Support mknodat

[CvvT]

Support mknodat but only regular file is allowed. Others like char and block files return EPERM for now.

[github-actions]

🤖 SemverChecks 🤖 ⚠️ Potential breaking API changes detected ⚠️

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--- failure enum_no_repr_variant_discriminant_changed: enum variant had its discriminant change value ---

Description:
The enum's variant had its discriminant value change. This breaks downstream code that used its value via a numeric cast like `as isize`.
        ref: https://doc.rust-lang.org/reference/items/enumerations.html#assigning-discriminant-values
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.47.0/src/lints/enum_no_repr_variant_discriminant_changed.ron

Failed in:
  variant SyscallRequest::Unlinkat 57 -> 58 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2146
  variant SyscallRequest::Newfstatat 58 -> 59 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2152
  variant SyscallRequest::Eventfd2 59 -> 60 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2165
  variant SyscallRequest::Pipe2 60 -> 61 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2169
  variant SyscallRequest::Clone 61 -> 62 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2173
  variant SyscallRequest::Clone3 62 -> 63 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2176
  variant SyscallRequest::SetThreadArea 63 -> 64 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2181
  variant SyscallRequest::ClockGettime 64 -> 65 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2184
  variant SyscallRequest::ClockGetres 65 -> 66 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2188
  variant SyscallRequest::ClockNanosleep 66 -> 67 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2192
  variant SyscallRequest::Gettimeofday 67 -> 68 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2198
  variant SyscallRequest::Time 68 -> 69 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2202
  variant SyscallRequest::Getrlimit 69 -> 70 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2205
  variant SyscallRequest::Setrlimit 70 -> 71 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2209
  variant SyscallRequest::Prlimit 71 -> 72 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2213
  variant SyscallRequest::SetTidAddress 72 -> 73 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2224
  variant SyscallRequest::Gettid 73 -> 74 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2227
  variant SyscallRequest::SetRobustList 74 -> 75 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2228
  variant SyscallRequest::GetRobustList 75 -> 76 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2231
  variant SyscallRequest::GetRandom 76 -> 77 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2236
  variant SyscallRequest::Getpid 77 -> 78 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2241
  variant SyscallRequest::Getppid 78 -> 79 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2242
  variant SyscallRequest::Getuid 79 -> 80 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2243
  variant SyscallRequest::Geteuid 80 -> 81 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2244
  variant SyscallRequest::Getgid 81 -> 82 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2245
  variant SyscallRequest::Getegid 82 -> 83 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2246
  variant SyscallRequest::Sysinfo 83 -> 84 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2247
  variant SyscallRequest::CapGet 84 -> 85 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2250
  variant SyscallRequest::GetDirent64 85 -> 86 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2254
  variant SyscallRequest::SchedGetAffinity 86 -> 87 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2259
  variant SyscallRequest::SchedYield 87 -> 88 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2264
  variant SyscallRequest::Futex 88 -> 89 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2265
  variant SyscallRequest::Execve 89 -> 90 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2268
  variant SyscallRequest::Umask 90 -> 91 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2273
  variant SyscallRequest::Prctl 91 -> 92 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2276
  variant SyscallRequest::Alarm 92 -> 93 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2279
  variant SyscallRequest::SetITimer 93 -> 94 in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:2282

[sangho2]

Looks good to me. It seems that there are some corner cases.

[sangho2]

• mknod("/x", S_IFREG | 0000, 0) should create /x and return success, but this path creates the file and then can fail permission checks while leaving the file behind. It can also fail with EMFILE when the process is at its fd limit, even though mknod should not allocate a file descriptor.
• mknod("", S_IFREG | 0644, 0) should fail with ENOENT, but with AT_FDCWD this resolves to the current directory and can report EEXIST; with a real dirfd it goes through the unsupported FsPath::Fd path and reports EINVAL.