Commit graph

1222 commits

Author SHA1 Message Date
Jiyong Park
b66a78b2aa linker namespace name is duped when the namespace is created
A linker namespace lives longer than its caller. It is never deleted
once created in a process. Currently, the pointer to the name is simply
copied which results dangling reference when the name is actually from
temporary objects like std::object. Fixing the issue by strdup'ing the
name upon namespace creation.

Bug: 130388701
Test: atest CtsJniTestCases; the log does not show broken error messages
like
unexpected dlerror: dlopen failed: library "/system/lib64/android.frameworks.cameraservice.common@2.0.so" needed or dlopened by "/data/app/android.jni.cts-HP6GyGXYy5honHQAffUXgw==/lib/arm64/libjnitest.so" is not accessible for the namespace " mT?"

Change-Id: I25d9d76f8520f490755c189ded5659e6c9741f79
2019-05-23 23:58:12 +09:00
Treehugger Robot
72aafad950 Merge "Don't resolve already resolved paths when parsing ld.config.txt" 2019-05-17 04:15:41 +00:00
Peter Collingbourne
8bb97d7781 Merge "Add bootstrap directory to bootstrap linker's search path." 2019-05-17 02:26:29 +00:00
Jiyong Park
341b61e694 Don't resolve already resolved paths when parsing ld.config.txt
When parsing ld.config.txt, paths in *.search.paths properties are
resolved using resolved_paths(). This is causing a number of newfstatat
system calls during a process start-up and is contributing about 3.6%
of the entire linker initialization time.

Optimize the overhead by not resolving already resolved paths; resolved
paths are cached.

Bug: 132348336
Test: strace -C -e newfstatat ls shows the number of the syscalls is
reduced from 131 to 99
Test: simpleperf record --call-graph fp -f 10000000 -o /data/perf.data ls
simpleperf report -g -i /data/perf.data
shows percentage of get_paths() from 2.9% to 2.5%

Change-Id: I79823255a89f6e2a63b80c74e6768850276ab536
2019-05-17 10:09:13 +09:00
Peter Collingbourne
ea11be0cc8 Add bootstrap directory to bootstrap linker's search path.
A proposed set of changes:
https://android-review.googlesource.com/q/topic:"no-dup-hwasans"

will cause the HWASAN runtime to be moved from /system/lib64 to
/system/lib64/bootstrap. This causes a problem in the case where libc is built
with HWASAN but init is not built with HWASAN. In this case, libc.so will have
a DT_NEEDED dependency on the HWASAN runtime but init will not. Currently,
init and other bootstrap executables arrange to load bootstrap libraries by
setting rpath, but rpath only has an effect on libraries directly depended
on by the main executable, not libraries indirectly depended on by it. This
means that the loading of the HWASAN runtime will fail.

Instead of relying on rpath to find the bootstrap libraries, modify the
bootstrap linker so that it searches the bootstrap library directory after
searching the rpath.

Change-Id: I297be32e04ecd316ee12b8e694588e1249e2bb89
2019-05-16 16:10:41 -07:00
Elliott Hughes
90f96b9f48 linker: support ldd(1)-like behavior via --list.
Given that we have both linker and linker64, I didn't really want to have
to have ldd and ldd64, so this change just adds the --list option to the
linkers and a shell script wrapper "ldd" that calls the appropriate
linker behind the scenes.

Test: adb shell linker --list `which app_process32`
Test: adb shell linker64 --list `which date`
Test: adb shell ldd `which app_process32`
Test: adb shell ldd `which date`
Change-Id: I33494bda1cc3cafee54e091f97c0f2ae52d1f74b
2019-05-09 22:12:17 -07:00
Dimitry Ivanov
78e42d81ec Merge "Enable native_bridge_support" 2019-05-07 11:30:58 +00:00
Yi Kong
af1467b2cd Merge "Exclude libgcc_stripped wherever libgcc is excluded" 2019-05-07 02:57:24 +00:00
Yi Kong
7ac2afbde3 Exclude libgcc_stripped wherever libgcc is excluded
Test: manual testing
Bug: 130267141
Bug: 29275768
Change-Id: If50420c05d36e6f680a36673e7c26ca7deb93b28
2019-05-06 17:02:53 -07:00
dimitry
7f04880820 Enable native_bridge_support
Enable native bridge support for bionic libraries.
Makes it possible to use them in binaries for translated
architectures.

