Summary:
This patch implements 'getenv'. I was torn on how to implement this,
since realistically we only have access to this environment pointer in
the "loader" interface. An alternative would be to use an RPC call every
time, but I think that's overkill for what this will be used for. A
better solution is just to emit a common `DataEnvironment` that contains
all of the host visible resources to initialize. Right now this is the
`env_ptr`, `clock_freq`, and `rpc_client`.
I did this by making the `app.h` interface that Linux uses more general,
could possibly move that into a separate patch, but I figured it's
easier to see with the usage.
Otherwise the startup objects will fail to link since they were cross compiled,
but the linker is not informed of the intent to cross compile, which results in
linker errors when the host architecture does not match the target
architecture.
Summary:
Currently, doing `ninja install` will fail in fullbuild mode due to the
startup utilities not being built by default. This was hidden previously
by the fact that if tests were run, it would build the startup utilities
and thus they would be present.
This patch solves this issue by making the `libc-startup` target a
dependncy on the final library. Furthermore we simply factor out the
library install directory into the base CMake directory next to the
include directory handling. This change makes the `crt` files get
installed in `lib/x86_64-unknown-linu-gnu` instead of just `lib`.
This fixes an error I had where doing a runtimes failed to install its
libraries because the install step always errored.
* separate initialization routines into _start and do_start for all
architectures.
* lift do_start as a separate object library to avoid code duplication.
* (addtionally) address the problem of building hermetic libc with
-fstack-pointer-*
The `crt1.o` is now a merged result of three components:
```
___
|___ x86_64
| |_______ start.cpp.o <- _start (loads process initial stack and aligns stack pointer)
| |_______ tls.cpp.o <- init_tls, cleanup_tls, set_thread_pointer (TLS related routines)
|___ do_start.cpp.o <- do_start (sets up global variables and invokes the main function)
```
As part of startup refactoring, this patch adds a function to merge
multiple objects into a single relocatable object:
cc -r obj1.o obj2.o -o obj.o
A relocatable object is an object file that is not fully linked into an
executable or a shared library. It is an intermediate file format that
can be passed into the linker.
A crt object can have arch-specific code and arch-agnostic code. To
reduce code cohesion, the implementation is splitted into multiple
units. As a result, we need to merge them into a single relocatable
object.
Instead of using a custom target to copy the startup object file to a
file with the desired name, a normal object library with a special
property is used.
Follow up patches will do more cleanup wrt how the startup objects are
used in integration tests.
Reviewed By: jhuber6
Differential Revision: https://reviews.llvm.org/D143464
We currently put everything in one single archive libc.a which breaks in
certain situations where the compiler drivers expect libm.a also. With
this change, we separate out libc.a and libm.a functions as is done
conventionally and put them in two different static archives.
One will now have to build two targets, `libc` and `libm` which produce
`libc.a` and `libm.a` respectively. Under default build, one still builds only
one target named `libc` which produces `libllvmlibc.a`.
Reviewed By: jhuber6
Differential Revision: https://reviews.llvm.org/D143005
