On 6/17/21 4:29 AM, nobuta.keiya@xxxxxxxxxxx wrote: > >> It's my understanding that the two pieces of work required to enable live >> patching on arm are in flight upstream; >> - Reliable stack traces as implemented by Madhavan T. Venkataraman [1] >> - Objtool as implemented by Julien Thierry [2] >> >> This is the remaining part required to enable live patching on arm. >> Based on work by Torsten Duwe [3] >> >> Allocate a task flag used to represent the patch pending state for the >> task. Also implement generic functions klp_arch_set_pc() & >> klp_get_ftrace_location(). >> >> In klp_arch_set_pc() it is sufficient to set regs->pc as in >> ftrace_common_return() the return address is loaded from the stack. >> >> ldr x9, [sp, #S_PC] >> <snip> >> ret x9 >> >> In klp_get_ftrace_location() it is necessary to advance the address by >> AARCH64_INSN_SIZE (4) to point to the BL in the callsite as 2 nops were >> placed at the start of the function, one to be patched to save the LR and >> another to be patched to branch to the ftrace call, and >> klp_get_ftrace_location() is expected to return the address of the BL. It >> may also be necessary to advance the address by another AARCH64_INSN_SIZE >> if CONFIG_ARM64_BTI_KERNEL is enabled due to the instruction placed at the >> branch target to satisfy BTI, >> >> Signed-off-by: Suraj Jitindar Singh <surajjs@xxxxxxxxxx> >> >> [1] https://lkml.org/lkml/2021/5/26/1212 >> [2] https://lkml.org/lkml/2021/3/3/1135 >> [3] https://lkml.org/lkml/2018/10/26/536 >> --- > > AFAIU Madhavan's patch series linked in the above [1] is currently awaiting > review by Mark Rutland. It seems that not only this patch series but also the > implementation of arch_stack_walk_reliable() at the below link is required > to enable livepatch. > Yes. I have a patch ready for that. But I can submit that only after the previous series has been accepted. Thanks Madhavan
