From: Mark Brown <broonie@kernel.org> To: madvenka@linux.microsoft.com Cc: mark.rutland@arm.com, 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 v11 4/5] arm64: Introduce stack trace reliability checks in the unwinder Date: Thu, 25 Nov 2021 14:56:44 +0000 [thread overview] Message-ID: <YZ+kLPT+h6ZGw20p@sirena.org.uk> (raw) In-Reply-To: <20211123193723.12112-5-madvenka@linux.microsoft.com> [-- Attachment #1: Type: text/plain, Size: 1493 bytes --] On Tue, Nov 23, 2021 at 01:37:22PM -0600, madvenka@linux.microsoft.com wrote: > Introduce arch_stack_walk_reliable() for ARM64. This works like > arch_stack_walk() except that it returns -EINVAL if the stack trace is not > reliable. > Until all the reliability checks are in place, arch_stack_walk_reliable() > may not be used by livepatch. But it may be used by debug and test code. Probably also worth noting that this doesn't select HAVE_RELIABLE_STACKTRACE which is what any actual users are going to use to identify if the architecture has the feature. I would have been tempted to add arch_stack_walk() as a separate patch but equally having the user code there (even if it itself can't yet be used...) helps with reviewing the actual unwinder so I don't mind. > +static void unwind_check_reliability(struct task_struct *task, > + struct stackframe *frame) > +{ > + if (frame->fp == (unsigned long)task_pt_regs(task)->stackframe) { > + /* Final frame; no more unwind, no need to check reliability */ > + return; > + } If the unwinder carries on for some reason (the code for that is elsewhere and may be updated separately...) then this will start checking again. I'm not sure if this is a *problem* as such but the thing about this being the final frame coupled with not actually explicitly stopping the unwind here makes me think this should at least be clearer, the comment begs the question about what happens if something decides it is not in fact the final frame. [-- Attachment #2: signature.asc --] [-- Type: application/pgp-signature, Size: 488 bytes --]
WARNING: multiple messages have this Message-ID (diff)
From: Mark Brown <broonie@kernel.org> To: madvenka@linux.microsoft.com Cc: mark.rutland@arm.com, 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 v11 4/5] arm64: Introduce stack trace reliability checks in the unwinder Date: Thu, 25 Nov 2021 14:56:44 +0000 [thread overview] Message-ID: <YZ+kLPT+h6ZGw20p@sirena.org.uk> (raw) In-Reply-To: <20211123193723.12112-5-madvenka@linux.microsoft.com> [-- Attachment #1.1: Type: text/plain, Size: 1493 bytes --] On Tue, Nov 23, 2021 at 01:37:22PM -0600, madvenka@linux.microsoft.com wrote: > Introduce arch_stack_walk_reliable() for ARM64. This works like > arch_stack_walk() except that it returns -EINVAL if the stack trace is not > reliable. > Until all the reliability checks are in place, arch_stack_walk_reliable() > may not be used by livepatch. But it may be used by debug and test code. Probably also worth noting that this doesn't select HAVE_RELIABLE_STACKTRACE which is what any actual users are going to use to identify if the architecture has the feature. I would have been tempted to add arch_stack_walk() as a separate patch but equally having the user code there (even if it itself can't yet be used...) helps with reviewing the actual unwinder so I don't mind. > +static void unwind_check_reliability(struct task_struct *task, > + struct stackframe *frame) > +{ > + if (frame->fp == (unsigned long)task_pt_regs(task)->stackframe) { > + /* Final frame; no more unwind, no need to check reliability */ > + return; > + } If the unwinder carries on for some reason (the code for that is elsewhere and may be updated separately...) then this will start checking again. I'm not sure if this is a *problem* as such but the thing about this being the final frame coupled with not actually explicitly stopping the unwind here makes me think this should at least be clearer, the comment begs the question about what happens if something decides it is not in fact the final frame. [-- Attachment #1.2: signature.asc --] [-- Type: application/pgp-signature, Size: 488 bytes --] [-- Attachment #2: Type: text/plain, Size: 176 bytes --] _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-11-25 14:58 UTC|newest] Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top [not found] <8b861784d85a21a9bf08598938c11aff1b1249b9> 2021-11-23 19:37 ` [PATCH v11 0/5] arm64: Reorganize the unwinder and implement stack trace reliability checks madvenka 2021-11-23 19:37 ` madvenka 2021-11-23 19:37 ` [PATCH v11 1/5] arm64: Call stack_backtrace() only from within walk_stackframe() madvenka 2021-11-23 19:37 ` madvenka 2021-11-25 13:48 ` Mark Brown 2021-11-25 13:48 ` Mark Brown 2021-11-30 15:05 ` Mark Rutland 2021-11-30 15:05 ` Mark Rutland 2021-11-30 17:13 ` Madhavan T. Venkataraman 2021-11-30 17:13 ` Madhavan T. Venkataraman 2021-11-30 18:29 ` Mark Rutland 2021-11-30 18:29 ` Mark Rutland 2021-11-30 20:29 ` Madhavan T. Venkataraman 2021-11-30 20:29 ` Madhavan T. Venkataraman 2021-12-10 4:13 ` Madhavan T. Venkataraman 2021-12-10 4:13 ` Madhavan T. Venkataraman 2021-11-23 19:37 ` [PATCH v11 2/5] arm64: Rename unwinder functions madvenka 2021-11-23 19:37 ` madvenka 2021-11-24 17:10 ` Mark Brown 2021-11-24 17:10 ` Mark Brown 2021-11-30 15:08 ` Mark Rutland 2021-11-30 15:08 ` Mark Rutland 2021-11-30 17:15 ` Madhavan T. Venkataraman 2021-11-30 17:15 ` Madhavan T. Venkataraman 2021-11-23 19:37 ` [PATCH v11 3/5] arm64: Make the unwind loop in unwind() similar to other architectures madvenka 2021-11-23 19:37 ` madvenka 2021-11-25 14:30 ` Mark Brown 2021-11-25 14:30 ` Mark Brown 2021-11-23 19:37 ` [PATCH v11 4/5] arm64: Introduce stack trace reliability checks in the unwinder madvenka 2021-11-23 19:37 ` madvenka 2021-11-25 14:56 ` Mark Brown [this message] 2021-11-25 14:56 ` Mark Brown 2021-11-25 16:59 ` Madhavan T. Venkataraman 2021-11-25 16:59 ` Madhavan T. Venkataraman 2021-11-26 13:29 ` Mark Brown 2021-11-26 13:29 ` Mark Brown 2021-11-26 17:23 ` Madhavan T. Venkataraman 2021-11-26 17:23 ` Madhavan T. Venkataraman 2021-11-23 19:37 ` [PATCH v11 5/5] arm64: Create a list of SYM_CODE functions, check return PC against list madvenka 2021-11-23 19:37 ` madvenka 2021-11-25 15:05 ` Mark Brown 2021-11-25 15:05 ` Mark Brown
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