path: root/arch/powerpc/net/bpf_jit_comp32.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * eBPF JIT compiler for PPC32
 *
 * Copyright 2020 Christophe Leroy <christophe.leroy@csgroup.eu>
 *		  CS GROUP France
 *
 * Based on PPC64 eBPF JIT compiler by Naveen N. Rao
 */
#include <linux/moduleloader.h>
#include <asm/cacheflush.h>
#include <asm/asm-compat.h>
#include <linux/netdevice.h>
#include <linux/filter.h>
#include <linux/if_vlan.h>
#include <asm/kprobes.h>
#include <linux/bpf.h>

#include "bpf_jit.h"

/*
 * Stack layout:
 *
 *		[	prev sp		] <-------------
 *		[   nv gpr save area	] 16 * 4	|
 * fp (r31) -->	[   ebpf stack space	] upto 512	|
 *		[     frame header	] 16		|
 * sp (r1) --->	[    stack pointer	] --------------
 */

/* for gpr non volatile registers r17 to r31 (14) + tail call */
#define BPF_PPC_STACK_SAVE	(15 * 4 + 4)
/* stack frame, ensure this is quadword aligned */
#define BPF_PPC_STACKFRAME(ctx)	(STACK_FRAME_MIN_SIZE + BPF_PPC_STACK_SAVE + (ctx)->stack_size)

#define PPC_EX32(r, i)		EMIT(PPC_RAW_LI((r), (i) < 0 ? -1 : 0))

/* PPC NVR range -- update this if we ever use NVRs below r17 */
#define BPF_PPC_NVR_MIN		_R17
#define BPF_PPC_TC		_R16

/* BPF register usage */
#define TMP_REG			(MAX_BPF_JIT_REG + 0)

/* BPF to ppc register mappings */
void bpf_jit_init_reg_mapping(struct codegen_context *ctx)
{
	/* function return value */
	ctx->b2p[BPF_REG_0] = _R12;
	/* function arguments */
	ctx->b2p[BPF_REG_1] = _R4;
	ctx->b2p[BPF_REG_2] = _R6;
	ctx->b2p[BPF_REG_3] = _R8;
	ctx->b2p[BPF_REG_4] = _R10;
	ctx->b2p[BPF_REG_5] = _R22;
	/* non volatile registers */
	ctx->b2p[BPF_REG_6] = _R24;
	ctx->b2p[BPF_REG_7] = _R26;
	ctx->b2p[BPF_REG_8] = _R28;
	ctx->b2p[BPF_REG_9] = _R30;
	/* frame pointer aka BPF_REG_10 */
	ctx->b2p[BPF_REG_FP] = _R18;
	/* eBPF jit internal registers */
	ctx->b2p[BPF_REG_AX] = _R20;
	ctx->b2p[TMP_REG] = _R31;		/* 32 bits */
}

static int bpf_jit_stack_offsetof(struct codegen_context *ctx, int reg)
{
	if ((reg >= BPF_PPC_NVR_MIN && reg < 32) || reg == BPF_PPC_TC)
		return BPF_PPC_STACKFRAME(ctx) - 4 * (32 - reg);

	WARN(true, "BPF JIT is asking about unknown registers, will crash the stack");
	/* Use the hole we have left for alignment */
	return BPF_PPC_STACKFRAME(ctx) - 4;
}

#define SEEN_VREG_MASK		0x1ff80000 /* Volatile registers r3-r12 */
#define SEEN_NVREG_FULL_MASK	0x0003ffff /* Non volatile registers r14-r31 */
#define SEEN_NVREG_TEMP_MASK	0x00001e01 /* BPF_REG_5, BPF_REG_AX, TMP_REG */

static inline bool bpf_has_stack_frame(struct codegen_context *ctx)
{
	/*
	 * We only need a stack frame if:
	 * - we call other functions (kernel helpers), or
	 * - we use non volatile registers, or
	 * - we use tail call counter
	 * - the bpf program uses its stack area
	 * The latter condition is deduced from the usage of BPF_REG_FP
	 */
	return ctx->seen & (SEEN_FUNC | SEEN_TAILCALL | SEEN_NVREG_FULL_MASK) ||
	       bpf_is_seen_register(ctx, bpf_to_ppc(BPF_REG_FP));
}

void bpf_jit_realloc_regs(struct codegen_context *ctx)
{
	unsigned int nvreg_mask;

	if (ctx->seen & SEEN_FUNC)
		nvreg_mask = SEEN_NVREG_TEMP_MASK;
	else
		nvreg_mask = SEEN_NVREG_FULL_MASK;

	while (ctx->seen & nvreg_mask &&
	      (ctx->seen & SEEN_VREG_MASK) != SEEN_VREG_MASK) {
		int old =