x86/entry: Harden return-to-user
Make the CONFIG_DEBUG_ENTRY=y check that validates CS is a user segment
unconditional and move it nearer to IRET.
PRE:
140,026,608 cycles:k ( +- 0.01% )
236,696,176 instructions:k # 1.69 insn per cycle ( +- 0.00% )
POST:
139,957,681 cycles:k ( +- 0.01% )
236,681,819 instructions:k # 1.69 insn per cycle ( +- 0.00% )
(this is with --repeat 100 and the run-to-run variance is bigger than
the difference shown)
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20231120143626.753200755@infradead.org
1 file changed
