tcg: Clean up direct block chaining safety checks
authorSergey Fedorov <serge.fdrv@gmail.com>
Fri, 8 Apr 2016 16:48:12 +0000 (19:48 +0300)
committerRichard Henderson <rth@twiddle.net>
Fri, 13 May 2016 00:06:41 +0000 (14:06 -1000)
commit5b053a4a28278bca606eeff7d1c0730df1b047e9
treee9567828b03440c0d228edfc0aef296dafb34800
parentf9c5b66f487a04d3747dc6997b1503f9258df945
tcg: Clean up direct block chaining safety checks

We don't take care of direct jumps when address mapping changes. Thus we
must be sure to generate direct jumps so that they always keep valid
even if address mapping changes. Luckily, we can only allow to execute a
TB if it was generated from the pages which match with current mapping.

Document tcg_gen_goto_tb() declaration and note the reason for
destination PC limitations.

Some targets with variable length instructions allow TB to straddle a
page boundary. However, we make sure that both of TB pages match the
current address mapping when looking up TBs. So it is safe to do direct
jumps into the both pages. Correct the checks for some of those targets.

Given that, we can safely patch a TB which spans two pages. Remove the
unnecessary check in cpu_exec() and allow such TBs to be patched.

Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com>
Signed-off-by: Sergey Fedorov <sergey.fedorov@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>
cpu-exec.c
target-arm/translate.c
target-cris/translate.c
target-i386/translate.c
target-m68k/translate.c
target-s390x/translate.c
tcg/tcg-op.h