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Always read the VFP regs in the arm64 fill_fpregs

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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
This commit is contained in:
Andrew Turner 2023-01-18 09:30:20 +00:00
parent 1d577bedba
commit 95dd6974b5
1 changed files with 9 additions and 8 deletions
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17
sys/arm64/arm64/exec_machdep.c
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@ -153,16 +153,17 @@ fill_fpregs(struct thread *td, struct fpreg *regs)
*/
if (td == curthread)
vfp_save_state(td, pcb);
}
KASSERT(pcb->pcb_fpusaved == &pcb->pcb_fpustate,
("Called fill_fpregs while the kernel is using the VFP"));
memcpy(regs->fp_q, pcb->pcb_fpustate.vfp_regs,
sizeof(regs->fp_q));
regs->fp_cr = pcb->pcb_fpustate.vfp_fpcr;
regs->fp_sr = pcb->pcb_fpustate.vfp_fpsr;
} else
KASSERT(pcb->pcb_fpusaved == &pcb->pcb_fpustate,
("Called fill_fpregs while the kernel is using the VFP"));
memcpy(regs->fp_q, pcb->pcb_fpustate.vfp_regs,
sizeof(regs->fp_q));
regs->fp_cr = pcb->pcb_fpustate.vfp_fpcr;
regs->fp_sr = pcb->pcb_fpustate.vfp_fpsr;
#else
memset(regs, 0, sizeof(*regs));
#endif
memset(regs, 0, sizeof(*regs));
return (0);
}