Add implementations of POSIX mmap and munmap functions.

Summary:
A set of of linux x86_64 internal syscall helpers have also been added.

This change does not try to be perfect with respect to OS and machine
abstractions. A TODO note has been added at places where such abstractions
would help and make the arrangement scalable and cleaner. Addressing the
TODOs and building such abstractions is not in the scope of this change.
It is hoped that follow up changes cleaning up the problem areas and
addressing the TODOs will better illustrate the need for the changes.

This change also does not try to imitate mmap and munmap implementations
of other libcs. The idea here is to put in the bare minimum required to
obtain a working mmap and munmap, and then add the rest of the
functionality on an as needed basis.

Reviewers: abrachet, phosek, stanshebs, theraven

Subscribers: mgorny, MaskRay, jfb, libc-commits

Tags: #libc-project

Differential Revision: https://reviews.llvm.org/D71634

Author: Siva Chandra Reddy

libc/CMakeLists.txt

@@ -19,7 +19,8 @@ set(LIBC_TARGET_MACHINE ${CMAKE_SYSTEM_PROCESSOR})
 include(CMakeParseArguments)
 include(LLVMLibCRules)
 
-add_subdirectory(include)
 add_subdirectory(src)
+add_subdirectory(config)
+add_subdirectory(include)
 add_subdirectory(lib)
 add_subdirectory(utils)

libc/cmake/modules/LLVMLibCRules.cmake

@@ -250,7 +250,7 @@ function(add_redirector_object target_name)
   )
 endfunction(add_redirector_object)
 
-# Rule to build a shared library of redirector objects
+# Rule to build a shared library of redirector objects.
 function(add_redirector_library target_name)
   cmake_parse_arguments(
     "REDIRECTOR_LIBRARY"
@@ -287,6 +287,15 @@ function(add_redirector_library target_name)
   )
 endfunction(add_redirector_library)
 
+# Rule to add a gtest unittest.
+# Usage
+#    add_libc_unittest(
+#      <target name>
+#      SUITE <name of the suite this test belongs to>
+#      SRCS  <list of .cpp files for the test>
+#      HDRS  <list of .h files for the test>
+#      DEPENDS <list of dependencies>
+#    )
 function(add_libc_unittest target_name)
   if(NOT LLVM_INCLUDE_TESTS)
     return()
@@ -306,15 +315,19 @@ function(add_libc_unittest target_name)
     message(FATAL_ERROR "'add_libc_unittest' target requires a DEPENDS list of 'add_entrypoint_object' targets.")
   endif()
 
-  set(entrypoint_objects "")
+  set(library_deps "")
   foreach(dep IN LISTS LIBC_UNITTEST_DEPENDS)
     get_target_property(dep_type ${dep} "TARGET_TYPE")
-    string(COMPARE EQUAL ${dep_type} ${ENTRYPOINT_OBJ_TARGET_TYPE} dep_is_entrypoint)
-    if(NOT dep_is_entrypoint)
-      message(FATAL_ERROR "Dependency '${dep}' of 'add_entrypoint_unittest' is not an 'add_entrypoint_object' target.")
+    if (dep_type)
+      string(COMPARE EQUAL ${dep_type} ${ENTRYPOINT_OBJ_TARGET_TYPE} dep_is_entrypoint)
+      if(dep_is_entrypoint)
+        get_target_property(obj_file ${dep} "OBJECT_FILE_RAW")
+        list(APPEND library_deps ${obj_file})
+        continue()
+      endif()
     endif()
-    get_target_property(obj_file ${dep} "OBJECT_FILE_RAW")
-    list(APPEND entrypoint_objects "${obj_file}")
+    # TODO: Check if the dep is a normal CMake library target. If yes, then add it
+    # to the list of library_deps.
   endforeach(dep)
 
   add_executable(
@@ -329,15 +342,23 @@ function(add_libc_unittest target_name)
       ${LLVM_MAIN_SRC_DIR}/utils/unittest/googletest/include
       ${LLVM_MAIN_SRC_DIR}/utils/unittest/googlemock/include
       ${LIBC_SOURCE_DIR}
+      ${LIBC_BUILD_DIR}
   )
-  target_link_libraries(${target_name} PRIVATE ${entrypoint_objects} gtest_main gtest)
+
+  if(library_deps)
+    target_link_libraries(${target_name} PRIVATE ${library_deps})
+  endif()
+
   set_target_properties(${target_name} PROPERTIES RUNTIME_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})
 
