[tip:perf/urgent] kprobes/x86: Mark 2 bytes NOP as boostable

tip-bot for Wang Nan
2015-02-19T00:26:31Z

Commit-ID: b7e37567d080301d38a302bb93ba79d1ca446dca
Gitweb: http://git.kernel.org/tip/b7e37567d080301d38a302bb93ba79d1ca446dca
Author: Wang Nan <wangnan0@huawei.com>
AuthorDate: Tue, 10 Feb 2015 09:34:05 +0800
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 18 Feb 2015 21:50:12 +0100

kprobes/x86: Mark 2 bytes NOP as boostable

Currently, x86 kprobes is unable to boost 2 bytes nop like:

nopl 0x0(%rax,%rax,1)

which is 0x0f 0x1f 0x44 0x00 0x00.

Such nops have exactly 5 bytes to hold a relative jmp
instruction. Boosting them should be obviously safe.

This patch enable boosting such nops by simply updating
twobyte_is_boostable[] array.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: <lizefan@huawei.com>
Link: http://lkml.kernel.org/r/1423532045-41049-1-git-send-email-wangnan0@huawei.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>