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[RFC 0/2] Fix Coverity and other errors in ppc440_uc DMA

From: Peter Maydell
Subject: [RFC 0/2] Fix Coverity and other errors in ppc440_uc DMA
Date: Tue, 26 Jul 2022 19:23:39 +0100

This patchset is mainly trying to fix a problem that Coverity spotted
in the dcr_write_dma() function in hw/ppc/ppc440_uc.c, where the code
is not correctly using the cpu_physical_memory_map() function.
While I was fixing that I noticed a second problem in this code,
where it doesn't have a fallback for when cpu_physical_memory_map()
says "I couldn't map that for you".

I've marked these patches as RFC, partly because I don't have any
guest that would exercise the code changes[*], and partly because
I don't have any documentation of the hardware to tell me how it
should behave, so patch 2 in particular has some FIXMEs. I also
notice that the code doesn't update any of the registers like the
count or source/base addresses when the DMA transfer happens, which
seems odd, but perhaps the real hardware does work like that.

I think we should probably take patch 1 (which is a fairly minimal
fix of the use-of-uninitialized-data problem), but patch 2 is a bit
more unfinished.

[*] The commit 3c409c1927efde2fc that added this code says it's used
by AmigaOS.)

-- PMM

Peter Maydell (2):
  hw/ppc/ppc440_uc: Initialize length passed to
  hw/ppc/ppc440_uc: Handle mapping failure in DMA engine

 hw/ppc/ppc440_uc.c | 34 +++++++++++++++++++++++++++++++++-
 1 file changed, 33 insertions(+), 1 deletion(-)


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