[PATCH] um: always use the internal copy of the FP registers

[Benjamin Berg]

On Fri, 2024-09-13 at 10:22 +0200, Benjamin Berg wrote:
> From: Benjamin Berg <benjamin.berg at intel.com>
> 
> When switching from userspace to the kernel, all registers including the
> FP registers are copied into the kernel and restored later on. As such,
> the true source for the FP register state is actually already in the
> kernel and they should never be grabbed from the userspace process.
> 
> Change the various places to simply copy the data from the internal FP
> register storage area. Note that on i386 the format of PTRACE_GETFPREGS
> and PTRACE_GETFPXREGS is different enough that conversion would be
> needed. With this patch, -EINVAL is returned if the non-native format is
> requested.
> 
> The upside is, that this patchset fixes setting registers via ptrace
> (which simply did not work before) as well as fixing setting floating
> point registers using the mcontext on signal return on i386.
> 
> Signed-off-by: Benjamin Berg <benjamin.berg at intel.com>

Hi,

I did test this mcontext restore and ptrace register setting both on
i386 and x86_64 using the attached program.

Benjamin
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