When parsing name and linking sections, we currently require that the object
must have a code section (it seems that this was intended to verify section
ordering). However it can be useful for binaries to have their code sections
stripped out (e.g. if we just want the debug info). In that case we need
the rest of the known sections (so e.g. we know how many functions there
are, to verify the name section) but not the actual code.
I've removed the restriction completely. I think this is OK because the
section-parsing code already checks function and global indices in many
places for validity and will return appropriate errors if the relevant sections
are missing. Also we can't just replace the requirement of seeing a code section
with a requirement that we see a function or global section, because a binary
may just not have any functions or globals.
But there's only an problem if the name or linking section tries to name a
nonexistent function.
Part of a fix for https://github.com/emscripten-core/emscripten/issues/13084
Differential Revision: https://reviews.llvm.org/D128094
There are 3 places where we were using WASM_SEC_TAG as the "last" known
section type, which requires updating (or leaves a bug) when a new known
section type is added. Instead add a "last type" to the enum for this
purpose.
Differential Revision: https://reviews.llvm.org/D127164
Currently there are 2 duplicate implementation, and I want to add
a use in a 3rd place. Combine them in lib/BinaryFormat so they can
be shared.
Also update toString for symbol and reloc types to use StringRef
Differential Revision: https://reviews.llvm.org/D126553
This change continues to lay the ground work for supporting extended
const expressions in the linker.
The included test covers object file reading and writing and the YAML
representation.
Differential Revision: https://reviews.llvm.org/D121349
Most notably,
llvm/Object/Binary.h no longer includes llvm/Support/MemoryBuffer.h
llvm/Object/MachOUniversal*.h no longer include llvm/Object/Archive.h
llvm/Object/TapiUniversal.h no longer includes llvm/Object/TapiFile.h
llvm-project preprocessed size:
before: 1068185081
after: 1068324320
Discourse thread: https://discourse.llvm.org/t/include-what-you-use-include-cleanup
Differential Revision: https://reviews.llvm.org/D119457
[NFC] This patch fixes URLs containing "master". Old URLs were either broken or
redirecting to the new URL.
Reviewed By: #libc, ldionne, mehdi_amini
Differential Revision: https://reviews.llvm.org/D113186
This makes Wasm EH work with dynamic linking. So far we were only able
to handle destructors, which do not use any tags or LSDA info.
1. This uses `TargetExternalSymbol` for `GCC_except_tableN` symbols,
which points to the address of per-function LSDA info. It is more
convenient to use than `MCSymbol` because it can take additional
target flags.
2. When lowering `wasm_lsda` intrinsic, if PIC is enabled, make the
symbol relative to `__memory_base` and generate the `add` node. If
PIC is disabled, continue to use the absolute address.
3. Make tag symbols (`__cpp_exception` and `__c_longjmp`) undefined in
the backend, because it is hard to make it work with dynamic
linking's loading order. Instead, we make all tag symbols undefined
in the LLVM backend and import it from JS.
4. Add support for undefined tags to the linker.
Companion patches:
- https://github.com/WebAssembly/binaryen/pull/4223
- https://github.com/emscripten-core/emscripten/pull/15266
Reviewed By: sbc100
Differential Revision: https://reviews.llvm.org/D111388
This removes `WasmTagType`. `WasmTagType` contained an attribute and a
signature index:
```
struct WasmTagType {
uint8_t Attribute;
uint32_t SigIndex;
};
```
Currently the attribute field is not used and reserved for future use,
and always 0. And that this class contains `SigIndex` as its property is
a little weird in the place, because the tag type's signature index is
not an inherent property of a tag but rather a reference to another
section that changes after linking. This makes tag handling in the
linker also weird that tag-related methods are taking both `WasmTagType`
and `WasmSignature` even though `WasmTagType` contains a signature
index. This is because the signature index changes in linking so it
doesn't have any info at this point. This instead moves `SigIndex` to
`struct WasmTag` itself, as we did for `struct WasmFunction` in D111104.
In this CL, in lib/MC and lib/Object, this now treats tag types in the
same way as function types. Also in YAML, this removes `struct Tag`,
because now it only contains the tag index. Also tags set `SigIndex` in
`WasmImport` union, as functions do.
I think this makes things simpler and makes tag handling more in line
with function handling. These two shares similar properties in that both
of them have signatures, but they are kind of nominal so having the same
signature doesn't mean they are the same element.
