X-Git-Url: https://git.distorted.org.uk/~mdw/termux-packages/blobdiff_plain/99dd1a492e62e8b1483e856d8b94ed9ef0d5f523..0ae97c5e985892744202a4d264b268f887eb3c0d:/packages/termux-elf-cleaner/termux-elf-cleaner.cpp

diff --git a/packages/termux-elf-cleaner/termux-elf-cleaner.cpp b/packages/termux-elf-cleaner/termux-elf-cleaner.cpp
new file mode 100644
index 00000000..83a4e405
--- /dev/null
+++ b/packages/termux-elf-cleaner/termux-elf-cleaner.cpp
@@ -0,0 +1,147 @@
+#include <algorithm>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#ifdef __APPLE__
+# include "elf.h"
+#else
+# include <elf.h>
+#endif
+
+#define DT_VERNEEDED 0x6ffffffe
+#define DT_VERNEEDNUM 0x6fffffff
+
+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, char const* file_name)
+{
+	if (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, "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);
+
+	for (unsigned int i = 1; i < elf_hdr->e_shnum; i++) {
+		ElfSectionHeaderType* section_header_entry = section_header_table + i;
+		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, "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;
+			}
+
+			size_t const dynamic_section_entries = section_header_entry->sh_size / sizeof(ElfDynamicSectionEntryType);
+			ElfDynamicSectionEntryType* const dynamic_section =
+				reinterpret_cast<ElfDynamicSectionEntryType*>(bytes + section_header_entry->sh_offset);
+
+			unsigned int last_nonnull_entry_idx = 0;
+			for (unsigned int j = dynamic_section_entries - 1; j > 0; j--) {
+				ElfDynamicSectionEntryType* dynamic_section_entry = dynamic_section + j;
+				if (dynamic_section_entry->d_tag != DT_NULL) {
+					last_nonnull_entry_idx = j;
+					break;
+				}
+			}
+
+			for (unsigned int j = 0; j < dynamic_section_entries; j++) {
+				ElfDynamicSectionEntryType* dynamic_section_entry = dynamic_section + j;
+				char const* removed_name = nullptr;
+				switch (dynamic_section_entry->d_tag) {
+					case DT_VERNEEDED: removed_name = "DT_VERNEEDED"; break;
+					case DT_VERNEEDNUM: removed_name = "DT_VERNEEDNUM"; break;
+					case DT_VERDEF: removed_name = "DT_VERDEF"; break;
+					case DT_VERDEFNUM: removed_name = "DT_VERDEFNUM"; break;
+					case DT_RPATH: removed_name = "DT_RPATH"; break;
+					case DT_RUNPATH: removed_name = "DT_RUNPATH"; break;
+				}
+				if (removed_name != nullptr) {
+					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:
+					std::swap(dynamic_section[j--], dynamic_section[last_nonnull_entry_idx--]);
+				}
+			}
+		}
+	}
+	return true;
+}
+
+
+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]);
+		fprintf(stderr, "       Processes ELF files to remove DT_VERNEEDED, DT_VERNEEDNUM, DT_RPATH\n"
+				"       and DT_RUNPATH entries (which the Android linker warns about)\n");
+		return 1;
+	}
+
+	for (int i = 1; i < argc; i++) {
+		char const* file_name = argv[i];
+		int fd = open(file_name, O_RDWR);
+		if (fd < 0) {
+			char* error_message;
+			if (asprintf(&error_message, "open(\"%s\")", file_name) == -1) error_message = (char*) "open()";
+			perror(error_message);
+			return 1;
+		}
+
+		struct stat st;
+		if (fstat(fd, &st) < 0) { perror("fstat()"); return 1; }
+
+		if (st.st_size < (long long) sizeof(Elf32_Ehdr)) {
+			close(fd);
+			continue;
+		}
+
+		void* mem = mmap(0, st.st_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+		if (mem == MAP_FAILED) { perror("mmap()"); return 1; }
+
+		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;
+		}
+
+		if (bytes[/*EI_DATA*/5] != 1) {
+			fprintf(stderr, "termux-elf-cleaner: Not little endianness in '%s'\n", file_name);
+			munmap(mem, st.st_size);
+			close(fd);
+			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 {
+			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; }
+
+		munmap(mem, st.st_size);
+		close(fd);
+	}
+	return 0;
+}
+