kprobes/x86: Support kprobes jump optimization on x86

Introduce x86 arch-specific optimization code, which supports
both of x86-32 and x86-64.

This code also supports safety checking, which decodes whole of
a function in which probe is inserted, and checks following
conditions before optimization:
 - The optimized instructions which will be replaced by a jump instruction
   don't straddle the function boundary.
 - There is no indirect jump instruction, because it will jumps into
   the address range which is replaced by jump operand.
 - There is no jump/loop instruction which jumps into the address range
   which is replaced by jump operand.
 - Don't optimize kprobes if it is in functions into which fixup code will
   jumps.

This uses text_poke_multibyte() which doesn't support modifying
code on NMI/MCE handler. However, since kprobes itself doesn't
support NMI/MCE code probing, it's not a problem.

Changes in v9:
 - Use *_text_reserved() for checking the probe can be optimized.
 - Verify jump address range is in 2G range when preparing slot.
 - Backup original code when switching optimized buffer, instead of
   preparing buffer, because there can be int3 of other probes in
   preparing phase.
 - Check kprobe is disabled in arch_check_optimized_kprobe().
 - Strictly check indirect jump opcodes (ff /4, ff /5).

Changes in v6:
 - Split stop_machine-based jump patching code.
 - Update comments and coding style.

Changes in v5:
 - Introduce stop_machine-based jump replacing.

Signed-off-by: Masami Hiramatsu <[email protected]>
Cc: systemtap <[email protected]>
Cc: DLE <[email protected]>
Cc: Ananth N Mavinakayanahalli <[email protected]>
Cc: Jim Keniston <[email protected]>
Cc: Srikar Dronamraju <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Anders Kaseorg <[email protected]>
Cc: Tim Abbott <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Jason Baron <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Ananth N Mavinakayanahalli <[email protected]>
LKML-Reference: <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>

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