[libc][SysMMan] implement mincore (#73704)

Implement `mincore` as specified in
https://man7.org/linux/man-pages/man2/mincore.2.html

libc/config/linux/aarch64/entrypoints.txt

@@ -136,6 +136,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.sys.mman.mprotect
     libc.src.sys.mman.munmap
     libc.src.sys.mman.posix_madvise
+    libc.src.sys.mman.mincore
 
     # sys/random.h entrypoints
     libc.src.sys.random.getrandom

libc/config/linux/riscv/entrypoints.txt

@@ -142,6 +142,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.sys.mman.mprotect
     libc.src.sys.mman.munmap
     libc.src.sys.mman.posix_madvise
+    libc.src.sys.mman.mincore
 
     # sys/random.h entrypoints
     libc.src.sys.random.getrandom

libc/config/linux/x86_64/entrypoints.txt

@@ -142,6 +142,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.sys.mman.mprotect
     libc.src.sys.mman.munmap
     libc.src.sys.mman.posix_madvise
+    libc.src.sys.mman.mincore
 
     # sys/random.h entrypoints
     libc.src.sys.random.getrandom

libc/spec/linux.td

@@ -76,7 +76,20 @@ def Linux : StandardSpec<"Linux"> {
 
   HeaderSpec SysMMan = HeaderSpec<
       "sys/mman.h",
-      [Macro<"MAP_ANONYMOUS">]
+      [Macro<"MAP_ANONYMOUS">],
+      [], // Types
+      [], // Enumerations
+      [
+        FunctionSpec<
+            "mincore",
+            RetValSpec<IntType>,
+            [
+              ArgSpec<VoidPtr>,
+              ArgSpec<SizeTType>,
+              ArgSpec<UnsignedCharPtr>,
+            ]
+        >,
+      ]  // Functions
   >;
 
 

libc/spec/spec.td

@@ -49,6 +49,7 @@ def FloatType : NamedType<"float">;
 def DoubleType : NamedType<"double">;
 def LongDoubleType : NamedType<"long double">;
 def CharType : NamedType<"char">;
+def UnsignedCharType : NamedType<"unsigned char">;
 
 // TODO: Add compatibility layer to use C23 type _Float128 if possible.
 def Float128Type : NamedType<"__float128">;
@@ -109,6 +110,7 @@ def IntPtr : PtrType<IntType>;
 def RestrictedIntPtr : RestrictedPtrType<IntType>;
 def FloatPtr : PtrType<FloatType>;
 def DoublePtr : PtrType<DoubleType>;
+def UnsignedCharPtr : PtrType<UnsignedCharType>;
 
 def SigHandlerT : NamedType<"__sighandler_t">;
 

libc/src/sys/mman/CMakeLists.txt

@@ -36,3 +36,10 @@ add_entrypoint_object(
   DEPENDS
     .${LIBC_TARGET_OS}.posix_madvise
 )
+
+add_entrypoint_object(
+  mincore
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.mincore
+)

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

@@ -61,3 +61,16 @@ add_entrypoint_object(
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
 )
+
+add_entrypoint_object(
+  mincore
+  SRCS
+    mincore.cpp
+  HDRS
+    ../mincore.h
+  DEPENDS
+    libc.include.sys_mman
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)

libc/src/sys/mman/linux/mincore.cpp

@@ -0,0 +1,28 @@
+//===---------- Linux implementation of the mincore function --------------===//
+//
+// 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/sys/mman/mincore.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+
+#include "src/errno/libc_errno.h"
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(int, mincore, (void *addr, size_t len, unsigned char *vec)) {
+  long ret = syscall_impl(SYS_mincore, reinterpret_cast<long>(addr), len,
+                          reinterpret_cast<long>(vec));
+  if (ret < 0) {
+    libc_errno = static_cast<int>(-ret);
+    return -1;
+  }
+  return 0;
+}
+
+} // namespace LIBC_NAMESPACE

libc/src/sys/mman/mincore.h

@@ -0,0 +1,20 @@
+//===-- Implementation header for mincore function --------------*- 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_SRC_SYS_MMAN_MINCORE_H
+#define LLVM_LIBC_SRC_SYS_MMAN_MINCORE_H
+
+#include <sys/mman.h> // For size_t
+
+namespace LIBC_NAMESPACE {
+
+int mincore(void *addr, size_t len, unsigned char *vec);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_SYS_MMAN_MINCORE_H

libc/test/src/sys/mman/linux/CMakeLists.txt

@@ -62,3 +62,19 @@ add_libc_unittest(
     libc.src.sys.mman.posix_madvise
     libc.test.UnitTest.ErrnoSetterMatcher
 )
+
+add_libc_unittest(
+  mincore_test
+  SUITE
+    libc_sys_mman_unittests
+  SRCS
+    mincore_test.cpp
+  DEPENDS
+    libc.include.sys_mman
+    libc.src.errno.errno
+    libc.src.sys.mman.mmap
+    libc.src.sys.mman.munmap
+    libc.src.sys.mman.madvise
+    libc.src.sys.mman.mincore
+    libc.test.UnitTest.ErrnoSetterMatcher
+)

