Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: - [Low] Build failure due to missing `ftrace_static_tramp_end` symbol when `CONFIG_DYNAMIC_FTRACE_WITH_ARGS` is disabled. --
commit 459a25e6b720c08167da420eb83180b2856610e3 Author: Josef Bacik <[email protected]> arm64: ftrace: Maintain Tasks RCU trampoline nesting in ftrace_caller Bracket the call out to the ftrace_ops callback in ftrace_caller with an increment/decrement of current->rcu_tramp_nesting, using x12/w13 which are scratch there. The read-modify-write is not atomic, but only current modifies the count and every interrupting user is balanced, so nothing is lost. > diff --git a/arch/arm64/kernel/entry-ftrace.S > b/arch/arm64/kernel/entry-ftrace.S > index 025140caafe74..46a102e7199ac 100644 > --- a/arch/arm64/kernel/entry-ftrace.S > +++ b/arch/arm64/kernel/entry-ftrace.S > @@ -14,6 +14,33 @@ > #include <asm/insn.h> > > #ifdef CONFIG_DYNAMIC_FTRACE_WITH_ARGS [ ... ] > @@ -178,6 +209,10 @@ SYM_CODE_START(ftrace_stub_direct_tramp) > SYM_CODE_END(ftrace_stub_direct_tramp) > #endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */ > > +/* End of [ftrace_caller, ...) for arch_rcu_tasks_ip_in_trampoline(). */ > +SYM_CODE_START(ftrace_static_tramp_end) > +SYM_CODE_END(ftrace_static_tramp_end) > + > #else /* CONFIG_DYNAMIC_FTRACE_WITH_ARGS */ > > /* [Severity: Low] Will this cause a linker error when compiling with CONFIG_RCU_TASKS_PREEMPT_QS=y but CONFIG_DYNAMIC_FTRACE_WITH_ARGS=n? The ftrace_static_tramp_end label is defined here exclusively inside the CONFIG_DYNAMIC_FTRACE_WITH_ARGS block. The legacy mcount-based ftrace path in the #else block lacks this definition. > diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c > index e1a3c0b3a0514..1b7ac2afed0df 100644 > --- a/arch/arm64/kernel/ftrace.c > +++ b/arch/arm64/kernel/ftrace.c > @@ -17,6 +17,22 @@ > #include <asm/insn.h> > #include <asm/text-patching.h> > > +#ifdef CONFIG_RCU_TASKS_PREEMPT_QS > +extern void ftrace_static_tramp_end(void); > + > +/* > + * See rcu_tasks_ip_in_trampoline(). ftrace_caller and > ftrace_stub_direct_tramp > + * are core kernel text but must be treated as trampolines: a task preempted > in > + * them may be carrying an ops pointer (x11) or a direct-call BPF trampoline > + * address (x17) whose lifetime is guarded only by Tasks RCU. > + */ > +bool arch_rcu_tasks_ip_in_trampoline(unsigned long ip) > +{ > + return ip >= (unsigned long)ftrace_caller && > + ip < (unsigned long)ftrace_static_tramp_end; > +} > +#endif [Severity: Low] Since arch_rcu_tasks_ip_in_trampoline() unconditionally references ftrace_static_tramp_end here under CONFIG_RCU_TASKS_PREEMPT_QS, this might lead to an undefined reference at link time if CONFIG_DYNAMIC_FTRACE_WITH_ARGS is disabled. -- Sashiko AI review ยท https://sashiko.dev/#/patchset/20260910-b4-rcu-tasks-preempt-qs-v1-0-d4469f4cc...@toxicpanda.com?part=9
