Unverified Commit 838b3e28 authored by Li Zhengyu's avatar Li Zhengyu Committed by Palmer Dabbelt
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RISC-V: Load purgatory in kexec_file 



This patch supports kexec_file to load and relocate purgatory.
It works well on riscv64 QEMU, being tested with devmem.

Signed-off-by: default avatarLi Zhengyu <lizhengyu3@huawei.com>
Link: https://lore.kernel.org/r/20220408100914.150110-7-lizhengyu3@huawei.com


Signed-off-by: default avatarPalmer Dabbelt <palmer@rivosinc.com>
parent 736e30af

arch/riscv/kernel/elf_kexec.c

+151 −0
Original line number Diff line number Diff line
@@ -182,6 +182,7 @@ static void *elf_kexec_load(struct kimage *image, char *kernel_buf, 
	unsigned long new_kernel_pbase = 0UL;

	unsigned long initrd_pbase = 0UL;

	unsigned long headers_sz;

	unsigned long kernel_start;

	void *fdt, *headers;

	struct elfhdr ehdr;

	struct kexec_buf kbuf;
@@ -196,6 +197,7 @@ static void *elf_kexec_load(struct kimage *image, char *kernel_buf, 
			     &old_kernel_pbase, &new_kernel_pbase);

	if (ret)

		goto out;

	kernel_start = image->start;

	pr_notice("The entry point of kernel at 0x%lx\n", image->start);



	/* Add the kernel binary to the image */
@@ -246,6 +248,22 @@ static void *elf_kexec_load(struct kimage *image, char *kernel_buf, 
		cmdline = modified_cmdline;

	}



#ifdef CONFIG_ARCH_HAS_KEXEC_PURGATORY

	/* Add purgatory to the image */

	kbuf.top_down = true;

	kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;

	ret = kexec_load_purgatory(image, &kbuf);

	if (ret) {

		pr_err("Error loading purgatory ret=%d\n", ret);

		goto out;

	}

	ret = kexec_purgatory_get_set_symbol(image, "riscv_kernel_entry",

					     &kernel_start,

					     sizeof(kernel_start), 0);

	if (ret)

		pr_err("Error update purgatory ret=%d\n", ret);

#endif /* CONFIG_ARCH_HAS_KEXEC_PURGATORY */



	/* Add the initrd to the image */

	if (initrd != NULL) {

		kbuf.buffer = initrd;
@@ -291,6 +309,139 @@ static void *elf_kexec_load(struct kimage *image, char *kernel_buf, 
	return ret ? ERR_PTR(ret) : NULL;

}



#define RV_X(x, s, n)  (((x) >> (s)) & ((1 << (n)) - 1))

#define RISCV_IMM_BITS 12

#define RISCV_IMM_REACH (1LL << RISCV_IMM_BITS)

#define RISCV_CONST_HIGH_PART(x) \

	(((x) + (RISCV_IMM_REACH >> 1)) & ~(RISCV_IMM_REACH - 1))

#define RISCV_CONST_LOW_PART(x) ((x) - RISCV_CONST_HIGH_PART(x))



#define ENCODE_ITYPE_IMM(x) \

	(RV_X(x, 0, 12) << 20)

#define ENCODE_BTYPE_IMM(x) \

	((RV_X(x, 1, 4) << 8) | (RV_X(x, 5, 6) << 25) | \

	(RV_X(x, 11, 1) << 7) | (RV_X(x, 12, 1) << 31))

#define ENCODE_UTYPE_IMM(x) \

	(RV_X(x, 12, 20) << 12)

#define ENCODE_JTYPE_IMM(x) \

	((RV_X(x, 1, 10) << 21) | (RV_X(x, 11, 1) << 20) | \

	(RV_X(x, 12, 8) << 12) | (RV_X(x, 20, 1) << 31))

#define ENCODE_CBTYPE_IMM(x) \

	((RV_X(x, 1, 2) << 3) | (RV_X(x, 3, 2) << 10) | (RV_X(x, 5, 1) << 2) | \

	(RV_X(x, 6, 2) << 5) | (RV_X(x, 8, 1) << 12))

#define ENCODE_CJTYPE_IMM(x) \

	((RV_X(x, 1, 3) << 3) | (RV_X(x, 4, 1) << 11) | (RV_X(x, 5, 1) << 2) | \

	(RV_X(x, 6, 1) << 7) | (RV_X(x, 7, 1) << 6) | (RV_X(x, 8, 2) << 9) | \

	(RV_X(x, 10, 1) << 8) | (RV_X(x, 11, 1) << 12))