libc/test/src/sys/mman/linux/mincore_test.cpp

@@ -0,0 +1,115 @@
+//===-- Unittests for mincore ---------------------------------------------===//
+//
+// 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/errno/libc_errno.h"
+#include "src/sys/mman/madvise.h"
+#include "src/sys/mman/mincore.h"
+#include "src/sys/mman/mmap.h"
+#include "src/sys/mman/munmap.h"
+#include "test/UnitTest/ErrnoSetterMatcher.h"
+#include "test/UnitTest/LibcTest.h"
+#include "test/UnitTest/Test.h"
+
+#include <linux/param.h> // For EXEC_PAGESIZE
+#include <sys/mman.h>
+
+using LIBC_NAMESPACE::testing::ErrnoSetterMatcher::Fails;
+using LIBC_NAMESPACE::testing::ErrnoSetterMatcher::Succeeds;
+
+TEST(LlvmLibcMincoreTest, UnMappedMemory) {
+  libc_errno = 0;
+  unsigned char vec;
+  int res = LIBC_NAMESPACE::mincore(nullptr, 1, &vec);
+  EXPECT_THAT(res, Fails(ENOMEM, -1));
+}
+
+TEST(LlvmLibcMincoreTest, InvalidVec) {
+  void *addr = LIBC_NAMESPACE::mmap(nullptr, 4 * EXEC_PAGESIZE, PROT_READ,
+                                    MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+  EXPECT_NE(addr, MAP_FAILED);
+  EXPECT_EQ(reinterpret_cast<unsigned long>(addr) % EXEC_PAGESIZE, 0ul);
+  libc_errno = 0;
+  int res = LIBC_NAMESPACE::mincore(addr, 1, nullptr);
+  EXPECT_THAT(res, Fails(EFAULT, -1));
+  void *area =
+      LIBC_NAMESPACE::mmap(nullptr, EXEC_PAGESIZE, PROT_READ | PROT_WRITE,
+                           MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+  EXPECT_NE(area, MAP_FAILED);
+  unsigned char *ptr = static_cast<unsigned char *>(area) + EXEC_PAGESIZE - 3;
+  res = LIBC_NAMESPACE::mincore(addr, 4 * EXEC_PAGESIZE, ptr);
+  EXPECT_THAT(res, Fails(EFAULT, -1));
+  EXPECT_THAT(LIBC_NAMESPACE::munmap(addr, EXEC_PAGESIZE), Succeeds());
+  EXPECT_THAT(LIBC_NAMESPACE::munmap(area, 2), Succeeds());
+}
+
+TEST(LlvmLibcMincoreTest, UnalignedAddr) {
+  void *addr = LIBC_NAMESPACE::mmap(nullptr, EXEC_PAGESIZE, PROT_READ,
+                                    MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+  EXPECT_NE(addr, MAP_FAILED);
+  EXPECT_EQ(reinterpret_cast<unsigned long>(addr) % EXEC_PAGESIZE, 0ul);
+  libc_errno = 0;
+  int res = LIBC_NAMESPACE::mincore(static_cast<char *>(addr) + 1, 1, nullptr);
+  EXPECT_THAT(res, Fails(EINVAL, -1));
+  EXPECT_THAT(LIBC_NAMESPACE::munmap(addr, EXEC_PAGESIZE), Succeeds());
+}
+
+TEST(LlvmLibcMincoreTest, NoError) {
+  void *addr = LIBC_NAMESPACE::mmap(nullptr, EXEC_PAGESIZE, PROT_READ,
+                                    MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+  EXPECT_NE(addr, MAP_FAILED);
+  EXPECT_EQ(reinterpret_cast<unsigned long>(addr) % EXEC_PAGESIZE, 0ul);
+  unsigned char vec;
+  libc_errno = 0;
+  int res = LIBC_NAMESPACE::mincore(addr, 1, &vec);
+  EXPECT_THAT(res, Succeeds());
+  EXPECT_THAT(LIBC_NAMESPACE::munmap(addr, EXEC_PAGESIZE), Succeeds());
+}
+
+TEST(LlvmLibcMincoreTest, NegativeLength) {
+  void *addr = LIBC_NAMESPACE::mmap(nullptr, EXEC_PAGESIZE, PROT_READ,
+                                    MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+  EXPECT_NE(addr, MAP_FAILED);
+  EXPECT_EQ(reinterpret_cast<unsigned long>(addr) % EXEC_PAGESIZE, 0ul);
+  unsigned char vec;
+  libc_errno = 0;
+  int res = LIBC_NAMESPACE::mincore(addr, -1, &vec);
+  EXPECT_THAT(res, Fails(ENOMEM, -1));
+  EXPECT_THAT(LIBC_NAMESPACE::munmap(addr, EXEC_PAGESIZE), Succeeds());
+}
+
+TEST(LlvmLibcMincoreTest, PageOut) {
+  unsigned char vec;
+  void *addr =
+      LIBC_NAMESPACE::mmap(nullptr, EXEC_PAGESIZE, PROT_READ | PROT_WRITE,
+                           MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+  EXPECT_NE(addr, MAP_FAILED);
+  EXPECT_EQ(reinterpret_cast<unsigned long>(addr) % EXEC_PAGESIZE, 0ul);
+
+  // touch the page
+  {
+    static_cast<char *>(addr)[0] = 0;
+    libc_errno = 0;
+    int res = LIBC_NAMESPACE::mincore(addr, 1, &vec);
+    EXPECT_EQ(vec & 1u, 1u);
+    EXPECT_THAT(res, Succeeds());
+  }
+
+  // page out the memory
+  {
+    libc_errno = 0;
+    EXPECT_THAT(LIBC_NAMESPACE::madvise(addr, EXEC_PAGESIZE, MADV_DONTNEED),
+                Succeeds());
+
+    libc_errno = 0;
+    int res = LIBC_NAMESPACE::mincore(addr, EXEC_PAGESIZE, &vec);
+    EXPECT_EQ(vec & 1u, 0u);
+    EXPECT_THAT(res, Succeeds());
+  }
+
+  EXPECT_THAT(LIBC_NAMESPACE::munmap(addr, EXEC_PAGESIZE), Succeeds());
+}