vxBoot - 1.1.1 : GOT patch
@update <> CMakeList.txt : dump version + add new sources files <> include/vxBoot/loader : remove useless define and add Elf32_Sym @fix <> vxBoot/loader/got : relocalize the .got section to _GLOBAL_OFFSET_TABLE_
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@ -1,5 +1,5 @@
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cmake_minimum_required(VERSION 3.15)
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project(vxBoot VERSION 1.1.0 LANGUAGES C)
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project(vxBoot VERSION 1.1.1 LANGUAGES C)
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include(GenerateG1A)
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include(GenerateG3A)
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@ -94,24 +94,35 @@ typedef struct {
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/* Legal values for sh_type (section type). */
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#define SHT_NULL 0 /* Section header table entry unused */
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#define SHT_PROGBITS 1 /* Program data */
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#define SHT_SYMTAB 2 /* Symbol table */
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#define SHT_STRTAB 3 /* String table */
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#define SHT_RELA 4 /* Relocation entries with addends */
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#define SHT_HASH 5 /* Symbol hash table */
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#define SHT_DYNAMIC 6 /* Dynamic linking information */
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#define SHT_NOTE 7 /* Notes */
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#define SHT_NOBITS 8 /* Program space with no data (bss) */
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#define SHT_REL 9 /* Relocation entries, no addends */
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#define SHT_SHLIB 10 /* Reserved */
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#define SHT_DYNSYM 11 /* Dynamic linker symbol table */
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#define SHT_INIT_ARRAY 14 /* Array of constructors */
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#define SHT_FINI_ARRAY 15 /* Array of destructors */
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#define SHT_PREINIT_ARRAY 16 /* Array of pre-constructors */
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#define SHT_GROUP 17 /* Section group */
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#define SHT_SYMTAB_SHNDX 18 /* Extended section indices */
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#define SHT_NUM 19 /* Number of defined types. */
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#define SHT_NULL 0 /* Section header table entry unused */
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#define SHT_PROGBITS 1 /* Program data */
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#define SHT_SYMTAB 2 /* Symbol table */
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#define SHT_STRTAB 3 /* String table */
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#define SHT_RELA 4 /* Relocation entries with addends */
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#define SHT_HASH 5 /* Symbol hash table */
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#define SHT_DYNAMIC 6 /* Dynamic linking information */
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#define SHT_NOTE 7 /* Notes */
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#define SHT_NOBITS 8 /* Program space with no data (bss) */
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#define SHT_REL 9 /* Relocation entries, no addends */
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#define SHT_SHLIB 10 /* Reserved */
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#define SHT_DYNSYM 11 /* Dynamic linker symbol table */
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#define SHT_INIT_ARRAY 14 /* Array of constructors */
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#define SHT_FINI_ARRAY 15 /* Array of destructors */
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#define SHT_PREINIT_ARRAY 16 /* Array of pre-constructors */
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#define SHT_GROUP 17 /* Section group */
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#define SHT_SYMTAB_SHNDX 18 /* Extended section indices */
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#define SHT_NUM 19 /* Number of defined types. */
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/* Symbol table entry. */
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typedef struct {
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uint32_t st_name; /* Symbol name (string tbl index) */
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uint32_t st_value; /* Symbol value */
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uint32_t st_size; /* Symbol size */
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unsigned char st_info; /* Symbol type and binding */
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unsigned char st_other; /* Symbol visibility */
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uint16_t st_shndx; /* Section index */
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} Elf32_Sym;
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//---
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// Loader API
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@ -4,15 +4,15 @@
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#include <string.h>
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/* loader_got_patch() : Try to patch the GOT section */
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int loader_got_patch(
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/* loader_get_section() : Try to find section information using its name */
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static int loader_get_section(
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Elf32_Shdr *shdr,
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char const * const name,
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struct smemfs_inode const * restrict const inode,
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struct kernel_info * const kernel,
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Elf32_Ehdr *hdr
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) {
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Elf32_Shdr shdr;
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uintptr_t *got;
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char name[5];
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char buff[16];
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off_t stroff;
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off_t shoff;
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@ -22,28 +22,88 @@ int loader_got_patch(
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/* find the section string table ".strtable" */
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smemfs_pread(
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inode,
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&shdr, sizeof(Elf32_Shdr),
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shdr, sizeof(Elf32_Shdr),
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shoff + (sizeof(Elf32_Shdr) * hdr->e_shstrndx)
