kernel.git/arch/powerpc/kernel/optprobes.c, branch linux-4.11.yHosts the 0x221E linux distro kernel.
https://git.0xinfinity.dev/distro/kernel.git/atom?h=linux-4.11.y2017-02-10T02:28:05Zpowerpc/kprobes: Optimize kprobe in kretprobe_trampoline()2017-02-10T02:28:05ZAnju T2017-02-08T09:50:52Zurn:sha1:762df10bad6954b353ee649c387a8ffacf6dc347
Kprobe placed on the kretprobe_trampoline() during boot time can be
optimized, since the instruction at probe point is a 'nop'.
Signed-off-by: Anju T Sudhakar <anju@linux.vnet.ibm.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
powerpc/kprobes: Implement Optprobes2017-02-10T02:28:04ZAnju T2017-02-08T09:50:51Zurn:sha1:51c9c0843993528bffc920c54c2121d9e6f8b090
Current infrastructure of kprobe uses the unconditional trap instruction
to probe a running kernel. Optprobe allows kprobe to replace the trap
with a branch instruction to a detour buffer. Detour buffer contains
instructions to create an in memory pt_regs. Detour buffer also has a
call to optimized_callback() which in turn call the pre_handler(). After
the execution of the pre-handler, a call is made for instruction
emulation. The NIP is determined in advanced through dummy instruction
emulation and a branch instruction is created to the NIP at the end of
the trampoline.
To address the limitation of branch instruction in POWER architecture,
detour buffer slot is allocated from a reserved area. For the time
being, 64KB is reserved in memory for this purpose.
Instructions which can be emulated using analyse_instr() are the
candidates for optimization. Before optimization ensure that the address
range between the detour buffer allocated and the instruction being
probed is within +/- 32MB.
Signed-off-by: Anju T Sudhakar <anju@linux.vnet.ibm.com>
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>