Bug: http://b/77159578
Test: make
Change-Id: Iccd4ad7aecfa5260cc15f09ca975d2e18987278a
2019-05-06 17:13:51 +02:00
Elliott Hughes
b51bb50471 Track libziparchive API change.
Bug: http://b/129068177
Test: treehugger
Change-Id: Ieccd528a34b66de59fad78586dead6b1df9cae98
2019-05-03 22:45:41 -07:00
dimitry
afe30a5281 Remove dependency on unused libutils
Test: make
Change-Id: I64f9390c680eeedec7acb8465bfde254b3c96904
2019-04-30 13:01:42 +02:00
Treehugger Robot
401e2efa39 Merge "Only write main library's RELRO by default." 2019-04-22 23:26:36 +00:00
Elliott Hughes
584bc626b6 Move libdl and linker to static NOTICE files.
The libstdc++ directory has no copyright headers, so it was a no-op
anyway.

The interesting part will be switching libc and libm over to genrules...

Test: N/A
Change-Id: Iec92562af40c451fdcb4a7468984878ec5dba2ce
2019-04-19 14:18:07 -07:00
Vic Yang
7b9db347ae Fix linker compilation with timing enabled
Test: Build with TIMING set to 1 in linker_debug.h.
Change-Id: Ia11021f6221bc985abddb379e813e4e353fd7149
2019-04-16 14:54:58 -07:00
Torne (Richard Coles)
5d10374947 Only write main library's RELRO by default.
ANDROID_DLEXT_WRITE_RELRO was inadvertently writing out the RELRO
section of all libraries loaded during a given dlopen() call instead of
only the main library; since the other libraries are loaded at
unpredictable addresses this additional data is rarely useful.

Fix this to only happen when the
ANDROID_DLEXT_RESERVED_ADDRESS_RECURSIVE flag is being used.

Bug: 128623590
Test: DlExtRelroSharingTest.CheckRelroSizes
Change-Id: I05e8651d06ce2de77b8c85fe2b6238f9c09691ad
2019-04-11 13:57:31 -04:00
Ryan Prichard
93ea856949 Merge changes I59a8bc4a,Ic437d352
* changes:
  Fix dlsym and dladdr for TLS symbols
  Fix BionicAllocator comment
2019-04-04 20:38:47 +00:00
Ryan Prichard
e4d620bc80 Fix dlsym and dladdr for TLS symbols
* dlsym: call __tls_get_addr for TLS symbols

 * dladdr: skip TLS symbols

Bug: b/123772574
Test: bionic unit tests
Change-Id: I59a8bc4a7d455e1018b0d577b027b6417c8487cd
2019-04-03 18:19:50 -07:00
Torne (Richard Coles)
fa9f7f28d4 Fix DLEXT_WRITE_RELRO when loading multiple libs.
ANDROID_DLEXT_WRITE_RELRO was causing the GNU RELRO sections of
libraries to become corrupted if more than one library was being loaded
at once (i.e. if the root library has DT_NEEDED entries for libraries
that weren't already loaded). The file offset was not being correctly
propagated between calls, so after writing out the (correct) RELRO data
to the file, it was mapping the data at file offset 0 for all libraries,
which corrupted the data for all but one of the libraries.

Fix this by passing file_offset as a pointer the same way that
phdr_table_map_gnu_relro does.

Bug: 128623590
Test: tbd
Change-Id: I196cd336bd5a67454e89fd85487356b1c7856871
2019-04-02 18:06:12 -04:00
Vic Yang
976d4b4634 Use std::move() for rvalue-reference setters and ctors
Also update an rvalue reference to lvalue reference where it's
unnecessary to make it clearer.

Test: Build and boot cuttlefish.
Change-Id: Ib799666ab075523e6446f34c7da2b1eb311f98ab
2019-03-20 10:20:49 -07:00
Vic Yang
2d020e43fb linker: Add support for "whitelisted" property in linker config files
In order to enable no-vendor-variant VNDK, we need a way to restrict a
namespace to only a list of whitelisted libraries.  We add a new
"whitelisted" property for this.  If the property is not set, all
libraries in the search paths are available in a namespace.  If the
property is set, only the libraries named are available.

