fxBoot/src/hypervisor/internal/elf/reloc.c

//---
//	fxBoot:loader:entry - ELF Loader entry
//---
#include "fxBoot/hypervisor.h"
#include "fxBoot/fs/smemfs.h"
#include "fxBoot/elf.h"
#include "fxBoot/terminal.h"

#include <gint/std/stdlib.h>
#include <gint/std/string.h>

#include "./src/hypervisor/internal/elf.h"

//---
// Internal helpers
//---
/* relocinfo: Internal structure used to stoe all ELF information */
struct relocinfo {
	Elf32_Ehdr *ehdr;
	Elf32_Shdr ehdr_dynamic;
	Elf32_Dyn *dynamic;
	Elf32_Sym *dynsym;
	char *dynstr;
	char *shstrtab;
	struct smemfs_inode *inode;
};

/* reloc_dump_section(): Dump one section */
static void *reloc_dump_section(struct smemfs_inode *inode, Elf32_Shdr *shdr)
{
	void *section;

	section = malloc(shdr->sh_size);
	if (section == NULL)
		return (NULL);
	if (smemfs_pread(inode, section, shdr->sh_size, shdr->sh_offset)
			!= (ssize_t)shdr->sh_size) {
		free(section);
		return (NULL);
	}
	return (section);
}

/* reloc_get_dynamic_info(): Dump all dynamic information */
static int reloc_get_dynamic_info(struct relocinfo *elf)
{
	Elf32_Shdr shdr;
	off_t offset;
	void **tmp;

	/* get ELF section header string table */
	offset  = elf->ehdr->e_shoff;
	offset += elf->ehdr->e_shstrndx * elf->ehdr->e_shentsize;
	if (smemfs_pread(elf->inode, &shdr, elf->ehdr->e_shentsize, offset)
			!= elf->ehdr->e_shentsize) {
		return (-1);
	}
	elf->shstrtab = reloc_dump_section(elf->inode, &shdr);
	if (elf->shstrtab == NULL)
		return (-2);

	/* get ELF information */
	elf->dynstr = NULL;
	elf->dynamic = NULL;
	for (int i = 1 ; i < elf->ehdr->e_shnum ; ++i) {
		offset = elf->ehdr->e_shoff + (i * elf->ehdr->e_shentsize);
		if (smemfs_pread(elf->inode, &shdr,
					elf->ehdr->e_shentsize, offset)
				!= elf->ehdr->e_shentsize) {
			continue;
		}
		tmp = NULL;
		if (strcmp(".dynamic", &elf->shstrtab[shdr.sh_name]) == 0) {
			memcpy(&elf->ehdr_dynamic, &shdr, sizeof(Elf32_Shdr));
			tmp = (void*)&elf->dynamic;
		}
		if (strcmp(".dynstr", &elf->shstrtab[shdr.sh_name]) == 0)
			tmp = (void*)&elf->dynstr;
		if (strcmp(".dynsym", &elf->shstrtab[shdr.sh_name]) == 0)
			tmp = (void*)&elf->dynsym;
		if (tmp == NULL)
			continue;
		*tmp = reloc_dump_section(elf->inode, &shdr);
	}
	return (0);
}

/* reloc_get_dynsym(): Try to find the dynamic symbol address */
static void *reloc_get_dynsym(struct relocinfo *info, int symid)
{
	char *name;

	if (info->dynsym == NULL || info->dynstr == NULL)
		return (NULL);
	//FIXME: check symid validity !
	name = &info->dynstr[info->dynsym[symid].st_name];
	for (int i = 0; gint_reloc[i].name != NULL; ++i) {
		if (strcmp(name, gint_reloc[i].name) != 0)
			continue;
		terminal_write("  * reloc '%s'\n", name);
		return ((void*)gint_reloc[i].addr);
	}
	terminal_write("unknown '%s' symbols\n", name);
	return (NULL);
}

/* reloc_section(): Relocalise section's symbols */
static int reloc_rela(struct hworld *world,
				struct relocinfo *info, Elf32_Shdr *shdr)
{
	Elf32_Rela rela;
	uint32_t *prog;
	off_t offset;
	void *dyn;

	if (shdr->sh_size == 0 || shdr->sh_entsize == 0) {
		terminal_write("empty section\n");
		return (0);
	}
	prog = (void*)world->memory.program.start;
	for (uint32_t i = 0 ; i < shdr->sh_size / shdr->sh_entsize ; ++i) {
		offset = shdr->sh_offset + (i * shdr->sh_entsize);
		if (smemfs_pread(info->inode, &rela, shdr->sh_entsize, offset)
				!= (ssize_t)shdr->sh_entsize) {
			return (hel_reloc_size_error);
		}
		if (ELF32_R_TYPE(rela.r_info) == R_SH_RELATIVE) {
			offset  = rela.r_offset;
			offset -= world->memory.program.elf.vmin;
			prog[offset >> 2] -= world->memory.program.elf.vmin;
			prog[offset >> 2] +=
				(uintptr_t)world->memory.program.start;
			continue;
		}
		if (ELF32_R_TYPE(rela.r_info) == R_SH_JMP_SLOT) {
			dyn = reloc_get_dynsym(info, ELF32_R_SYM(rela.r_info));
			if (dyn == NULL)
				return (-1);
			offset  = rela.r_offset;
			offset -= world->memory.program.elf.vmin;
			prog[offset >> 2] = (uintptr_t)dyn;
			world->private.env = HYPERVISOR_ENV_GINT;
			continue;
		}
		terminal_write("unknown type %x\n", rela.r_info);
		return (-1);
	}
	return (hel_reloc_success);
}

//---
//	Public helpers
//---
/* loader_reloc_sym(): Relocalise all symbols */
int hypervisor_elf_loader_reloc_sym(struct hworld *world,
				struct smemfs_inode *inode, Elf32_Ehdr *ehdr)
{
	struct relocinfo info;
	Elf32_Shdr shdr;
	off_t offset;


	/* get dynamic information */
	info.inode = inode;
	info.ehdr = ehdr;
	if (reloc_get_dynamic_info(&info) != 0)
		return (-1);

	/* find all reloc section */
	//TODO : support SH_REL
	//TODO : check if the GOT, PLT sections are relocalized !
	for (int i = 1 ; i < ehdr->e_shnum ; ++i) {
		offset = ehdr->e_shoff + (i * ehdr->e_shentsize);
		if (smemfs_pread(inode, &shdr, ehdr->e_shentsize, offset)
				!= ehdr->e_shentsize) {
			return (hel_reloc_size_error);
		}
		if (shdr.sh_type == SHT_RELA
		&& reloc_rela(world, &info, &shdr) != hel_reloc_success)
			return (hel_reloc_error);
		if (shdr.sh_type == SHT_REL) {
			terminal_write("SHT_REL not yet supported\n");
			return (hel_reloc_error);
		}
	}
	return (hel_reloc_success);
}