FreeBSD -- Mishandling of x86 debug exceptions

Problem Description:
The MOV SS and POP SS instructions inhibit debug exceptions
until the instruction boundary following the next instruction.
If that instruction is a system call or similar instruction
that transfers control to the operating system, the debug
exception will be handled in the kernel context instead of
the user context.
Impact:
An authenticated local attacker may be able to read
sensitive data in kernel memory, control low-level operating
system functions, or may panic the system.