[libc] add sysconf with pagesize

[michaelrj]

Summary

The sysconf function has many options, this patch adds the basic funtion
and the pagesize option. More options will be added in future patches.

[sivachandra]

libc/include/llvm-libc-macros/linux/unistd-macros.h

18

Should we equivalently define _SC_PAGE_SIZE also?

libc/spec/posix.td

512

Why did this get modified?

libc/src/unistd/linux/sysconf.cpp

23

Can we return here? Also, add a TODO here saying that we should ideally get the page size from the auxvector.

26

Can we set errno to EINVAL and return -1?

[michaelrj]

cleanup and address comments

libc/spec/posix.td

512

I edited the wrong spec when setting up sysconf and apparently forgot to fix it.

[sivachandra]

One nit inline.

libc/spec/posix.td

512

symlinkat returns an int value.

[michaelrj]

fix final comment before land

libc/config/linux/x86_64/entrypoints.txt

set(TARGET_LIBC_ENTRYPOINTS
     libc.src.unistd.pread
     libc.src.unistd.pwrite
     libc.src.unistd.read
     libc.src.unistd.readlink
     libc.src.unistd.readlinkat
     libc.src.unistd.rmdir
     libc.src.unistd.symlink
     libc.src.unistd.symlinkat
+    libc.src.unistd.sysconf
     libc.src.unistd.truncate
     libc.src.unistd.unlink
     libc.src.unistd.unlinkat
     libc.src.unistd.write
 )
 
 set(TARGET_LIBM_ENTRYPOINTS
     # fenv.h entrypoints

libc/include/llvm-libc-macros/linux/unistd-macros.h

 #define __LLVM_LIBC_MACROS_LINUX_UNISTD_MACROS_H
 
 // Values for mode argument to the access(...) function.
 #define F_OK 0
 #define X_OK 1
 #define W_OK 2
 #define R_OK 4
 
+#define _SC_PAGESIZE 1
+#define _SC_PAGE_SIZE _SC_PAGESIZE
+
 // Macro to set up the call to the __llvm_libc_syscall function
 // This is to prevent the call from having fewer than 6 arguments, since six
 // arguments are always passed to the syscall. Unnecessary arguments are
 // ignored.
 #define __syscall_helper(sysno, arg1, arg2, arg3, arg4, arg5, arg6, ...)       \
   __llvm_libc_syscall((long)(sysno), (long)(arg1), (long)(arg2), (long)(arg3), \
                       (long)(arg4), (long)(arg5), (long)(arg6))
 #define syscall(...) __syscall_helper(__VA_ARGS__, 0, 1, 2, 3, 4, 5, 6)
 
 #endif // __LLVM_LIBC_MACROS_LINUX_UNISTD_MACROS_H

libc/spec/posix.td

[
         FunctionSpec<
           "symlink",
           RetValSpec<IntType>,
           [ArgSpec<ConstCharPtr>, ArgSpec<ConstCharPtr>]
         >,
         FunctionSpec<
           "symlinkat",
           RetValSpec<IntType>,
           [ArgSpec<IntType>, ArgSpec<ConstCharPtr>, ArgSpec<IntType>, ArgSpec<ConstCharPtr>]
         >,
         FunctionSpec<
+          "sysconf",
+          RetValSpec<IntType>,
+          [ArgSpec<IntType>]
+        >,
+        FunctionSpec<
           "__llvm_libc_syscall",
           RetValSpec<LongType>,
           [ArgSpec<LongType>,ArgSpec<LongType>,ArgSpec<LongType>,ArgSpec<LongType>,ArgSpec<LongType>,ArgSpec<LongType>,ArgSpec<LongType>]
         >,
         FunctionSpec<
           "truncate",
           RetValSpec<IntType>,
           [ArgSpec<IntType>, ArgSpec<OffTType>]

libc/src/unistd/CMakeLists.txt

 add_entrypoint_object(
   __llvm_libc_syscall
   ALIAS
   DEPENDS
     .${LIBC_TARGET_OS}.__llvm_libc_syscall
 )
 
 add_entrypoint_object(
+  sysconf
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.sysconf
+)
+
+add_entrypoint_object(
   truncate
   ALIAS
   DEPENDS
     .${LIBC_TARGET_OS}.truncate
 )
 
 add_entrypoint_object(
   unlink

libc/src/unistd/linux/CMakeLists.txt

HDRS
     ../syscall.h
   DEPENDS
     libc.include.unistd
     libc.src.__support.OSUtil.osutil
     libc.src.errno.errno
 )
 
 add_entrypoint_object(
+  sysconf
+  SRCS
+    sysconf.cpp
+  HDRS
+    ../sysconf.h
+  DEPENDS
+    libc.include.unistd
+    libc.src.errno.errno
+)
+
+add_entrypoint_object(
   truncate
   SRCS
     truncate.cpp
   HDRS
     ../truncate.h
   DEPENDS
     libc.include.unistd
     libc.include.sys_syscall

libc/src/unistd/linux/sysconf.cpp

+//===-- Linux implementation of sysconf -----------------------------------===//
+//
+// 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/unistd/sysconf.h"
+
+#include "src/__support/common.h"
+
+#include <errno.h>
+#include <linux/param.h> // For EXEC_PAGESIZE.
+#include <unistd.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(long, sysconf, (int name)) {
+  long ret = 0;
+  if (name == _SC_PAGESIZE) {
+    // TODO: get this information from the auxvector.
+    return EXEC_PAGESIZE;
+  }
+  // TODO: Complete the rest of the sysconf options.
+  if (ret < 0) {
+    errno = EINVAL;
+    return -1;
+  }
+  return ret;
+}
+
+} // namespace __llvm_libc

libc/src/unistd/sysconf.h

+//===-- Implementation header for sysconf -----------------------*- 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_UNISTD_SYSCONF_H
+#define LLVM_LIBC_SRC_UNISTD_SYSCONF_H
+
+#include <unistd.h>
+
+namespace __llvm_libc {
+
+long sysconf(int name);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_UNISTD_SYSCONF_H

libc/test/src/unistd/CMakeLists.txt

add_libc_unittest(
   DEPENDS
     libc.src.unistd.__llvm_libc_syscall
     libc.include.errno
     libc.include.unistd
     libc.include.fcntl
     libc.include.sys_syscall
     libc.test.errno_setter_matcher
 )
+
+
+add_libc_unittest(
+  sysconf_test
+  SUITE
+    libc_unistd_unittests
+  SRCS
+    sysconf_test.cpp
+  DEPENDS
+    libc.include.unistd
+    libc.src.unistd.sysconf
+)

libc/test/src/unistd/sysconf_test.cpp

+//===-- Unittests for sysconf ---------------------------------------------===//
+//
+// 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/unistd/sysconf.h"
+#include "utils/UnitTest/Test.h"
+
+#include <unistd.h>
+
+TEST(LlvmLibcSysconfTest, PagesizeTest) {
+  long pagesize = __llvm_libc::sysconf(_SC_PAGESIZE);
+  ASSERT_GT(pagesize, 0l);
+}