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5c8f6a2e31
In the native case, PER_CPU_VAR(cpu_tss_rw + TSS_sp0) is the
trampoline stack. But XEN pv doesn't use trampoline stack, so
PER_CPU_VAR(cpu_tss_rw + TSS_sp0) is also the kernel stack.
In that case, source and destination stacks are identical, which means
that reusing swapgs_restore_regs_and_return_to_usermode() in XEN pv
would cause %rsp to move up to the top of the kernel stack and leave the
IRET frame below %rsp.
This is dangerous as it can be corrupted if #NMI / #MC hit as either of
these events occurring in the middle of the stack pushing would clobber
data on the (original) stack.
And, with XEN pv, swapgs_restore_regs_and_return_to_usermode() pushing
the IRET frame on to the original address is useless and error-prone
when there is any future attempt to modify the code.
[ bp: Massage commit message. ]
Fixes:
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||
|---|---|---|
| .. | ||
| apic.c | ||
| debugfs.c | ||
| debugfs.h | ||
| efi.c | ||
| enlighten.c | ||
| enlighten_hvm.c | ||
| enlighten_pv.c | ||
| enlighten_pvh.c | ||
| grant-table.c | ||
| irq.c | ||
| Kconfig | ||
| Makefile | ||
| mmu.c | ||
| mmu.h | ||
| mmu_hvm.c | ||
| mmu_pv.c | ||
| multicalls.c | ||
| multicalls.h | ||
| p2m.c | ||
| pci-swiotlb-xen.c | ||
| platform-pci-unplug.c | ||
| pmu.c | ||
| pmu.h | ||
| setup.c | ||
| smp.c | ||
| smp.h | ||
| smp_hvm.c | ||
| smp_pv.c | ||
| spinlock.c | ||
| suspend.c | ||
| suspend_hvm.c | ||
| suspend_pv.c | ||
| time.c | ||
| trace.c | ||
| vga.c | ||
| xen-asm.S | ||
| xen-head.S | ||
| xen-ops.h | ||