elf.c

#include "elf.h"

#define SYMBOL_TYPE_FUNCTION 0x2
#define ELF32_ST_TYPE(i) ((i)&0xf)


elf_t elf_from_multiboot(multiboot_t *mb)
{
    elf_section_header_t *sh = (elf_section_header_t*)mb->addr;

    elf_t elf;
    
    uint32_t shstrtab = sh[mb->shndx].addr; // shstr = section header string 
    for (int i=0; i<mb->num; i++) {
        const char *name = (const char*)(shstrtab + sh[i].name);
        if (!strcmp(name, ".strtab")) {
            elf.strtab = (const char*)sh[i].addr;
            elf.strtabsz = sh[i].size;
        }

        if (!strcmp(name, ".symtab")) {
            elf.symtab = (elf_symbol_t*)sh[i].addr;
            elf.symtabsz = sh[i].size;
        }
    }
    return elf;
}

const char *elf_lookup_symbol(uint32_t addr, elf_t *elf)
{
    for (int i=0; i<(elf->symtabsz/sizeof(elf_symbol_t)); i++) {
        if (ELF32_ST_TYPE(elf->symtab[i].info) != SYMBOL_TYPE_FUNCTION)
            continue;

        if ((addr >= elf->symtab[i].value) && (addr < elf->symtab[i].value + elf->symtab[i].size)) {
            const char *name = (const char*)((uint32_t)elf->strtab + elf->symtab[i].name);
            return name;
        }
    }

    return "Unknown symbol";
}