• Wang Nan's avatar
    ARM: kprobes: enable OPTPROBES for ARM 32 · 0dc016db
    Wang Nan authored
    This patch introduce kprobeopt for ARM 32.
    
    Limitations:
     - Currently only kernel compiled with ARM ISA is supported.
    
     - Offset between probe point and optinsn slot must not larger than
       32MiB. Masami Hiramatsu suggests replacing 2 words, it will make
       things complex. Futher patch can make such optimization.
    
    Kprobe opt on ARM is relatively simpler than kprobe opt on x86 because
    ARM instruction is always 4 bytes aligned and 4 bytes long. This patch
    replace probed instruction by a 'b', branch to trampoline code and then
    calls optimized_callback(). optimized_callback() calls opt_pre_handler()
    to execute kprobe handler. It also emulate/simulate replaced instruction.
    
    When unregistering kprobe, the deferred manner of unoptimizer may leave
    branch instruction before optimizer is called. Different from x86_64,
    which only copy the probed insn after optprobe_template_end and
    reexecute them, this patch call singlestep to emulate/simulate the insn
    directly. Futher patch can optimize this behavior.
    Signed-off-by: default avatarWang Nan <wangnan0@huawei.com>
    Acked-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
    Cc: Will Deacon <will.deacon@arm.com>
    Reviewed-by: default avatarJon Medhurst (Tixy) <tixy@linaro.org>
    Signed-off-by: default avatarJon Medhurst <tixy@linaro.org>
    0dc016db
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