/* SPDX-License-Identifier: GPL-2.0 */
/* Copyright (c) 2025 IBM Corporation, Saket Kumar Bhaskar <skb99@linux.ibm.com> */

#include <linux/linkage.h>
#include <asm/ppc_asm.h>

/*
 * arch_bpf_timed_may_goto() trampoline for powerpc64
 *
 * Custom BPF convention (verifier/JIT):
 *      - input:  stack offset in BPF_REG_AX (r12)
 *      - output: updated count in BPF_REG_AX (r12)
 *
 * Call bpf_check_timed_may_goto(ptr) with normal powerpc64 ABI:
 *      - r3 = ptr, return in r3
 *
 * Preserve BPF regs R0-R5 (mapping: r8, r3-r7).
 */

SYM_FUNC_START(arch_bpf_timed_may_goto)
        /* Prologue: save LR, allocate frame */
        mflr    r0
        std     r0, 16(r1)
        stdu    r1, -112(r1)

        /* Save BPF registers R0 - R5 (r8, r3-r7) */
        std     r3, 32(r1)
        std     r4, 40(r1)
        std     r5, 48(r1)
        std     r6, 56(r1)
        std     r7, 64(r1)
        std     r8, 72(r1)

        /*
         * r3 = BPF_REG_FP + BPF_REG_AX
         * BPF_REG_FP is r31; BPF_REG_AX is r12 (stack offset in bytes).
         */
        add     r3, r31, r12
        bl      bpf_check_timed_may_goto

        /* Put return value back into AX */
        mr      r12, r3

        /* Restore BPF registers R0 - R5 (r8, r3-r7) */
        ld      r3, 32(r1)
        ld      r4, 40(r1)
        ld      r5, 48(r1)
        ld      r6, 56(r1)
        ld      r7, 64(r1)
        ld      r8, 72(r1)

        /* Epilogue: pop frame, restore LR, return */
        addi    r1, r1, 112
        ld      r0, 16(r1)
        mtlr    r0
        blr
SYM_FUNC_END(arch_bpf_timed_may_goto)