[libc] move __stack_chk_fail to src/ from startup/

__stack_chk_fail should be provided by libc.a, not startup files.

Add __stack_chk_fail to existing linux and arm entrypoints. On Windows (when
not targeting MinGW), it seems that the corresponding function identifier is
__security_check_cookie, so no entrypoint is added for Windows. Baremetal
targets also ought to be compileable with `-fstack-protector*`

There is no common header for this prototype, since calls to __stack_chk_fail
are meant to be inserted by the compiler upon function return when compiled
`-fstack-protector*`.

Author: nickdesaulniers

libc/config/baremetal/arm/entrypoints.txt

@@ -17,6 +17,9 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.ctype.tolower
     libc.src.ctype.toupper
 
+    # compiler entrypoints (no corresponding header)
+    libc.src.compiler.__stack_chk_fail
+
     # errno.h entrypoints
     libc.src.errno.errno
 
@@ -69,7 +72,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.stdio.snprintf
     libc.src.stdio.vsprintf
     libc.src.stdio.vsnprintf
- 
+
     # stdlib.h entrypoints
     libc.src.stdlib.abs
     libc.src.stdlib.atoi

libc/config/baremetal/riscv/entrypoints.txt

@@ -17,6 +17,9 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.ctype.tolower
     libc.src.ctype.toupper
 
+    # compiler entrypoints (no corresponding header)
+    libc.src.compiler.__stack_chk_fail
+
     # errno.h entrypoints
     libc.src.errno.errno
 

libc/config/linux/aarch64/entrypoints.txt

@@ -16,7 +16,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.ctype.toascii
     libc.src.ctype.tolower
     libc.src.ctype.toupper
-    
+
     # errno.h entrypoints
     libc.src.errno.errno
 
@@ -239,7 +239,7 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.asinf
     libc.src.math.asinhf
     libc.src.math.atanf
-    libc.src.math.atanhf    
+    libc.src.math.atanhf
     libc.src.math.copysign
     libc.src.math.copysignf
     libc.src.math.copysignl
@@ -353,6 +353,9 @@ set(TARGET_LIBM_ENTRYPOINTS
 
 if(LLVM_LIBC_FULL_BUILD)
   list(APPEND TARGET_LIBC_ENTRYPOINTS
+    # compiler entrypoints (no corresponding header)
+    libc.src.compiler.__stack_chk_fail
+
     # network.h entrypoints
     libc.src.network.htonl
     libc.src.network.htons

libc/config/linux/arm/entrypoints.txt

@@ -66,7 +66,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.inttypes.imaxdiv
     libc.src.inttypes.strtoimax
     libc.src.inttypes.strtoumax
- 
+
     # stdlib.h entrypoints
     libc.src.stdlib.abs
     libc.src.stdlib.atoi
@@ -88,7 +88,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.stdlib.strtoll
     libc.src.stdlib.strtoul
     libc.src.stdlib.strtoull
-    
+
     # sys/mman.h entrypoints
     libc.src.sys.mman.mmap
     libc.src.sys.mman.munmap

libc/config/linux/riscv/entrypoints.txt

@@ -362,6 +362,9 @@ set(TARGET_LIBM_ENTRYPOINTS
 
 if(LLVM_LIBC_FULL_BUILD)
   list(APPEND TARGET_LIBC_ENTRYPOINTS
+    # compiler entrypoints (no corresponding header)
+    libc.src.compiler.__stack_chk_fail
+
     # assert.h entrypoints
     libc.src.assert.__assert_fail
 

libc/config/linux/x86_64/entrypoints.txt

@@ -375,6 +375,9 @@ if(LLVM_LIBC_FULL_BUILD)
     # assert.h entrypoints
     libc.src.assert.__assert_fail
 
+    # compiler entrypoints (no corresponding header)
+    libc.src.compiler.__stack_chk_fail
+
     # dirent.h entrypoints
     libc.src.dirent.closedir
     libc.src.dirent.dirfd

libc/src/CMakeLists.txt

@@ -29,10 +29,11 @@ if(NOT LLVM_LIBC_FULL_BUILD)
 endif()
 
 add_subdirectory(assert)
+add_subdirectory(compiler)
 add_subdirectory(network)
+add_subdirectory(search)
 add_subdirectory(setjmp)
 add_subdirectory(signal)
 add_subdirectory(spawn)
 add_subdirectory(threads)
 add_subdirectory(time)
-add_subdirectory(search)

libc/src/compiler/CMakeLists.txt

@@ -0,0 +1,18 @@
+if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
+  add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
+else()
+  add_subdirectory(generic)
+endif()
+
+if(TARGET libc.src.compiler.${LIBC_TARGET_OS}.__stack_chk_fail)
+  set(stack_chk_fail_dep libc.src.compiler.${LIBC_TARGET_OS}.__stack_chk_fail)
+else()
+  set(stack_chk_fail_dep libc.src.compiler.generic.__stack_chk_fail)
+endif()
+
+add_entrypoint_object(
+  __stack_chk_fail
+  ALIAS
+  DEPENDS
+    ${stack_chk_fail_dep}
+)

libc/src/compiler/generic/CMakeLists.txt

@@ -0,0 +1,11 @@
+add_entrypoint_object(
+  __stack_chk_fail
+  SRCS
+    __stack_chk_fail.cpp
+  HDRS
+    ../__stack_chk_fail.h
+  DEPENDS
+    libc.include.assert
+    libc.src.__support.OSUtil.osutil
+    libc.src.stdlib.abort
+)

libc/src/compiler/generic/__stack_chk_fail.cpp

@@ -0,0 +1,21 @@
+//===-- Implementation of __stack_chk_fail --------------------------------===//
+//
+// 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/compiler/__stack_chk_fail.h"
+#include "src/__support/OSUtil/io.h"
+#include "src/stdlib/abort.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(void, __stack_chk_fail, (void)) {
+  LIBC_NAMESPACE::write_to_stderr("stack smashing detected");
+  LIBC_NAMESPACE::abort();
+}
+
+} // namespace LIBC_NAMESPACE
+

libc/startup/linux/x86_64/start.cpp

@@ -25,11 +25,6 @@
 
 extern "C" int main(int, char **, char **);
 
-extern "C" void __stack_chk_fail() {
-  LIBC_NAMESPACE::write_to_stderr("stack smashing detected");
-  LIBC_NAMESPACE::abort();
-}
-
 namespace LIBC_NAMESPACE {
 
 #ifdef SYS_mmap2