From ad2d28dbe7f4976b12b613cd01d8db102d9b9f3f Mon Sep 17 00:00:00 2001
From: Alan Griffiths <alan@octopull.co.uk>
Date: Wed, 30 Aug 2023 14:30:52 +0100
Subject: [PATCH 1/3] Regardless of any preprocessing "magic" done to the
 `mmap` symbol, we can get the actual name of the function using `__func__`.

---
 tests/mir_test_framework/mmap_wrapper.cpp | 22 +---------------------
 1 file changed, 1 insertion(+), 21 deletions(-)

diff --git a/tests/mir_test_framework/mmap_wrapper.cpp b/tests/mir_test_framework/mmap_wrapper.cpp
index c63591fa7b2..1bc3b30483a 100644
--- a/tests/mir_test_framework/mmap_wrapper.cpp
+++ b/tests/mir_test_framework/mmap_wrapper.cpp
@@ -39,18 +39,6 @@ mtf::MmapHandlerHandle mtf::add_mmap_handler(MmapHandler handler)
     return MmapInterposer::add(std::move(handler));
 }
 
-auto real_mmap_symbol_name() -> char const*
-{
-#if _FILE_OFFSET_BITS == 64
-    // mmap64 is defined everywhere, so even though off_t == off64_t on 64-bit platforms
-    // this is still appropriate.
-    return "mmap64";
-#else
-    // This will get us the 32-bit off_t version on 32-bit platforms
-    return "mmap";
-#endif
-}
-
 void* mmap(void *addr, size_t length, int prot, int flags, int fd, off_t offset)
 {
     if (auto val = MmapInterposer::run(addr, length, prot, flags, fd, offset))
@@ -59,15 +47,7 @@ void* mmap(void *addr, size_t length, int prot, int flags, int fd, off_t offset)
     }
 
     void* (*real_mmap)(void *addr, size_t length, int prot, int flags, int fd, off_t offset);
-    *(void **)(&real_mmap) = dlsym(RTLD_NEXT, real_mmap_symbol_name());
-
-#if _FILE_OFFSET_BITS == 64
-    // Empirically, mmap64 is NOT defined everywhere, but on 64-bit platforms this is appropriate
-    if (!real_mmap)
-    {
-        *(void **)(&real_mmap) = dlsym(RTLD_NEXT, "mmap");
-    }
-#endif
+    *(void **)(&real_mmap) = dlsym(RTLD_NEXT, __func__);
 
     if (!real_mmap)
     {

From 8f832592da2cfe6563f12a14bc8a107cd51fd365 Mon Sep 17 00:00:00 2001
From: Alan Griffiths <alan@octopull.co.uk>
Date: Wed, 30 Aug 2023 15:38:48 +0100
Subject: [PATCH 2/3] When we can find mmap64, we use mmap64

---
 tests/mir_test_framework/mmap_wrapper.cpp | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/tests/mir_test_framework/mmap_wrapper.cpp b/tests/mir_test_framework/mmap_wrapper.cpp
index 1bc3b30483a..f28b1ddab4d 100644
--- a/tests/mir_test_framework/mmap_wrapper.cpp
+++ b/tests/mir_test_framework/mmap_wrapper.cpp
@@ -47,7 +47,15 @@ void* mmap(void *addr, size_t length, int prot, int flags, int fd, off_t offset)
     }
 
     void* (*real_mmap)(void *addr, size_t length, int prot, int flags, int fd, off_t offset);
-    *(void **)(&real_mmap) = dlsym(RTLD_NEXT, __func__);
+
+    // Where mmap64 is defined, even if off_t == off64_t on 64-bit platforms, this is still appropriate.
+    *(void **)(&real_mmap) = dlsym(RTLD_NEXT, "mmap64");
+
+    // Empirically, mmap64 is NOT defined everywhere, but then this is appropriate
+    if (!real_mmap)
+    {
+        *(void **)(&real_mmap) = dlsym(RTLD_NEXT, __func__);
+    }
 
     if (!real_mmap)
     {

From da806f608f2734ca20790c454b0b6bce4c84abe6 Mon Sep 17 00:00:00 2001
From: Alan Griffiths <alan@octopull.co.uk>
Date: Wed, 30 Aug 2023 16:37:15 +0100
Subject: [PATCH 3/3] Only resolve the function on the first invocation

---
 tests/mir_test_framework/mmap_wrapper.cpp | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/tests/mir_test_framework/mmap_wrapper.cpp b/tests/mir_test_framework/mmap_wrapper.cpp
index f28b1ddab4d..ad3f8672fd6 100644
--- a/tests/mir_test_framework/mmap_wrapper.cpp
+++ b/tests/mir_test_framework/mmap_wrapper.cpp
@@ -46,10 +46,13 @@ void* mmap(void *addr, size_t length, int prot, int flags, int fd, off_t offset)
         return *val;
     }
 
-    void* (*real_mmap)(void *addr, size_t length, int prot, int flags, int fd, off_t offset);
+    static void* (*real_mmap)(void *addr, size_t length, int prot, int flags, int fd, off_t offset);
 
     // Where mmap64 is defined, even if off_t == off64_t on 64-bit platforms, this is still appropriate.
-    *(void **)(&real_mmap) = dlsym(RTLD_NEXT, "mmap64");
+    if (!real_mmap)
+    {
+        *(void **)(&real_mmap) = dlsym(RTLD_NEXT, "mmap64");
+    }
 
     // Empirically, mmap64 is NOT defined everywhere, but then this is appropriate
     if (!real_mmap)