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Date: Wed, 11 May 2016 13:29:48 +0100
From: Matt Fleming <matt@codeblueprint.co.uk>
To: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Shannon Zhao <zhaoshenglong@huawei.com>,
        "linux-arm-kernel@lists.infradead.org" 
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        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        shannon.zhao@linaro.org, peter.huangpeng@huawei.com
Subject: Re: [PATCH] Xen: EFI: Parse DT parameters for Xen specific UEFI
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On Fri, 06 May, at 09:52:42AM, Mathieu Poirier wrote:
> > +static int __init efi_remap_init(void)
> > +{
> > +       u64 mapsize;
> > +
> > +       pr_info("Remapping and enabling EFI services.\n");
> > +
> > +       mapsize = memmap.map_end - memmap.map;
> > +       memmap.map = (__force void *)ioremap_cache(memmap.phys_map,
> > +                                                  mapsize);
> > +       if (!memmap.map) {
> > +               pr_err("Failed to remap EFI memory map\n");
> > +               return -ENOMEM;
> > +       }
> > +       memmap.map_end = memmap.map + mapsize;
> > +       efi.memmap = &memmap;
> > +
> > +       efi.systab = (__force void *)ioremap_cache(efi_system_table,
> > +                                                  sizeof(efi_system_table_t));
> > +       if (!efi.systab) {
> 
> Is there a reason why memmap.map isn't iounmap() in the error path?
> The original code didn't have it either, hence the question.

I suspect that is a bug.

In reality, if you can't access the EFI System Table because you fail
to map it I would guess you are going to crash very, very quickly
anyhow.