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torvalds
GitHub Repository: torvalds/linux
 Path: blob/master/arch/arm64/net/bpf_timed_may_goto.S
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/* SPDX-License-Identifier: GPL-2.0 */

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/* Copyright (c) 2025 Puranjay Mohan <[email protected]> */

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#include <linux/linkage.h>

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SYM_FUNC_START(arch_bpf_timed_may_goto)

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	/* Allocate stack space and emit frame record */

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	stp     x29, x30, [sp, #-64]!

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	mov     x29, sp

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	/* Save BPF registers R0 - R5 (x7, x0-x4)*/

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	stp	x7, x0, [sp, #16]

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	stp	x1, x2, [sp, #32]

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	stp	x3, x4, [sp, #48]

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	/*

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	 * Stack depth was passed in BPF_REG_AX (x9), add it to the BPF_FP

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	 * (x25) to get the pointer to count and timestamp and pass it as the

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	 * first argument in x0.

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	 *

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	 * Before generating the call to arch_bpf_timed_may_goto, the verifier

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	 * generates a load instruction using FP, i.e. REG_AX = *(u64 *)(FP -

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	 * stack_off_cnt), so BPF_REG_FP (x25) is always set up by the arm64

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	 * jit in this case.

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	 */

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	add	x0, x9, x25

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	bl	bpf_check_timed_may_goto

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	/* BPF_REG_AX(x9) will be stored into count, so move return value to it. */

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	mov	x9, x0

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	/* Restore BPF registers R0 - R5 (x7, x0-x4) */

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	ldp	x7, x0, [sp, #16]

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	ldp	x1, x2, [sp, #32]

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	ldp	x3, x4, [sp, #48]

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	/* Restore FP and LR */

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	ldp     x29, x30, [sp], #64

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	ret

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SYM_FUNC_END(arch_bpf_timed_may_goto)

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