From 51c9c0843993528bffc920c54c2121d9e6f8b090 Mon Sep 17 00:00:00 2001 From: Anju T Date: Wed, 8 Feb 2017 15:20:51 +0530 Subject: powerpc/kprobes: Implement Optprobes 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 Signed-off-by: Naveen N. Rao Acked-by: Masami Hiramatsu Signed-off-by: Michael Ellerman --- arch/powerpc/include/asm/code-patching.h | 1 + 1 file changed, 1 insertion(+) (limited to 'arch/powerpc/include/asm/code-patching.h') diff --git a/arch/powerpc/include/asm/code-patching.h b/arch/powerpc/include/asm/code-patching.h index 75ee4f4ac840..8ab937771068 100644 --- a/arch/powerpc/include/asm/code-patching.h +++ b/arch/powerpc/include/asm/code-patching.h @@ -35,6 +35,7 @@ int instr_is_branch_to_addr(const unsigned int *instr, unsigned long addr); unsigned long branch_target(const unsigned int *instr); unsigned int translate_branch(const unsigned int *dest, const unsigned int *src); +extern bool is_conditional_branch(unsigned int instr); #ifdef CONFIG_PPC_BOOK3E_64 void __patch_exception(int exc, unsigned long addr); #define patch_exception(exc, name) do { \ -- cgit v1.2.3