[libc] Implement 'getenv' on the GPU target (#102376)

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.

libc/config/CMakeLists.txt

@@ -1,3 +1,7 @@
-#TODO: Properly select the correct subdirectory.
-
-add_subdirectory(linux)
+add_header_library(
+  app_h
+  HDRS
+    app.h
+  DEPENDS
+    libc.src.__support.common
+)

libc/config/app.h

@@ -0,0 +1,20 @@
+//===-- Classes to capture properites of applications -----------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_CONFIG_APP_H
+#define LLVM_LIBC_CONFIG_APP_H
+
+#include "src/__support/macros/properties/architectures.h"
+
+#if defined(LIBC_TARGET_ARCH_IS_GPU)
+#include "gpu/app.h"
+#elif defined(__linux__)
+#include "linux/app.h"
+#endif
+
+#endif // LLVM_LIBC_CONFIG_APP_H

libc/config/gpu/app.h

@@ -0,0 +1,28 @@
+//===-- Classes to capture properites of GPU applications -------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_CONFIG_GPU_APP_H
+#define LLVM_LIBC_CONFIG_GPU_APP_H
+
+#include "src/__support/macros/config.h"
+#include "src/__support/macros/properties/architectures.h"
+
+#include <stdint.h>
+
+namespace LIBC_NAMESPACE_DECL {
+
+// TODO: Move other global values here and export them to the host.
+struct DataEnvironment {
+  uintptr_t *env_ptr;
+};
+
+extern DataEnvironment app;
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_CONFIG_GPU_APP_H

libc/config/gpu/entrypoints.txt

@@ -167,6 +167,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.stdlib.strtoull
     libc.src.stdlib.at_quick_exit
     libc.src.stdlib.quick_exit
+    libc.src.stdlib.getenv
 
     # TODO: Implement these correctly
     libc.src.stdlib.aligned_alloc

libc/config/linux/CMakeLists.txt

@@ -1,7 +0,0 @@
-add_header_library(
-  app_h
-  HDRS
-    app.h
-  DEPENDS
-    libc.src.__support.common
-)

libc/src/__support/threads/linux/CMakeLists.txt

@@ -77,7 +77,7 @@ add_object_library(
     thread.cpp
   DEPENDS
     .futex_utils
-    libc.config.linux.app_h
+    libc.config.app_h
     libc.include.sys_syscall
     libc.include.fcntl
     libc.src.errno.errno

libc/src/__support/threads/linux/thread.cpp

@@ -7,7 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "src/__support/threads/thread.h"
-#include "config/linux/app.h"
+#include "config/app.h"
 #include "src/__support/CPP/atomic.h"
 #include "src/__support/CPP/string_view.h"
 #include "src/__support/CPP/stringstream.h"

libc/src/stdlib/CMakeLists.txt

@@ -62,7 +62,7 @@ add_entrypoint_object(
   HDRS
     getenv.h
   DEPENDS
-    libc.config.linux.app_h
+  libc.config.app_h
 )
 
 add_entrypoint_object(

libc/src/stdlib/getenv.cpp

@@ -7,7 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "src/stdlib/getenv.h"
-#include "config/linux/app.h"
+#include "config/app.h"
 #include "src/__support/CPP/string_view.h"
 #include "src/__support/common.h"
 #include "src/__support/macros/config.h"

libc/src/sys/auxv/linux/CMakeLists.txt

@@ -11,7 +11,7 @@ add_entrypoint_object(
     libc.src.__support.threads.callonce
     libc.src.__support.common
     libc.src.errno.errno
-    libc.config.linux.app_h
+    libc.config.app_h
     libc.src.fcntl.open
     libc.src.unistd.read
     libc.src.unistd.close

libc/src/sys/auxv/linux/getauxval.cpp

@@ -7,7 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "src/sys/auxv/getauxval.h"
-#include "config/linux/app.h"
+#include "config/app.h"
 #include "src/__support/common.h"
 #include "src/__support/macros/config.h"
 #include "src/errno/libc_errno.h"

libc/startup/gpu/CMakeLists.txt

@@ -34,7 +34,7 @@ function(add_startup_object name)
       RUNTIME_OUTPUT_DIRECTORY ${LIBC_LIBRARY_DIR}
       RUNTIME_OUTPUT_NAME ${name}.o)
     target_link_options(${fq_target_name}.exe PRIVATE
-                        "-nostdlib" "-flto" "-Wl,--lto-emit-llvm")
+                        "-r" "-nostdlib" "-flto" "-Wl,--lto-emit-llvm")
   endif()
 endfunction()
 

libc/startup/gpu/amdgpu/CMakeLists.txt

@@ -3,6 +3,7 @@ add_startup_object(
   SRC
     start.cpp
   DEPENDS
+    libc.config.app_h
     libc.src.__support.RPC.rpc_client
     libc.src.__support.GPU.utils
     libc.src.stdlib.exit

