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 "bpf_jit64.h"

static void bpf_jit_fill_ill_insns(void *area, unsigned int size)
{
	memset32(area, BREAKPOINT_INSTRUCTION, size/4);
}

static inline void bpf_flush_icache(void *start, void *end)
{
	smp_wmb();
	flush_icache_range((unsigned long)start, (unsigned long)end);
}

static inline bool bpf_is_seen_register(struct codegen_context *ctx, int i)
{
	return (ctx->seen & (1 << (31 - b2p[i])));
}

static inline void bpf_set_seen_register(struct codegen_context *ctx, int i)
{
	ctx->seen |= (1 << (31 - b2p[i]));
}

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_REG_FP);
}

/*
 * When not setting up our own stackframe, the redzone usage is:
 *
 *		[	prev sp		] <-------------
 *		[	  ...       	] 		|
 * sp (r1) --->	[    stack pointer	] --------------
 *		[   nv gpr save area	] 6*8
 *		[    tail_call_cnt	] 8
 *		[    local_tmp_var	] 8
 *		[   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 + 16);
}

static int bpf_jit_stack_tailcallcnt(struct codegen_context *ctx)
{
	return bpf_jit_stack_local(ctx) + 8;
}

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();
}

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

	/*
	 * 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(b2p[TMP_REG_1], 0));
		/* this goes in the redzone */
		PPC_BPF_STL(b2p[TMP_REG_1], 1, -(BPF_PPC_STACK_SAVE + 8));
	} else {
		EMIT(PPC_RAW_NOP());
		EMIT(PPC_RAW_NOP());
	}

#define BPF_TAILCALL_PROLOGUE_SIZE	8

	if (bpf_has_stack_frame(ctx)) {
		/*
		 * We need a stack frame, but we don't necessarily need to
		 * save/restore LR unless we call other functions
		 */
		if (ctx->seen & SEEN_FUNC) {
			EMIT(PPC_INST_MFLR | __PPC_RT(R0));
			PPC_BPF_STL(0, 1, PPC_LR_STKOFF);
		}

		PPC_BPF_STLU(1, 1, -(BPF_PPC_STACKFRAME + ctx->stack_size));
	}

	/*