Auto merge of #2477 - Fanael:linux-openat2, r=JohnTitor

linux: Add open_how and related flags

This makes `openat2` usable.

build.rs

@@ -72,6 +72,11 @@ fn main() {
         println!("cargo:rustc-cfg=libc_cfg_target_vendor");
     }
 
+    // Rust >= 1.40 supports #[non_exhaustive].
+    if rustc_minor_ver >= 40 || rustc_dep_of_std {
+        println!("cargo:rustc-cfg=libc_non_exhaustive");
+    }
+
     if rustc_minor_ver >= 51 || rustc_dep_of_std {
         println!("cargo:rustc-cfg=libc_ptr_addr_of");
     }

libc-test/build.rs

@@ -2689,6 +2689,8 @@ fn test_linux(target: &str) {
         "linux/netfilter_ipv6.h",
         "linux/netfilter_ipv6/ip6_tables.h",
         "linux/netlink.h",
+        // FIXME: requires more recent kernel headers:
+        // "linux/openat2.h",
         "linux/quota.h",
         "linux/random.h",
         "linux/reboot.h",
@@ -2830,6 +2832,9 @@ fn test_linux(target: &str) {
             // Requires glibc 2.33 or newer.
             "mallinfo2" => true,
 
+            // Might differ between kernel versions
+            "open_how" => true,
+
             _ => false,
         }
     });
@@ -2972,6 +2977,14 @@ fn test_linux(target: &str) {
             | "CLOSE_RANGE_UNSHARE"
             | "CLOSE_RANGE_CLOEXEC" => true,
 
+            // FIXME: requires more recent kernel headers:
+            | "RESOLVE_BENEATH"
+            | "RESOLVE_CACHED"
+            | "RESOLVE_IN_ROOT"
+            | "RESOLVE_NO_MAGICLINKS"
+            | "RESOLVE_NO_SYMLINKS"
+            | "RESOLVE_NO_XDEV" => true,
+
             // FIXME: Not currently available in headers on ARM, MIPS and musl.
             "NETLINK_GET_STRICT_CHK" if arm || mips || musl => true,
 

libc-test/semver/linux.txt

@@ -1753,6 +1753,12 @@ RENAME_NOREPLACE
 RENAME_WHITEOUT
 REP_CNT
 REP_MAX
+RESOLVE_BENEATH
+RESOLVE_CACHED
+RESOLVE_IN_ROOT
+RESOLVE_NO_MAGICLINKS
+RESOLVE_NO_SYMLINKS
+RESOLVE_NO_XDEV
 RLIMIT_AS
 RLIMIT_CORE
 RLIMIT_CPU
@@ -2850,6 +2856,7 @@ nlmsgerr
 nlmsghdr
 off64_t
 open64
+open_how
 open_memstream
 openat
 openat64

src/unix/linux_like/linux/mod.rs

@@ -1825,6 +1825,14 @@ pub const MFD_HUGETLB: ::c_uint = 0x0004;
 pub const CLOSE_RANGE_UNSHARE: ::c_uint = 1 << 1;
 pub const CLOSE_RANGE_CLOEXEC: ::c_uint = 1 << 2;
 
+// linux/openat2.h
+pub const RESOLVE_NO_XDEV: ::__u64 = 0x01;
+pub const RESOLVE_NO_MAGICLINKS: ::__u64 = 0x02;
+pub const RESOLVE_NO_SYMLINKS: ::__u64 = 0x04;
+pub const RESOLVE_BENEATH: ::__u64 = 0x08;
+pub const RESOLVE_IN_ROOT: ::__u64 = 0x10;
+pub const RESOLVE_CACHED: ::__u64 = 0x20;
+
 // these are used in the p_type field of Elf32_Phdr and Elf64_Phdr, which has
 // the type Elf32Word and Elf64Word respectively. Luckily, both of those are u32
 // so we can use that type here to avoid having to cast.
@@ -3945,3 +3953,10 @@ cfg_if! {
     }
 }
 expand_align!();
+
+cfg_if! {
+    if #[cfg(libc_non_exhaustive)] {
+        mod non_exhaustive;
+        pub use self::non_exhaustive::*;
+    }
+}

src/unix/linux_like/linux/non_exhaustive.rs

@@ -0,0 +1,9 @@
+s! {
+    // linux/openat2.h
+    #[non_exhaustive]
+    pub struct open_how {
+        pub flags: ::__u64,
+        pub mode: ::__u64,
+        pub resolve: ::__u64,
+    }
+}