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Added|Changed|Fixed|Removed: Refactor
termux-exec especially for ch…
…anges in f261b26 for `system_linker_exec` - The `src/exec-variants.c` has been moved to `src/exec/exec-variants.c` which handles hooks into the entire `exec()` family of functions except `execve()`. The handling of `execve` done by `src/exe/termux-exec.c` has been moved to `src/exec/exec.c`. The `src/exe/termux-exec.c` now exclusively only defines the functions intercepted by `libtermux-exec.so` and directs them to their hooks in respective source files. - The `__attribute__((visibility("default")))` needs to be set for all the intercepted functions in `src/exe/termux-exec.c` as `libtermux-exec.so` is compiled with `-fvisibility=hidden`, so that no other function in the library other than ones explicitly labelled are exported. This can be confirmed by running `nm --demangle --dynamic --defined-only --extern-only /home/builder/.termux-build/termux-exec/src/build/usr/lib/libtermux-exec.so` after building the package. - Revert order of functions in `src/exec/exec_variants.c` back to the one in AOSP and uncomment the `NULL` path checks for `execvpe()` and add its original license to file header. Log entries are also added to each variant to know which variant was originally hooked. - Removed the singular `TERMUX_EXEC_OPTOUT` environment variable. Opt outs should be confined to specific hooks and logics. - Added the `bool` environment variable `TERMUX_EXEC__INTERCEPT_EXECVE` for whether `execve` would be hooked for shebang fix or `system_linker_exec`. The default value is `true`. The other wrapper functions in the `exec()` family of functions declared in `unistd.h` are always intercepted to solve some other issues on older Android versions, check [`libc/bionic/exec.cpp`](https://cs.android.com/android/platform/superproject/+/android-14.0.0_r1:bionic/libc/bionic/exec.cpp) git history. - Added the `string` `TERMUX_EXEC__SYSTEM_LINKER_EXEC` environment variable for whether to use `system_linker_exec` if `TERMUX_EXEC__INTERCEPT_EXECVE` is enabled. If set to `disable`, `system_linker_exec` will be disabled. If set to `enable`, then `system_linker_exec` will be enabled but only if required. If set to `force`, then `system_linker_exec` will be force enabled even if not required and is supported. The default value is `enable`. Check `should_system_linker_exec()` in `exec.h` and `exec.h` for more info and how its handled. Docs will be added in a later commit. The `system_linker_exec` will now engage for executable or interpreter paths that are under `TERMUX_APP__DATA_DIR` or `TERMUX_APP__LEGACY_DATA_DIR` instead of `TERMUX__ROOTFS` (`TERMUX_BASE_DIR`). - Read `ANDROID__BUILD_VERSION_SDK` environment variable exported by Termux app to get Android build version sdk, and if its not set, then from the `android_get_device_api_level()` call provided by `<android/api-level.h>`, which gets it from the system properties, which should be slower. - Port normalize and absolutize path functions from `portal-io` library and AOSP that has been tested on hundreds of test cases to handle all the required cases. - Fix the order for normalize, absolutize and replacing termux bin prefix for both executable path and interpreter, check comment in `execve_intercept()`. - Fix relative paths for interpreter path by absolutizing it. Previously, only prefix was being replaced. - Fix `argv[0]` for executing shell scripts where it should be set to the original interpreter set in the file as is instead of the `argv[0]` to `execve()` being hooked for the executable. - Increase buffer size for executable file shebang header from `256` to `340` defined by `FILE_HEADER__BUFFER_LEN` as per termux path limits, check comment in `exec.h` file and [Termux File Path Limits](https://github.com/termux/termux-packages/wiki/Termux-file-system-layout#file-path-limits) docs. - Decrease max length of valid `TERMUX__ROOTFS` from `200` to `86` defined by `TERMUX__ROOTFS_DIR_MAX_LEN`, check `termux_files.h` file and [Termux File Path Limits](https://github.com/termux/termux-packages/wiki/Termux-file-system-layout#file-path-limits) docs. - Add buffer overflow checks in `termux_prefix_path()` and return errors for it. - Fix replacing prefix if termux rootfs is `/` or `/system` and executable equals the bin directory itself instead of a subfile. - Fix `fexecve()` where executable path would be `/proc/self/fd/<n>` and checking if its under Termux app data directory directory would give wrong results. The `is_path_under_termux_app_data_dir()` function handles this by getting real path of file and ensuring that the real path is for the same file for which fd was open by comparing `stat.st_dev` and `stat.st_ino`. - Fix checking if executable is under Termux directories, like Termux app data directory (previously rootfs/base). Previously, `strstr(executable_path, termux_base_dir)` was used, which would check first occurrence of the substring `termux_base_dir` in `executable_path`, and not whether `executable_path` is under `termux_base_dir`. This is now properly handled by `is_path_in_dir_path()` via `is_path_under_termux_app_data_dir()`. - Do not use `TERMUX__PREFIX` to get Termux rootfs directory by getting its parent directory and use `TERMUX__ROOTFS` environment variable directly. There may also be cases where they `TERMUX__PREFIX` equals `TERMUX__ROOTFS`, and getting parent directory would result in wrong results. If environment variable is not set or is invalid as per `TERMUX__ROOTFS_DIR_MAX_LEN`, then we use the default Termux prefix for which package was compiled for as long as its executable and readable to ensure termux-exec was not compiled for a different package. - Fix the environment `envp` being copied twice during `execve` for system bin paths, once for unsetting `LD_` variables and then to set `TERMUX_EXEC__PROC_SELF_EXE`. The `modify_exec_env()` function now handles all changes to environment with a single copy. - Fix `TERMUX_EXEC__PROC_SELF_EXE` being set even if `system_linker_exec` is not being used on `targetSdkVersion <= 28`, etc, and also not being unset when going from `system_linker_exec` to direct execution like system binaries. Packages will be patched to detect if `system_linker_exec` is being used to modify their behaviour, which shouldn't be modified for direct execution. - The `modify_exec_args()` function now handles all changes to the arguments. - Fix issues where `errno` may already be set when `execve` is entered, check comment in `init()` function of `termux-exec.c` where it is set to `0`. - Fix hardcoded `com.termux` values being used, all constants are replaced during building including the root scope of environment variables that are read and as per `TERMUX_ENV__S_ROOT` defined in `properties.sh` of `termux-pacakges` as `TERMUX_`. - Fix `string_starts_with()` giving wrong results for `NULL` and empty strings. - Added logger framework with multiple log levels with log entries for all the important variable states to track logic. The singular `TERMUX_EXEC_DEBUG` environment variable has been removed. The `int` `TERMUX_EXEC__LOG_LEVEL` environment variable controls the log level based on `(OFF=0, NORMAL=1, DEBUG=2, VERBOSE=3, VVERBOSE=4 and VVVERBOSE=5)`. The default value is `1`. Normally, `termux-exec` does not log anything at default log level `1` (`NORMAL`) for hooks even and will require setting log level to `>= 2` (`DEBUG`) to see log messages. To enable `VVERBOSE` logging for a command, you can run something like `TERMUX_EXEC__LOG_LEVEL=4 id -u`. - Added `TERMUX_EXEC_PKG__VERSION` `Makefile` parameter that gets logged on hook for `termux-exec` package version currently installed. - Create or move all build files under the `build/` directory. It's better to build a directory structure for the files to be added to prefix under the `build/usr` directory than have a mix of using files under both `src/` and `build/` during installation. This way `src/` directory also doesn't get modified and will not contain the files with replaced constants that were created from `*.in` files. This also makes it easier to clean and build the deb since all built files exist under the same directory, which `termux-create-package` can also use with `source_recurse`. - Move unit tests from `termux-exec.c` to `tests/unit-tests.c` since tests shouldn't be in source files. - Added testing framework via `tests/termux-exec-tests.in` that calls `tests/unit-tests.c` to run unit tests, and `runtime-binary-tests.c` and `tests/runtime-script-tests.in` for runtime tests. Old tests files in random places have been removed. The testing is done for `termux-exec` and other termux internal packages including `termux-core`, `termux-tools`, `termux-am`, `termux-api`, `tudo` and `sudo` to ensure a fully working termux environment. The entire `exec()` family of functions is also tested by `runtime-binary-tests.c`. Currently, `termux-api` will not work in secondary users due to abstact namespace sockets being used. Docs will be added in a later commit. In future, tests can be moved to each package's own repo and a separate "tests caller" package can be added that runs tests for all packages that are installed. Tests can be run with `TERMUX_EXEC__LOG_LEVEL=1 "${TERMUX__PREFIX:-$PREFIX}/libexec/installed-tests/termux-exec/termux-exec-tests -vv all"`. - The recursive replacement of termux constants is done with `find -exec sed` with `TERMUX_CONSTANTS_SED_ARGS` passed to it. Using `foreach` with the `call` function for `replace-termux-constants` does not work for some reason if multiple files exists, because somehow function definition itself like `@sed` gets passed to `sed` command as argument. So `replace-termux-constants` is only called for individual files. The sed replacements surround arguments with double quotes instead of single quotes, so it could potentially break on more cases during shell expansion, although regex variables weren't being escaped before either. - The `termux-exec-package.json` will now have correct version and be consistent with `build.sh`, and also include tests files, which wasn't being done before. - The `termux-exec-package.json` previously had hardcoded `aarch64` as architecture, now we find and replace it for the compiler based on which predefined architecture macro is defined.
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