1/*
  2 * Code to prepare detour buffer for optprobes in Kernel.
  3 *
  4 * Copyright 2017, Anju T, IBM Corp.
  5 *
  6 * This program is free software; you can redistribute it and/or
  7 * modify it under the terms of the GNU General Public License
  8 * as published by the Free Software Foundation; either version
  9 * 2 of the License, or (at your option) any later version.
 10 */
 11
 12#include <asm/ppc_asm.h>
 13#include <asm/ptrace.h>
 14#include <asm/asm-offsets.h>
 15
 16#define	OPT_SLOT_SIZE	65536
 17
 18	.balign	4
 19
 20	/*
 21	 * Reserve an area to allocate slots for detour buffer.
 22	 * This is part of .text section (rather than vmalloc area)
 23	 * as this needs to be within 32MB of the probed address.
 24	 */
 25	.global optinsn_slot
 26optinsn_slot:
 27	.space	OPT_SLOT_SIZE
 28
 29	/*
 30	 * Optprobe template:
 31	 * This template gets copied into one of the slots in optinsn_slot
 32	 * and gets fixed up with real optprobe structures et al.
 33	 */
 34	.global optprobe_template_entry
 35optprobe_template_entry:
 36	/* Create an in-memory pt_regs */
 37	stdu	r1,-INT_FRAME_SIZE(r1)
 38	SAVE_GPR(0,r1)
 39	/* Save the previous SP into stack */
 40	addi	r0,r1,INT_FRAME_SIZE
 41	std	r0,GPR1(r1)
 42	SAVE_10GPRS(2,r1)
 43	SAVE_10GPRS(12,r1)
 44	SAVE_10GPRS(22,r1)
 45	/* Save SPRS */
 46	mfmsr	r5
 47	std	r5,_MSR(r1)
 48	li	r5,0x700
 49	std	r5,_TRAP(r1)
 50	li	r5,0
 51	std	r5,ORIG_GPR3(r1)
 52	std	r5,RESULT(r1)
 53	mfctr	r5
 54	std	r5,_CTR(r1)
 55	mflr	r5
 56	std	r5,_LINK(r1)
 57	mfspr	r5,SPRN_XER
 58	std	r5,_XER(r1)
 59	mfcr	r5
 60	std	r5,_CCR(r1)
 61	lbz     r5,PACAIRQSOFTMASK(r13)
 62	std     r5,SOFTE(r1)
 63
 64	/*
 65	 * We may get here from a module, so load the kernel TOC in r2.
 66	 * The original TOC gets restored when pt_regs is restored
 67	 * further below.
 68	 */
 69	ld	r2,PACATOC(r13)
 70
 71	.global optprobe_template_op_address
 72optprobe_template_op_address:
 73	/*
 74	 * Parameters to optimized_callback():
 75	 * 1. optimized_kprobe structure in r3
 76	 */
 77	nop
 78	nop
 79	nop
 80	nop
 81	nop
 82	/* 2. pt_regs pointer in r4 */
 83	addi	r4,r1,STACK_FRAME_OVERHEAD
 84
 85	.global optprobe_template_call_handler
 86optprobe_template_call_handler:
 87	/* Branch to optimized_callback() */
 88	nop
 89
 90	/*
 91	 * Parameters for instruction emulation:
 92	 * 1. Pass SP in register r3.
 93	 */
 94	addi	r3,r1,STACK_FRAME_OVERHEAD
 95
 96	.global optprobe_template_insn
 97optprobe_template_insn:
 98	/* 2, Pass instruction to be emulated in r4 */
 99	nop
100	nop
101
102	.global optprobe_template_call_emulate
103optprobe_template_call_emulate:
104	/* Branch to emulate_step()  */
105	nop
106
107	/*
108	 * All done.
109	 * Now, restore the registers...
110	 */
111	ld	r5,_MSR(r1)
112	mtmsr	r5
113	ld	r5,_CTR(r1)
114	mtctr	r5
115	ld	r5,_LINK(r1)
116	mtlr	r5
117	ld	r5,_XER(r1)
118	mtxer	r5
119	ld	r5,_CCR(r1)
120	mtcr	r5
121	REST_GPR(0,r1)
122	REST_10GPRS(2,r1)
123	REST_10GPRS(12,r1)
124	REST_10GPRS(22,r1)
125	/* Restore the previous SP */
126	addi	r1,r1,INT_FRAME_SIZE
127
128	.global optprobe_template_ret
129optprobe_template_ret:
130	/* ... and jump back from trampoline */
131	nop
132
133	.global optprobe_template_end
134optprobe_template_end: