linux-kernel - Re: [PATCH] pci: imx6: support kernels built in Thumb-2 mode

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Date:   Wed, 28 Nov 2018 18:56:18 +0000
From:   Trent Piepho <tpiepho@...inj.com>
To:     "robin.murphy@....com" <robin.murphy@....com>,
        "stefan@...er.ch" <stefan@...er.ch>,
        "hongxing.zhu@....com" <hongxing.zhu@....com>,
        "l.stach@...gutronix.de" <l.stach@...gutronix.de>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "festevam@...il.com" <festevam@...il.com>,
        "andrew.smirnov@...il.com" <andrew.smirnov@...il.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "leonard.crestez@....com" <leonard.crestez@....com>
Subject: Re: [PATCH] pci: imx6: support kernels built in Thumb-2 mode

On Wed, 2018-11-28 at 16:16 +0000, Robin Murphy wrote:
> 
> >   
> > +static int imx6q_pcie_abort_handler_thumb2(unsigned long addr,
> > +		unsigned int fsr, struct pt_regs *regs)
> > +{
> > +	unsigned long pc = instruction_pointer(regs);
> > +	unsigned long instr = *(unsigned long *)pc;
> > +	unsigned long thumb2_instr = __mem_to_opcode_thumb16(instr);
> > +	int reg = thumb2_instr & 7;
> > +
> > +	if (!__opcode_is_thumb16(instr & 0x0000ffffUL))
> > +		return 1;
> 
> There are plenty of 32-bit Thumb encodings of various LDR/STR variants, 
> and I doubt we can guarantee that the offset, target register, and/or 
> addressing mode for a config space access will *always* suit the 
> (relatively limited) 16-bit ones.

It might be the case that PLD/PLI, 32-bit thumb2 instructions, could
trigger an abort too.