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Date: Tue, 2 Jun 2020 08:14:50 -0500 From: Josh Poimboeuf <jpoimboe@...hat.com> To: "Wangshaobo (bobo)" <bobo.shaobowang@...wei.com> Cc: huawei.libin@...wei.com, xiexiuqi@...wei.com, cj.chengjian@...wei.com, mingo@...hat.com, x86@...nel.org, linux-kernel@...r.kernel.org, live-patching@...r.kernel.org, mbenes@...e.cz, devel@...ukata.com, viro@...iv.linux.org.uk, esyr@...hat.com Subject: Re: Question: livepatch failed for new fork() task stack unreliable On Tue, Jun 02, 2020 at 09:22:30AM +0800, Wangshaobo (bobo) wrote: > so i think this question is related to ORC unwinder, could i ask if you have > strategy or plan to avoid this problem ? I suspect something like this would fix it (untested): diff --git a/arch/x86/kernel/stacktrace.c b/arch/x86/kernel/stacktrace.c index 6ad43fc44556..8cf95ded1410 100644 --- a/arch/x86/kernel/stacktrace.c +++ b/arch/x86/kernel/stacktrace.c @@ -50,7 +50,7 @@ int arch_stack_walk_reliable(stack_trace_consume_fn consume_entry, if (regs) { /* Success path for user tasks */ if (user_mode(regs)) - return 0; + break; /* * Kernel mode registers on the stack indicate an @@ -81,10 +81,6 @@ int arch_stack_walk_reliable(stack_trace_consume_fn consume_entry, if (unwind_error(&state)) return -EINVAL; - /* Success path for non-user tasks, i.e. kthreads and idle tasks */ - if (!(task->flags & (PF_KTHREAD | PF_IDLE))) - return -EINVAL; - return 0; } diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c index 7f969b2d240f..d7396431261a 100644 --- a/arch/x86/kernel/unwind_orc.c +++ b/arch/x86/kernel/unwind_orc.c @@ -540,7 +540,7 @@ bool unwind_next_frame(struct unwind_state *state) state->sp = sp; state->regs = NULL; state->prev_regs = NULL; - state->signal = false; + state->signal = ((void *)state->ip == ret_from_fork); break; case ORC_TYPE_REGS:
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