Merge pull request #501 from usertam/patch/clean-up-and-readme

Fix compiler warnings and update README.OSX

Author: wolfcw

README.OSX

@@ -166,3 +166,50 @@ The environment variable FAKETIME can be changed at application run-time
 and always takes precedence over other user-controlled settings. It can
 be re-set to 0 (zero) to work around potential incompatibilities or if
 you do not want libfaketime applied to your software.
+
+5) Working with the new arm64e system binaries in Apple Silicon
+---------------------------------------------------------------
+
+Since Apple Silicon, Apple started shipping system binaries compiled against
+the `arm64e` ABI. This new ABI enforces Pointer Authentication Codes (PACs),
+and enforces assembly instructions to sign and check pointer signatures to
+prevent malicious control flow altering.
+
+    $ file /bin/date
+    /bin/date: Mach-O universal binary with 2 architectures: [x86_64:Mach-O 64-bit executable x86_64] [arm64e:Mach-O 64-bit executable arm64e]
+    /bin/date (for architecture x86_64):    Mach-O 64-bit executable x86_64
+    /bin/date (for architecture arm64e):    Mach-O 64-bit executable arm64e
+
+Most importantly, the new `arm64e` ABI is incompatible with the normal `arm64`
+ABI we are used to; this is done so that everything `arm64e` is PAC-enforced.
+
+As a result, this will happen when we try to hook naive `arm64` libfaketime on
+system binaries (and vice versa with `arm64e` libfaketime on `arm64` binaries):
+
+    $ DYLD_INSERT_LIBRARIES=libfaketime.1.dylib /bin/date
+    dyld[5788]: terminating because inserted dylib 'libfaketime.1.dylib' could not be loaded:
+    tried: 'libfaketime.1.dylib' (mach-o file, but is an incompatible architecture (have 'arm64', need 'arm64e'))
+
+Since PR #497, we now compile libfaketime with a fat library/binary setup, so
+that we support both ABIs at the same time:
+
+    $ file libfaketime.1.dylib
+    libfaketime.1.dylib: Mach-O universal binary with 2 architectures: [arm64:Mach-O 64-bit dynamically linked shared library arm64] [arm64e:Mach-O 64-bit dynamically linked shared library arm64e]
+    libfaketime.1.dylib (for architecture arm64):   Mach-O 64-bit dynamically linked shared library arm64
+    libfaketime.1.dylib (for architecture arm64e):  Mach-O 64-bit dynamically linked shared library arm64e
+
+Unfortunately, Apple does not support running third-party `arm64e` code yet,
+since the ABI is still unstable. This means that you cannot use libfaketime
+on system `arm64e` binaries out of the box, at the time of writing.
+
+If you really need to, you may disable SIP in the recovery terminal:
+
+    (in recovery)       # csrutil disable
+
+And enable the experimental ABI after boot:
+
+    (in regular boot)   $ sudo nvram boot-args=-arm64e_preview_abi
+
+Then `arm64e` should work as-is. This use case is rather uncommon since most
+userspace binaries will remain `arm64` for the time being, until Apple really
+doubles down on `arm64e`. Regardless, we should be prepared for that.

src/libfaketime.c

@@ -208,10 +208,12 @@ static int          (*real_xstat)           (int, const char *, struct stat *);
 static int          (*real_fxstat)          (int, int, struct stat *);
 static int          (*real_fxstatat)        (int, int, const char *, struct stat *, int);
 static int          (*real_lxstat)          (int, const char *, struct stat *);
+#if !defined(__APPLE__) || !__DARWIN_ONLY_64_BIT_INO_T
 static int          (*real_xstat64)         (int, const char *, struct stat64 *);
 static int          (*real_fxstat64)        (int, int , struct stat64 *);
 static int          (*real_fxstatat64)      (int, int , const char *, struct stat64 *, int);
 static int          (*real_lxstat64)        (int, const char *, struct stat64 *);
+#endif
 #ifdef STATX_TYPE
 static int          (*real_statx)           (int dirfd, const char *pathname, int flags, unsigned int mask, struct statx *statxbuf);
 #endif
@@ -983,6 +985,7 @@ static inline void fake_statbuf (struct stat *buf) {
 #endif
 }
 