libc/startup/gpu/amdgpu/start.cpp

@@ -6,6 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "config/gpu/app.h"
 #include "src/__support/GPU/utils.h"
 #include "src/__support/RPC/rpc_client.h"
 #include "src/__support/macros/config.h"
@@ -16,6 +17,8 @@ extern "C" int main(int argc, char **argv, char **envp);
 
 namespace LIBC_NAMESPACE_DECL {
 
+DataEnvironment app;
+
 extern "C" uintptr_t __init_array_start[];
 extern "C" uintptr_t __init_array_end[];
 extern "C" uintptr_t __fini_array_start[];
@@ -40,6 +43,8 @@ static void call_fini_array_callbacks() {
 
 extern "C" [[gnu::visibility("protected"), clang::amdgpu_kernel]] void
 _begin(int argc, char **argv, char **env) {
+  __atomic_store_n(&LIBC_NAMESPACE::app.env_ptr,
+                   reinterpret_cast<uintptr_t *>(env), __ATOMIC_RELAXED);
   // We want the fini array callbacks to be run after other atexit
   // callbacks are run. So, we register them before running the init
   // array callbacks as they can potentially register their own atexit

libc/startup/gpu/nvptx/CMakeLists.txt

@@ -3,6 +3,7 @@ add_startup_object(
   SRC
     start.cpp
   DEPENDS
+    libc.config.app_h
     libc.src.__support.RPC.rpc_client
     libc.src.__support.GPU.utils
     libc.src.stdlib.exit

libc/startup/gpu/nvptx/start.cpp

@@ -6,6 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "config/gpu/app.h"
 #include "src/__support/GPU/utils.h"
 #include "src/__support/RPC/rpc_client.h"
 #include "src/__support/macros/config.h"
@@ -16,6 +17,8 @@ extern "C" int main(int argc, char **argv, char **envp);
 
 namespace LIBC_NAMESPACE_DECL {
 
+DataEnvironment app;
+
 extern "C" {
 // Nvidia's 'nvlink' linker does not provide these symbols. We instead need
 // to manually create them and update the globals in the loader implememtation.
@@ -46,6 +49,9 @@ static void call_fini_array_callbacks() {
 
 extern "C" [[gnu::visibility("protected"), clang::nvptx_kernel]] void
 _begin(int argc, char **argv, char **env) {
+  __atomic_store_n(&LIBC_NAMESPACE::app.env_ptr,
+                   reinterpret_cast<uintptr_t *>(env), __ATOMIC_RELAXED);
+
   // We want the fini array callbacks to be run after other atexit
   // callbacks are run. So, we register them before running the init
   // array callbacks as they can potentially register their own atexit

libc/startup/linux/CMakeLists.txt

@@ -95,7 +95,7 @@ add_object_library(
   HDRS
     do_start.h
   DEPENDS
-    libc.config.linux.app_h
+    libc.config.app_h
     libc.include.sys_mman
     libc.include.sys_syscall
     libc.include.llvm-libc-macros.link_macros

libc/startup/linux/aarch64/CMakeLists.txt

@@ -3,7 +3,7 @@ add_startup_object(
   SRC
     tls.cpp
   DEPENDS
-    libc.config.linux.app_h
+    libc.config.app_h
     libc.include.sys_mman
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
@@ -18,7 +18,7 @@ add_startup_object(
   SRC
     start.cpp
   DEPENDS
-    libc.config.linux.app_h
+    libc.config.app_h
   COMPILE_OPTIONS
     -fno-omit-frame-pointer
     -ffreestanding # To avoid compiler warnings about calling the main function.

libc/startup/linux/do_start.h

@@ -6,7 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "config/linux/app.h"
+#include "config/app.h"
 #include "src/__support/macros/config.h"
 
 namespace LIBC_NAMESPACE_DECL {

libc/startup/linux/riscv/CMakeLists.txt

@@ -3,7 +3,7 @@ add_startup_object(
   SRC
     tls.cpp
   DEPENDS
-    libc.config.linux.app_h
+    libc.config.app_h
     libc.include.sys_mman
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
@@ -18,7 +18,7 @@ add_startup_object(
   SRC
     start.cpp
   DEPENDS
-    libc.config.linux.app_h
+    libc.config.app_h
     libc.src.__support.macros.attributes
   COMPILE_OPTIONS
     -fno-omit-frame-pointer

libc/startup/linux/x86_64/CMakeLists.txt

@@ -3,7 +3,7 @@ add_startup_object(
   SRC
     tls.cpp
   DEPENDS
-    libc.config.linux.app_h
+    libc.config.app_h
     libc.include.sys_mman
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
@@ -20,7 +20,7 @@ add_startup_object(
   SRC
     start.cpp
   DEPENDS
-    libc.config.linux.app_h
+    libc.config.app_h
     libc.src.__support.macros.attributes
   COMPILE_OPTIONS
     -fno-stack-protector

libc/test/integration/src/stdlib/CMakeLists.txt

@@ -13,4 +13,3 @@ add_integration_test(
     FRANCE=Paris
     GERMANY=Berlin
 )
-