Initial commit

1 files changed, 141 insertions, 0 deletions

diff --git a/write_elf.c b/write_elf.c
new file mode 100644
index 0000000..62b6cd3
--- /dev/null
+++ b/write_elf.c
@@ -0,0 +1,141 @@
+#include "instructions.h"
+#include "registers.h"
+#include <elf.h>
+#include <err.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+unsigned char some_opcodes[]  = {MOVDI(REG_EAX, 0x3c),
+                                 // 0xb8, 0x3c, 0x00, 0x00, 0x00,
+                                 MOVDI(REG_EDI, 0x41),
+                                 // 0xbf, 0x41, 0x00, 0x00, 0x00,
+                                 SYSCALL};
+unsigned int some_opcodes_len = sizeof(some_opcodes) / sizeof(some_opcodes[0]);
+
+int
+write_elf(char* restrict file, size_t opcodes_len, char* restrict opcodes) {
+  int error                   = 0;
+
+  Elf64_Phdr header_program[] = {
+    //{
+    //  .p_type   = PT_LOAD,
+    //  .p_flags  = PF_R,
+    //  .p_offset = 0, /* Segment file offset */
+    //  .p_vaddr  = 0x400000, /* Segment virtual address */
+    //  .p_paddr  = 0x400000,        /* Segment physical address */
+    //  .p_filesz = 0xb0,        /* Segment size in file */
+    //  .p_memsz  = 0xb0,      /* Segment size in memory */
+    //  .p_align  = 0x1000, /* Segment alignment */
+    //},
+    {
+     .p_type  = PT_LOAD,
+     .p_flags = PF_X | PF_R,
+     .p_offset =
+        sizeof(Elf64_Ehdr) + sizeof(Elf64_Phdr), /* Segment file offset */
+      .p_vaddr  = 0x400000 + sizeof(Elf64_Ehdr) +
+                  sizeof(Elf64_Phdr), /* Segment virtual address */
+      .p_paddr  = 0x400000 + sizeof(Elf64_Ehdr) +
+                  sizeof(Elf64_Phdr), /* Segment physical address */
+      .p_filesz = opcodes_len,        /* Segment size in file */
+      .p_memsz  = opcodes_len,        /* Segment size in memory */
+      .p_align  = 0x1,                /* Segment alignment */
+    },
+  };
+
+  Elf64_Shdr header_section[] = {
+    {
+     // .init
+     // Index in section header string table
+     .sh_name      = 0,
+     .sh_type      = 0,
+     .sh_flags     = 0,
+     .sh_addr      = 0,
+     .sh_offset    = 0,
+     .sh_size      = 0,
+     .sh_link      = 0,
+     .sh_info      = 0,
+     .sh_addralign = 0,
+     .sh_entsize   = 0,
+     },
+    {
+     // .init
+     // Index in section header string table
+     .sh_name   = 0,
+     .sh_type   = SHT_PROGBITS,
+     .sh_flags  = SHF_ALLOC | SHF_EXECINSTR,
+     .sh_addr   = 0x401000,
+     .sh_offset = 0x1000,
+     .sh_size   = opcodes_len,
+     /* todo: deps on type */
+     .sh_link = 0,
+     /* todo: deps on type */
+     .sh_info      = 0,
+     .sh_addralign = 4,
+     .sh_entsize   = 0,
+     },
+    {
+     // .shstrtab Section Header String Table
+     // Index in section header string table
+     .sh_name   = 1,
+     .sh_type   = SHT_STRTAB,
+     .sh_flags  = 0,
+     .sh_addr   = 0x100,
+     .sh_offset = 0x2000,
+     .sh_size   = opcodes_len,
+     /* todo: deps on type */
+     .sh_link = 0,
+     /* todo: deps on type */
+     .sh_info      = 0,
+     .sh_addralign = 1,
+     .sh_entsize   = 0,
+     },
+  };
+
+  unsigned char string_header_table[] = {0, '.', 'i', 'n', 'i', 't', 0};
+
+  Elf64_Ehdr header                   = {
+    // memset(&header, 0, sizeof(Elf64_Ehdr));
+    .e_ident   = {ELFMAG0, ELFMAG1, ELFMAG2, ELFMAG3, ELFCLASS64, ELFDATA2LSB,
+                  EV_CURRENT, ELFOSABI_SYSV},
+    .e_type    = ET_EXEC,
+    .e_machine = EM_X86_64,
+    .e_version = EV_CURRENT,
+    .e_entry   = 0x400000 + sizeof(Elf64_Ehdr) +
+                 sizeof(Elf64_Phdr), // point to VIRTUAL address of _start
+    .e_phoff   = sizeof(Elf64_Ehdr)  /* Program header table offset */,
+    .e_shoff   = 0, //  sizeof(Elf64_Ehdr) + sizeof(header_program)  /* Section
+  // header table offset */,
+    .e_flags     = 0,
+    .e_ehsize    = sizeof(Elf64_Ehdr),
+    .e_phentsize = sizeof(Elf64_Phdr),
+    // If larger than PN_XNUM, then set to PN_XNUM and store real number in
+    // sh_info of first program header entry
+    .e_phnum     = 1,
+    .e_shentsize = sizeof(header_section[0]),
+    // If larger than SHN_LORESERVE, then set to 0 and store real number in
+    // sh_size of first section header entry
+    .e_shnum = 0, //  sizeof(header_section) / sizeof(header_section[0]),
+    // If larger than SHN_LORESERVE, then set to SHN_XINDEX and store real index
+    // in
+    // sh_link of first section header entry
+    .e_shstrndx = 0,
+  };
+
+  size_t bytes_written = 0;
+  FILE* fd             = fopen(file, "w");
+
+  fwrite(&header, sizeof(Elf64_Ehdr), 1, fd);
+  fwrite(&header_program, sizeof(Elf64_Phdr),
+         sizeof(header_program) / sizeof(header_program[0]), fd);
+  // fseek(fd, 0x1000, SEEK_SET);
+
+  do {
+    bytes_written += fwrite(opcodes, sizeof(char), opcodes_len, fd);
+  } while (bytes_written != opcodes_len);
+  error = fclose(fd);
+  if (error) {
+    err(EXIT_FAILURE, "no way");
+  }
+  return 0;
+}