exe: implement querying of executable metadata from simple elf executables

src/exe.c

@@ -0,0 +1,79 @@
+#include "exe.h"
+
+#include "elf.h"
+
+static enum ec3_status get_elf_executable_info(
+	FILE *fp,
+	struct ec3_tag_executable_info *out)
+{
+	elf_ehdr_t hdr;
+	fseek(fp, 0, SEEK_SET);
+	size_t r = fread(&hdr, sizeof hdr, 1, fp);
+	if (r != 1) {
+		return EC3_ERR_IO_FAILURE;
+	}
+
+	out->exe_elf.elf_entry = hdr.e_entry;
+
+	bool text_found = false, data_found = false;
+
+	for (size_t i = 0; i < hdr.e_phnum; i++) {
+		elf_phdr_t phdr;
+		size_t offset = hdr.e_phoff + (i * hdr.e_phentsize);
+		fseek(fp, offset, SEEK_SET);
+		r = fread(&phdr, sizeof phdr, 1, fp);
+
+		if (r != 1) {
+			return EC3_ERR_IO_FAILURE;
+		}
+
+		if (phdr.p_type != PT_LOAD) {
+			continue;
+		}
+
+		if ((phdr.p_flags & (PF_R | PF_X)) == (PF_R | PF_X)) {
+			if (text_found) {
+				out->exe_format = EC3_EXEC_OTHER;
+				return EC3_SUCCESS;
+			}
+
+			out->exe_elf.elf_text_offset = phdr.p_offset;
+			out->exe_elf.elf_text_filesz = phdr.p_filesz;
+			out->exe_elf.elf_text_vaddr = phdr.p_vaddr;
+			out->exe_elf.elf_text_memsz = phdr.p_memsz;
+			out->exe_elf.elf_text_align = phdr.p_align;
+			text_found = true;
+		}
+
+		if ((phdr.p_flags & (PF_R | PF_W)) == (PF_R | PF_W)) {
+			if (data_found) {
+				out->exe_format = EC3_EXEC_OTHER;
+				return EC3_SUCCESS;
+			}
+
+			out->exe_elf.elf_data_offset = phdr.p_offset;
+			out->exe_elf.elf_data_filesz = phdr.p_filesz;
+			out->exe_elf.elf_data_vaddr = phdr.p_vaddr;
+			out->exe_elf.elf_data_memsz = phdr.p_memsz;
+			out->exe_elf.elf_data_align = phdr.p_align;
+			data_found = true;
+		}
+	}
+
+	return EC3_SUCCESS;
+}
+
+enum ec3_status get_executable_info_from_file(
+	FILE *fp,
+	enum ec3_executable_format format,
+	struct ec3_tag_executable_info *out)
+{
+	out->exe_format = format;
+
+	switch (format) {
+	case EC3_EXEC_ELF:
+		return get_elf_executable_info(fp, out);
+	default:
+		return EC3_SUCCESS;
+	}
+}