Also a drive-by fix: the reserved 'attirubute' part's encoding changed
from uleb32 to uint8 a while ago. This was fixed in lib/MC and
lib/Object but not in YAML. This doesn't change object files because the
field's value is always 0 and its encoding is the same for the both
encoding.
This is effectively NFC; I didn't mark it as such just because it
changed YAML test results.
Reviewed By: sbc100, tlively
Differential Revision: https://reviews.llvm.org/D111086
This simplifies the code in a number of ways and avoids
having to track functions and their types separately.
Differential Revision: https://reviews.llvm.org/D111104
We previously had a limitation that TLS variables could not
be exported (and therefore could also not be imported). This
change removed that limitation.
Differential Revision: https://reviews.llvm.org/D108877
The re-use of this struct across iterations of the loop was causing
fields (specifically Name) to be incorrectly shared between multiple
sections.
Differential Revision: https://reviews.llvm.org/D108984
This changes the encoding of the `attribute` field, which currently only
contains the value `0` denoting this tag is for an exception, from
`varuint32` to `uint8`. This field is effectively unused at the moment
and reserved for future use, and it is not likely to need `varuint32`
even in future.
See https://github.com/WebAssembly/exception-handling/pull/162.
This does not change any encoded binaries because `0` is encoded in the
same way both in `varuint32` and `uint8`.
Reviewed By: tlively
Differential Revision: https://reviews.llvm.org/D104571
__table_base is know 64-bit, since in LLVM it represents a function pointer offset
__table_base32 is a copy in wasm32 for use in elem init expr, since no truncation may be used there.
New reloc R_WASM_TABLE_INDEX_REL_SLEB64 added
Differential Revision: https://reviews.llvm.org/D101784
This fixes a bug with string merging with string symbols that contain
NULLs, as is the case in the `merge-string.s` test.
The bug only showed when we run with `--relocatable` and then try read
the resulting object back in. In this case we would end up with string
symbols that extend past the end of the segment in which they live.
The problem comes from the fact that sections which are flagged as
string mergable assume that all strings are NULL terminated. The
merging algorithm will drop trailing chars that follow a NULL since they
are essentially unreachable. However, the "size" attribute (in the
symbol table) of such a truncated symbol is not updated resulting a
symbol size that can overlap the end of the segment.
I verified that this can happen in ELF too given the right conditions
and the its harmless enough. In practice Strings that contain embedded
null should not be part of a mergable section.
Differential Revision: https://reviews.llvm.org/D102281
This change was originally landed in: 5000a1b4b9
It was reverted in: 061e071d8c
This change adds support for a new WASM_SEG_FLAG_STRINGS flag in
the object format which works in a similar fashion to SHF_STRINGS
in the ELF world.
Unlike the ELF linker this support is currently limited:
- No support for SHF_MERGE (non-string merging)
- Always do full tail merging ("lo" can be merged with "hello")
- Only support single byte strings (p2align 0)
Like the ELF linker merging is only performed at `-O1` and above.
This fixes part of https://bugs.llvm.org/show_bug.cgi?id=48828,
although crucially it doesn't not currently support debug sections
because they are not represented by data segments (they are custom
sections)
Differential Revision: https://reviews.llvm.org/D97657
This change adds support for a new WASM_SEG_FLAG_STRINGS flag in
the object format which works in a similar fashion to SHF_STRINGS
in the ELF world.
Unlike the ELF linker this support is currently limited:
- No support for SHF_MERGE (non-string merging)
- Always do full tail merging ("lo" can be merged with "hello")
- Only support single byte strings (p2align 0)
Like the ELF linker merging is only performed at `-O1` and above.
This fixes part of https://bugs.llvm.org/show_bug.cgi?id=48828,
although crucially it doesn't not currently support debug sections
because they are not represented by data segments (they are custom
sections)
Differential Revision: https://reviews.llvm.org/D97657
When running in relocatable mode any input data segments that are part
of a comdat group should not be merged with other segments of the same
name. This is because the final linker needs to keep the separate so
they can be included/excluded individually.
Often this is not a problem since normally only one section with a given
name `foo` ends up in the output object file. However, the problem
occurs when one input contains `foo` which part of a comdat and another
object contains a local symbol `foo` we were attempting to merge them.
This behaviour matches (I believe) that of the ELF linker. See
`LinkerScript.cpp:addInputSec`.
