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Always read the VFP regs in the arm64 fill_fpregs

Description

Always read the VFP regs in the arm64 fill_fpregs

The PCB_FP_STARTED is used to indicate that the current VFP context
has been used since either 1. the start of the thread, or 2. exiting
a kernel FP context.

When case 2 was added to the kernel this could cause incorrect results
to be returned when a thread exits the kernel FP context and fill_fpregs
is called before it has restored the VFP state, e.g. by trappin on a
userspace VFP instruction.

In both of the cases the base save area is still valid so reduce the
use of the PCB_FP_STARTED flag check to help decide if we need to
store the current threads VFP state.

Sponsored by: Arm Ltd
Differential Revision: https://reviews.freebsd.org/D37994

(cherry picked from commit 95dd6974b591ce76bf8d29adcc0dd01b4b281ffd)

Details

Provenance
andrewAuthored on Jan 18 2023, 9:30 AM
Differential Revision
D37994: Always read the VFP regs in the arm64 fill_fpregs
Parents
rG289967bbad82: Stop using the rid as an index in the arm timer
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