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Differential D35628

x86/xen: stop assuming kernel memory loading order in PVH
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Authored by royger on Jun 28 2022, 3:53 PM.
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markj
cperciva
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rG77cb05db0cee: x86/xen: stop assuming kernel memory loading order in PVH
Summary

Do not assume that start_info will always be loaded at the highest
memory address, and instead check the position of all the loaded
elements in order to find the last loaded one, and thus a likely safe
place to use as early boot allocation memory space.

Reported by: markj, cpercival
Sponsored by: Citrix Systems R&D

Diff Detail

Repository
rS FreeBSD src repository - subversion
Lint
Lint Passed
Unit
No Test Coverage
Build Status
Buildable 46179
Build 43068: arc lint + arc unit

Event Timeline

royger created this revision.Jun 28 2022, 3:53 PM
Herald added subscribers: ehem_freebsd_m5p.com, imp. · View Herald TranscriptJun 28 2022, 3:53 PM
royger requested review of this revision.Jun 28 2022, 3:53 PM
Harbormaster completed remote builds in B46152: Diff 107482.Jun 28 2022, 3:53 PM
markj added inline comments.Jun 28 2022, 4:49 PM
sys/x86/xen/pv.c
154

max() is not really appropriate here. It only compares a pair of unsigned ints. (Yes, it's too confusing.) The MAX() macro is a better alternative. I think this happens to work because the addresses involved are small, but it'd still be better to switch away from its use.

176

Extra newline.

ehem_freebsd_m5p.com removed a subscriber: ehem_freebsd_m5p.com.Jun 28 2022, 11:26 PM
royger marked an inline comment as done.Jun 29 2022, 8:14 AM
royger added inline comments.
sys/x86/xen/pv.c
154

Yes, all addresses should be below 4G, and hence fit in an unsigned int. That mess with max() is confusing, will switch to MAX() instead.

royger updated this revision to Diff 107535.Jun 29 2022, 8:19 AM
  • Use MAX() instead of max().
  • Remove extra newline.
Harbormaster completed remote builds in B46179: Diff 107535.Jun 29 2022, 8:19 AM
markj accepted this revision.Jun 29 2022, 3:04 PM
This revision is now accepted and ready to land.Jun 29 2022, 3:04 PM
Closed by commit rG77cb05db0cee: x86/xen: stop assuming kernel memory loading order in PVH (authored by royger). · Explain WhyJun 30 2022, 6:54 AM
This revision was automatically updated to reflect the committed changes.
royger added a commit: rG77cb05db0cee: x86/xen: stop assuming kernel memory loading order in PVH.

Revision Contents
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PathSize
sys/
x86/
xen/
52 lines

Diff 107535

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sys/x86/xen/pv.c

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