Bug: 119423884
Test: Boot with no-vendor-variant VNDK enabled using the new property.
Change-Id: Id808c1733c8e2c2c3462b04c72461f9698403571
2019-03-20 10:20:49 -07:00
Martin Stjernholm
60916654cc Merge "Add more linker debug." 2019-03-19 14:08:10 +00:00
Martin Stjernholm
95252eedf3 Add more linker debug.
- Show which executable is being linked, which linker config file is
  being read, and which section in it is being used with, enabled on
  $LD_DEBUG>=1.

- Show more info to follow the dlopen() process, enabled with "dlopen"
  in the debug.ld.xxx property.

Test: Flash, boot, and look at logcat after "adb shell setprop debug.ld.all dlopen"
Bug: 120430775
Change-Id: I5441c8ced26ec0e2f04620c3d2a1ae860b792154
2019-03-19 14:03:18 +00:00
Jiyong Park
036e09c36e Don't install *.mountpoint targets
The *.mountpoint targets that installs /bionic/lib/lib*.so and
/bionic/bin/linker* are no longer needed.

Now, /system/lib/lib*.so and /system/bin/linker* are simply symlinks to
the corresponding files in the runtime apex. For example,

/system/lib/libc.so -> /apex/com.android.runtime/lib/bionic/libc.so

This is made possible because we now activate APEXes even before the
data partition is mounted. Before the data partition mounting, the
APEXes from the system partition are ativated. After the data partition
is mounted, updated APEXes in the partition (if any) are activated. As a
result, the symlink always points to the valid path regardless of
whether /data is mounted or not.

Bug: 125549215
Test: device boots
Change-Id: Ie7d83686abe00b3c436f9f9db75d4244200a0fc9
2019-03-14 07:35:52 +09:00
Ryan Prichard
92b3e1b37b Cosmetic changes to linker allocator and config
Make the num_free_blocks calculation clearer. There are
sizeof(page->bytes) bytes available for blocks, which is equal to
(kAllocateSize - 16). The previous calculation overestimates the amount
of space by 8 or 12 bytes, but that doesn't change the result because
both kAllocateSize and block_size_ are multiples of 16.

Bug: none
Test: boot device, bionic unit tests
Change-Id: Ia880cd5abc2a7bb4e9e6a8c0441d985f4df8fdc4
2019-03-12 01:11:24 +00:00
Ryan Prichard
b0e2dd090b Allow building the linker with -O0
The tlsdesc_resolver_dynamic function is only defined on arm64, but the
code was taking its address on all targets. (Apparently the optimizer was
removing the entire deferred_tlsdesc_relocs loop?)

Bug: none
Test: bionic unit tests
Test: add -O0 to cc_defaults in linker/Android.bp, device boots
Change-Id: I899c78018cbe82aeaca7856c9f7b04300c1d3196
2019-03-11 17:53:21 -07:00
Peter Collingbourne
b39cb3c31d linker: Handle libraries with disjoint mappings correctly.
It's possible and sometimes beneficial for a library to have disjoint mappings
and for other libraries to be mapped into the gap between the mappings using
ANDROID_DLEXT_RESERVED_ADDRESS. See for example the proposal for partitioning
in lld [1].

Because the find_containing_library and do_dl_unwind_find_exidx functions use
a simple bounds check to figure out whether a pointer belongs to a library
they will, given a pointer into a library mapped into the gap of a library
with disjoint mappings, return a pointer to the soinfo for the outer library
instead of the inner one, because the outer library will appear before the
inner one in the solist.

From a user perspective this means that we won't be able to unwind the inner
library's frames on 32-bit ARM with libgcc, dladdr() will return information
for the outer library given a pointer to the inner one and dlopen() et al will
use the linker namespace of the outer library when called from the inner one
(although they will usually be the same).

To make this work correctly, make it so that once find_containing_library
sees a match for the bounds check, it examines the library's PT_LOADs to
make sure that there is a mapping for the given address. This is similar
to how libgcc and libunwind_llvm already handle finding the PT_GNU_EH_FRAME
on non-ARM32 platforms [2,3]. do_dl_unwind_find_exidx is reimplemented in
terms of find_containing_library.

