linux/arch/s390/kernel/machine_kexec_file.c

// SPDX-License-Identifier: GPL-2.0
/*
 * s390 code for kexec_file_load system call
 *
 * Copyright IBM Corp. 2018
 *
 * Author(s): Philipp Rudo <prudo@linux.vnet.ibm.com>
 */

#include <linux/elf.h>
#include <linux/errno.h>
#include <linux/kexec.h>
#include <linux/module.h>
#include <linux/verification.h>
#include <asm/ipl.h>
#include <asm/setup.h>

const struct kexec_file_ops * const kexec_file_loaders[] = {
	&s390_kexec_elf_ops,
	&s390_kexec_image_ops,
	NULL,
};

#ifdef CONFIG_KEXEC_VERIFY_SIG
/*
 * Module signature information block.
 *
 * The constituents of the signature section are, in order:
 *
 *	- Signer's name
 *	- Key identifier
 *	- Signature data
 *	- Information block
 */
struct module_signature {
	u8	algo;		/* Public-key crypto algorithm [0] */
	u8	hash;		/* Digest algorithm [0] */
	u8	id_type;	/* Key identifier type [PKEY_ID_PKCS7] */
	u8	signer_len;	/* Length of signer's name [0] */
	u8	key_id_len;	/* Length of key identifier [0] */
	u8	__pad[3];
	__be32	sig_len;	/* Length of signature data */
};

#define PKEY_ID_PKCS7 2

int s390_verify_sig(const char *kernel, unsigned long kernel_len)
{
	const unsigned long marker_len = sizeof(MODULE_SIG_STRING) - 1;
	struct module_signature *ms;
	unsigned long sig_len;

	/* Skip signature verification when not secure IPLed. */
	if (!ipl_secure_flag)
		return 0;

	if (marker_len > kernel_len)
		return -EKEYREJECTED;

	if (memcmp(kernel + kernel_len - marker_len, MODULE_SIG_STRING,
		   marker_len))
		return -EKEYREJECTED;
	kernel_len -= marker_len;

	ms = (void *)kernel + kernel_len - sizeof(*ms);
	kernel_len -= sizeof(*ms);

	sig_len = be32_to_cpu(ms->sig_len);
	if (sig_len >= kernel_len)
		return -EKEYREJECTED;
	kernel_len -= sig_len;

	if (ms->id_type != PKEY_ID_PKCS7)
		return -EKEYREJECTED;

	if (ms->algo != 0 ||
	    ms->hash != 0 ||
	    ms->signer_len != 0 ||
	    ms->key_id_len != 0 ||
	    ms->__pad[0] != 0 ||
	    ms->__pad[1] != 0 ||
	    ms->__pad[2] != 0) {
		return -EBADMSG;
	}

	return verify_pkcs7_signature(kernel, kernel_len,
				      kernel + kernel_len, sig_len,
				      VERIFY_USE_PLATFORM_KEYRING,
				      VERIFYING_MODULE_SIGNATURE,
				      NULL, NULL);
}
#endif /* CONFIG_KEXEC_VERIFY_SIG */

static int kexec_file_update_purgatory(struct kimage *image,
				       struct s390_load_data *data)
{
	u64 entry, type;
	int ret;

	if (image->type == KEXEC_TYPE_CRASH) {
		entry = STARTUP_KDUMP_OFFSET;
		type = KEXEC_TYPE_CRASH;
	} else {
		entry = STARTUP_NORMAL_OFFSET;
		type = KEXEC_TYPE_DEFAULT;
	}

	ret = kexec_purgatory_get_set_symbol(image, "kernel_entry", &entry,
					     sizeof(entry), false);
	if (ret)
		return ret;

	ret = kexec_purgatory_get_set_symbol(image, "kernel_type", &type,
					     sizeof(type), false);
	if (ret)
		return ret;

	if (image->type == KEXEC_TYPE_CRASH) {
		u64 crash_size;

		ret = kexec_purgatory_get_set_symbol(image, "crash_start",
						     &crashk_res.start,
						     sizeof(crashk_res.start),
						     false);
		if (ret)
			return ret;

		crash_size = crashk_res.end - crashk_res.start + 1;
		ret = kexec_purgatory_get_set_symbol(image, "crash_size",
						     &crash_size,
						     sizeof(crash_size),
						     false);
	}
	return ret;
}

static int kexec_file_add_purgatory(struct kimage *image,
				    struct s390_load_data *data)
{
	struct kexec_buf buf;
	int ret;

	buf.image = image;

	data->memsz = ALIGN(data->memsz, PAGE_SIZE);
	buf.mem = data->memsz;
	if (image->type == KEXEC_TYPE_CRASH)
		buf.mem += crashk_res.start;

	ret = kexec_load_purgatory(image, &buf);
	if (ret)
		return ret;

	ret = kexec_file_update_purgatory(image, data);
	return ret;
}

static int kexec_file_add_initrd(struct kimage *image,
				 struct s390_load_data *data)
{
	struct kexec_buf buf;
	int ret;

	buf.image = image;

	buf.buffer = image->initrd_buf;
	buf.bufsz = image->initrd_buf_len;

