Expose libc_shared_globals to libc.so with symbol
Previously, the address of the global variable was communicated from the
dynamic linker to libc.so using a field of KernelArgumentBlock, which is
communicated using the TLS_SLOT_BIONIC_PREINIT slot.
As long as this function isn't called during relocations (i.e. while
executing an ifunc), it always return a non-NULL value. If it's called
before its PLT entry is relocated, I expect a crash.
I removed the __libc_init_shared_globals function. It's currently empty,
and I don't think there's one point in libc's initialization where
shared globals should be initialized.
Bug: http://b/25751302
Test: bionic unit tests
Change-Id: I614d25e7ef5e0d2ccc40d5c821dee10f1ec61c2e
diff --git a/linker/dlfcn.cpp b/linker/dlfcn.cpp
index 45ae6ed..5ae7b9b 100644
--- a/linker/dlfcn.cpp
+++ b/linker/dlfcn.cpp
@@ -38,6 +38,7 @@
#include <android/api-level.h>
#include <bionic/pthread_internal.h>
+#include "private/bionic_globals.h"
#include "private/bionic_tls.h"
#include "private/ScopedPthreadMutexLocker.h"
@@ -86,6 +87,7 @@
const void* caller_addr) __LINKER_PUBLIC__;
void __loader_add_thread_local_dtor(void* dso_handle) __LINKER_PUBLIC__;
void __loader_remove_thread_local_dtor(void* dso_handle) __LINKER_PUBLIC__;
+libc_shared_globals* __loader_shared_globals() __LINKER_PUBLIC__;
#if defined(__arm__)
_Unwind_Ptr __loader_dl_unwind_find_exidx(_Unwind_Ptr pc, int* pcount) __LINKER_PUBLIC__;
#endif
@@ -299,6 +301,10 @@
decrement_dso_handle_reference_counter(dso_handle);
}
+libc_shared_globals* __loader_shared_globals() {
+ return __libc_shared_globals();
+}
+
static uint8_t __libdl_info_buf[sizeof(soinfo)] __attribute__((aligned(8)));
static soinfo* __libdl_info = nullptr;
diff --git a/linker/ld_android.cpp b/linker/ld_android.cpp
index 0528cd8..152c2e2 100644
--- a/linker/ld_android.cpp
+++ b/linker/ld_android.cpp
@@ -53,6 +53,7 @@
__strong_alias(__loader_dlvsym, __internal_linker_error);
__strong_alias(__loader_add_thread_local_dtor, __internal_linker_error);
__strong_alias(__loader_remove_thread_local_dtor, __internal_linker_error);
+__strong_alias(__loader_shared_globals, __internal_linker_error);
#if defined(__arm__)
__strong_alias(__loader_dl_unwind_find_exidx, __internal_linker_error);
#endif
diff --git a/linker/linker.arm.map b/linker/linker.arm.map
index a58e7c8..be438ca 100644
--- a/linker/linker.arm.map
+++ b/linker/linker.arm.map
@@ -22,6 +22,7 @@
__loader_dl_unwind_find_exidx;
__loader_add_thread_local_dtor;
__loader_remove_thread_local_dtor;
+ __loader_shared_globals;
rtld_db_dlactivity;
local:
*;
diff --git a/linker/linker.generic.map b/linker/linker.generic.map
index 45bb0b5..f3c01c0 100644
--- a/linker/linker.generic.map
+++ b/linker/linker.generic.map
@@ -21,6 +21,7 @@
__loader_android_get_exported_namespace;
__loader_add_thread_local_dtor;
__loader_remove_thread_local_dtor;
+ __loader_shared_globals;
rtld_db_dlactivity;
local:
*;
diff --git a/linker/linker_main.cpp b/linker/linker_main.cpp
index 66766fe..963e82c 100644
--- a/linker/linker_main.cpp
+++ b/linker/linker_main.cpp
@@ -622,12 +622,6 @@
// couldn't make system calls on x86 at that point, but we can now...
if (!tmp_linker_so.protect_relro()) __linker_cannot_link(args.argv[0]);
- // Initialize the linker/libc.so shared global inside the linker.
- static libc_shared_globals shared_globals;
- __libc_shared_globals = &shared_globals;
- __libc_init_shared_globals(&shared_globals);
- args.shared_globals = __libc_shared_globals;
-
// Initialize the linker's static libc's globals
__libc_init_globals(args);
@@ -655,12 +649,12 @@
exit(0);
}
exe_to_load = args.argv[1];
- __libc_shared_globals->initial_linker_arg_count = 1;
+ __libc_shared_globals()->initial_linker_arg_count = 1;
}
// store argc/argv/envp to use them for calling constructors
- g_argc = args.argc - __libc_shared_globals->initial_linker_arg_count;
- g_argv = args.argv + __libc_shared_globals->initial_linker_arg_count;
+ g_argc = args.argc - __libc_shared_globals()->initial_linker_arg_count;
+ g_argv = args.argv + __libc_shared_globals()->initial_linker_arg_count;
g_envp = args.envp;
// Initialize static variables. Note that in order to