[1] http://lists.llvm.org/pipermail/llvm-dev/2019-February/130583.html
[2] e739ac0e25/libunwind/src/AddressSpace.hpp (L523)
[3] https://android.googlesource.com/toolchain/gcc/+/master/gcc-4.9/libgcc/unwind-dw2-fde-dip.c#294

Test: /data/nativetest{,64}/bionic-unit-tests/bionic-unit-tests on walleye-userdebug
Change-Id: I368fe6ad3c470b3dff80f7d9b04253566d63a7d2
2019-03-08 18:34:34 -08:00
Treehugger Robot
7cdbd0d477 Merge "linker: allow using reserved space for multiple libraries." 2019-02-21 16:06:17 +00:00
Torne (Richard Coles)
efbe9a5eef linker: allow using reserved space for multiple libraries.
Introduce a new flag ANDROID_DLEXT_RESERVED_ADDRESS_RECURSIVE which
instructs the linker to use the reserved address space to load all of
the newly-loaded libraries required by a dlopen() call instead of only
the main library. They will be loaded consecutively into that region if
they fit. The RELRO sections of all the loaded libraries will also be
considered for reading/writing shared RELRO data.

This will allow the WebView implementation to potentially consist of
more than one .so file while still benefiting from the RELRO sharing
optimisation, which would otherwise only apply to the "root" .so file.

Test: bionic-unit-tests (existing and newly added)
Bug: 110790153
Change-Id: I61da775c29fd5017d9a1e2b6b3757c3d20a355b3
2019-02-20 17:29:36 -05:00
vichang
54c864052b Merge "Redirect /system/lib/libicuuc.so regardless of duplication in /system" 2019-02-19 10:14:31 +00:00
Elliott Hughes
d102cf62d1 Merge "Switch linker tests to Android.bp." 2019-02-16 01:11:56 +00:00
Elliott Hughes
f84d0a95bd Merge "libasync_safe: stop clobbering other folks' identifiers." 2019-02-16 00:12:51 +00:00
Elliott Hughes
15a2b7b17b Switch linker tests to Android.bp.
Life is easier if we just keep test code in the same directory as the
stuff it's testing...

Test: tests still build and pass
Change-Id: I9b35d689098bdc28a71d69645b0ca9fdd6ea0108
2019-02-15 14:40:08 -08:00
Elliott Hughes
3019d78d4a libasync_safe: stop clobbering other folks' identifiers.
The log priorities and ids are in an NDK header, available to everyone.

Move CHECK into its own header for now. This would be better if it was
more like the <android-base/logging.h> CHECK family, but I don't have an
easy way to do that without lots of copy & paste, so punting for now.

Bug: https://issuetracker.google.com/issues/119713191
Test: boots
Change-Id: I4566be8a0a024fede0e2d257c98b908ec67af2a8
2019-02-14 14:23:13 -08:00
Pirama Arumuga Nainar
fcd35380dd Disable native_coverage for ld-android and linker
Bug: http://b/116873221

The coverage library, which depends on libc, cannot link with libraries
since they opt of libc.

Test: m NATIVE_COVERAGE=true COVERAGE_PATHS=bionic
Change-Id: Iaaca8bc30c8ba59e5d4f7092b1a0fce8e8c14c72
2019-02-14 13:50:55 -08:00
Victor Chang
af12c94e79 Redirect /system/lib/libicuuc.so regardless of duplication in /system
The change is a workaround of app compat issue until the app fixes the
issue.

Likely, the app does not only dlopen(), but open() the libicuuc.so
with the absolute path.

Note that platform uses the stub libandroidicu.so, not libicuuc directly.
This CL topic moves (not duplicates) libandroidicu from /system to
/apex. Even though /system/lib/libicuuc.so is kept in the default
namespace, but no one should be using it.

Some debug info after this CL:
$ adb shell cat /proc/<zygote pid>/maps | grep libicuuc
$ adb shell cat /proc/<app pid>/maps | grep libicuuc
Only /apex/com.android.runtime/lib64/libicuuc.so is found, not the
/system.

Bug: 124218500
Test: The app can be launched successfully
Test: CtsJniTestCases
Change-Id: I67a50f0ad934be567a63d4038215546c9b4e5f7e
2019-02-13 15:31:06 +00:00
Jiyong Park
efc503d677 Greylist libraries are attempted to be loaded in the default ns
Some of the greylist libraries can be in directories other than
/system/lib. For example, libnativehelper.so is moved from the directory
to /apex/com.android.runtime/lib.

