// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright IBM Corp. 2019
 */
#include <linux/pgtable.h>
#include <asm/physmem_info.h>
#include <asm/cpacf.h>
#include <asm/timex.h>
#include <asm/sclp.h>
#include <asm/kasan.h>
#include "decompressor.h"
#include "boot.h"

#define PRNG_MODE_TDES	 1
#define PRNG_MODE_SHA512 2
#define PRNG_MODE_TRNG	 3

struct prno_parm {
	u32 res;
	u32 reseed_counter;
	u64 stream_bytes;
	u8  V[112];
	u8  C[112];
};

struct prng_parm {
	u8  parm_block[32];
	u32 reseed_counter;
	u64 byte_counter;
};

static int check_prng(void)
{
	if (!cpacf_query_func(CPACF_KMC, CPACF_KMC_PRNG)) {
		sclp_early_printk("KASLR disabled: CPU has no PRNG\n");
		return 0;
	}
	if (cpacf_query_func(CPACF_PRNO, CPACF_PRNO_TRNG))
		return PRNG_MODE_TRNG;
	if (cpacf_query_func(CPACF_PRNO, CPACF_PRNO_SHA512_DRNG_GEN))
		return PRNG_MODE_SHA512;
	else
		return PRNG_MODE_TDES;
}

static int get_random(unsigned long limit, unsigned long *value)
{
	struct prng_parm prng = {
		/* initial parameter block for tdes mode, copied from libica */
		.parm_block = {
			0x0F, 0x2B, 0x8E, 0x63, 0x8C, 0x8E, 0xD2, 0x52,
			0x64, 0xB7, 0xA0, 0x7B, 0x75, 0x28, 0xB8, 0xF4,
			0x75, 0x5F, 0xD2, 0xA6, 0x8D, 0x97, 0x11, 0xFF,
			0x49, 0xD8, 0x23, 0xF3, 0x7E, 0x21, 0xEC, 0xA0
		},
	};
	unsigned long seed, random;
	struct prno_parm prno;
	__u64 entropy[4];
	int mode, i;

	mode = check_prng();
	seed = get_tod_clock_fast();
	switch (mode) {
	case PRNG_MODE_TRNG:
		cpacf_trng(NULL, 0, (u8 *) &random, sizeof(random));
		break;
	case PRNG_MODE_SHA512:
		cpacf_prno(CPACF_PRNO_SHA512_DRNG_SEED, &prno, NULL, 0,
			   (u8 *) &seed, sizeof(seed));
		cpacf_prno(CPACF_PRNO_SHA512_DRNG_GEN, &prno, (u8 *) &random,
			   sizeof(random), NULL, 0);
		break;
	case PRNG_MODE_TDES:
		/* add entropy */
		*(unsigned long *) prng.parm_block ^= seed;
		for (i = 0; i < 16; i++) {
			cpacf_kmc(CPACF_KMC_PRNG, prng.parm_block,
				  (u8 *) entropy, (u8 *) entropy,
				  sizeof(entropy));
			memcpy(prng.parm_block, entropy, sizeof(entropy));
		}
		random = seed;
		cpacf_kmc(CPACF_KMC_PRNG, prng.parm_block, (u8 *) &random,
			  (u8 *) &random, sizeof(random));
		break;
	default:
		return -1;
	}
	*value = random % limit;
	return 0;
}

unsigned long get_random_base(void)
{
	unsigned long vmlinux_size = vmlinux.image_size + vmlinux.bss_size;
	unsigned long minimal_pos = vmlinux.default_lma + vmlinux_size;
	unsigned long random;

	/* [vmlinux.default_lma + vmlinux.image_size + vmlinux.bss_size : physmem_info.usable] */
	if (get_random(physmem_info.usable - minimal_pos, &random))
		return 0;

	return physmem_alloc_range(RR_VMLINUX, vmlinux_size, THREAD_SIZE,
				   vmlinux.default_lma, minimal_pos + random, false);
}