[libc] Provide 'signal.h' header for the GPU

Summary:
This header is practically useless, but we provide it mostly for the
macros so that applications can compile. I'm only doing this for the
`libc++` unittests that want it, and it is part of the C standard
technically. I just made an RPC call to do `raise`. Anything more isn't
going to work since it'd be way too annoying to make the CPU call into
some signal handler the GPU registered.

Author: jhuber6

libc/config/gpu/entrypoints.txt

@@ -228,6 +228,9 @@ set(TARGET_LIBC_ENTRYPOINTS
     # wchar.h entrypoints
     libc.src.wchar.wctob
 
+    # signal.h entrypoints
+    libc.src.signal.raise
+
     # gpu/rpc.h entrypoints
     libc.src.gpu.rpc_host_call
 )

libc/config/gpu/headers.txt

@@ -2,6 +2,7 @@ set(TARGET_PUBLIC_HEADERS
     libc.include.assert
     libc.include.ctype
     libc.include.string
+    libc.include.signal
     libc.include.float
     libc.include.stdint
     libc.include.inttypes

libc/include/llvm-libc-macros/gpu/CMakeLists.txt

@@ -3,3 +3,9 @@ add_header(
   HDR
     time-macros.h
 )
+
+add_header(
+  signal_macros
+  HDR
+    signal-macros.h
+)

libc/include/llvm-libc-macros/gpu/signal-macros.h

@@ -0,0 +1,24 @@
+//===-- Definition of GPU signal number macros ----------------------------===//
+//
+// 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_MACROS_GPU_SIGNAL_MACROS_H
+#define LLVM_LIBC_MACROS_GPU_SIGNAL_MACROS_H
+
+#define SIGINT 2
+#define SIGILL 4
+#define SIGABRT 6
+#define SIGFPE 8
+#define SIGSEGV 11
+#define SIGTERM 15
+
+// Max signal number
+#define NSIG 64
+
+#define __NSIGSET_WORDS NSIG
+
+#endif // LLVM_LIBC_MACROS_GPU_SIGNAL_MACROS_H

libc/include/llvm-libc-macros/signal-macros.h

@@ -9,8 +9,10 @@
 #ifndef LLVM_LIBC_MACROS_SIGNAL_MACROS_H
 #define LLVM_LIBC_MACROS_SIGNAL_MACROS_H
 
-#ifdef __linux__
+#if defined(__linux__)
 #include "linux/signal-macros.h"
+#elif defined(__NVPTX__) || defined(__AMDGPU__)
+#include "gpu/signal-macros.h"
 #endif
 
 #endif // LLVM_LIBC_MACROS_SIGNAL_MACROS_H

libc/include/llvm-libc-types/rpc_opcodes_t.h

@@ -38,6 +38,7 @@ typedef enum {
   RPC_PRINTF_TO_STDERR_PACKED,
   RPC_PRINTF_TO_STREAM_PACKED,
   RPC_REMOVE,
+  RPC_RAISE,
   RPC_LAST = 0xFFFF,
 } rpc_opcode_t;
 

libc/include/llvm-libc-types/struct_sigaction.h

@@ -17,7 +17,7 @@ struct sigaction {
     void (*sa_handler)(int);
     void (*sa_sigaction)(int, siginfo_t *, void *);
   };
-  sigset_t sa_mask;
+  struct sigset_t sa_mask;
   int sa_flags;
 #ifdef __linux__
   // This field is present on linux for most targets.

libc/src/signal/gpu/CMakeLists.txt

@@ -0,0 +1,11 @@
+add_entrypoint_object(
+  raise
+  SRCS
+    raise.cpp
+  HDRS
+    ../raise.h
+  DEPENDS
+    libc.hdr.types.sigset_t
+    libc.src.__support.RPC.rpc_client
+)
+

libc/src/signal/gpu/raise.cpp

@@ -0,0 +1,30 @@
+//===-- GPU implementation of signal --------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/signal/raise.h"
+
+#include "hdr/types/sigset_t.h"
+#include "llvm-libc-types/rpc_opcodes_t.h"
+#include "src/__support/RPC/rpc_client.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, raise, (int sig)) {
+  // We want to first make sure the server is listening before we exit.
+  rpc::Client::Port port = rpc::client.open<RPC_RAISE>();
+  int ret;
+  port.send_and_recv(
+      [=](rpc::Buffer *buf) { buf->data[0] = static_cast<uint64_t>(sig); },
+      [&](rpc::Buffer *buf) { ret = static_cast<int>(buf->data[0]); });
+  port.close();
+  return ret;
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/test/src/signal/CMakeLists.txt

@@ -1,6 +1,6 @@
 add_custom_target(libc_signal_unittests)
 
-add_libc_unittest(
+add_libc_test(
   raise_test
   SUITE
     libc_signal_unittests
@@ -9,6 +9,7 @@ add_libc_unittest(
   DEPENDS
     libc.include.signal
     libc.src.signal.raise
+  UNIT_TEST_ONLY # Requires death tests.
 )
 
 add_libc_unittest(

libc/utils/gpu/server/rpc_server.cpp

@@ -22,6 +22,7 @@
 #include "src/stdio/gpu/file.h"
 #include <algorithm>
 #include <atomic>
+#include <csignal>
 #include <cstdio>
 #include <cstring>
 #include <memory>
@@ -389,6 +390,12 @@ rpc_status_t handle_server_impl(
     });
     break;
   }
+  case RPC_RAISE: {
+    port->recv_and_send([](rpc::Buffer *buffer) {
+      buffer->data[0] = raise(static_cast<int>(buffer->data[0]));
+    });
+    break;
+  }
   case RPC_NOOP: {
     port->recv([](rpc::Buffer *) {});
     break;