Previous behavior for greylist libraries is to find the lib under
/system/lib while "within" the current namespace which is usually the
classloader-namespace. Since the libs no longer exist there, linker
fails to load it and no further attempt is made.

This change fixes the problem by loading the greylist libs "from" the
default namespace. Since there is a link from the default namespace to
the namespace where the moved libraries are intended to be loaded (e.g.,
the 'runtime' namespace for libnativehelper.so), the call is successful.

Bug: 124201397
Test: bionic-unit-tests

Change-Id: I11d15993d18896bdf663c408f9e40d8a607c9b80
2019-02-12 23:07:08 +09:00
Ryan Prichard
808d176e7e Merge "Fix linker self-exec detection" 2019-02-08 22:33:11 +00:00
Ryan Prichard
1990ba5601 Fix linker self-exec detection
When the linker is invoked on itself, (`linker64 /system/bin/linker64`),
the linker prints an error, because self-invocation isn't allowed. The
current method for detecting self-invocation fails because the second
linker instance can crash in a constructor function before reaching
__linker_init.

Fix the problem by moving the error check into a constructor function,
which finishes initializing libc sufficiently to call async_safe_fatal.
The only important thing missing is __libc_sysinfo on 32-bit x86. The aux
vector isn't readily accessible, so use the fallback int 0x80.

Bug: http://b/123637025
Test: bionic unit tests (32-bit x86)
Change-Id: I8be6369e8be3938906628ae1f82be13e6c510119
2019-02-07 21:48:42 -08:00
Victor Chang
6cb719f0ed Revert "Revert "Allow dlopen("/system/lib/<soname>") for pre-Q""
This reverts commit 1906e77665
and fixes dlopen(nullptr)

It's enabled for the following .so libraries
libicuuc.so
libicui18n.so

This CL does not move the .so files into a APEX.
Thus, no visible effect before moving .so files.

Bug: 121248172
Test: dlfcn#dlopen_from_nullptr
Test: Perform the following test after moving libicuuc to /apex
      dlopen("/system/lib64/libicuuc.so") for targetSdkVersion < Q
Change-Id: Ia310ea566485fe00ca28e2203f4bffbd92243638
2019-02-07 01:17:37 +00:00
vichang
73ee7a6320 Merge "Revert "Allow dlopen("/system/lib/<soname>") for pre-Q"" 2019-02-06 17:03:41 +00:00
vichang
1906e77665 Revert "Allow dlopen("/system/lib/<soname>") for pre-Q"
This reverts commit f6e4cfd933.

Reason for revert: b/123972211

Change-Id: I1ea199c27e224bbd27dee7692f9f448ca9c2b6d1
2019-02-06 16:42:21 +00:00
vichang
9c48951a7d Merge "Allow dlopen("/system/lib/<soname>") for pre-Q" 2019-02-05 12:34:00 +00:00
Victor Chang
f6e4cfd933 Allow dlopen("/system/lib/<soname>") for pre-Q
It's enabled for the following .so libraries
libicuuc.so
libicui18n.so

This CL does not move the .so files into a APEX.
Thus, no visible effect before moving .so files.

Bug: 121248172
Test: Perform the following test after moving libicuuc to /apex
      dlopen("/system/lib64/libicuuc.so") for targetSdkVersion < Q
Change-Id: Ic00d281d59de924c01582c48d2a946e3f5f33a09
2019-02-04 23:45:19 +00:00
Vic Yang
bb7e1236f3 Purge linker block allocators before leaving linker
This is the second attempt to purge linker block allocators.  Unlike the
previously reverted change which purge allocators whenever all objects
are freed, we only purge right before control leaves the linker.  This
limits the performance impact to one munmap() call per dlopen(), in
most cases.

