This patch adds the necessary bionic code for the linker to protect
global data using MTE.
The implementation is described in the MemtagABI addendum to the
AArch64 ELF ABI:
https://github.com/ARM-software/abi-aa/blob/main/memtagabielf64/memtagabielf64.rst
In summary, this patch includes:
1. When MTE globals is requested, the linker maps writable SHF_ALLOC
sections as anonymous pages with PROT_MTE (copying the file contents
into the anonymous mapping), rather than using a file-backed private
mapping. This is required as file-based mappings are not necessarily
backed by the kernel with tag-capable memory. For sections already
mapped by the kernel when the linker is invoked via. PT_INTERP, we
unmap the contents, remap a PROT_MTE+anonymous mapping in its place,
and re-load the file contents from disk.
2. When MTE globals is requested, the linker tags areas of global memory
(as defined in SHT_AARCH64_MEMTAG_GLOBALS_DYNAMIC) with random tags,
but ensuring that adjacent globals are never tagged using the same
memory tag (to provide detemrinistic overflow detection).
3. Changes to RELATIVE, ABS64, and GLOB_DAT relocations to load and
store tags in the right places. This ensures that the address tags are
materialized into the GOT entries as well. These changes are a
functional no-op to existing binaries and/or non-MTE capable hardware.
Bug: N/A
Test: atest bionic-unit-tests CtsBionicTestCases --test-filter=*Memtag*
Change-Id: Id7b1a925339b14949d5a8f607dd86928624bda0e
To take advantage of file-backed huge pages for the text segments of key
shared libraries (go/android-hugepages), the dynamic linker must load
candidate ELF files at an appropriately aligned address and mark
executable segments with MADV_HUGEPAGE.
This patches uses segments' p_align values to determine when a file is
PMD aligned (2MB alignment), and performs load operations accordingly.
Bug: 158135888
Test: Verified PMD aligned libraries are backed with huge pages on
supporting kernel versions.
Change-Id: Ia2367fd5652f663d50103e18f7695c59dc31c7b9
This patch adds support to load BTI-enabled objects.
According to the ABI, BTI is recorded in the .note.gnu.property section.
The new parser evaluates the property section, if exists.
It searches for .note section with NT_GNU_PROPERTY_TYPE_0.
Once found it tries to find GNU_PROPERTY_AARCH64_FEATURE_1_AND.
The results are cached.
The main change in linker is when protection of loaded ranges gets
applied. When BTI is requested and the platform also supports it
the prot flags have to be amended with PROT_BTI for executable ranges.
Failing to add PROT_BTI flag would disable BTI protection.
Moreover, adding the new PROT flag for shared objects without BTI
compatibility would break applications.
Kernel does not add PROT_BTI to a loaded ELF which has interpreter.
Linker handles this case too.
Test: 1. Flame boots
2. Tested on FVP with BTI enabled
Change-Id: Iafdf223b74c6e75d9f17ca90500e6fe42c4c1218
Add inaccessible gaps between shared libraries to make it harder for the
attackers to defeat ASLR by random probing.
To avoid excessive page table bloat, only do this when a library is
about to cross a huge page boundary, effectively allowing several
smaller libraries to be lumped together.
Bug: 158113540
Test: look at /proc/$$/maps
Change-Id: I39c0100b81f72447e8b3c6faafa561111492bf8c
This reverts commit a8cf3fef2a.
Reason for revert: memory regression due to the fragmentation of the page tables
Bug: 159810641
Bug: 158113540
Change-Id: I6212c623ff440c7f6889f0a1e82cf7a96200a411
Improve ASLR by increasing the randomly sized gaps between shared
library mappings, and keep them mapped PROT_NONE.
Bug: 158113540
Test: look at /proc/$$/maps
Change-Id: Ie72c84047fb624fe2ac8b7744b2a2d0d255ea974
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
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
The executable can be inside a zip file using the same syntax used for
shared objects: path.zip!/libentry.so.
The linker currently requires an absolute path. This restriction could be
loosened, but it didn't seem important? If it allowed non-absolute paths,
we'd need to decide how to handle:
- foo/bar (relative to CWD?)
