The __eh_frame section contains relocations which can always be implicitly generated.
This patch tracks whether sections have only implicitly relocations and skips emitting them to the object file if that is the case.
The test case here ensures that this is the case for __eh_frame sections.
Reviewed by Lang Hames.
http://reviews.llvm.org/D15594
llvm-svn: 257099
The final section order in relocatable files was just a side effect
of the atom sorter. This meant that sections like __data were before
__text because __data has RW permissions and __text RX and RW was less
than RX in our enum.
Final linked images had an actual section/segment sorter. There was no
reason for the difference, so simplify a bunch of code and just use the
same sorted for everything.
Reviewed by Lang Hames.
http://reviews.llvm.org/D15868
llvm-svn: 256786
This is a basic initial implementation of the -flat_namespace and
-undefined options for LLD-darwin. It ignores several subtlties,
but the result is close enough that we can now link LLVM (but not
clang) on Darwin and pass all regression tests.
llvm-svn: 248732
I believe this patch eliminates all remaining uses of _context
or _linkingContext variable names. Consistent naming improves
readability.
llvm-svn: 234645
This patch defines implicit conversion between integers and PowerOf2
instances, so uses of the classes is now implicit and look like
regular integers. Now we are ready to remove the scaffolding.
llvm-svn: 233245
The new constructor's type is the same, but this one takes not a log2
value but an alignment value itself, so the meaning is totally differnet.
llvm-svn: 233244
This patch is to make instantiation and conversion to an integer explicit,
so that we can mechanically replace all occurrences of the class with
integer in the next step.
Now get() returns an alignment value rather than its log2 value.
llvm-svn: 233242
We are using log2 values and values themselves to represent alignments.
For example, alignment 8 is sometimes represented as 3 (8 == 2^3).
We want to stop using log2 values.
Because both types are regular arithmetic types, we cannot get help from
a compiler to find places we mix two representations. That makes this
merging work surprisingly hard because if I make a mistake, I'll just get
wrong results at runtime (Yay types!). In this patch, I introduced
a class to represents power-of-two values, which is basically an alias
for an integer type.
Once the migration is done, the class will be removed.
llvm-svn: 233232
Summary:
Work on adding -rpath support to the mach-o linker.
This patch is based on the ld64 behavior for the command line option validation.
It includes a basic test to check that the LC_RPATH load commands are properly generated when that option is used.
It also add LC_RPATH support to the binary reader, but I don't know how to test it though.
Reviewers: kledzik
Subscribers: llvm-commits
Projects: #lld
Differential Revision: http://reviews.llvm.org/D6724
llvm-svn: 224544
Mach-o does not use a simple SO_NEEDED to track dependent dylibs. Instead,
the linker copies four things from each dylib to each client: the runtime path
(aka "install name"), the build time, current version (dylib build number), and
compatibility version The build time is no longer used (it cause every rebuild
of a dylib to be different). The compatibility version is usually just 1.0
and never changes, or the dylib becomes incompatible.
This patch copies that information into the NormalizedMachO format and
propagates it to clients.
llvm-svn: 222300
On darwin in final linked images, the __TEXT segment covers that start of the
file. That means in memory a process can see the mach_header (and load commands)
for every loaded image in a process. There are APIs that take and return the
mach_header addresses as a way to specify a particular loaded image.
For completeness, any code can get the address of the mach_header of the image
it is in by using &__dso_handle. In addition there are mach-o type specific
symbols like __mh_execute_header.
The linker needs to supply a definition for any of these symbols if used. But
the address the symbol it resolves to is not in any section. Instead it is the
address of the start of the __TEXT segment.
I needed to make a small change to SimpleFileNode to not override
resetNextIndex() because the Driver creates a SimpleFileNode to hold the
internal/implicit files that the context/writer can create. For some reason
SimpleFileNode overrode resetNextIndex() to do nothing instead of reseting
the index (which mach-o needs if the internal file is an archive).
llvm-svn: 221822
The way lazy binding works in mach-o is that the linker generates a helper
function and has the stub (PLT) initially jump to it. The helper function
pushes an extra parameter then jumps into dyld. The extra parameter is an
offset into the lazy binding info where dyld will find the information about
which symbol to bind and way lazy binding pointer to update.
llvm-svn: 221654
Darwin uses two-level-namespace lookup for symbols which means the static
linker records where each symbol must be found at runtime. Thus defining a
symbol in a dylib loaded earlier will not effect where symbols needed by
later dylibs will be found. Instead overriding is done through a section
of type S_INTERPOSING which contains tuples of <interposer, interposee>.
llvm-svn: 221421
The job of the CompactUnwind pass is to turn __compact_unwind data (and
__eh_frame) into the compressed final form in __unwind_info. After it's done,
the original atoms are no longer relevant and should be deleted (they cause
problems during actual execution, quite apart from the fact that they're not
needed).
llvm-svn: 221301
In final linked shared images, the __TEXT segment contains both code and
the mach-o header/load-commands. In the case of a data-only dylib, there is
no code, so we need to force the addition of the __TEXT segment.
llvm-svn: 220597
To deal with cycles in shared library dependencies, the darwin linker supports
marking specific link dependencies as "upward". An upward link is when a
lower level library links against a higher level library.
llvm-svn: 219949
Not all situations are representable in the compressed __unwind_info format,
and when this happens the entry needs to point to the more general __eh_frame
description.
