mirror of https://github.com/m-labs/artiq.git
217 lines
6.3 KiB
C
217 lines
6.3 KiB
C
#include <stdio.h>
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#include <string.h>
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#include "elf_loader.h"
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#define EI_NIDENT 16
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struct elf32_ehdr {
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unsigned char ident[EI_NIDENT]; /* ident bytes */
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unsigned short type; /* file type */
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unsigned short machine; /* target machine */
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unsigned int version; /* file version */
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unsigned int entry; /* start address */
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unsigned int phoff; /* phdr file offset */
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unsigned int shoff; /* shdr file offset */
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unsigned int flags; /* file flags */
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unsigned short ehsize; /* sizeof ehdr */
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unsigned short phentsize; /* sizeof phdr */
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unsigned short phnum; /* number phdrs */
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unsigned short shentsize; /* sizeof shdr */
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unsigned short shnum; /* number shdrs */
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unsigned short shstrndx; /* shdr string index */
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} __attribute__((packed));
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static const unsigned char elf_magic_header[] = {
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0x7f, 0x45, 0x4c, 0x46, /* 0x7f, 'E', 'L', 'F' */
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0x01, /* Only 32-bit objects. */
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0x02, /* Only big-endian. */
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0x01, /* Only ELF version 1. */
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};
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#define ET_NONE 0 /* Unknown type. */
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#define ET_REL 1 /* Relocatable. */
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#define ET_EXEC 2 /* Executable. */
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#define ET_DYN 3 /* Shared object. */
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#define ET_CORE 4 /* Core file. */
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#define EM_OR1K 0x005c
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struct elf32_shdr {
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unsigned int name; /* section name */
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unsigned int type; /* SHT_... */
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unsigned int flags; /* SHF_... */
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unsigned int addr; /* virtual address */
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unsigned int offset; /* file offset */
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unsigned int size; /* section size */
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unsigned int link; /* misc info */
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unsigned int info; /* misc info */
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unsigned int addralign; /* memory alignment */
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unsigned int entsize; /* entry size if table */
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} __attribute__((packed));
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struct elf32_name {
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char name[12];
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} __attribute__((packed));
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struct elf32_rela {
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unsigned int offset; /* Location to be relocated. */
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unsigned int info; /* Relocation type and symbol index. */
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int addend; /* Addend. */
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} __attribute__((packed));
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#define ELF32_R_SYM(info) ((info) >> 8)
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#define ELF32_R_TYPE(info) ((unsigned char)(info))
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#define R_OR1K_INSN_REL_26 6
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struct elf32_sym {
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unsigned int name; /* String table index of name. */
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unsigned int value; /* Symbol value. */
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unsigned int size; /* Size of associated object. */
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unsigned char info; /* Type and binding information. */
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unsigned char other; /* Reserved (not used). */
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unsigned short shndx; /* Section index of symbol. */
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} __attribute__((packed));
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#define SANITIZE_OFFSET_SIZE(offset, size) \
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if(offset > 0x10000000) { \
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printf("Incorrect offset in ELF data"); \
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return 0; \
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} \
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if((offset + size) > elf_length) { \
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printf("Attempted to access past the end of ELF data"); \
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return 0; \
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}
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#define GET_POINTER_SAFE(target, target_type, offset) \
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SANITIZE_OFFSET_SIZE(offset, sizeof(target_type)); \
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target = (target_type *)((char *)elf_data + offset)
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void *find_symbol(const struct symbol *symbols, const char *name)
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{
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int i;
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i = 0;
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while((symbols[i].name != NULL) && (strcmp(symbols[i].name, name) != 0))
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i++;
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return symbols[i].target;
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}
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static int fixup(void *dest, int dest_length, struct elf32_rela *rela, void *target)
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{
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int type, offset;
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unsigned int *_dest = dest;
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unsigned int *_target = target;
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type = ELF32_R_TYPE(rela->info);