Fixes: https://github.com/emscripten-core/emscripten/issues/9726
Differential Revision: https://reviews.llvm.org/D101703
The number of events and the type index should be encoded in ULEB128,
but they were incorrctly encoded in LEB128. The smallest number with
which its LEB128 and ULEB128 encodings are different is 64.
There's no way we can generate 64 events in the C++ toolchain
implementation so we can't test that, but the attached test tests when
the type index is 64.
Reviewed By: dschuff
Differential Revision: https://reviews.llvm.org/D99627
This patch renames the "Initial" member of WasmLimits to the name used
in the spec, "Minimum".
In the core WebAssembly specification, the Limits data type has one
required "min" member and one optional "max" member, indicating the
minimum required size of the corresponding table or memory, and the
maximum size, if any.
Although the WebAssembly spec does instantiate locally-defined tables
and memories with the initial size being equal to the minimum size, it
can't impose such a requirement for imports. It doesn't make sense to
require an initial size for a memory import, for example. The compiler
can only sensibly express the minimum and maximum sizes.
See
https://github.com/WebAssembly/js-types/blob/master/proposals/js-types/Overview.md#naming-of-size-limits
for a related discussion that agrees that the right name of "initial" is
"minimum" when querying the type of a table or memory from JavaScript.
(Of course it still makes sense for JS to speak in terms of an initial
size when it explicitly instantiates memories and tables.)
Differential Revision: https://reviews.llvm.org/D99186
This `R_WASM_MEMORY_ADDR_SELFREL_I32` relocation represents an offset
between its relocating address and the symbol address. It's very similar
to `R_X86_64_PC32` but restricted to be used for only data segments.
```
S + A - P
```
A: Represents the addend used to compute the value of the relocatable
field.
P: Represents the place of the storage unit being relocated.
S: Represents the value of the symbol whose index resides in the
relocation entry.
Proposal: https://github.com/WebAssembly/tool-conventions/issues/162
Differential Revision: https://reviews.llvm.org/D96659
With reference types, tables can have non-zero table numbers. This
commit adds support for element sections against these tables.
Differential Revision: https://reviews.llvm.org/D97923
Element sections will also need flags, so we shouldn't squat the
WASM_SEGMENT namespace.
Depends on D90948.
Differential Revision: https://reviews.llvm.org/D92315
This commit adds table symbol support in a partial way, while still
including some special cases for the __indirect_function_table symbol.
No change in tests.
Differential Revision: https://reviews.llvm.org/D94075
Allow sections to be placed into COMDAT groups, in addtion to functions and data
segments.
Also make section symbols unnamed, which allows sections with identical names
(section names are independent of their section symbols, but previously we
gave the symbols the same name as their sections, which results in collisions
when sections are identically-named).
Differential Revision: https://reviews.llvm.org/D92691
The indirect function table, synthesized by the linker, is needed if and
only if there are TABLE_INDEX relocs.
Differential Revision: https://reviews.llvm.org/D91637
This commit factors out a WasmTableType definition from WasmTable, as is
the case for WasmGlobal and other data types. Also add support for
extracting the SymbolName for a table from the linking section's symbol
table.
Differential Revision: https://reviews.llvm.org/D91849
These relocations represent offsets from the __tls_base symbol.
Previously we were just using normal MEMORY_ADDR relocations and relying
on the linker to select a segment-offset rather and absolute value in
Symbol::getVirtualAddress(). Using an explicit relocation type allows
allow us to clearly distinguish absolute from relative relocations based
on the relocation information alone.
One place this is useful is being able to reject absolute relocation in
the PIC case, but still accept TLS relocations.
Differential Revision: https://reviews.llvm.org/D91276
Implementation of instructions table.get, table.set, table.grow,
table.size, table.fill, table.copy.
Missing instructions are table.init and elem.drop as they deal with
element sections which are not yet implemented.
Added more tests to tables.s
Differential Revision: https://reviews.llvm.org/D89797
Adds more testing in basic-assembly.s and a new test tables.s.
Adds support to yaml reading and writing of tables as well.
Differential Revision: https://reviews.llvm.org/D88815
Accounting for the fact that Wasm function indices are 32-bit, but in wasm64 we want uniform 64-bit pointers.
Includes reloc types for 64-bit table indices.
Differential Revision: https://reviews.llvm.org/D83729
Dan Gohman