Revert "[Sanitizers] Get link map on FreeBSD via documented API"

This reverts commit 92e267a94d, as it
appears Android is missing dlinfo(3).

compiler-rt/lib/sanitizer_common/sanitizer_fuchsia.cpp

@@ -66,10 +66,6 @@ uptr internal_getpid() {
   return pid;
 }
 
-int internal_dlinfo(void *handle, int request, void *p) {
-  UNIMPLEMENTED();
-}
-
 uptr GetThreadSelf() { return reinterpret_cast<uptr>(thrd_current()); }
 
 tid_t GetTid() { return GetThreadSelf(); }

compiler-rt/lib/sanitizer_common/sanitizer_libc.h

@@ -72,8 +72,6 @@ unsigned int internal_sleep(unsigned int seconds);
 uptr internal_getpid();
 uptr internal_getppid();
 
-int internal_dlinfo(void *handle, int request, void *p);
-
 // Threading
 uptr internal_sched_yield();
 

compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp

@@ -735,10 +735,6 @@ uptr internal_getppid() {
   return internal_syscall(SYSCALL(getppid));
 }
 
-int internal_dlinfo(void *handle, int request, void *p) {
-  return dlinfo(handle, request, p);
-}
-
 uptr internal_getdents(fd_t fd, struct linux_dirent *dirp, unsigned int count) {
 #if SANITIZER_FREEBSD
   return internal_syscall(SYSCALL(getdirentries), fd, (uptr)dirp, count, NULL);

compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp

@@ -208,10 +208,6 @@ uptr internal_getpid() {
   return getpid();
 }
 
-int internal_dlinfo(void *handle, int request, void *p) {
-  UNIMPLEMENTED();
-}
-
 int internal_sigaction(int signum, const void *act, void *oldact) {
   return sigaction(signum,
                    (const struct sigaction *)act, (struct sigaction *)oldact);

compiler-rt/lib/sanitizer_common/sanitizer_netbsd.cpp

@@ -265,11 +265,6 @@ uptr internal_getppid() {
   return _REAL(getppid);
 }
 
-int internal_dlinfo(void *handle, int request, void *p) {
-  DEFINE__REAL(int, dlinfo, void *a, int b, void *c);
-  return _REAL(dlinfo, handle, request, p);
-}
-
 uptr internal_getdents(fd_t fd, void *dirp, unsigned int count) {
   DEFINE__REAL(int, __getdents30, int a, void *b, size_t c);
   return _REAL(__getdents30, fd, dirp, count);

compiler-rt/lib/sanitizer_common/sanitizer_platform_limits_freebsd.cpp

@@ -52,7 +52,6 @@
 #include <netinet/ip_mroute.h>
 //
 #include <dirent.h>
-#include <dlfcn.h>
 #include <fstab.h>
 #include <fts.h>
 #include <glob.h>
@@ -87,15 +86,9 @@
 
 // Include these after system headers to avoid name clashes and ambiguities.
 #include "sanitizer_internal_defs.h"
-#include "sanitizer_libc.h"
 #include "sanitizer_platform_limits_freebsd.h"
 
 namespace __sanitizer {
-void *__sanitizer_get_link_map_by_dlopen_handle(void *handle) {
-  void *p = nullptr;
-  return internal_dlinfo(handle, RTLD_DI_LINKMAP, &p) == 0 ? p : nullptr;
-}
-
 unsigned struct_cap_rights_sz = sizeof(cap_rights_t);
 unsigned struct_utsname_sz = sizeof(struct utsname);
 unsigned struct_stat_sz = sizeof(struct stat);

compiler-rt/lib/sanitizer_common/sanitizer_platform_limits_freebsd.h

@@ -20,15 +20,15 @@
 #include "sanitizer_platform.h"
 #include "sanitizer_platform_limits_posix.h"
 
