From ab1cbd8bcec15b016c96134abbf145cfbeca83ca Mon Sep 17 00:00:00 2001
From: Miklos Szeredi <mszeredi@redhat.com>
Date: Thu, 14 May 2020 16:44:25 +0200
Subject: [PATCH] BACKPORT: vfs: add faccessat2 syscall

POSIX defines faccessat() as having a fourth "flags" argument, while the
linux syscall doesn't have it.  Glibc tries to emulate AT_EACCESS and
AT_SYMLINK_NOFOLLOW, but AT_EACCESS emulation is broken.

Add a new faccessat(2) syscall with the added flags argument and implement
both flags.

The value of AT_EACCESS is defined in glibc headers to be the same as
AT_REMOVEDIR.  Use this value for the kernel interface as well, together
with the explanatory comment.

Also add AT_EMPTY_PATH support, which is not documented by POSIX, but can
be useful and is trivial to implement.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
[Adrian Ratiu: 4.14 linux-headers backport]
---
 arch/arm/tools/syscall.tbl             | 1 +
 arch/arm64/include/asm/unistd.h        | 2 +-
 arch/arm64/include/asm/unistd32.h      | 2 ++
 arch/x86/entry/syscalls/syscall_32.tbl | 1 +
 arch/x86/entry/syscalls/syscall_64.tbl | 1 +
 include/linux/syscalls.h               | 2 ++
 include/uapi/asm-generic/unistd.h      | 5 ++++-
 7 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl
index 9d87127f33e8..ea8846b73445 100644
--- a/arch/arm/tools/syscall.tbl
+++ b/arch/arm/tools/syscall.tbl
@@ -435,3 +435,4 @@
 423	common	sched_rr_get_interval_time64	sys_sched_rr_get_interval
 425	common	io_uring_setup		sys_io_uring_setup
 426	common	io_uring_enter		sys_io_uring_enter
+439	common	faccessat2			sys_faccessat2
diff --git a/arch/arm64/include/asm/unistd.h b/arch/arm64/include/asm/unistd.h
index 718b1962a1b8..0dd4a8025c08 100644
--- a/arch/arm64/include/asm/unistd.h
+++ b/arch/arm64/include/asm/unistd.h
@@ -43,7 +43,7 @@
 #define __ARM_NR_compat_cacheflush	(__ARM_NR_COMPAT_BASE+2)
 #define __ARM_NR_compat_set_tls		(__ARM_NR_COMPAT_BASE+5)
 
-#define __NR_compat_syscalls		427
+#define __NR_compat_syscalls		440
 #endif
 
 #define __ARCH_WANT_SYS_CLONE
diff --git a/arch/arm64/include/asm/unistd32.h b/arch/arm64/include/asm/unistd32.h
index ba9554572592..27179bd921ff 100644
--- a/arch/arm64/include/asm/unistd32.h
+++ b/arch/arm64/include/asm/unistd32.h
@@ -863,6 +863,8 @@ __SYSCALL(__NR_sched_rr_get_interval_time64, sys_sched_rr_get_interval)
 __SYSCALL(__NR_io_uring_setup, sys_io_uring_setup)
 #define __NR_io_uring_enter 426
 __SYSCALL(__NR_io_uring_enter, sys_io_uring_enter)
+#define __NR_faccessat2 439
+__SYSCALL(__NR_faccessat2, sys_faccessat2)
 
 /*
  * Please add new compat syscalls above this comment and update
diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index b056050a44ba..7455df86745b 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -414,3 +414,4 @@
 423	i386	sched_rr_get_interval_time64	sys_sched_rr_get_interval	__ia32_sys_sched_rr_get_interval
 425	i386	io_uring_setup		sys_io_uring_setup		__ia32_sys_io_uring_setup
 426	i386	io_uring_enter		sys_io_uring_enter		__ia32_sys_io_uring_enter
+439	i386	faccessat2		sys_faccessat2
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index 9e69bd2fd081..74a44ceb3e94 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -341,6 +341,7 @@
 332	common	statx			sys_statx
 425	common	io_uring_setup		__x64_sys_io_uring_setup
 426	common	io_uring_enter		__x64_sys_io_uring_enter
+439	common	faccessat2		sys_faccessat2
 
 #
 # x32-specific system call numbers start at 512 to avoid cache impact
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index a78186d826d7..4437b0dc619d 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -809,6 +809,8 @@ asmlinkage long sys_renameat2(int olddfd, const char __user *oldname,
 asmlinkage long sys_futimesat(int dfd, const char __user *filename,
 			      struct timeval __user *utimes);
 asmlinkage long sys_faccessat(int dfd, const char __user *filename, int mode);
+asmlinkage long sys_faccessat2(int dfd, const char __user *filename, int mode,
+			       int flags);
 asmlinkage long sys_fchmodat(int dfd, const char __user * filename,
 			     umode_t mode);
 asmlinkage long sys_fchownat(int dfd, const char __user *filename, uid_t user,
diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h
index d97d59ebf682..e1c762e2baa6 100644
--- a/include/uapi/asm-generic/unistd.h
+++ b/include/uapi/asm-generic/unistd.h
@@ -781,8 +781,11 @@ __SYSCALL(__NR_io_uring_setup, sys_io_uring_setup)
 #define __NR_io_uring_enter 426
 __SYSCALL(__NR_io_uring_enter, sys_io_uring_enter)
 
+#define __NR_faccessat2 439
+__SYSCALL(__NR_faccessat2, sys_faccessat2)
+
 #undef __NR_syscalls
-#define __NR_syscalls 427
+#define __NR_syscalls 440
 
 /*
  * All syscalls below here should go away really,
-- 
2.31.1