	data->memsz = ALIGN(data->memsz, PAGE_SIZE);
	buf.mem = data->memsz;
	if (image->type == KEXEC_TYPE_CRASH)
		buf.mem += crashk_res.start;
	buf.memsz = buf.bufsz;

	data->parm->initrd_start = buf.mem;
	data->parm->initrd_size = buf.memsz;
	data->memsz += buf.memsz;

	ret = kexec_add_buffer(&buf);
	return ret;
}

void *kexec_file_add_components(struct kimage *image,
				int (*add_kernel)(struct kimage *image,
						  struct s390_load_data *data))
{
	struct s390_load_data data = {0};
	int ret;

	ret = add_kernel(image, &data);
	if (ret)
		return ERR_PTR(ret);

	if (image->cmdline_buf_len >= ARCH_COMMAND_LINE_SIZE)
		return ERR_PTR(-EINVAL);
	memcpy(data.parm->command_line, image->cmdline_buf,
	       image->cmdline_buf_len);

	if (image->type == KEXEC_TYPE_CRASH) {
		data.parm->oldmem_base = crashk_res.start;
		data.parm->oldmem_size = crashk_res.end - crashk_res.start + 1;
	}

	if (image->initrd_buf) {
		ret = kexec_file_add_initrd(image, &data);
		if (ret)
			return ERR_PTR(ret);
	}

	ret = kexec_file_add_purgatory(image, &data);
	if (ret)
		return ERR_PTR(ret);

	if (data.kernel_mem == 0) {
		unsigned long restart_psw =  0x0008000080000000UL;
		restart_psw += image->start;
		memcpy(data.kernel_buf, &restart_psw, sizeof(restart_psw));
		image->start = 0;
	}

	return NULL;
}

int arch_kexec_apply_relocations_add(struct purgatory_info *pi,
				     Elf_Shdr *section,
				     const Elf_Shdr *relsec,
				     const Elf_Shdr *symtab)
{
	Elf_Rela *relas;
	int i;

	relas = (void *)pi->ehdr + relsec->sh_offset;

	for (i = 0; i < relsec->sh_size / sizeof(*relas); i++) {
		const Elf_Sym *sym;	/* symbol to relocate */
		unsigned long addr;	/* final location after relocation */
		unsigned long val;	/* relocated symbol value */
		void *loc;		/* tmp location to modify */

		sym = (void *)pi->ehdr + symtab->sh_offset;
		sym += ELF64_R_SYM(relas[i].r_info);

		if (sym->st_shndx == SHN_UNDEF)
			return -ENOEXEC;

		if (sym->st_shndx == SHN_COMMON)
			return -ENOEXEC;

		if (sym->st_shndx >= pi->ehdr->e_shnum &&
		    sym->st_shndx != SHN_ABS)
			return -ENOEXEC;

		loc = pi->purgatory_buf;
		loc += section->sh_offset;
		loc += relas[i].r_offset;

		val = sym->st_value;
		if (sym->st_shndx != SHN_ABS)
			val += pi->sechdrs[sym->st_shndx].sh_addr;
		val += relas[i].r_addend;

		addr = section->sh_addr + relas[i].r_offset;

		switch (ELF64_R_TYPE(relas[i].r_info)) {
		case R_390_8:		/* Direct 8 bit.   */
			*(u8 *)loc = val;
			break;
		case R_390_12:		/* Direct 12 bit.  */
			*(u16 *)loc &= 0xf000;
			*(u16 *)loc |= val & 0xfff;
			break;
		case R_390_16:		/* Direct 16 bit.  */
			*(u16 *)loc = val;
			break;
		case R_390_20:		/* Direct 20 bit.  */
			*(u32 *)loc &= 0xf00000ff;
			*(u32 *)loc |= (val & 0xfff) << 16;	/* DL */
			*(u32 *)loc |= (val & 0xff000) >> 4;	/* DH */
			break;
		case R_390_32:		/* Direct 32 bit.  */
			*(u32 *)loc = val;
			break;
		case R_390_64:		/* Direct 64 bit.  */
			*(u64 *)loc = val;
			break;
		case R_390_PC16:	/* PC relative 16 bit.	*/
			*(u16 *)loc = (val - addr);
			break;
		case R_390_PC16DBL:	/* PC relative 16 bit shifted by 1.  */
			*(u16 *)loc = (val - addr) >> 1;
			break;
		case R_390_PC32DBL:	/* PC relative 32 bit shifted by 1.  */
			*(u32 *)loc = (val - addr) >> 1;
			break;
		case R_390_PC32:	/* PC relative 32 bit.	*/
			*(u32 *)loc = (val - addr);
			break;
		case R_390_PC64:	/* PC relative 64 bit.	*/
			*(u64 *)loc = (val - addr);
			break;
		default:
			break;
		}
	}
	return 0;
}

int arch_kexec_kernel_image_probe(struct kimage *image, void *buf,
				  unsigned long buf_len)
{
	/* A kernel must be at least large enough to contain head.S. During
	 * load memory in head.S will be accessed, e.g. to register the next
	 * command line. If the next kernel were smaller the current kernel
	 * will panic at load.
	 *
	 * 0x11000 = sizeof(head.S)
	 */
	if (buf_len < 0x11000)
		return -ENOEXEC;

	return kexec_image_probe_default(image, buf, buf_len);
}