rts: Introduce mmapAnonForLinker

Previously most of the uses of mmapForLinker were mapping anonymous
memory, resulting in a great deal of unnecessary repetition. Factor this
out into a new helper.

Also fixes a few places where error checking was missing or suboptimal.

8 files changed, 41 insertions, 26 deletions

diff --git a/rts/Linker.c b/rts/Linker.c
index ef08a282dc..6873b1a9b7 100644
--- a/rts/Linker.c
+++ b/rts/Linker.c
@@ -1080,7 +1080,7 @@ mmap_again:
                fixed = MAP_FIXED;
                goto mmap_again;
 #else
-               errorBelch("loadObj: failed to mmap() memory below 2Gb; "
+               errorBelch("mmapForLinker: failed to mmap() memory below 2Gb; "
                           "asked for %lu bytes at %p. "
                           "Try specifying an address with +RTS -xm<addr> -RTS",
                           size, map_addr);
@@ -1140,6 +1140,16 @@ mmap_again:
    return result;
 }
 
+/*
+ * Map read/write pages in low memory. Returns NULL on failure.
+ */
+void *
+mmapAnonForLinker (size_t bytes)
+{
+  return mmapForLinker (bytes, PROT_READ|PROT_WRITE, MAP_ANONYMOUS, -1, 0);
+}
+
+
 /* Note [Memory protection in the linker]
  * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  * For many years the linker would simply map all of its memory
diff --git a/rts/LinkerInternals.h b/rts/LinkerInternals.h
index 27ca52f0e3..954c36764e 100644
--- a/rts/LinkerInternals.h
+++ b/rts/LinkerInternals.h
@@ -362,6 +362,7 @@ void exitLinker( void );
 void freeObjectCode (ObjectCode *oc);
 SymbolAddr* loadSymbol(SymbolName *lbl, RtsSymbolInfo *pinfo);
 
+void *mmapAnonForLinker (size_t bytes);
 void *mmapForLinker (size_t bytes, uint32_t prot, uint32_t flags, int fd, int offset);
 void mmapForLinkerMarkExecutable (void *start, size_t len);
 
diff --git a/rts/linker/Elf.c b/rts/linker/Elf.c
index b70eab0916..050de23dac 100644
--- a/rts/linker/Elf.c
+++ b/rts/linker/Elf.c
@@ -714,7 +714,11 @@ ocGetNames_ELF ( ObjectCode* oc )
                * address might be out of range for sections that are mmaped.
                */
               alloc = SECTION_MMAP;
-              start = mmapForLinker(size, PROT_READ | PROT_WRITE, MAP_ANONYMOUS, -1, 0);
+              start = mmapAnonForLinker(size);
+              if (start == NULL) {
+                barf("failed to mmap memory for bss. "
+                     "errno = %d", errno);
+              }
               mapped_start = start;
               mapped_offset = 0;
               mapped_size = roundUpToPage(size);
@@ -756,9 +760,9 @@ ocGetNames_ELF ( ObjectCode* oc )
           unsigned nstubs = numberOfStubsForSection(oc, i);
           unsigned stub_space = STUB_SIZE * nstubs;
 
-          void * mem = mmapForLinker(size+stub_space, PROT_READ | PROT_WRITE, MAP_ANON, -1, 0);
+          void * mem = mmapAnonForLinker(size+stub_space);
 
-          if( mem == MAP_FAILED ) {
+          if( mem == NULL ) {
               barf("failed to mmap allocated memory to load section %d. "
                    "errno = %d", i, errno);
           }
@@ -865,11 +869,10 @@ ocGetNames_ELF ( ObjectCode* oc )
       }
       void * common_mem = NULL;
       if(common_size > 0) {
-          common_mem = mmapForLinker(common_size,
-                            PROT_READ | PROT_WRITE,
-                            MAP_ANON | MAP_PRIVATE,
-                            -1, 0);
-          CHECK(common_mem != NULL);
+          common_mem = mmapAnonForLinker(common_size);
+          if (common_mem == NULL) {
+            barf("ocGetNames_ELF: Failed to allocate memory for SHN_COMMONs");
+          }
       }
 
       //TODO: we ignore local symbols anyway right? So we can use the
diff --git a/rts/linker/LoadArchive.c b/rts/linker/LoadArchive.c
index 55081489f5..9dda0e99e8 100644
--- a/rts/linker/LoadArchive.c
+++ b/rts/linker/LoadArchive.c
@@ -489,7 +489,7 @@ static HsInt loadArchive_ (pathchar *path)
 
