From 2ceef01afecafbd4aa80276869993cb53bdadcf4 Mon Sep 17 00:00:00 2001 From: Jakob Unterwurzacher Date: Thu, 7 Dec 2017 00:05:28 +0100 Subject: [PATCH] syscallcompat: add Faccessat MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add faccessat(2) with a hack for symlink, because the kernel does not actually looks at the passed flags. From man 2 faccessat: C library/kernel differences The raw faccessat() system call takes only the first three argu‐ ments. The AT_EACCESS and AT_SYMLINK_NOFOLLOW flags are actually implemented within the glibc wrapper function for faccessat(). --- internal/syscallcompat/sys_common.go | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/internal/syscallcompat/sys_common.go b/internal/syscallcompat/sys_common.go index 440b42f..896aaf7 100644 --- a/internal/syscallcompat/sys_common.go +++ b/internal/syscallcompat/sys_common.go @@ -1,6 +1,8 @@ package syscallcompat import ( + "syscall" + "golang.org/x/sys/unix" ) @@ -21,3 +23,18 @@ func Readlinkat(dirfd int, path string) (string, error) { } } } + +// Faccessat exists both in Linux and in MacOS 10.10+, but the Linux version +// DOES NOT support any flags. Emulate AT_SYMLINK_NOFOLLOW like glibc does. +func Faccessat(dirfd int, path string, mode uint32) error { + var st unix.Stat_t + err := Fstatat(dirfd, path, &st, unix.AT_SYMLINK_NOFOLLOW) + if err != nil { + return err + } + if st.Mode&syscall.S_IFMT == syscall.S_IFLNK { + // Pretend that a symlink is always accessible + return nil + } + return unix.Faccessat(dirfd, path, mode, 0) +}