   add_dependencies(
     ${target_name}
     ${LIBC_UNITTEST_DEPENDS}
     gtest
   )
+
+  target_link_libraries(${target_name} PRIVATE gtest_main gtest)
+
   add_custom_command(
     TARGET ${target_name}
     POST_BUILD

libc/config/CMakeLists.txt

@@ -0,0 +1 @@
+add_subdirectory(linux)

libc/config/linux/CMakeLists.txt

@@ -0,0 +1 @@
+add_subdirectory(x86_64)

libc/config/linux/api.td

@@ -4,25 +4,20 @@ include "spec/linux.td"
 include "spec/posix.td"
 include "spec/stdc.td"
 
-def FloatT : TypeDecl<"float_t"> {
-  let Decl = [{
-    #if __FLT_EVAL_METHOD__ == 1
-      typedef float float_t
-    #elif __FLT_EVAL_METHOD__ == 2
-      ...
-    #else
-      ...
-    #endif
-  }]; // This is only an example and not exactly how it will appear
-}
-
 def SizeT : TypeDecl<"size_t"> {
   let Decl = [{
     #define __need_size_t
     #include <stddef.h>
   }];
 }
 
+def OffT : TypeDecl<"off_t"> {
+  let Decl = [{
+    #define __need_off_t
+    #include <__posix-types.h>
+  }];
+}
+
 def NullMacro : MacroDef<"NULL"> {
   let Defn = [{
     #define __need_NULL
@@ -42,10 +37,6 @@ def MathAPI : PublicAPI<"math.h"> {
    "acos",
    "acosl",
   ];
-
-  let TypeDeclarations = [
-    FloatT,
-  ];
 }
 
 def StringAPI : PublicAPI<"string.h"> {
@@ -111,3 +102,34 @@ def ErrnoAPI : PublicAPI<"errno.h"> {
     MacroDefineIfNot<"EHWPOISON", "133">,
   ];
 }
+
+def SysMManAPI : PublicAPI<"sys/mman.h"> {
+  let Macros = [
+    SimpleMacroDef<"PROT_NONE", "0">,
+    SimpleMacroDef<"PROT_READ", "1">,
+    SimpleMacroDef<"PROT_WRITE", "2">,
+    SimpleMacroDef<"PROT_EXEC", "4">,
+
+    SimpleMacroDef<"MAP_FIXED", "1">,
+    SimpleMacroDef<"MAP_PRIVATE", "2">,
+    SimpleMacroDef<"MAP_SHARED", "4">,
+
+    SimpleMacroDef<"MAP_FAILED", "((void*)-1)">,
+
+    // TODO: The value of 0x20 is good for x86_64, but has to be extended
+    // in some manner to accommodate other machine architectures.
+    SimpleMacroDef<"MAP_ANONYMOUS", "0x20">
+
+    // TODO: Add other MAP_* macros used by Linux.
+  ];
+
+  let TypeDeclarations = [
+    SizeT,
+    OffT,
+  ];
+
+  let Functions = [
+    "mmap",
+    "munmap",
+  ];
+}

…c/__support/linux/entrypoint_macro.h.inc libc/config/linux/platfrom_defs.h.inclibc/src/__support/linux/entrypoint_macro.h.inc renamed to libc/config/linux/platfrom_defs.h.inc libc/src/__support/linux/entrypoint_macro.h.inc renamed to libc/config/linux/platfrom_defs.h.inc

@@ -1,4 +1,4 @@
-//===---- Definition of LLVM_LIBC_ENTRYPOINT macro for ELF paltforms ----*-===//
+//===----- Definition of platform specific macros for ELF paltforms -------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
@@ -11,3 +11,9 @@
 #define ENTRYPOINT_SECTION_ATTRIBUTE(name) \
     __attribute__((section(".llvm.libc.entrypoint."#name)))
 #define LLVM_LIBC_ENTRYPOINT(name) ENTRYPOINT_SECTION_ATTRIBUTE(name) name
+
+// TODO: Get rid of the PAGE_SIZE macro. It is present only as an interim
+// measure until we can move the implementations of mmap and munmap to under
+// the config/linux directory. After that, the implementations can use
+// EXEC_PAGESIZE until page size can be read from the aux vector. 
+#define PAGE_SIZE 4096