#define ENCODE_UJTYPE_IMM(x) \

	(ENCODE_UTYPE_IMM(RISCV_CONST_HIGH_PART(x)) | \

	(ENCODE_ITYPE_IMM(RISCV_CONST_LOW_PART(x)) << 32))

#define ENCODE_UITYPE_IMM(x) \

	(ENCODE_UTYPE_IMM(x) | (ENCODE_ITYPE_IMM(x) << 32))



#define CLEAN_IMM(type, x) \

	((~ENCODE_##type##_IMM((uint64_t)(-1))) & (x))



int arch_kexec_apply_relocations_add(struct purgatory_info *pi,

				     Elf_Shdr *section,

				     const Elf_Shdr *relsec,

				     const Elf_Shdr *symtab)

{

	const char *strtab, *name, *shstrtab;

	const Elf_Shdr *sechdrs;

	Elf_Rela *relas;

	int i, r_type;



	/* String & section header string table */

	sechdrs = (void *)pi->ehdr + pi->ehdr->e_shoff;

	strtab = (char *)pi->ehdr + sechdrs[symtab->sh_link].sh_offset;

	shstrtab = (char *)pi->ehdr + sechdrs[pi->ehdr->e_shstrndx].sh_offset;



	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 */

		unsigned long sec_base;	/* 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_name)

			name = strtab + sym->st_name;

		else

			name = shstrtab + sechdrs[sym->st_shndx].sh_name;



		loc = pi->purgatory_buf;

		loc += section->sh_offset;

		loc += relas[i].r_offset;



		if (sym->st_shndx == SHN_ABS)

			sec_base = 0;

		else if (sym->st_shndx >= pi->ehdr->e_shnum) {

			pr_err("Invalid section %d for symbol %s\n",

			       sym->st_shndx, name);

			return -ENOEXEC;

		} else

			sec_base = pi->sechdrs[sym->st_shndx].sh_addr;



		val = sym->st_value;

		val += sec_base;

		val += relas[i].r_addend;



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



		r_type = ELF64_R_TYPE(relas[i].r_info);



		switch (r_type) {

		case R_RISCV_BRANCH:

			*(u32 *)loc = CLEAN_IMM(BTYPE, *(u32 *)loc) |

				 ENCODE_BTYPE_IMM(val - addr);

			break;

		case R_RISCV_JAL:

			*(u32 *)loc = CLEAN_IMM(JTYPE, *(u32 *)loc) |

				 ENCODE_JTYPE_IMM(val - addr);

			break;

		/*

		 * With no R_RISCV_PCREL_LO12_S, R_RISCV_PCREL_LO12_I

		 * sym is expected to be next to R_RISCV_PCREL_HI20

		 * in purgatory relsec. Handle it like R_RISCV_CALL

		 * sym, instead of searching the whole relsec.

		 */

		case R_RISCV_PCREL_HI20:

		case R_RISCV_CALL:

			*(u64 *)loc = CLEAN_IMM(UITYPE, *(u64 *)loc) |

				 ENCODE_UJTYPE_IMM(val - addr);

			break;

		case R_RISCV_RVC_BRANCH:

			*(u32 *)loc = CLEAN_IMM(CBTYPE, *(u32 *)loc) |

				 ENCODE_CBTYPE_IMM(val - addr);

			break;

		case R_RISCV_RVC_JUMP:

			*(u32 *)loc = CLEAN_IMM(CJTYPE, *(u32 *)loc) |

				 ENCODE_CJTYPE_IMM(val - addr);

			break;

		case R_RISCV_ADD32:

			*(u32 *)loc += val;

			break;

		case R_RISCV_SUB32:

			*(u32 *)loc -= val;

			break;

		/* It has been applied by R_RISCV_PCREL_HI20 sym */

		case R_RISCV_PCREL_LO12_I:

		case R_RISCV_ALIGN:

		case R_RISCV_RELAX:

			break;

		default:

			pr_err("Unknown rela relocation: %d\n", r_type);

			return -ENOEXEC;

		}

	}

	return 0;

}



const struct kexec_file_ops elf_kexec_ops = {

	.probe = kexec_elf_probe,

	.load  = elf_kexec_load,