blob: 31e114a7f66b95f71f6102290dd40260410d9363 [file] [log] [blame]
//===---------- Linux implementation of the POSIX mmap function -----------===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#include "src/sys/mman/mmap.h"
#include "config/linux/syscall.h" // For internal syscall function.
#include "include/sys/syscall.h" // For syscall numbers.
#include "src/__support/common.h"
#include "src/errno/llvmlibc_errno.h"
#include <linux/param.h> // For EXEC_PAGESIZE.
namespace __llvm_libc {
// This function is currently linux only. It has to be refactored suitably if
// mmap is to be supported on non-linux operating systems also.
LLVM_LIBC_FUNCTION(void *, mmap,
(void *addr, size_t size, int prot, int flags, int fd,
off_t offset)) {
// A lot of POSIX standard prescribed validation of the parameters is not
// done in this function as modern linux versions do it in the syscall.
// TODO: Perform argument validation not done by the linux syscall.
// EXEC_PAGESIZE is used for the page size. While this is OK for x86_64, it
// might not be correct in general.
// TODO: Use pagesize read from the ELF aux vector instead of EXEC_PAGESIZE.
#ifdef SYS_mmap2
offset /= EXEC_PAGESIZE;
long syscall_number = SYS_mmap2;
#elif SYS_mmap
long syscall_number = SYS_mmap;
#error "Target platform does not have SYS_mmap or SYS_mmap2 defined"
long ret_val =
__llvm_libc::syscall(syscall_number, reinterpret_cast<long>(addr), size,
prot, flags, fd, offset);
// The mmap/mmap2 syscalls return negative values on error. These negative
// values are actually the negative values of the error codes. So, fix them
// up in case an error code is detected.
// A point to keep in mind for the fix up is that a negative return value
// from the syscall can also be an error-free value returned by the syscall.
// However, since a valid return address cannot be within the last page, a
// return value corresponding to a location in the last page is an error
// value.
if (ret_val < 0 && ret_val > -EXEC_PAGESIZE) {
llvmlibc_errno = -ret_val;
return MAP_FAILED;
return reinterpret_cast<void *>(ret_val);
} // namespace __llvm_libc