+#ifndef __APPLE__
 static inline void fake_stat64buf (struct stat64 *buf) {
 #ifndef st_atime
   lock_for_stat();
@@ -992,18 +995,13 @@ static inline void fake_stat64buf (struct stat64 *buf) {
   unlock_for_stat();
 #else
   lock_for_stat();
-#ifndef __APPLE__
-  fake_clock_gettime(CLOCK_REALTIME, &buf->st_ctim);
-  fake_clock_gettime(CLOCK_REALTIME, &buf->st_atim);
-  fake_clock_gettime(CLOCK_REALTIME, &buf->st_mtim);
-#else
   fake_clock_gettime(CLOCK_REALTIME, &buf->st_ctimespec);
   fake_clock_gettime(CLOCK_REALTIME, &buf->st_atimespec);
   fake_clock_gettime(CLOCK_REALTIME, &buf->st_mtimespec);
-#endif
   unlock_for_stat();
 #endif
 }
+#endif
 
 /* macOS dyld interposing uses the function's real name instead of real_name */
 #ifdef MACOS_DYLD_INTERPOSE
@@ -1113,42 +1111,34 @@ int __lxstat (int ver, const char *path, struct stat *buf)
 {
   STAT_HANDLER(lxstat, buf, ver, path, buf);
 }
-#endif
 
-#ifndef __APPLE__
 /* Contributed by Philipp Hachtmann in version 0.6 */
 int __xstat64 (int ver, const char *path, struct stat64 *buf)
 {
   STAT64_HANDLER(xstat64, buf, ver, path, buf);
 }
-#endif
 
-#ifndef __APPLE__
 /* Contributed by Philipp Hachtmann in version 0.6 */
 int __fxstat64 (int ver, int fildes, struct stat64 *buf)
 {
   STAT64_HANDLER(fxstat64, buf, ver, fildes, buf);
 }
-#endif
 
-#ifndef __APPLE__
 /* Added in v0.8 as suggested by Daniel Kahn Gillmor */
 #ifndef NO_ATFILE
 int __fxstatat64 (int ver, int fildes, const char *filename, struct stat64 *buf, int flag)
 {
   STAT64_HANDLER(fxstatat64, buf, ver, fildes, filename, buf, flag);
 }
 #endif
-#endif
 
-#ifndef __APPLE__
 /* Contributed by Philipp Hachtmann in version 0.6 */
 int __lxstat64 (int ver, const char *path, struct stat64 *buf)
 {
   STAT64_HANDLER(lxstat64, buf, ver, path, buf);
 }
-#endif
-#endif
+#endif  /* ifndef __APPLE__ */
+#endif  /* ifdef FAKE_STAT */
 
 #ifdef STATX_TYPE
 static inline void fake_statx_timestamp(struct statx_timestamp* p)
@@ -2689,10 +2679,12 @@ static void ftpl_really_init(void)
   real_fxstat =             dlsym(RTLD_NEXT, "__fxstat");
   real_fxstatat =           dlsym(RTLD_NEXT, "__fxstatat");
   real_lxstat =             dlsym(RTLD_NEXT, "__lxstat");
+#if !defined(__APPLE__) || !__DARWIN_ONLY_64_BIT_INO_T
   real_xstat64 =            dlsym(RTLD_NEXT,"__xstat64");
   real_fxstat64 =           dlsym(RTLD_NEXT, "__fxstat64");
   real_fxstatat64 =         dlsym(RTLD_NEXT, "__fxstatat64");
   real_lxstat64 =           dlsym(RTLD_NEXT, "__lxstat64");
+#endif
 #ifdef STATX_TYPE
   real_statx =              dlsym(RTLD_NEXT, "statx");
 #endif