From f1c89d50e140d92214eab3dfeb58570784d62fa8 Mon Sep 17 00:00:00 2001
From: Avril <flanchan@cumallover.me>
Date: Mon, 15 Apr 2024 16:50:57 +0100
Subject: [PATCH] Added IFUNC resolver for `memfd_secret()`.
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Fortune for memfd_secret-shim's current commit: Curse − 凶
---
 src/ifunc.h        | 18 ++++++++++++++++--
 src/memfd_secret.c | 19 +++++++++++++++----
 2 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/src/ifunc.h b/src/ifunc.h
index 732671a..4a2e379 100644
--- a/src/ifunc.h
+++ b/src/ifunc.h
@@ -2,10 +2,24 @@
 #define _IT_IFUNC_H
 //! ifunc helpers
 
+#if !IFUNC_PREFIX
+#define IFUNC_PREFIX _ifun__
+#endif
+
+#define _IFUNC_STR_(X) #X
+#define _IFUNC_STR(X) _IFUNC_STR_(X)
+
+#define _IFUNC_PREFIX_S _IFUNC_STR(IFUNC_PREFIX)
+
+#define _IFUNC_PASTE_(X,Y) X##Y
+#define _IFUNC_PASTE(X,Y) _IFUNC_PASTE_(X,Y)
+
+#define _IFUNC_PREFIX(X) _IFUNC_PASTE(IFUNC_PREFIX, X)
+
 #define IFUNC_NAME(name, ver) _impl__ ## name ## __ ## ver 
 #define IFUNC_IMPL(name, ver) __attribute__((copy(name))) IFUNC_NAME(name, ver)
-#define IFUNC_RESOLVER_A(attr, name)  __attribute__((returns_nonnull)) (* __attribute__(attr) _ifun__ ## name (void)) // When the ifunc resolver wants to return a function pointer that has attributes on it, the attribute inner list (e.g. `(returns_nonnull, const, nonnull)') can be provided as the first argument
+#define IFUNC_RESOLVER_A(attr, name)  __attribute__((returns_nonnull)) (* __attribute__(attr) _IFUNC_PREFIX(name) /*_ifun__ ## name*/ (void)) // When the ifunc resolver wants to return a function pointer that has attributes on it, the attribute inner list (e.g. `(returns_nonnull, const, nonnull)') can be provided as the first argument
 #define IFUNC_RESOLVER(name)  IFUNC_RESOLVER_A((copy(name)), name)
-#define IFUNC_DEF(name, params) name params __attribute__((__ifunc__("_ifun__" #name)))
+#define IFUNC_DEF(name, params) name params __attribute__((__ifunc__(_IFUNC_PREFIX_S #name)))
 
 #endif /* _IT_IFUNC_H */
diff --git a/src/memfd_secret.c b/src/memfd_secret.c
index 520759d..3c5320a 100644
--- a/src/memfd_secret.c
+++ b/src/memfd_secret.c
@@ -25,7 +25,8 @@ __attribute__((gnu_inline))
 static inline
 int _has_memfd_secret_raw()
 {
-	int fd = _memfd_secret(FD_CLOEXEC);
+	// Attempt syscall
+	int fd = _memfd_secret_raw(FD_CLOEXEC);
 
 	// If failure to create new fd was caused by `ENOSYS`, it is not available.
 	if(fd < 0 && errno == ENOSYS)
@@ -52,9 +53,12 @@ int _has_memfd_secret() {
 	return ok;
 }
 
+int IFUNC_DEF(memfd_secret, (unsigned int));
+
 /// Set as IFUNC target for systems with `memfd_secret()` support enabled.
-__attribute__((visibility("hidden"))) //XXX: `hidden` is the "can only be accessed outside .so from returned internal function pointer", right? and `internal` is "can *never* be accessed outside of .so"? (TODO: Check. Idk if this is the other way around.)
-int memfd_secret_$enabled(unsigned int flags)
+__attribute__((visibility("hidden")))
+int IFUNC_IMPL(memfd_secret, $enabled) (unsigned int flags)
+
 {
 	return _memfd_secret_raw(flags);
 }
@@ -63,7 +67,7 @@ int memfd_secret_$enabled(unsigned int flags)
 ///
 /// The call is forwarded to `memfd_create()` instead. 
 __attribute__((visibility("hidden")))
-int memfd_secret_$disabled(unsigned int flags)
+int IFUNC_IMPL(memfd_secret, $disabled) (unsigned int flags)
 {
 	if( FD_CLOEXEC != MEMFD_CLOEXEC ) { // NOTE: This is a constant expression, and this code will be removed if they are equal.
 		//TODO: Translate mask `flags`, from `FD_CLOEXEC` (if it is set) -> `MEMFD_CLOEXEC`.
@@ -71,5 +75,12 @@ int memfd_secret_$disabled(unsigned int flags)
 	return memfd_create("memfd_secret@?", flags);
 }
 
+int IFUNC_RESOLVER(memfd_secret) (unsigned int flags)
+{
+	return _has_memfd_secret()
+		? &IFUNC_NAME(memfd_secret, $enabled)
+		: &IFUNC_NAME(memfd_secret, $disabled);
+}
+
 //TODO: IFUNC resolver for `memfd_secret()` (Above two targets^^)
 //TODO: Use `ifunc.h`'s macros for defining the ifunc instead of manually, it de-clutters shit and removed repetition.