On Thu, 28 Oct 2021 14:24:00 +0200 Christophe Leroy <christophe.leroy@xxxxxxxxxx> wrote: > This series implements livepatch on PPC32. > > This is largely copied from what's done on PPC64. > > Christophe Leroy (5): > livepatch: Fix build failure on 32 bits processors > powerpc/ftrace: No need to read LR from stack in _mcount() > powerpc/ftrace: Add module_trampoline_target() for PPC32 > powerpc/ftrace: Activate HAVE_DYNAMIC_FTRACE_WITH_REGS on PPC32 > powerpc/ftrace: Add support for livepatch to PPC32 > > arch/powerpc/Kconfig | 2 +- > arch/powerpc/include/asm/livepatch.h | 4 +- > arch/powerpc/kernel/module_32.c | 33 +++++ > arch/powerpc/kernel/trace/ftrace.c | 53 +++----- > arch/powerpc/kernel/trace/ftrace_32.S | 187 ++++++++++++++++++++++++-- > kernel/livepatch/core.c | 4 +- > 6 files changed, 230 insertions(+), 53 deletions(-) > This is great that you are doing this, but I wonder if it would even be easier, and more efficient, if you could implement HAVE_DYNAMIC_FTRACE_WITH_ARGS? Then you don't need to save all regs for live kernel patching. And I am also working on function tracing with arguments with this too. That is, to call a generic ftrace callback, you need to save all the args that are stored in registers to prevent the callback from clobbering them. As live kernel patching only needs to have the arguments of the functions, you save time from having to save the other regs as well. The callbacks now have "struct ftrace_regs" instead of pt_regs, because it will allow non ftrace_regs_caller functions to access the arguments if it is supported. Look at how x86_64 implements this. It should be possible to do this for all other archs as well. Also note, by doing this, we can then get rid of the ftrace_graph_caller, and have function graph tracer be a function tracing callback, as it will allow ftrace_graph_caller to have access to the stack and the return as well. If you need any more help or information to do this, I'd be happy to assist you. Note, you can implement this first, (I looked over the patches and they seem fine) and then update both ppc64 and ppc32 to implement DYNAMIC_FTRACE_WITH_ARGS. Cheers, -- Steve