- foo (search PATH / LD_LIBRARY_PATH, or also relative to CWD?)
- foo.zip!/bar (normalize_path() requires an absolute path)
The linker adjusts the argc/argv passed to main() and to constructor
functions to hide the initial linker argument, but doesn't adjust the auxv
vector or files like /proc/self/{exe,cmdline,auxv,stat}. Those files will
report that the kernel loaded the linker as an executable.
I think the linker_logger.cpp change guarding against (g_argv == NULL)
isn't actually necessary, but it seemed like a good idea given that I'm
delaying initialization of g_argv until after C++ constructors have run.
Bug: http://b/112050209
Test: bionic unit tests
Change-Id: I846faf98b16fd34218946f6167e8b451897debe5
We've been using #pragma once for new internal files, but let's be more bold.
Bug: N/A
Test: builds
Change-Id: I7e2ee2730043bd884f9571cdbd8b524043030c07
Improve sanity-checks of elf-file by adding alignment check
of mapped sections and section headers.
Bug: http://b/30687964
Change-Id: I7f06ddaa56a13989ce7be847b3a73c352e32c008
dlclose used to unmap the part of the reserved region
for ANDROID_DLEXT_RESERVED_ADDRESS that was neccessary
to map PT_LOAD segments. With this change dlclose
replaces mapped PT_LOAD segments with a PROT_NONE,
MAP_ANONYMOUS | MAP_NORESERVE.
Previously caller was unmapping the reserved region after
the failed dlclose which led to race condition when someone
else reused the region freed by dlclose but before the unmap
by the chromium code.
Bug: http://code.google.com/p/chromium/issues/detail?id=568880
Change-Id: I0f5eaa2bf6641f83dde469b631c518482acc59a2
The linker crashes if native library has invalid section
headers. This change adds boundary checks on target offsets
and generates dlerror instead of crash.
Bug: http://b/25800330
Change-Id: Ibe282029997302b9b557637c3aad064d7d0febc5
Setup a /system/bin/linker_asan as a symlink to "linker".
Read the linker name from PT_INTERP, and if it is linker_asan,
switch default library lookup paths to the ASan set, which
starts with the path to the instrumented libraries
(/data/lib), followed by /system/lib as a fallback.
This ensures that ASan binaries prefer ASan libraries, when
available. This approach is way better then RPATH/RUNPATH and even
better than LD_LIBRARY_PATH:
- RUNPATH is per-DSO, while default paths are global.
- LD_LIBRARY_PATH is overwritten by android_update_LD_LIBRARY_PATH.
- neither RUNPATH nor LD_LIBRARY_PATH appear in
android_get_LD_LIBRARY_PATH which is used to build java.lang.path.
Having ASan libraries in java.lang.path is a good thing.
Bug: 22355945
Change-Id: I1d2791fbf5740618f18f71a3ae3d873714669d3f
Get dynamic flags from phdr table's correct entry rather the first
entry, so that the following DT_DEBUG entry can be set.
Also fix the undefined reference to LoadTask::deleter issue under gcc
-O0 option.
Bug: 17524778
Change-Id: I9c679af197b034761fb739d6c980e628ff2ab84c
This patch fixes the problem with symbol search order
for dlsym(RTLD_DEFAULT/RTLD_NEXT, .) by loading libraries
and ld_preloads in correct order.
Bug: https://code.google.com/p/android/issues/detail?id=74255
Change-Id: If1ba5c807322409faa914e27ecb675e2c4541f0d
Attempt: 2
This patch fixes the problem with symbol search order
for dlsym(RTLD_DEFAULT/RTLD_NEXT, .) by loading libraries
and ld_preloads in correct order.
Bug: https://code.google.com/p/android/issues/detail?id=74255
Change-Id: I4cf84c70dbaabe99310230dfda12385ae5401859
Add flags and a file descriptor to android_dlopen_ext() to allow writing
the RELRO section of the loaded library to a file after relocation
processing, and to allow mapping identical pages from the file over the
top of relocated memory in another process. Explicitly comparing the
pages is required in case a page contains a reference to a symbol
defined in another library loaded at a random base address.
