elf_parser.c

#include <assert.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/stat.h>

#include "log.h"
#include "elf.h"
#include "cpu.h"

//#define DEBUG

void elf_parse(struct cpu *c, char* file_name){
    struct stat st;
    FILE *fp;
    int file_size;
    uint8_t* file_buffer;

    if(stat(file_name, &st) != 0){
        log_printf("Failed to get file size :%s\n", file_name);
        exit(1);
    }
    file_size = st.st_size;

    if((fp = fopen(file_name, "rb")) == NULL){
        log_printf("Failed to open file :%s\n", file_name);
        exit(1);
    }

    file_buffer = malloc(file_size);

    int load_size = fread(file_buffer, sizeof(uint8_t), file_size, fp);
    if(load_size != file_size){
        log_printf("File size is not matched: %s\n", file_name);
        exit(1);
    }
#ifdef DEBUG
    log_printf("Loaded File: %s (%dbyte)\n", file_name, load_size);
#endif

    Elf32_Ehdr *Ehdr = (Elf32_Ehdr *)file_buffer;
    if(!IS_ELF(*Ehdr)){
        log_printf("Unkown file format\n");
        exit(1);
    }
    if(!IS_ELF32(*Ehdr)){
        log_printf("Not ELF32 format\n");
        exit(1);
    }
#ifdef DEBUG
    log_printf("Type:ELF32\n");
    log_printf("Entry point:%d\n\n", Ehdr->e_entry);
#endif

    Elf32_Shdr *Shdr = (Elf32_Shdr *)(file_buffer + Ehdr->e_shoff);
    char *shstr = file_buffer + Shdr[Ehdr->e_shstrndx].sh_offset;
    for(int i=0; i<Ehdr->e_shnum;i++){
        char *name = &shstr[Shdr[i].sh_name];
#ifdef DEBUG
        log_printf("Shdr:%d sh_name:%s\n", i, &shstr[Shdr[i].sh_name]);
        log_printf("Shdr:%d sh_type:%04X\n", i, Shdr[i].sh_type);
        log_printf("Shdr:%d sh_flags:%04X\n", i, Shdr[i].sh_flags);
        log_printf("Shdr:%d sh_addr:%04X\n", i, Shdr[i].sh_addr);
        log_printf("Shdr:%d sh_offset:%04X\n", i, Shdr[i].sh_offset);
        log_printf("Shdr:%d sh_size:%04X\n", i, Shdr[i].sh_size);
        log_printf("\n");
#endif

        if (strcmp(".text", name) == 0) {   // ROM
            // For now we assume that .text section begins at address 0.
            assert(Shdr[i].sh_addr == 0 && "The beginning address of .text section should be 0.");

            uint8_t *obj = (uint8_t *)(file_buffer+Shdr[i].sh_offset);
            for(int j=0;j<Shdr[i].sh_size;j+=2){
                assert(j + 1 < INST_ROM_SIZE && "Too large program (.text) data.");

                log_printf("ROM: %04X %02X%02X\n", j, obj[j], obj[j+1]);
                c->inst_rom[j] = obj[j];
                c->inst_rom[j+1] = obj[j+1];
            }
            log_printf("\n");
        }
        else if (0x00010000 <= Shdr[i].sh_addr && Shdr[i].sh_addr <= 0x0001ffff) {  // RAM
            uint8_t *obj = (uint8_t *)(file_buffer+Shdr[i].sh_offset);
            uint8_t data_ram_offset = Shdr[i].sh_addr & 0x0000ffff;

            if (strcmp(".bss", name) == 0) {
                // .bss section shouldn't be loaded to RAM, but be placed after all other sections.
                // FIXME: Check if this sections is placed after all other sections.
                continue;
            }

            for(int j=0;j<Shdr[i].sh_size;j+=2){
                assert(data_ram_offset + j + 1 < DATA_RAM_SIZE && "Too large data (.data/.rodata).");

                log_printf("RAM: %04X %02X%02X\n", data_ram_offset + j, obj[j], obj[j+1]);
                c->data_ram[data_ram_offset+ j] = obj[j];
                c->data_ram[data_ram_offset+ j+1] = obj[j+1];
            }
            log_printf("\n");
        }
    }

    // Since RV16K specification says the initial value of PC is 0, e_entry should be 0.
    c->pc = Ehdr->e_entry;
    assert(c->pc == 0 && "The entry point of the program should be address 0.");
}