Re: [Qemu-devel] [PATCH v2 0/4] hw/arm/boot: handle large Images more gracefully

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

Cc'ing Drew and Eric

On 6/7/19 3:07 PM, Peter Maydell wrote:
> Ping for code review, please?
> 
> thanks
> -- PMM
> 
> On Thu, 16 May 2019 at 15:47, Peter Maydell <peter.maydell@linaro.org> wrote:
>>
>>
>> This patchset attempts to fix https://bugs.launchpad.net/qemu/+bug/1823998
>> which reports that we don't handle kernels larger than 128MB
>> correctly, because we allow the initrd to be placed over the
>> tail end of the kernel. AArch64 kernel Image files (since v3.17)
>> report the total size they require (including any BSS area that
>> isn't in the Image itself), so we can use that to be sure we
>> place the initrd sufficiently far into the RAM.
>>
>> Patches 1 and 2 are new since v1; patches 3 and 4 are the old
>> patches 1 and 2 (and are basically unchanged since v1).
>>
>> Patches 1 and 2 in this series are new. Patch 1 fixes bugs
>> in the existing code where we were assuming that we could
>> treat info->ram_size as the address of the end of RAM, which
>> isn't true if the RAM doesn't start at address 0. (This
>> generally went unnoticed thanks to the magic of unsigned integer
>> underflow turning end-start calculations into very large max_size
>> values for load_ramdisk_as() and friends.)
>> Patch 2 adds some explicit checks that we don't try to put things
>> entirely off the end of RAM (which avoids those accidental
>> underflows).
>> Patch 3 in this series adjusts our "where do we put the initrd"
>> heuristic so that it always places it at least after whatever
>> our best guess at the kernel size is. (This might still not
>> be right for images like self-decompressing 32-bit kernels, where
>> there's no way to know how big the kernel will be after
>> decompression.)
>> Patch 4 makes load_aarch64_image() return the
>> kernel size as indicated in the Image file header, so that for
>> the specific case of AArch64 Image files we will definitely not
>> put the initrd on top of them.
>>
>> thanks
>> -- PMM
>>
>> Peter Maydell (4):
>>   hw/arm/boot: Don't assume RAM starts at address zero
>>   hw/arm/boot: Diagnose layouts that put initrd or DTB off the end of
>>     RAM
>>   hw/arm/boot: Avoid placing the initrd on top of the kernel
>>   hw/arm/boot: Honour image size field in AArch64 Image format kernels
>>
>>  hw/arm/boot.c | 83 ++++++++++++++++++++++++++++++++++++++-------------
>>  1 file changed, 62 insertions(+), 21 deletions(-)
>>
>> --
>> 2.20.1
>>
>