+// FreeBSD's dlopen() returns a pointer to an Obj_Entry structure that
+// incorporates the map structure.
+#define GET_LINK_MAP_BY_DLOPEN_HANDLE(handle) \
+  ((link_map *)((handle) == nullptr ? nullptr : ((char *)(handle) + 560)))
 // Get sys/_types.h, because that tells us whether 64-bit inodes are
 // used in struct dirent below.
 #include <sys/_types.h>
 
 namespace __sanitizer {
-void *__sanitizer_get_link_map_by_dlopen_handle(void *handle);
-#define GET_LINK_MAP_BY_DLOPEN_HANDLE(handle) \
-  (link_map *)__sanitizer_get_link_map_by_dlopen_handle(handle)
-
 extern unsigned struct_utsname_sz;
 extern unsigned struct_stat_sz;
 #if defined(__powerpc64__)

compiler-rt/lib/sanitizer_common/sanitizer_platform_limits_netbsd.cpp

@@ -213,7 +213,6 @@ struct urio_command {
 #include <dev/wscons/wsdisplay_usl_io.h>
 #include <fs/autofs/autofs_ioctl.h>
 #include <dirent.h>
-#include <dlfcn.h>
 #include <glob.h>
 #include <grp.h>
 #include <ifaddrs.h>
@@ -259,15 +258,9 @@ struct urio_command {
 
 // Include these after system headers to avoid name clashes and ambiguities.
 #include "sanitizer_internal_defs.h"
-#include "sanitizer_libc.h"
 #include "sanitizer_platform_limits_netbsd.h"
 
 namespace __sanitizer {
-void *__sanitizer_get_link_map_by_dlopen_handle(void* handle) {
-  void *p = nullptr;
-  return internal_dlinfo(handle, RTLD_DI_LINKMAP, &p) == 0 ? p : nullptr;
-}
-
 unsigned struct_utsname_sz = sizeof(struct utsname);
 unsigned struct_stat_sz = sizeof(struct stat);
 unsigned struct_rusage_sz = sizeof(struct rusage);

compiler-rt/lib/sanitizer_common/sanitizer_platform_limits_netbsd.h

@@ -19,11 +19,18 @@
 #include "sanitizer_internal_defs.h"
 #include "sanitizer_platform.h"
 
-namespace __sanitizer {
-void *__sanitizer_get_link_map_by_dlopen_handle(void *handle);
-# define GET_LINK_MAP_BY_DLOPEN_HANDLE(handle) \
-    (link_map *)__sanitizer_get_link_map_by_dlopen_handle(handle)
+#define _GET_LINK_MAP_BY_DLOPEN_HANDLE(handle, shift) \
+  ((link_map *)((handle) == nullptr ? nullptr : ((char *)(handle) + (shift))))
 
+#if defined(__x86_64__)
+#define GET_LINK_MAP_BY_DLOPEN_HANDLE(handle) \
+  _GET_LINK_MAP_BY_DLOPEN_HANDLE(handle, 264)
+#elif defined(__i386__)
+#define GET_LINK_MAP_BY_DLOPEN_HANDLE(handle) \
+  _GET_LINK_MAP_BY_DLOPEN_HANDLE(handle, 136)
+#endif
+
+namespace __sanitizer {
 extern unsigned struct_utsname_sz;
 extern unsigned struct_stat_sz;
 extern unsigned struct_rusage_sz;

compiler-rt/lib/sanitizer_common/sanitizer_rtems.cpp

@@ -49,10 +49,6 @@ uptr internal_getpid() {
   return getpid();
 }
 
-int internal_dlinfo(void *handle, int request, void *p) {
-  UNIMPLEMENTED();
-}
-
 bool FileExists(const char *filename) {
   struct stat st;
   if (stat(filename, &st))

compiler-rt/lib/sanitizer_common/sanitizer_win.cpp

@@ -94,10 +94,6 @@ uptr internal_getpid() {
   return GetProcessId(GetCurrentProcess());
 }
 
-int internal_dlinfo(void *handle, int request, void *p) {
-  UNIMPLEMENTED();
-}
-
 // In contrast to POSIX, on Windows GetCurrentThreadId()
 // returns a system-unique identifier.
 tid_t GetTid() {