Just x86_64 implementation for now.
rdar://problem/18208653
llvm-svn: 219836
This is a minimally useful pass to construct the __unwind_info section in a
final object from the various __compact_unwind inputs. Currently it doesn't
produce any compressed pages, only works for x86_64 and will fail if any
function ends up without __compact_unwind.
rdar://problem/18208653
llvm-svn: 218703
llvm\tools\lld\lib\readerwriter\macho\macholinkingcontext.cpp(647):
warning C4715: 'lld::MachOLinkingContext::exportSymbolNamed' :
not all control paths return a value
llvm\tools\lld\lib\readerwriter\macho\machonormalizedfilefromatoms.cpp(723):
warning C4715: '`anonymous namespace'::Util::getSymbolTableRegion' :
not all control paths return a value
While all enum values do appear in the switch, an uninitialized or corrupted
enum variable would not be caught without the default: case in the switch.
llvm-svn: 218197
On darwin, the linker tools records which dylib (DSO) each undefined was found
in, and then at runtime, the loader (dyld) only looks in that one specific
dylib for each undefined symbol. Now that llvm-objdump can display that info
I can write test cases.
llvm-svn: 217898
Most of the changes are in the new file ArchHandler_arm64.cpp. But a few
things had to be fixed to support 16KB pages (instead of 4KB) which iOS arm64
requires. In addition the StubInfo struct had to be expanded because
arm64 uses two instruction (ADRP/LDR) to load a global which requires two
relocations. The other mach-o arches just needed one relocation.
llvm-svn: 217469
There is a bit (MH_PIE) in the flags field of the mach_header which tells
the kernel is a program was built position independent (for ASLR). The linker
automatically attempts to build programs PIE if they are built for a recent
OS version. But the -pie and -no_pie options override that default behavior.
llvm-svn: 217408
On Darwin at runtime, dyld will prefer to use the export trie of a dylib instead
of the traditional symbol table (which is large and requires a binary search).
This change enables the linker to generate an export trie and to prefer it if
found in a dylib being linked against. This also simples the yaml for dylibs
because the yaml form of the trie can be reduced to just a sequence of names.
llvm-svn: 217066
Mach-O symbols can have an attribute on them means their content should never be
dead code stripped. This translates to deadStrip() == deadStripNever.
llvm-svn: 216234
Both options control the final scope of atoms.
When -exported_symbols_list <file> is used, the file is parsed into one
symbol per line in the file. Only those symbols will be exported (global)
in the final linked image.
The -keep_private_externs option is only used with -r mode. Normally, -r
mode reduces private extern (scopeLinkageUnit) symbols to non-external. But
add the -keep_private_externs option keeps them private external.
llvm-svn: 216146
Mach-o uses "two-level namespace" where each undefined symbols is associated
with a specific dylib. This means at runtime the loader (dyld) does need to
search all loaded dylibs for that symbol but rather just the one specified.
Now that llvm-nm -m prints out that info, properly set that info, and test
it in the hello world test cases.
llvm-svn: 215598
The -sectalign option is used to increase the alignment required for a section.
It required some reworking of how the __TEXT segment is laid out because that
segment also contains the mach_header and load commands. And the size of load
commands depend on the number of segments, sections, and dependent dylibs used.
Using this option will simplify some future test cases because the final
address of code can be pinned down, making tests of its content easier.
llvm-svn: 214268
All iOS arm processor support switching between arm and thumb mode at call sites
by using the BLX instruction (instead of BL). But the compiler does not know
the implementation mode for extern functions, so the linker must update BL/BLX
instructions to match what is linked is actually linked together. In addition,
pointers to functions (such as vtables) must have the low bit set if the target
of the pointer is a thumb mode function.
llvm-svn: 214140
Sometimes compilers emit data into code sections (e.g. constant pools or
jump tables). These runs of data can throw off disassemblers. The solution
in mach-o is that ranges of data-in-code are encoded into a table pointed to
by the LC_DATA_IN_CODE load command.
The way the data-in-code information is encoded into lld's Atom model is that
that start and end of each data run is marked with a Reference whose offset
is the start/end of the data run. For arm, the switch back to code also marks
whether it is thumb or arm code.
llvm-svn: 213901
This patch just supports marking ranges that are thumb code (vs arm code).
Future patches will mark data and jump table ranges. The ranges are encoded
as References with offsetInAtom being the start of the range and the target
being the same atom.
llvm-svn: 213712
