Implement dynamic TLS accesses and allocation
Initialize a thread's DTV to an empty zeroed DTV. Allocate the DTV and
any ELF module's TLS segment on-demand in __tls_get_addr. Use a generation
counter, incremented in the linker, to signal when threads should
update/reallocate their DTV objects.
A generation count of 0 always indicates the constant zero DTV.
Once a DTV is allocated, it isn't freed until the thread exits, because
a signal handler could interrupt the fast path of __tls_get_addr between
accessing the DTV slot and reading a field of the DTV. Bionic keeps a
linked list of DTV objects so it can free them at thread-exit.
Dynamic TLS memory is allocated using a BionicAllocator instance in
libc_shared_globals. For async-signal safety, access to the
linker/libc-shared state is protected by first blocking signals, then by
acquiring the reader-writer lock, TlsModules::rwlock. A write lock is
needed to allocate or free memory.
In pthread_exit, unconditionally block signals before freeing dynamic
TLS memory or freeing the shadow call stack.
ndk_cruft.cpp: Avoid including pthread_internal.h inside an extern "C".
(The header now includes a C++ template that doesn't compile inside
extern "C".)
Bug: http://b/78026329
Bug: http://b/123094171
Test: bionic unit tests
Change-Id: I3c9b12921c9e68b33dcc1d1dd276bff364eff5d7
diff --git a/linker/linker_soinfo.h b/linker/linker_soinfo.h
index 14571de..3499cf7 100644
--- a/linker/linker_soinfo.h
+++ b/linker/linker_soinfo.h
@@ -35,6 +35,7 @@
#include "private/bionic_elf_tls.h"
#include "linker_namespaces.h"
+#include "linker_tls.h"
#define FLAG_LINKED 0x00000001
#define FLAG_EXE 0x00000004 // The main executable
@@ -102,14 +103,9 @@
// TODO(dimitry): remove reference from soinfo member functions to this class.
class VersionTracker;
-// The first ELF TLS module has ID 1. Zero is reserved for the first word of
-// the DTV, a generation count, and unresolved weak symbols also use module
-// ID 0.
-static constexpr size_t kUninitializedModuleId = 0;
-
struct soinfo_tls {
TlsSegment segment;
- size_t module_id = kUninitializedModuleId;
+ size_t module_id = kTlsUninitializedModuleId;
};
#if defined(__work_around_b_24465209__)