/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
 * Code to prepare detour buffer for optprobes in Kernel.
 *
 * Copyright 2017, Anju T, IBM Corp.
 */

#include <asm/ppc_asm.h>
#include <asm/ptrace.h>
#include <asm/asm-offsets.h>

#ifdef CONFIG_PPC64
#define SAVE_30GPRS(base) SAVE_GPRS(2, 31, base)
#define REST_30GPRS(base) REST_GPRS(2, 31, base)
#define TEMPLATE_FOR_IMM_LOAD_INSNS     nop; nop; nop; nop; nop
#else
#define SAVE_30GPRS(base) stmw  r2, GPR2(base)
#define REST_30GPRS(base) lmw   r2, GPR2(base)
#define TEMPLATE_FOR_IMM_LOAD_INSNS     nop; nop; nop
#endif

#define OPT_SLOT_SIZE   65536

        .balign 4

        /*
         * Reserve an area to allocate slots for detour buffer.
         * This is part of .text section (rather than vmalloc area)
         * as this needs to be within 32MB of the probed address.
         */
        .global optinsn_slot
optinsn_slot:
        .space  OPT_SLOT_SIZE

        /*
         * Optprobe template:
         * This template gets copied into one of the slots in optinsn_slot
         * and gets fixed up with real optprobe structures et al.
         */
        .global optprobe_template_entry
optprobe_template_entry:
        /* Create an in-memory pt_regs */
        PPC_STLU        r1,-INT_FRAME_SIZE(r1)
        SAVE_GPR(0,r1)
        /* Save the previous SP into stack */
        addi    r0,r1,INT_FRAME_SIZE
        PPC_STL r0,GPR1(r1)
        SAVE_30GPRS(r1)
        /* Save SPRS */
        mfmsr   r5
        PPC_STL r5,_MSR(r1)
        li      r5,0x700
        PPC_STL r5,_TRAP(r1)
        li      r5,0
        PPC_STL r5,ORIG_GPR3(r1)
        PPC_STL r5,RESULT(r1)
        mfctr   r5
        PPC_STL r5,_CTR(r1)
        mflr    r5
        PPC_STL r5,_LINK(r1)
        mfspr   r5,SPRN_XER
        PPC_STL r5,_XER(r1)
        mfcr    r5
        PPC_STL r5,_CCR(r1)
#ifdef CONFIG_PPC64
        lbz     r5,PACAIRQSOFTMASK(r13)
        std     r5,SOFTE(r1)
#endif

        /*
         * We may get here from a module, so load the kernel TOC in r2.
         * The original TOC gets restored when pt_regs is restored
         * further below.
         */
#ifdef CONFIG_PPC64
        LOAD_PACA_TOC()
#endif

        .global optprobe_template_op_address
optprobe_template_op_address:
        /*
         * Parameters to optimized_callback():
         * 1. optimized_kprobe structure in r3
         */
        TEMPLATE_FOR_IMM_LOAD_INSNS

        /* 2. pt_regs pointer in r4 */
        addi    r4,r1,STACK_INT_FRAME_REGS

        .global optprobe_template_call_handler
optprobe_template_call_handler:
        /* Branch to optimized_callback() */
        nop

        /*
         * Parameters for instruction emulation:
         * 1. Pass SP in register r3.
         */
        addi    r3,r1,STACK_INT_FRAME_REGS

        .global optprobe_template_insn
optprobe_template_insn:
        /* 2, Pass instruction to be emulated in r4 */
        TEMPLATE_FOR_IMM_LOAD_INSNS

        .global optprobe_template_call_emulate
optprobe_template_call_emulate:
        /* Branch to emulate_step()  */
        nop

        /*
         * All done.
         * Now, restore the registers...
         */
        PPC_LL  r5,_MSR(r1)
        mtmsr   r5
        PPC_LL  r5,_CTR(r1)
        mtctr   r5
        PPC_LL  r5,_LINK(r1)
        mtlr    r5
        PPC_LL  r5,_XER(r1)
        mtxer   r5
        PPC_LL  r5,_CCR(r1)
        mtcr    r5
        REST_GPR(0,r1)
        REST_30GPRS(r1)
        /* Restore the previous SP */
        addi    r1,r1,INT_FRAME_SIZE

        .global optprobe_template_ret
optprobe_template_ret:
        /* ... and jump back from trampoline */
        nop

        .global optprobe_template_end
optprobe_template_end: