linux-kernel - Re: [RFC PATCH v2 5/8] arm64: Detect an FTRACE frame and mark a stack trace unreliable

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Message-ID: <f9e21fe1-e646-bb36-c711-94cbbc60af8a@linux.microsoft.com>
Date:   Tue, 23 Mar 2021 09:15:36 -0500
From:   "Madhavan T. Venkataraman" <madvenka@...ux.microsoft.com>
To:     Mark Rutland <mark.rutland@....com>
Cc:     broonie@...nel.org, jpoimboe@...hat.com, jthierry@...hat.com,
        catalin.marinas@....com, will@...nel.org,
        linux-arm-kernel@...ts.infradead.org,
        live-patching@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2 5/8] arm64: Detect an FTRACE frame and mark a stack
 trace unreliable

Hi Mark,

I have a general question. When exceptions are nested, how does it work? Let us consider 2 cases:

1. Exception in a page fault handler itself. In this case, I guess one more pt_regs will get
   established in the task stack for the second exception.

2. Exception in an interrupt handler. Here the interrupt handler is running on the IRQ stack.
   Will the pt_regs get created on the IRQ stack?

Also, is there a maximum nesting for exceptions?

Madhavan