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);
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stroff = shdr.sh_offset;
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stroff = shdr->sh_offset;
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/* walk throught each section and find the .got section */
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for (int i = 0; i < hdr->e_shnum; ++i) {
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smemfs_pread(inode, &shdr, sizeof(Elf32_Shdr), shoff);
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smemfs_pread(inode, name, 5, shdr.sh_name + stroff);
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if (strcmp(name, ".got") != 0) {
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shoff += sizeof(Elf32_Shdr);
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continue;
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}
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got = kernel->memory.program.start;
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got = (void*)((uintptr_t)got + (uintptr_t)shdr.sh_addr);
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terminal_write(" GOT section found at %p...\n", got);
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for (uint32_t j = 0 ; j < shdr.sh_size >> 2 ; ++j) {
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terminal_write(" path symbols %p...\n", got[j]);
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got[j] += (uintptr_t)kernel->hardware.ram.physical.kernel_addr;
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got[j] |= (uintptr_t)0x80000000;
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}
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return (0);
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smemfs_pread(inode, shdr, sizeof(Elf32_Shdr), shoff);
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smemfs_pread(inode, buff, 16, shdr->sh_name + stroff);
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if (strcmp(buff, name) == 0)
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return (0);
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shoff += sizeof(Elf32_Shdr);
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}
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return (-1);
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}
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/* loader_get_symbols() : get symbols information */
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static int loader_get_symbol(
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Elf32_Sym *sym,
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char const * const name,
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struct smemfs_inode const * restrict const inode,
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Elf32_Ehdr *hdr
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){
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Elf32_Shdr symhdr;
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Elf32_Shdr strhdr;
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char buff[64];
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int off;
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/* frist, find the symtab section */
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loader_get_section(&symhdr, ".symtab", inode, hdr);
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loader_get_section(&strhdr, ".strtab", inode, hdr);
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/* walk throut the table */
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off = symhdr.sh_offset;
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for (uint32_t i = 0 ; i < symhdr.sh_size / sizeof(Elf32_Sym) ; ++i) {
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smemfs_pread(inode, sym, sizeof(Elf32_Sym), off);
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smemfs_pread(inode, buff, 64, sym->st_name + strhdr.sh_offset);
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if (strcmp(buff, name) == 0)
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return (0);
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off += sizeof(Elf32_Sym);
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}
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return (-1);
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}
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/* loader_got_patch() : Try to patch the GOT/PLT section */
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int loader_got_patch(
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struct smemfs_inode const * restrict const inode,
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struct kernel_info * const kernel,
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Elf32_Ehdr *hdr
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) {
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Elf32_Shdr shdr;
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Elf32_Sym sym;
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uintptr_t *__got__;
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uintptr_t *got;
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uintptr_t addr;
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/* first, try to find the __GLOBAL_OFFSET_TABLE__ symbol */
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if (loader_get_symbol(&sym, "_GLOBAL_OFFSET_TABLE_", inode, hdr)) {
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terminal_write("_GLOBAL_OFFSET_TABLE_ not found...\n");
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return (0);
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}
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__got__ = kernel->memory.program.start;
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__got__ = (void*)((uintptr_t)__got__ + (uintptr_t)sym.st_value);
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terminal_write(" __GOT__ found at %p...\n", __got__);
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/* and we need to relocalise the "real" GOT section and update the
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hardcoded address in the same time */
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loader_get_section(&shdr, ".got", inode, hdr);
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got = kernel->memory.program.start;
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got = (void*)((uintptr_t)got + (uintptr_t)shdr.sh_addr);
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terminal_write(" GOT found at %p...\n", got);
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/* perform transation */
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for (uint32_t i = 0 ; i < shdr.sh_size >> 2 ; ++i) {
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terminal_write(" path symbols %p...\n", got[i]);
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addr = got[i];
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addr += (uintptr_t)kernel->hardware.ram.physical.kernel_addr;
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addr |= (uintptr_t)0x80000000;
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__got__[i] = addr;
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}
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return (0);
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}
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