[llvm] [llvm][Support][Memory] Add memfd based fallback for strict W^X Linux systems (PR #98538)

[Jannik Glückert via llvm-commits]

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@@ -67,6 +72,24 @@ static int getPosixProtectionFlags(unsigned Flags) {
   return PROT_NONE;
 }
 
+#if defined(__linux__)
+#ifndef MFD_CLOEXEC
+#define MFD_CLOEXEC 0x0001U
+#endif
+#ifndef MFD_EXEC
+#define MFD_EXEC 0x0010U
+#endif
+
+static inline int memfd_create(const char *name, int flags) {
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Jannik2099 wrote:

not super relevant as it's static, but perhaps mimic the libc & syscall prototype, where `flags` is `unsigned int` ?

https://github.com/llvm/llvm-project/pull/98538