Bug: 13005501
Change-Id: Ibb5b2d384edfaa5acf3e97a5f8b6115c10497a1e
Add flags and parameters to android_dlopen_ext() to allow loading a
library at an already-reserved fixed address. If the library to be
loaded will not fit within the space reserved, then the linker will
either fail, or allocate its own address space as usual, according to
which flag has been specified. This behaviour only applies to the
specific library requested; any other libraries loaded as dependencies
will be loaded in the normal fashion.
There is a new gtest included to cover the functionality added.
Bug: 13005501
Change-Id: I5d1810375b20fc51ba6a9b3191a25f9792c687f1
Remove the linker's reliance on BSD cruft and use the glibc-style
ElfW macro. (Other code too, but the linker contains the majority
of the code that needs to work for Elf32 and Elf64.)
All platforms need dl_iterate_phdr_static, so it doesn't make sense
to have that part of the per-architecture configuration.
Bug: 12476126
Change-Id: I1d7f918f1303a392794a6cd8b3512ff56bd6e487
We don't need our own architecture macros; the standard ones will do.
This patch also fixes some __x86_64__ tests to be USE_RELA tests instead,
because they're not actually x86_64-specific.
I've cleaned up architecture-specific code slightly so where possible
all the code corresponding to a particular architecture is together.
This patch also fixes a bug in LP64 DT_PLTGOT handling, which should be
an error rather than falling through into DT_DEBUG! There was another #ifdef
bug where we'd only report unexpected DT_ entries on MIPS.
Change-Id: Id1d04e372611f641c1aa278a18e379f28af9eaf5
This is primarily for MIPS exutables that do not have a
DT_MIPS_RLD_MAP entry.
Change-Id: I4c221d92debcfed961eeee2515123f3fb21ec8e6
Signed-off-by: Chris Dearman <chris@mips.com>
I still want to break linker_format out into its own library so we can reuse
it for malloc debugging and so forth. (There are many similar pieces of code
in bionic, but the linker's one seems to be the most complete/functional.)
Change-Id: If3721853d28937c8e821ca1d23cf200e228a409a
This patch removes the DT_NEEDED hack which stores pointers
to soinfo structs in the .dynamic section of the library
being loaded.
Instead, it caches the soinfo struct pointers on the stack
during relocation time. After relocation time, i.e. when
calling constructors and destructors of the shared library
and its dependencies, uncached access is used instead,
doing lookups using the string table entries pointed to by
the DT_NEEDED entries.
By removing this hack, it is no longer needed to undo the
PT_GNURELRO protection, i.e., all non-writable mappings
can remain non-writable during their entire lifespan.
Even though, strictly speaking, the algorithmic complexity
has increased somewhat, the real-world adverse effect
is negligible on the systems I have tested.
Change-Id: I2361502560b96b5878f7f94a8e8a215350d70d64
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@gmail.com>
Also make the errors more readable, since none of us seemed to know
what they actually meant. The new style is still as verbose as the
old, but that's probably necessary in the absence of chained exceptions
in C. Here's what you'd see if you try to boot after removing
libsurfaceflinger.so:
32267 32267 E AndroidRuntime: java.lang.UnsatisfiedLinkError: Cannot load library: (linker.c:1629, pid 32259) soinfo_link_image: could not load library "libsystem_server.so" needed by "libandroid_servers.so"; caused by (linker.c:1629, pid 32259) soinfo_link_image: could not load library "libsurfaceflinger.so" needed by "libsystem_server.so"; caused by (linker.c:709, pid 32259) load_library: library "libsurfaceflinger.so" not found
This patch also fixes almost all of the compiler warnings.
Change-Id: I64bb59aed6d4e039c15ea45be2367f319ef879f8
This patch introduces two new source files containing a set of functions
to manage the program header table in an ELF binary, including the ability
to load PT_LOAD segments, and apply PT_GNU_RELRO protection.
Note: the files are not used currently, this will appear in a series
of future patches that will gradually modify linker.c to use
the phdr_table_xxx functions properly.
Change-Id: Ia3d4c1ff5fc3e265d8258b64b492f4e643f51bdc
