rts/PEi386: Fix relocation overflow behavior

This fixes handling of overflowed relocations on PEi386 targets:

 * Refuse to create jump islands for relocations of data symbols
 * Correctly handle the `__imp___acrt_iob_func` symbol, which is an new
   type of symbol: `SYM_TYPE_INDIRECT_DATA`

3 files changed, 27 insertions, 16 deletions

diff --git a/rts/LinkerInternals.h b/rts/LinkerInternals.h
index 61c054363f..b1cd3a8a9a 100644
--- a/rts/LinkerInternals.h
+++ b/rts/LinkerInternals.h
@@ -49,6 +49,7 @@ typedef struct _Section    Section;
 typedef enum _SymType {
     SYM_TYPE_CODE, /* the symbol is a function and can be relocated via a jump island */
     SYM_TYPE_DATA, /* the symbol is data */
+    SYM_TYPE_INDIRECT_DATA, /* see Note [Relocating iob_func on Windows] */
 } SymType;
 
 
diff --git a/rts/RtsSymbols.c b/rts/RtsSymbols.c
index 400e3122bc..b4e6da9470 100644
--- a/rts/RtsSymbols.c
+++ b/rts/RtsSymbols.c
@@ -175,9 +175,9 @@ extern char **environ;
       /* ^^ Need to figure out why this is needed.  */   \
       /* See Note [_iob_func symbol] */                  \
       RTS_WIN64_ONLY(SymI_HasProto_redirect(             \
-         __imp___acrt_iob_func, __rts_iob_func, STRENGTH_WEAK))   \
+         __imp___acrt_iob_func, __rts_iob_func, STRENGTH_WEAK, SYM_TYPE_INDIRECT_DATA))   \
       RTS_WIN32_ONLY(SymI_HasProto_redirect(             \
-         __imp____acrt_iob_func, __rts_iob_func, STRENGTH_WEAK))  \
+         __imp____acrt_iob_func, __rts_iob_func, STRENGTH_WEAK, SYM_TYPE_INDIRECT_DATA))  \
       SymI_HasProto(__mingw_vsnwprintf)                  \
       /* ^^ Need to figure out why this is needed.  */   \
       SymI_HasProto(__mingw_vfprintf)                    \
@@ -1072,7 +1072,7 @@ extern char **environ;
 
 // Symbols defined by libc
 #define RTS_LIBC_SYMBOLS                               \
-      SymI_HasProto_redirect(atexit, atexit, STRENGTH_STRONG) /* See Note [Strong symbols] */ \
+      SymI_HasProto_redirect(atexit, atexit, STRENGTH_STRONG, CODE_TYPE_CODE) /* See Note [Strong symbols] */ \
       SymI_HasProto(environ)
 
 #if !defined(DYNAMIC) && defined(linux_HOST_OS)
@@ -1104,7 +1104,7 @@ extern char **environ;
 #define SymE_HasProto(vvv)    SymI_HasProto(vvv)
 #endif
 #define SymI_HasProto(vvv) /**/
-#define SymI_HasProto_redirect(vvv,xxx,strength) /**/
+#define SymI_HasProto_redirect(vvv,xxx,strength,ty) /**/
 #define SymI_HasProto_deprecated(vvv) /**/
 RTS_SYMBOLS
 RTS_RET_SYMBOLS
@@ -1142,9 +1142,9 @@ RTS_LIBFFI_SYMBOLS
 
 // SymI_HasProto_redirect allows us to redirect references to one symbol to
 // another symbol.  See newCAF/newRetainedCAF/newGCdCAF for an example.
-#define SymI_HasProto_redirect(vvv,xxx,strength) \
+#define SymI_HasProto_redirect(vvv,xxx,strength,ty) \
     { MAYBE_LEADING_UNDERSCORE_STR(#vvv),    \
-      (void*)(&(xxx)), strength, SYM_TYPE_CODE },
+      (void*)(&(xxx)), strength, ty },
 
