Merge bitcoin/bitcoin#23196: util: Make syscall sandbox compilable with kernel 4.4.0

ac402e749c util: Conditionalize some syscalls in syscall name table (W. J. van der Laan)
64085b37f8 util: Add __NR_copy_file_range syscall constant for sandbox (W. J. van der Laan)

Pull request description:

  Make the new syscall sandbox compilable with kernel 4.4.0.
  This defines a further syscall constant `__NR_copy_file_range` to make sure all syscalls used in the profile are available even if not defined in the kernel headers.

  Also, make a few syscalls optional in the syscall name table:

  - `__NR_pkey_alloc`
  - `__NR_pkey_free`
  - `__NR_pkey_mprotect`
  - `__NR_preadv2`
  - `__NR_pwritev2`

ACKs for top commit:
  practicalswift:
    cr ACK ac402e749c

Tree-SHA512: be6c55bf0a686bcdfad0b80b950d0d7d77a559ac234fc997b47514bdba44865a371c96dd8d34a811ba46424a84f410e23f75485b9b1e69e529b7d40e0b4b91b8

src/util/syscall_sandbox.cpp

@@ -58,6 +58,10 @@ bool g_syscall_sandbox_log_violation_before_terminating{false};
 #define __NR_membarrier 324
 #endif
 
+#ifndef __NR_copy_file_range
+#define __NR_copy_file_range 326
+#endif
+
 // This list of syscalls in LINUX_SYSCALLS is only used to map syscall numbers to syscall names in
 // order to be able to print user friendly error messages which include the syscall name in addition
 // to the syscall number.
@@ -268,15 +272,23 @@ const std::map<uint32_t, std::string> LINUX_SYSCALLS{
     {__NR_pipe, "pipe"},
     {__NR_pipe2, "pipe2"},
     {__NR_pivot_root, "pivot_root"},
+#ifdef __NR_pkey_alloc
     {__NR_pkey_alloc, "pkey_alloc"},
+#endif
+#ifdef __NR_pkey_free
     {__NR_pkey_free, "pkey_free"},
+#endif
+#ifdef __NR_pkey_mprotect
     {__NR_pkey_mprotect, "pkey_mprotect"},
+#endif
     {__NR_poll, "poll"},
     {__NR_ppoll, "ppoll"},
     {__NR_prctl, "prctl"},
     {__NR_pread64, "pread64"},
     {__NR_preadv, "preadv"},
+#ifdef __NR_preadv2
     {__NR_preadv2, "preadv2"},
+#endif
     {__NR_prlimit64, "prlimit64"},
     {__NR_process_vm_readv, "process_vm_readv"},
     {__NR_process_vm_writev, "process_vm_writev"},
@@ -285,7 +297,9 @@ const std::map<uint32_t, std::string> LINUX_SYSCALLS{
     {__NR_putpmsg, "putpmsg"},
     {__NR_pwrite64, "pwrite64"},
     {__NR_pwritev, "pwritev"},
+#ifdef __NR_pwritev2
     {__NR_pwritev2, "pwritev2"},
+#endif
     {__NR_query_module, "query_module"},
     {__NR_quotactl, "quotactl"},
     {__NR_read, "read"},