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eeb89e2bb1
When PTI is enabled on x86-32 the kernel uses the GDT mapped in the fixmap
for the simple reason that this address is also mapped for user-space.
The efi_call_phys_prolog()/efi_call_phys_epilog() wrappers change the GDT
to call EFI runtime services and switch back to the kernel GDT when they
return. But the switch-back uses the writable GDT, not the fixmap GDT.
When that happened and and the CPU returns to user-space it switches to the
user %cr3 and tries to restore user segment registers. This fails because
the writable GDT is not mapped in the user page-table, and without a GDT
the fault handlers also can't be launched. The result is a triple fault and
reboot of the machine.
Fix that by restoring the GDT back to the fixmap GDT which is also mapped
in the user page-table.
Fixes:
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|---|---|---|
| .. | ||
| atom | ||
| ce4100 | ||
| efi | ||
| geode | ||
| goldfish | ||
| intel | ||
| intel-mid | ||
| intel-quark | ||
| iris | ||
| olpc | ||
| scx200 | ||
| sfi | ||
| ts5500 | ||
| uv | ||
| Makefile | ||