 // SymI_HasProto_deprecated allows us to redirect references from their deprecated
 // names to the undeprecated ones. e.g. access -> _access.
diff --git a/rts/linker/PEi386.c b/rts/linker/PEi386.c
index 00c28a959d..b8bcc8abec 100644
--- a/rts/linker/PEi386.c
+++ b/rts/linker/PEi386.c
@@ -1780,16 +1780,24 @@ ocAllocateExtras_PEi386 ( ObjectCode* oc )
 }
 
 static size_t
-makeSymbolExtra_PEi386( ObjectCode* oc, uint64_t index STG_UNUSED, size_t s, char* symbol STG_UNUSED )
+makeSymbolExtra_PEi386( ObjectCode* oc, uint64_t index STG_UNUSED, size_t s, char* symbol STG_UNUSED, SymType type )
 {
     SymbolExtra *extra = m32_alloc(oc->rx_m32, sizeof(SymbolExtra), 8);
 
-    // jmp *-14(%rip)
-    static uint8_t jmp[] = { 0xFF, 0x25, 0xF2, 0xFF, 0xFF, 0xFF };
-    extra->addr = (uint64_t)s;
-    memcpy(extra->jumpIsland, jmp, 6);
-
-    return (size_t)extra->jumpIsland;
+    if (type == SYM_TYPE_CODE) {
+        // jmp *-14(%rip)
+        extra->addr = (uint64_t)s;
+        static uint8_t jmp[] = { 0xFF, 0x25, 0xF2, 0xFF, 0xFF, 0xFF };
+        memcpy(extra->jumpIsland, jmp, 6);
+        return (size_t)&extra->jumpIsland;
+    } else if (type == SYM_TYPE_INDIRECT_DATA) {
+        void *v = *(void**) s;
+        extra->addr = (uint64_t)v;
+        return (size_t)&extra->addr;
+    } else {
+        extra->addr = (uint64_t)s;
+        return (size_t)&extra->addr;
+    }
 }
 
 void ocProtectExtras(ObjectCode* oc STG_UNUSED) { }
@@ -1842,6 +1850,8 @@ ocResolve_PEi386 ( ObjectCode* oc )
          uint64_t symIndex = reloc->SymbolTableIndex;
          sym = &oc->info->symbols[symIndex];
 
+         SymType sym_type;
+
          IF_DEBUG(linker_verbose,
                   debugBelch(
                             "reloc sec %2d num %3d:  type 0x%-4x   "
@@ -1859,7 +1869,7 @@ ocResolve_PEi386 ( ObjectCode* oc )
          } else {
             copyName ( getSymShortName (info, sym), oc, symbol,
                        sizeof(symbol)-1 );
-            S = (size_t) lookupDependentSymbol( (char*)symbol, oc, NULL );
+            S = (size_t) lookupDependentSymbol( (char*)symbol, oc, &sym_type );
             if ((void*)S == NULL) {
                 errorBelch(" | %" PATH_FMT ": unknown symbol `%s'", oc->fileName, symbol);
                 releaseOcInfo (oc);
@@ -1927,7 +1937,7 @@ ocResolve_PEi386 ( ObjectCode* oc )
                    if (((int64_t) v > (int64_t) INT32_MAX) || ((int64_t) v < (int64_t) INT32_MIN)) {
                        copyName (getSymShortName (info, sym), oc,
                                  symbol, sizeof(symbol)-1);
-                       S = makeSymbolExtra_PEi386(oc, symIndex, S, (char *)symbol);
+                       S = makeSymbolExtra_PEi386(oc, symIndex, S, (char *)symbol, sym_type);
                        /* And retry */
                        v = S + A;
 
@@ -1951,7 +1961,7 @@ ocResolve_PEi386 ( ObjectCode* oc )
                        /* Make the trampoline then */
                        copyName (getSymShortName (info, sym),
                                  oc, symbol, sizeof(symbol)-1);
-                       S = makeSymbolExtra_PEi386(oc, symIndex, S, (char *)symbol);
+                       S = makeSymbolExtra_PEi386(oc, symIndex, S, (char *)symbol, sym_type);
                        /* And retry */
                        v = S + (int32_t)A - ((intptr_t)pP) - 4;
                        if ((v > (int64_t) INT32_MAX) || (v < (int64_t) INT32_MIN)) {