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| author | Anju T <anju@linux.vnet.ibm.com> | 2017-02-08 15:20:51 +0530 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2017-02-10 13:28:04 +1100 |
| commit | 51c9c0843993528bffc920c54c2121d9e6f8b090 (patch) | |
| tree | 1ffd280d9ca0ce51faaa957d23c1e217ee0e2e20 /arch/powerpc/include | |
| parent | 30176466e36aadba01e1a630cf42397a3438efa4 (diff) | |
| download | linux-51c9c0843993528bffc920c54c2121d9e6f8b090.tar.bz2 | |
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 <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>
Diffstat (limited to 'arch/powerpc/include')
| -rw-r--r-- | arch/powerpc/include/asm/code-patching.h | 1 | ||||
| -rw-r--r-- | arch/powerpc/include/asm/kprobes.h | 24 |
2 files changed, 24 insertions, 1 deletions
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 { \ diff --git a/arch/powerpc/include/asm/kprobes.h b/arch/powerpc/include/asm/kprobes.h index 77885d89f548..d821835ade86 100644 --- a/arch/powerpc/include/asm/kprobes.h +++ b/arch/powerpc/include/asm/kprobes.h @@ -40,7 +40,23 @@ struct pt_regs; struct kprobe; typedef ppc_opcode_t kprobe_opcode_t; -#define MAX_INSN_SIZE 1 + +extern kprobe_opcode_t optinsn_slot; + +/* Optinsn template address */ +extern kprobe_opcode_t optprobe_template_entry[]; +extern kprobe_opcode_t optprobe_template_op_address[]; +extern kprobe_opcode_t optprobe_template_call_handler[]; +extern kprobe_opcode_t optprobe_template_insn[]; +extern kprobe_opcode_t optprobe_template_call_emulate[]; +extern kprobe_opcode_t optprobe_template_ret[]; +extern kprobe_opcode_t optprobe_template_end[]; + +/* Fixed instruction size for powerpc */ +#define MAX_INSN_SIZE 1 +#define MAX_OPTIMIZED_LENGTH sizeof(kprobe_opcode_t) /* 4 bytes */ +#define MAX_OPTINSN_SIZE (optprobe_template_end - optprobe_template_entry) +#define RELATIVEJUMP_SIZE sizeof(kprobe_opcode_t) /* 4 bytes */ #ifdef PPC64_ELF_ABI_v2 /* PPC64 ABIv2 needs local entry point */ @@ -126,6 +142,12 @@ struct kprobe_ctlblk { struct prev_kprobe prev_kprobe; }; +struct arch_optimized_insn { + kprobe_opcode_t copied_insn[1]; + /* detour buffer */ + kprobe_opcode_t *insn; +}; + extern int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val, void *data); extern int kprobe_fault_handler(struct pt_regs *regs, int trapnr); |