fix(luajit) allow regular pointers to be used as lightuserdata in ARM64

patches/1.15.8.1/LuaJIT-2.1-20190507_03-arm64-lightuserdata.patch

@@ -0,0 +1,113 @@
+This patch allows for regular pointers to be used as lightuserdata in ARM64.
+
+The source of the problem is that ARM64 has 48 bits of addressable memory in
+userspace (256 GiB), but LuaJIT only supports 47 bits for lightuserdata (128
+GiB). This means that half of the memory is not addressable.
+
+This is what the ARM64 user space memory layout looks like on Linux:
+
+     / 0000000000000000 1111111111111111 1111111111111111 1111111111111111 |
+A 32G| ...                                                                 |
+     \ 0000000000000000 1110000000000000 0000000000000000 0000000000000000 V stack
+     / 0000000000000000 1101111111111111 1111111111111111 1111111111111111
+B 32G| ...                                                                
+     \ 0000000000000000 1100000000000000 0000000000000000 0000000000000000
+     / 0000000000000000 1011111111111111 1111111111111111 1111111111111111
+C 32G| ...                                                                
+     \ 0000000000000000 1010000000000000 0000000000000000 0000000000000000
+     / 0000000000000000 1001111111111111 1111111111111111 1111111111111111
+D 32G| ...                                                                
+     \ 0000000000000000 1000000000000000 0000000000000000 0000000000000000
+     / 0000000000000000 0111111111111111 1111111111111111 1111111111111111
+E 32G| ...                                                                
+     \ 0000000000000000 0110000000000000 0000000000000000 0000000000000000
+     / 0000000000000000 0101111111111111 1111111111111111 1111111111111111
+F 32G| ...                                                                
+     \ 0000000000000000 0100000000000000 0000000000000000 0000000000000000
+     / 0000000000000000 0011111111111111 1111111111111111 1111111111111111
+G 32G| ...                                                                
+     \ 0000000000000000 0010000000000000 0000000000000000 0000000000000000
+     / 0000000000000000 0001111111111111 1111111111111111 1111111111111111 ^ heap
+H 32G| ...                                                                
+     \ 0000000000000000 0000000000000000 0000000000000000 0000000000000000
+
+Notice that the stack grows downwards from the top, and the heap grows upwards
+from the bottom. By losing bit 48, that means that only the bottom 128 GiB
+are addressable, meaning that all pointers to the stack and to static variables
+are invalid, and cause a "bad light userdata pointer" error.
+
+This patch modifies ARM64 support so that instead of losing access to the top
+128 GiB, we lose access to sections in the _middle_, allowing for normal
+heap and stack pointers to be valid.
+
+This greatly restores compatibility with third-party Lua modules, most of
+which do not expect over 64 GiB of addressable space but _do_ expect to be
+able to store lightuserdata of static variables: it allows, for example,
+lua-cjson 2.1.0.6 to run unmodified with LuaJIT on ARM64 (because it stores
+lightuserdata pointing to static variables).
+
+The original version of this patch discarded the exact middle section of
+the address space (i.e. sections A B for stack and G H for heap were valid,
+C D E F were invalid). However, existing libraries for LuaJIT mitigate this
+problem by masking bit 48 in stack pointers, resulting in addresses in the
+E section. For this reason, the revised version of this patch discards
+sections B C D F, providing 32G for stack addresses (A), 64G for heap address
+(G H) and 32G for masked stack addresses (E).
+
+Signed-off-by: Hisham Muhammad <hisham@gobolinux.org>
+
+diff -ur a/LuaJIT-2.1-20190507/src/lj_api.c b/LuaJIT-2.1-20190507/src/lj_api.c
+--- a/LuaJIT-2.1-20190507/src/lj_api.c	2019-05-02 17:58:14.000000000 -0300
++++ b/LuaJIT-2.1-20190507/src/lj_api.c	2019-08-09 15:36:18.435306003 -0300
+@@ -594,9 +594,17 @@
+   cTValue *o = index2adr(L, idx);
+   if (tvisudata(o))
+     return uddata(udataV(o));
+-  else if (tvislightud(o))
+-    return lightudV(o);
+-  else
++  else if (tvislightud(o)) {
++    void *p = lightudV(o);
++#if LJ_TARGET_ARM64 
++    switch ((uintptr_t) p & (7UL << 45)) {
++    case (7UL << 45): /* 111 -> 010 */
++    case (2UL << 45): /* 010 -> 111 */
++      p = (void*) ((uintptr_t) p ^ (5UL << 45));
++    }
++#endif
++    return p;
++  } else
+     return NULL;
+ }
+
+@@ -696,6 +704,13 @@
+
+ LUA_API void lua_pushlightuserdata(lua_State *L, void *p)
+ {
++#if LJ_TARGET_ARM64
++  switch ((uintptr_t) p & (7UL << 45)) {
++  case (7UL << 45): /* 111 -> 010 */
++  case (2UL << 45): /* 010 -> 111 */
++    p = (void*) ((uintptr_t) p ^ (5UL << 45));
++  }
++#endif
+   setlightudV(L->top, checklightudptr(L, p));
+   incr_top(L);
+ }
+diff -ur a/LuaJIT-2.1-20190507/src/lj_cconv.c b/LuaJIT-2.1-20190507/src/lj_cconv.c
+--- a/LuaJIT-2.1-20190507/src/lj_cconv.c	2019-05-02 17:58:14.000000000 -0300
++++ b/LuaJIT-2.1-20190507/src/lj_cconv.c	2019-08-09 15:38:14.356301250 -0300
+@@ -612,6 +612,13 @@
+       tmpptr = *(void **)tmpptr;
+   } else if (tvislightud(o)) {
+     tmpptr = lightudV(o);
++#if LJ_TARGET_ARM64
++    switch ((uintptr_t) tmpptr & (7UL << 45)) {
++    case (7UL << 45): /* 111 -> 010 */
++    case (2UL << 45): /* 010 -> 111 */
++      tmpptr = (void*) ((uintptr_t) tmpptr ^ (5UL << 45));
++    }
++#endif
+   } else if (tvisfunc(o)) {
+     void *p = lj_ccallback_new(cts, d, funcV(o));
+     if (p) {