powerpc64/modules: replace stub allocation sentinel with an explicit
>     counter
> 
>  arch/powerpc/include/asm/module.h  |  1 +
>  arch/powerpc/kernel/module_64.c    | 26 ++++++++------------------
>  arch/powerpc/kernel/trace/ftrace.c | 10 ++++++++--
>  3 files changed, 17 insertions(+), 20 deletions(-)

Thanks for fixing this! For the series:
Acked-by: Naveen N Rao (AMD) <naveen at kernel.org>


- Naveen