Use libc for syscall constants

This patch switches from internally defined system call constants for
the landlock system calls to the ones defined by `libc`.

Besides removing unnecessary code already provided by the latest libc,
this also adds support for additional architectures like ARM since the
existing constants were limited to x86_64.

Signed-off-by: Christian Duerr <chris.durr@phylum.io>

Cargo.toml

@@ -16,7 +16,7 @@ readme = "README.md"
 
 [dependencies]
 enumflags2 = "0.7"
-libc = "0.2"
+libc = "0.2.134"
 thiserror = "1.0"
 
 [dev-dependencies]

src/uapi/mod.rs

@@ -27,27 +27,23 @@ pub use self::landlock::{
     LANDLOCK_CREATE_RULESET_VERSION,
 };
 
-use libc::{__u32, c_int, c_void, size_t, syscall};
-
-#[cfg(target_arch = "x86_64")]
-const __NR_LANDLOCK_CREATE_RULESET: u32 = 444;
-#[cfg(target_arch = "x86_64")]
-const __NR_LANDLOCK_ADD_RULE: u32 = 445;
-#[cfg(target_arch = "x86_64")]
-const __NR_LANDLOCK_RESTRICT_SELF: u32 = 446;
+use libc::{
+    __u32, c_int, c_void, size_t, syscall, SYS_landlock_add_rule, SYS_landlock_create_ruleset,
+    SYS_landlock_restrict_self,
+};
 
 #[rustfmt::skip]
 pub unsafe fn landlock_create_ruleset(attr: *const landlock_ruleset_attr, size: size_t,
                                       flags: __u32) -> c_int {
-    syscall(__NR_LANDLOCK_CREATE_RULESET as i64, attr, size, flags) as c_int
+    syscall(SYS_landlock_create_ruleset, attr, size, flags) as c_int
 }
 
 #[rustfmt::skip]
 pub unsafe fn landlock_add_rule(ruleset_fd: c_int, rule_type: landlock_rule_type,
                                 rule_attr: *const c_void, flags: __u32) -> c_int {
-    syscall(__NR_LANDLOCK_ADD_RULE as i64, ruleset_fd, rule_type, rule_attr, flags) as c_int
+    syscall(SYS_landlock_add_rule, ruleset_fd, rule_type, rule_attr, flags) as c_int
 }
 
 pub unsafe fn landlock_restrict_self(ruleset_fd: c_int, flags: __u32) -> c_int {
-    syscall(__NR_LANDLOCK_RESTRICT_SELF as i64, ruleset_fd, flags) as c_int
+    syscall(SYS_landlock_restrict_self, ruleset_fd, flags) as c_int
 }