Detour buffer contains instructions to create an in memory pt_regs. After the execution of prehandler a call is made for instruction emulation. The NIP is decided after the probed instruction is executed. Hence a branch instruction is created to the NIP returned by emulate_step().
Instruction slot for detour buffer is allocated from the reserved area. For the time being 64KB is reserved in memory for this purpose. Signed-off-by: Anju T Sudhakar <[email protected]> --- arch/powerpc/include/asm/kprobes.h | 24 +++++++ arch/powerpc/kernel/optprobes_head.S | 119 +++++++++++++++++++++++++++++++++++ 2 files changed, 143 insertions(+) create mode 100644 arch/powerpc/kernel/optprobes_head.S diff --git a/arch/powerpc/include/asm/kprobes.h b/arch/powerpc/include/asm/kprobes.h index 2c9759bd..2109ce03 100644 --- a/arch/powerpc/include/asm/kprobes.h +++ b/arch/powerpc/include/asm/kprobes.h @@ -38,7 +38,25 @@ struct pt_regs; struct kprobe; typedef ppc_opcode_t kprobe_opcode_t; + +extern kprobe_opcode_t optinsn_slot; +/* Optinsn template address */ +extern kprobe_opcode_t optprobe_template_entry[]; +extern kprobe_opcode_t optprobe_template_call_handler[]; +extern kprobe_opcode_t optprobe_template_call_emulate[]; +extern kprobe_opcode_t optprobe_template_ret[]; +extern kprobe_opcode_t optprobe_template_insn[]; +extern kprobe_opcode_t optprobe_template_kp_addr[]; +extern kprobe_opcode_t optprobe_template_op_address1[]; +extern kprobe_opcode_t optprobe_template_end[]; + #define MAX_INSN_SIZE 1 +#define MAX_OPTIMIZED_LENGTH 4 +#define MAX_OPTINSN_SIZE \ + (((unsigned long)&optprobe_template_end - \ + (unsigned long)&optprobe_template_entry) / \ + sizeof(kprobe_opcode_t)) +#define RELATIVEJUMP_SIZE 4 #ifdef PPC64_ELF_ABI_v2 /* PPC64 ABIv2 needs local entry point */ @@ -124,6 +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); diff --git a/arch/powerpc/kernel/optprobes_head.S b/arch/powerpc/kernel/optprobes_head.S new file mode 100644 index 0000000..73db1df --- /dev/null +++ b/arch/powerpc/kernel/optprobes_head.S @@ -0,0 +1,119 @@ +/* + * Code to prepare detour buffer for optprobes in Kernel. + * + * Copyright 2016, Anju T, IBM Corp. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version + * 2 of the License, or (at your option) any later version. + */ + +#include <asm/ppc_asm.h> +#include <asm/ptrace.h> +#include <asm/asm-offsets.h> + +#define OPT_SLOT_SIZE 65536 + +.balign 2 +.global optinsn_slot +optinsn_slot: + /* Reserve an area to allocate slots for detour buffer */ + .space OPT_SLOT_SIZE + +/* Create an in-memory pt_regs */ +.global optprobe_template_entry +optprobe_template_entry: + stdu r1,-INT_FRAME_SIZE(r1) + SAVE_GPR(0,r1) + /* Save the previous SP into stack */ + addi r0,r1,INT_FRAME_SIZE + std r0,GPR1(r1) + SAVE_10GPRS(2,r1) + SAVE_10GPRS(12,r1) + SAVE_10GPRS(22,r1) + /* Save SPRS */ + mfmsr r5 + std r5,_MSR(r1) + li r5,0 + std r5,ORIG_GPR3(r1) + std r5,_TRAP(r1) + std r5,RESULT(r1) + mfctr r5 + std r5,_CTR(r1) + mflr r5 + std r5,_LINK(r1) + mfspr r5,SPRN_XER + std r5,_XER(r1) + mfcr r5 + std r5,_CCR(r1) + lbz r5,PACASOFTIRQEN(r13) + std r5,SOFTE(r1) + mfdar r5 + std r5,_DAR(r1) + mfdsisr r5 + std r5,_DSISR(r1) + +/* Save p->addr into stack */ +.global optprobe_template_kp_addr +optprobe_template_kp_addr: + nop + nop + nop + nop + nop + std r3,_NIP(r1) + +/* Pass parameters for optimized_callback */ +.global optprobe_template_op_address1 +optprobe_template_op_address1: + nop + nop + nop + nop + nop + addi r4,r1,STACK_FRAME_OVERHEAD + +/* Branch to optimized_callback() */ +.global optprobe_template_call_handler +optprobe_template_call_handler: + nop + /* Pass parameters for instruction emulation */ + addi r3,r1,STACK_FRAME_OVERHEAD +.global optprobe_template_insn +optprobe_template_insn: + nop + nop + +/* Branch to instruction emulation */ +.global optprobe_template_call_emulate +optprobe_template_call_emulate: + nop + /* Restore the registers */ + ld r5,_MSR(r1) + mtmsr r5 + ld r5,_CTR(r1) + mtctr r5 + ld r5,_LINK(r1) + mtlr r5 + ld r5,_XER(r1) + mtxer r5 + ld r5,_CCR(r1) + mtcr r5 + ld r5,_DAR(r1) + mtdar r5 + ld r5,_DSISR(r1) + mtdsisr r5 + REST_GPR(0,r1) + REST_10GPRS(2,r1) + REST_10GPRS(12,r1) + REST_10GPRS(22,r1) + /* Restore the previous SP */ + addi r1,r1,INT_FRAME_SIZE + +/* Jump back to the normal workflow from trampoline */ +.global optprobe_template_ret +optprobe_template_ret: + nop +.global optprobe_template_end +optprobe_template_end: -- 1.8.3.1