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offset = rela->offset/4;
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if(type == R_OR1K_INSN_REL_26) {
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int val;
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val = _target - (_dest + offset);
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_dest[offset] = (_dest[offset] & 0xfc000000) | (val & 0x03ffffff);
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} else
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printf("Unsupported relocation type: %d\n", type);
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return 1;
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}
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int load_elf(symbol_resolver resolver, void *elf_data, int elf_length, void *dest, int dest_length)
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{
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struct elf32_ehdr *ehdr;
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struct elf32_shdr *strtable;
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unsigned int shdrptr;
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int i;
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unsigned int textoff, textsize;
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unsigned int textrelaoff, textrelasize;
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unsigned int symtaboff, symtabsize;
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unsigned int strtaboff, strtabsize;
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/* validate ELF */
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GET_POINTER_SAFE(ehdr, struct elf32_ehdr, 0);
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if(memcmp(ehdr->ident, elf_magic_header, sizeof(elf_magic_header)) != 0) {
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printf("Incorrect ELF header\n");
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return 0;
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}
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if(ehdr->type != ET_REL) {
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printf("ELF is not relocatable\n");
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return 0;
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}
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if(ehdr->machine != EM_OR1K) {
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printf("ELF is for a different machine\n");
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return 0;
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}
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/* extract section info */
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GET_POINTER_SAFE(strtable, struct elf32_shdr, ehdr->shoff + ehdr->shentsize*ehdr->shstrndx);
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textoff = textsize = 0;
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textrelaoff = textrelasize = 0;
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symtaboff = symtabsize = 0;
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strtaboff = strtabsize = 0;
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shdrptr = ehdr->shoff;
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for(i=0;i<ehdr->shnum;i++) {
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struct elf32_shdr *shdr;
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struct elf32_name *name;
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GET_POINTER_SAFE(shdr, struct elf32_shdr, shdrptr);
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GET_POINTER_SAFE(name, struct elf32_name, strtable->offset + shdr->name);
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if(strncmp(name->name, ".text", 5) == 0) {
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textoff = shdr->offset;
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textsize = shdr->size;
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} else if(strncmp(name->name, ".rela.text", 10) == 0) {
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textrelaoff = shdr->offset;
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textrelasize = shdr->size;
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} else if(strncmp(name->name, ".symtab", 7) == 0) {
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symtaboff = shdr->offset;
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symtabsize = shdr->size;
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} else if(strncmp(name->name, ".strtab", 7) == 0) {
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strtaboff = shdr->offset;
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strtabsize = shdr->size;
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}
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shdrptr += ehdr->shentsize;
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}
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SANITIZE_OFFSET_SIZE(textoff, textsize);
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SANITIZE_OFFSET_SIZE(textrelaoff, textrelasize);
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SANITIZE_OFFSET_SIZE(symtaboff, symtabsize);
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SANITIZE_OFFSET_SIZE(strtaboff, strtabsize);
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/* load .text section */
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if(textsize > dest_length) {
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printf(".text section is too large\n");
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return 0;
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}
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memcpy(dest, (char *)elf_data + textoff, textsize);
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/* process .text relocations */
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for(i=0;i<textrelasize;i+=sizeof(struct elf32_rela)) {
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struct elf32_rela *rela;
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struct elf32_sym *sym;
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char *name;
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GET_POINTER_SAFE(rela, struct elf32_rela, textrelaoff + i);
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GET_POINTER_SAFE(sym, struct elf32_sym, symtaboff + sizeof(struct elf32_sym)*ELF32_R_SYM(rela->info));
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if(sym->name != 0) {
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void *target;
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name = (char *)elf_data + strtaboff + sym->name;
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target = resolver(name);
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if(target == NULL) {
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printf("Undefined symbol: %s\n", name);
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return 0;
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}
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if(!fixup(dest, dest_length, rela, target))
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return 0;
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} else {
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printf("Unsupported relocation\n");
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return 0;
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}
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}
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return 1;
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}
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