path: root/arch/powerpc/net/bpf_jit_comp64.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * bpf_jit_comp64.c: eBPF JIT compiler
 *
 * Copyright 2016 Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
 *		  IBM Corporation
 *
 * Based on the powerpc classic BPF JIT compiler by Matt Evans
 */
#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 <asm/security_features.h>

#include "bpf_jit.h"

/*
 * Stack layout:
 * Ensure the top half (upto local_tmp_var) stays consistent
 * with our redzone usage.
 *
 *		[	prev sp		] <-------------
 *		[   nv gpr save area	] 5*8		|
 *		[    tail_call_cnt	] 8		|
 *		[    local_tmp_var	] 16		|
 * fp (r31) -->	[   ebpf stack space	] upto 512	|
 *		[     frame header	] 32/112	|
 * sp (r1) --->	[    stack pointer	] --------------
 */

/* for gpr non volatile registers BPG_REG_6 to 10 */
#define BPF_PPC_STACK_SAVE	(5*8)
/* for bpf JIT code internal usage */
#define BPF_PPC_STACK_LOCALS	24
/* stack frame excluding BPF stack, ensure this is quadword aligned */
#define BPF_PPC_STACKFRAME	(STACK_FRAME_MIN_SIZE + \
				 BPF_PPC_STACK_LOCALS + BPF_PPC_STACK_SAVE)

/* BPF register usage */
#define TMP_REG_1	(MAX_BPF_JIT_REG + 0)
#define TMP_REG_2	(MAX_BPF_JIT_REG + 1)

/* BPF to ppc register mappings */
void bpf_jit_init_reg_mapping(struct codegen_context *ctx)
{
	/* function return value */
	ctx->b2p[BPF_REG_0] = _R8;
	/* function arguments */
	ctx->b2p[BPF_REG_1] = _R3;
	ctx->b2p[BPF_REG_2] = _R4;
	ctx->b2p[BPF_REG_3] = _R5;
	ctx->b2p[BPF_REG_4] = _R6;
	ctx->b2p[BPF_REG_5] = _R7;
	/* non volatile registers */
	ctx->b2p[BPF_REG_6] = _R27;
	ctx->b2p[BPF_REG_7] = _R28;
	ctx->b2p[BPF_REG_8] = _R29;
	ctx->b2p[BPF_REG_9] = _R30;
	/* frame pointer aka BPF_REG_10 */
	ctx->b2p[BPF_REG_FP] = _R31;
	/* eBPF jit internal registers */
	ctx->b2p[BPF_REG_AX] = _R12;
	ctx->b2p[TMP_REG_1] = _R9;
	ctx->b2p[TMP_REG_2] = _R10;
}

/* PPC NVR range -- update this if we ever use NVRs below r27 */
#define BPF_PPC_NVR_MIN		_R27

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
	 * - the bpf program uses its stack area
	 * The latter condition is deduced from the usage of BPF_REG_FP
	 */
	return ctx->seen & SEEN_FUNC || bpf_is_seen_register(ctx, bpf_to_ppc(BPF_REG_FP));
}

/*
 * When not setting up our own stackframe, the redzone usage is:
 *
 *		[	prev sp		] <-------------
 *		[	  ...       	] 		|
 * sp (r1) --->	[    stack pointer	] --------------
 *		[   nv gpr save area	] 5*8
 *		[    tail_call_cnt	] 8
 *		[    local_tmp_var	] 16
 *		[   unused red zone	] 208 bytes protected
 */
static int bpf_jit_stack_local(struct codegen_context *ctx)
{
	if (bpf_has_stack_frame(ctx))
		return STACK_FRAME_MIN_SIZE + ctx->stack_size;
	else
		return -(BPF_PPC_STACK_SAVE + 24);
}

static int bpf_jit_stack_tailcallcnt(struct codegen_context *ctx)
{
	return bpf_jit_stack_local(ctx) + 16;
}

static int bpf_jit_stack_offsetof(struct codegen_context *ctx, int reg)
{
	if (reg >= BPF_PPC_NVR_MIN && reg < 32)
		return (bpf_has_stack_frame(ctx) ?
			(BPF_PPC_STACKFRAME + ctx->stack_size) : 0)
				- (8 * (32 - reg));

	pr_err("BPF JIT is asking about unknown registers");
	BUG();
}

void bpf_jit_realloc_regs(struct codegen_context *ctx)
{
}

void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx)
{
	int i;

#ifndef CONFIG_PPC_KERNEL_PCREL
	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2))
		EMIT(PPC_RAW_LD(_R2, _R13, offsetof(struct paca_struct, kernel_toc)));
#endif

	/*
	 * Initialize tail_call_cnt if we do tail calls.
	 * Otherwise, put in NOPs so that it can be skipped when we are
	 * invoked through a tail call.
	 */
	if (ctx->seen & SEEN_TAILCALL) {
		EMIT(PPC_RAW_LI(bpf_to_ppc(TMP_REG_1), 0));
		/* this goes in the redzone */