termux-elf-cleaner: Better error messages

packages/termux-tools/termux-elf-cleaner.cpp

@@ -20,17 +20,17 @@
 template<typename ElfHeaderType /*Elf{32,64}_Ehdr*/,
 	 typename ElfSectionHeaderType /*Elf{32,64}_Shdr*/,
 	 typename ElfDynamicSectionEntryType /* Elf{32,64}_Dyn */>
-bool process_elf(uint8_t* bytes, size_t elf_file_size)
+bool process_elf(uint8_t* bytes, size_t elf_file_size, char const* file_name)
 {
 	if (sizeof(ElfSectionHeaderType) > elf_file_size) {
-		fprintf(stderr, "ERROR: Elf header would end at %zu but file size only %zu\n", sizeof(ElfSectionHeaderType), elf_file_size);
+		fprintf(stderr, "termux-elf-cleaner: Elf header for '%s' would end at %zu but file size only %zu\n", file_name, sizeof(ElfSectionHeaderType), elf_file_size);
 		return false;
 	}
 	ElfHeaderType* elf_hdr = reinterpret_cast<ElfHeaderType*>(bytes);
 
 	size_t last_section_header_byte = elf_hdr->e_shoff + sizeof(ElfSectionHeaderType) * elf_hdr->e_shnum;
 	if (last_section_header_byte > elf_file_size) {
-		fprintf(stderr, "ERROR: Section header would end at %zu but file size only %zu\n", last_section_header_byte, elf_file_size);
+		fprintf(stderr, "termux-elf-cleaner: Section header for '%s' would end at %zu but file size only %zu\n", file_name, last_section_header_byte, elf_file_size);
 		return false;
 	}
 	ElfSectionHeaderType* section_header_table = reinterpret_cast<ElfSectionHeaderType*>(bytes + elf_hdr->e_shoff);
@@ -40,7 +40,7 @@ bool process_elf(uint8_t* bytes, size_t elf_file_size)
 		if (section_header_entry->sh_type == SHT_DYNAMIC) {
 			size_t const last_dynamic_section_byte = section_header_entry->sh_offset + section_header_entry->sh_size;
 			if (last_dynamic_section_byte > elf_file_size) {
-				fprintf(stderr, "ERROR: Dynamic section would end at %zu but file size only %zu\n", last_dynamic_section_byte, elf_file_size);
+				fprintf(stderr, "termux-elf-cleaner: Dynamic section for '%s' would end at %zu but file size only %zu\n", file_name, last_dynamic_section_byte, elf_file_size);
 				return false;
 			}
 
@@ -67,7 +67,7 @@ bool process_elf(uint8_t* bytes, size_t elf_file_size)
 					case DT_RUNPATH: removed_name = "DT_RUNPATH"; break;
 				}
 				if (removed_name != nullptr) {
-					printf("Removing the %s dynamic section entry\n", removed_name);
+					printf("termux-elf-cleaner: Removing the %s dynamic section entry from '%s'\n", removed_name, file_name);
 					// Tag the entry with DT_NULL and put it last:
 					dynamic_section_entry->d_tag = DT_NULL;
 					// Decrease j to process new entry index:
@@ -80,7 +80,7 @@ bool process_elf(uint8_t* bytes, size_t elf_file_size)
 }
 
 
-int main(int argc, char **argv)
+int main(int argc, char const** argv)
 {
 	if (argc < 2 || (argc == 2 && strcmp(argv[1], "-h")==0)) {
 		fprintf(stderr, "usage: %s <filename>\n", argv[0]);
@@ -90,7 +90,8 @@ int main(int argc, char **argv)
 	}
 
 	for (int i = 1; i < argc; i++) {
-		int fd = open(argv[i], O_RDWR);
+		char const* file_name = argv[i];
+		int fd = open(file_name, O_RDWR);
 		if (fd < 0) { perror("open()"); return 1; }
 
 		struct stat st;
@@ -103,19 +104,25 @@ int main(int argc, char **argv)
 
 		uint8_t* bytes = reinterpret_cast<uint8_t*>(mem);
 		if (!(bytes[0] == 0x7F && bytes[1] == 'E' && bytes[2] == 'L' && bytes[3] == 'F')) {
+			// Not the ELF magic number.
 			munmap(mem, st.st_size);
 			close(fd);
 			continue;
 		}
 
-		uint8_t bit_value = bytes[4];
-		if (!(bit_value == 1 || bit_value == 2)) {
-			printf("ERROR: Incorrect bit value: %d\n", bit_value);
-			return 1;
-		} else if (bit_value == 1) {
-			if (!process_elf<Elf32_Ehdr, Elf32_Shdr, Elf32_Dyn>(bytes, st.st_size)) return 1;
+		if (bytes[/*EI_DATA*/5] != 1) {
+			fprintf(stderr, "termux-elf-cleaner: Not little endianness in '%s'\n", file_name);
+			continue;
+		}
+
+		uint8_t const bit_value = bytes[/*EI_CLASS*/4];
+		if (bit_value == 1) {
+			if (!process_elf<Elf32_Ehdr, Elf32_Shdr, Elf32_Dyn>(bytes, st.st_size, file_name)) return 1;
+		} else if (bit_value == 2) {
+			if (!process_elf<Elf64_Ehdr, Elf64_Shdr, Elf64_Dyn>(bytes, st.st_size, file_name)) return 1;
 		} else {
-			if (!process_elf<Elf64_Ehdr, Elf64_Shdr, Elf64_Dyn>(bytes, st.st_size)) return 1;
+			printf("termux-elf-cleaner: Incorrect bit value %d in '%s'\n", bit_value, file_name);
+			return 1;
 		}
 
 		if (msync(mem, st.st_size, MS_SYNC) < 0) { perror("msync()"); return 1; }