Bug: 112073665
Test: Boot and check memory usage with 'showmap'.
Test: Run camear cold start performance test.
Change-Id: I02c7c44935f768e065fbe7ff0389a84bd44713f0
2019-01-30 22:13:13 -08:00
Jiyong Park
fbc4c8edd6 Move the dynamic linker to ./bootstrap subdir
The dynamic linker installed to /system partition is only for
bootstraping, i.e. to be used only by early processes. The existing path
/system/bin/linker[64] will be a symlink to the mount pointpoint
/bionic/bin/linker[64] which will be bind-mounted with either the
bootstrap linker or the default linker in the runtime APEX. Since the
path is taken by the symlink, bootstrap linker is moved to ./boostrap
subdirectory.

Bug: 120266448
Test: m linker; the linker is found under /system/bin/bootstrap/
Change-Id: I163e0c8a1738b94565a6b60f48e65841ba058a91
2019-01-31 13:44:20 +09:00
Jiyong Park
a5f914aef1 Add bionic mount points under /bionic
This change adds following files and symlinks:

Files:
/bionic/lib[64]/lib{c|dl|m}.so
/bionic/bin/linker[64]

Symlinks:
/system/lib[64]/lib{c|dl|m}.so -> /bionic/lib[64]/lib{c|dl|m}.so
/system/bin/linker[64] -> /bionic/bin/linker[64]
/system/bin/linker_asan[64] -> /bionic/bin/linker[64]

The files serve as mount points for either the bootstrap Bionic or the
default Bionic from the runtime APEX. init does the bind-mounting during
booting.

The symlinks are there to not change the ordinary paths to the bionic
files; there are many places that the paths are implied or hard-coded,
e.g., dlopen("/system/lib/libc.so") or DT_INTERP pointing to
/system/bin/linker in the vendor prebuilts.

Bug: 120266448
Test: m blueline, cf_x86, aosp_arm
The aforementioned files and symlinks are found

Change-Id: I97e38c29409ac0610dde285db8df6e94a7930094
2019-01-31 13:44:20 +09:00
Vic Yang
7bb60fcbcd Revert "linker: Purge block allocator memory when possible"
This reverts commit fb78a4ac1b.

Reason for revert: Performance regression.

Change-Id: Ib12335fc7478dad933da00b8bc525366c9330a17
2019-01-29 20:21:41 -08:00
Ryan Prichard
ffaae70936 Implement arm64 TLSDESC
Each TLSDESC relocation relocates a 2-word descriptor in the GOT that
contains:
 - the address of a TLS resolver function
 - an argument to pass (indirectly) to the resolver function

(Specifically, the address of the 2-word descriptor is passed to the
resolver.)

The loader resolves R_GENERIC_TLSDESC relocations using one of three
resolver functions that it defines:
 - tlsdesc_resolver_static
 - tlsdesc_resolver_dynamic
 - tlsdesc_resolver_unresolved_weak

The resolver functions are written in assembly because they have a
restrictive calling convention. They're only allowed to modify x0 and
(apparently) the condition codes.

For a relocation to memory in static TLS (i.e. the executable or an solib
loaded initially), the loader uses a simple resolver function,
tlsdesc_resolver_static, that returns the static offset it receives from
the loader.

For relocations to dynamic TLS memory (i.e. memory in a dlopen'ed solib),
the loader uses tlsdesc_resolver_dynamic, which allocates TLS memory on
demand. It inlines the fast path of __tls_get_addr, then falls back to
__tls_get_addr when it needs to allocate memory. The loader handles these
dynamic TLS relocations in two passes:
 - In the first pass, it allocates a table of TlsDynamicResolverArg
   objects, one per dynamic TLSDESC relocation.
 - In the second pass, once the table is finalized, it writes the
   addresses of the TlsDynamicResolverArg objects into the TLSDESC
   relocations.

tlsdesc_resolver_unresolved_weak returns a negated thread pointer so that
taking the address of an unresolved weak TLS symbols produces NULL.

The loader handles R_GENERIC_TLSDESC in a target-independent way, but
only for arm64, because Bionic has only implemented the resolver functions
for arm64.

Bug: http://b/78026329
Test: bionic unit tests
Test: check that backtrace works inside a resolver function and inside
  __tls_get_addr called from a resolver
  (gdbclient.py, b __tls_get_addr, bt)
Merged-In: I752e59ff986292449892c449dad2546e6f0ff7b6
Change-Id: I752e59ff986292449892c449dad2546e6f0ff7b6
2019-01-29 08:33:09 +00:00
Ryan Prichard
16455b5100 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
2019-01-25 17:53:01 -08:00