From mboxrd@z Thu Jan  1 00:00:00 1970
From: keith.busch@intel.com (Keith Busch)
Date: Tue, 6 Nov 2018 09:47:52 -0700
Subject: [PATCH 00/12] error handling and pciehp maintenance
In-Reply-To: <20181106163400.GA21193@e107981-ln.cambridge.arm.com>
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 <20181004221137.GB21834@localhost.localdomain>
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 <20181008161847.GA30971@localhost.localdomain>
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Message-ID: <20181106164751.GA6217@localhost.localdomain>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Tue, Nov 06, 2018 at 04:34:08PM +0000, Lorenzo Pieralisi wrote:
> The question is whether we really need to dynamically patch the kernel
> with ftrace to achieve what that patch does.
> 
> Furthermore, it would also be good to report what bugs we are actually
> fixing, from what you are writing falling back to the current method if
> !DYNAMIC_FTRACE_WITH_REGS is broken in many ways and I would start with
> fixing the current behaviour with something that does not depend on arch
> features that may not even be implemented.

There are two problems with the current method:

  1. It may dereference pci_dev after it was freed
  2. The pci_dev's children inherit its fake pci_bus's ops on
     enumeration

Both result in kernel panic.

The dynamic kernel patch just seemed like a cool way to inject errors
without messing with the driver's structures. But if there's a more
elegant way to do it, I'm all for it.