x86/fpu: Rename and sanitize fpu__save/copy()

Both function names are a misnomer.

fpu__save() is actually about synchronizing the hardware register state
into the task's memory state so that either coredump or a math exception
handler can inspect the state at the time where the problem happens.

The function guarantees to preserve the register state, while "save" is a
common terminology for saving the current state so it can be modified and
restored later. This is clearly not the case here.

Rename it to fpu_sync_fpstate().

fpu__copy() is used to clone the current task's FPU state when duplicating
task_struct. While the register state is a copy the rest of the FPU state
is not.

Name it accordingly and remove the really pointless @src argument along
with the warning which comes along with it.

Nothing can ever copy the FPU state of a non-current task. It's clearly
just a consequence of arch_dup_task_struct(), but it makes no sense to
proliferate that further.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121455.196727450@linutronix.de

1 files changed, 3 insertions, 2 deletions

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 853ea7a80806..4c9c4aa83216 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -1046,9 +1046,10 @@ static void math_error(struct pt_regs *regs, int trapnr)
 	}
 
 	/*
-	 * Save the info for the exception handler and clear the error.
+	 * Synchronize the FPU register state to the memory register state
+	 * if necessary. This allows the exception handler to inspect it.
 	 */
-	fpu__save(fpu);
+	fpu_sync_fpstate(fpu);
 
 	task->thread.trap_nr	= trapnr;
 	task->thread.error_code = 0;