From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 27AE4C433F5 for ; Thu, 6 Jan 2022 16:37:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241289AbiAFQhc (ORCPT ); Thu, 6 Jan 2022 11:37:32 -0500 Received: from foss.arm.com ([217.140.110.172]:56466 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241323AbiAFQhc (ORCPT ); Thu, 6 Jan 2022 11:37:32 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id C37291042; Thu, 6 Jan 2022 08:37:31 -0800 (PST) Received: from FVFF77S0Q05N (unknown [10.57.10.56]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D09E43F5A1; Thu, 6 Jan 2022 08:37:29 -0800 (PST) Date: Thu, 6 Jan 2022 16:37:27 +0000 From: Mark Rutland To: madvenka@linux.microsoft.com Cc: broonie@kernel.org, jpoimboe@redhat.com, ardb@kernel.org, nobuta.keiya@fujitsu.com, sjitindarsingh@gmail.com, catalin.marinas@arm.com, will@kernel.org, jmorris@namei.org, linux-arm-kernel@lists.infradead.org, live-patching@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v12 05/10] arm64: Copy unwind arguments to unwind_state Message-ID: References: <0d0eb36f348fb5a6af6eb592c0525f6e94007328> <20220103165212.9303-1-madvenka@linux.microsoft.com> <20220103165212.9303-6-madvenka@linux.microsoft.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220103165212.9303-6-madvenka@linux.microsoft.com> Precedence: bulk List-ID: X-Mailing-List: live-patching@vger.kernel.org On Mon, Jan 03, 2022 at 10:52:07AM -0600, madvenka@linux.microsoft.com wrote: > From: "Madhavan T. Venkataraman" > > Copy the following arguments passed to arch_stack_walk() to unwind_state > so that they can be passed to unwind functions via unwind_state rather > than as separate arguments: > > - task I agree the task should be placed in the unwind state, since it's a key part of the environment for the unwind. > - regs This isn't relevant in all cases, and so for now I'd strongly prefer *not* to have this in the unwind state as it's liable to lead to confusion and get misused. > - consume_entry > - cookie These are only relevant for the invocation of the consume_entry() function, and so similarly I do not think they should be part of the state. It's simpler for these to be local variables. > > Signed-off-by: Madhavan T. Venkataraman > --- > arch/arm64/include/asm/stacktrace.h | 12 ++++++++ > arch/arm64/kernel/stacktrace.c | 45 ++++++++++++++++------------- > 2 files changed, 37 insertions(+), 20 deletions(-) > > diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h > index fc828c3c5dfd..322817d40a75 100644 > --- a/arch/arm64/include/asm/stacktrace.h > +++ b/arch/arm64/include/asm/stacktrace.h > @@ -51,6 +51,14 @@ struct stack_info { > * @kr_cur: When KRETPOLINES is selected, holds the kretprobe instance > * associated with the most recently encountered replacement lr > * value. > + * > + * @task: Pointer to the task structure. > + * > + * @regs: Registers, if any. > + * > + * @consume_pc Consume PC function pointer. > + * > + * @cookie Argument to consume_pc(). > */ > struct unwind_state { > unsigned long fp; > @@ -61,6 +69,10 @@ struct unwind_state { > #ifdef CONFIG_KRETPROBES > struct llist_node *kr_cur; > #endif > + struct task_struct *task; > + struct pt_regs *regs; > + stack_trace_consume_fn consume_pc; > + void *cookie; > }; > > extern void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk, > diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c > index bd797e3f7789..3ecb8242caa5 100644 > --- a/arch/arm64/kernel/stacktrace.c > +++ b/arch/arm64/kernel/stacktrace.c > @@ -33,8 +33,17 @@ > */ > > > -static void unwind_init_common(struct unwind_state *state) > +static void unwind_init_common(struct unwind_state *state, > + struct task_struct *task, > + struct pt_regs *regs, > + stack_trace_consume_fn consume_pc, > + void *cookie) > { > + state->task = task; > + state->regs = regs; > + state->consume_pc = consume_pc; > + state->cookie = cookie; > + > #ifdef CONFIG_KRETPROBES > state->kr_cur = NULL; > #endif > @@ -56,11 +65,10 @@ static void unwind_init_common(struct unwind_state *state) > /* > * TODO: document requirements here. > */ > -static inline void unwind_init_regs(struct unwind_state *state, > - struct pt_regs *regs) > +static inline void unwind_init_regs(struct unwind_state *state) > { > - state->fp = regs->regs[29]; > - state->pc = regs->pc; > + state->fp = state->regs->regs[29]; > + state->pc = state->regs->pc; > } > > /* > @@ -80,11 +88,10 @@ static __always_inline void unwind_init_current(struct unwind_state *state) > * > * The caller guarantees that the task is not running. > */ > -static inline void unwind_init_task(struct unwind_state *state, > - struct task_struct *task) > +static inline void unwind_init_task(struct unwind_state *state) > { > - state->fp = thread_saved_fp(task); > - state->pc = thread_saved_pc(task); > + state->fp = thread_saved_fp(state->task); > + state->pc = thread_saved_pc(state->task); > } > > /* > @@ -94,9 +101,9 @@ static inline void unwind_init_task(struct unwind_state *state, > * records (e.g. a cycle), determined based on the location and fp value of A > * and the location (but not the fp value) of B. > */ > -static int notrace unwind_next(struct task_struct *tsk, > - struct unwind_state *state) > +static int notrace unwind_next(struct unwind_state *state) > { > + struct task_struct *tsk = state->task; > unsigned long fp = state->fp; > struct stack_info info; > > @@ -170,16 +177,14 @@ static int notrace unwind_next(struct task_struct *tsk, > } > NOKPROBE_SYMBOL(unwind_next); > > -static void notrace unwind(struct task_struct *tsk, > - struct unwind_state *state, > - bool (*fn)(void *, unsigned long), void *data) > +static void notrace unwind(struct unwind_state *state) > { > while (1) { > int ret; > > - if (!fn(data, state->pc)) > + if (!state->consume_pc(state->cookie, state->pc)) > break; > - ret = unwind_next(tsk, state); > + ret = unwind_next(state); > if (ret < 0) > break; > } > @@ -225,14 +230,14 @@ noinline notrace void arch_stack_walk(stack_trace_consume_fn consume_entry, > { > struct unwind_state state; > > - unwind_init_common(&state); > + unwind_init_common(&state, task, regs, consume_entry, cookie); > > if (regs) > - unwind_init_regs(&state, regs); > + unwind_init_regs(&state); > else if (task == current) > unwind_init_current(&state); > else > - unwind_init_task(&state, task); > + unwind_init_task(&state); > > - unwind(task, &state, consume_entry, cookie); > + unwind(&state); I don't like the changes here in particular since they hide the information flow relevant to each case. Thanks, Mark. > } > -- > 2.25.1 >