Initial Implementation of ELF

1 files changed, 68 insertions, 0 deletions

diff --git a/elf.c b/elf.c
new file mode 100755
index 0000000..2219d5f
--- /dev/null
+++ b/elf.c
@@ -0,0 +1,68 @@
+#include "elf.h"
+#include <stdio.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <arpa/inet.h>
+
+static inline bool IsBigEndian(void);
+
+/* Elf Header for Little Endian Machines */
+const uint8_t e_ident_le[EI_NIDENT] = {
+	0x7f, 0x45, 0x4c, 0x46,	// ELF Magic Number
+	BIT_WIDTH,				// 32-bit format
+	_LITTLE_ENDIAN_,		// Little Endian
+	ELF_VERSION,			// ELF Version
+	0x00,					// Target OS
+	0x00,					// Target ABI
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00	// Padding
+};
+
+/* Elf Header for Big Endian Machines */
+const uint8_t e_ident_be[EI_NIDENT] = {
+	0x7f, 0x45, 0x4c, 0x46,	// ELF Magic Number
+	BIT_WIDTH,				// 32-bit format
+	_BIG_ENDIAN_,			// Big Endian
+	ELF_VERSION,			// ELF Version
+	0x00,					// Target OS
+	0x00,					// Target ABI
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00	// Padding
+};
+
+/* ReadElf: Read the elf header into e from file fp */
+ElfHeader_t ReadElf(FILE *fp) {
+	ElfHeader_t e;
+	fread(&e, sizeof(e), 1, fp);
+	if (ferror(fp)) {
+		perror("ReadElf");
+	}
+	return e;
+}
+
+/* ValidateElf: Validate the elf header for the given system */
+bool ValidateElf(ElfHeader_t e) {
+	const uint8_t * const e_ident = IsBigEndian() ? e_ident_be : e_ident_le;
+	for (size_t i = 0; i < EI_NIDENT; i++) {
+		if (e.e_ident[i] != e_ident[i]) {
+			return false;
+		}
+	}
+	if (e.e_machine != MIPS || e.e_version != ELF_VERSION ||
+			e.e_type != ET_EXEC || e.e_phentsize != sizeof(ProgramHeader_t)) {
+		return false;
+	}
+	return true;
+}
+
+/* ReadProgramHeader: Read n program headers into array p of size n from file
+ * fp */
+void ReadProgramHeader(size_t n, ProgramHeader_t p[n], FILE *fp) {
+	fread(p, sizeof(ProgramHeader_t), n, fp);
+	if (ferror(fp)) {
+		perror("ReadElf");
+	}
+}
+
+static inline bool IsBigEndian(void) {
+	int32_t x = 10;
+	return x == htonl(x);
+}