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 837F0C433EF for ; Thu, 6 Jan 2022 20:17:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243642AbiAFURd (ORCPT ); Thu, 6 Jan 2022 15:17:33 -0500 Received: from linux.microsoft.com ([13.77.154.182]:43578 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243582AbiAFURc (ORCPT ); Thu, 6 Jan 2022 15:17:32 -0500 Received: from [192.168.254.32] (unknown [47.187.212.181]) by linux.microsoft.com (Postfix) with ESMTPSA id 75A7B20B7179; Thu, 6 Jan 2022 12:17:31 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 75A7B20B7179 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1641500252; bh=Hh0ZW8EfXcZcHkCAjia0bYshL301LrZuYH2kh2Opuv0=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=P5EypePoLb/EQ/hWUmzTdmQ10elVlRKQ4nJDP8rp15UUW/IYDaGZzF+TfBN7tUKn6 KYIyVpFHZJn4qzA+2oaWffU7HDILuzyN7wklK5CzF6kIZczInrF+LEK4dQUjzNE9qb lS4aIl5BTRtupLc1iqy0UVhZa3SchawkJHKkJrQA= Subject: Re: [PATCH v12 05/10] arm64: Copy unwind arguments to unwind_state To: Mark Rutland 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 References: <0d0eb36f348fb5a6af6eb592c0525f6e94007328> <20220103165212.9303-1-madvenka@linux.microsoft.com> <20220103165212.9303-6-madvenka@linux.microsoft.com> From: "Madhavan T. Venkataraman" Message-ID: <6fce7dd5-2f45-5034-bdf8-6c3a3499e9e7@linux.microsoft.com> Date: Thu, 6 Jan 2022 14:17:30 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: live-patching@vger.kernel.org On 1/6/22 10:37 AM, Mark Rutland wrote: > 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. > OK. >> >> 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. > Per previous comment I agreed to, I will pass all the arguments other than task directly. Thanks. Madhavan