 #if defined(darwin_HOST_OS) || defined(ios_HOST_OS)
             if (RTS_LINKER_USE_MMAP)
-                image = mmapForLinker(memberSize, PROT_READ | PROT_WRITE, MAP_ANONYMOUS, -1, 0);
+                image = mmapAnonForLinker(memberSize);
             else {
                 /* See loadObj() */
                 misalignment = machoGetMisalignment(f);
@@ -549,7 +549,7 @@ while reading filename from `%" PATH_FMT "'", path);
             }
             DEBUG_LOG("Found GNU-variant file index\n");
 #if RTS_LINKER_USE_MMAP
-            gnuFileIndex = mmapForLinker(memberSize + 1, PROT_READ | PROT_WRITE, MAP_ANONYMOUS, -1, 0);
+            gnuFileIndex = mmapAnonForLinker(memberSize + 1);
 #else
             gnuFileIndex = stgMallocBytes(memberSize + 1, "loadArchive(image)");
 #endif
diff --git a/rts/linker/M32Alloc.c b/rts/linker/M32Alloc.c
index 3adb8d934d..f1440e093c 100644
--- a/rts/linker/M32Alloc.c
+++ b/rts/linker/M32Alloc.c
@@ -263,8 +263,8 @@ m32_alloc_page(void)
      * pages.
      */
     const size_t pgsz = getPageSize();
-    char *chunk = mmapForLinker(pgsz * M32_MAP_PAGES, PROT_READ | PROT_WRITE, MAP_ANONYMOUS, -1, 0);
-    if (chunk > (char *) 0xffffffff) {
+    uint8_t *chunk = mmapAnonForLinker(pgsz * M32_MAP_PAGES);
+    if (chunk > (uint8_t *) 0xffffffff) {
       barf("m32_alloc_page: failed to get allocation in lower 32-bits");
     }
 
@@ -407,7 +407,14 @@ m32_alloc(struct m32_allocator_t *alloc, size_t size, size_t alignment)
    if (m32_is_large_object(size,alignment)) {
       // large object
       size_t alsize = ROUND_UP(sizeof(struct m32_page_t), alignment);
-      struct m32_page_t *page = mmapForLinker(alsize+size, PROT_READ | PROT_WRITE, MAP_ANONYMOUS,-1,0);
+      struct m32_page_t *page = mmapAnonForLinker(alsize+size);
+      if (page == NULL) {
+          sysErrorBelch("m32_alloc: Failed to map pages for %zd bytes", size);
+          return NULL;
+      } else if (page > (struct m32_page_t *) 0xffffffff) {
+          debugBelch("m32_alloc: warning: Allocation of %zd bytes resulted in pages above 4GB (%p)",
+                     size, page);
+      }
       page->filled_page.size = alsize + size;
       m32_allocator_push_filled_list(&alloc->unprotected_list, (struct m32_page_t *) page);
       return (char*) page + alsize;
diff --git a/rts/linker/MachO.c b/rts/linker/MachO.c
index d3da3ebdcf..e39379fd7e 100644
--- a/rts/linker/MachO.c
+++ b/rts/linker/MachO.c
@@ -507,11 +507,8 @@ makeGot(ObjectCode * oc) {
 
     if(got_slots > 0) {
         oc->info->got_size =  got_slots * sizeof(void*);
-        oc->info->got_start = mmapForLinker(oc->info->got_size,
-                                   PROT_READ | PROT_WRITE,
-                                   MAP_ANON | MAP_PRIVATE,
-                                   -1, 0);
-        if( oc->info->got_start == MAP_FAILED ) {
+        oc->info->got_start = mmapAnonForLinker(oc->info->got_size);
+        if( oc->info->got_start == NULL ) {
             barf("MAP_FAILED. errno=%d", errno );
             return EXIT_FAILURE;
         }
@@ -1113,7 +1110,7 @@ ocBuildSegments_MachO(ObjectCode *oc)
         return 1;
     }
 
-    mem = mmapForLinker(size_compound, PROT_READ | PROT_WRITE, MAP_ANON, -1, 0);
+    mem = mmapAnonForLinker(size_compound);
     if (NULL == mem) return 0;
 
     IF_DEBUG(linker, debugBelch("ocBuildSegments: allocating %d segments\n", n_activeSegments));
diff --git a/rts/linker/SymbolExtras.c b/rts/linker/SymbolExtras.c
index 7f77d5120a..9d4eb89400 100644
--- a/rts/linker/SymbolExtras.c
+++ b/rts/linker/SymbolExtras.c
@@ -81,7 +81,7 @@ int ocAllocateExtras(ObjectCode* oc, int count, int first, int bssSize)
       // symbol_extras is aligned to a page boundary so it can be mprotect'd.
       bssSize = roundUpToPage(bssSize);
       size_t allocated_size = n + bssSize + extras_size;
-      void *new = mmapForLinker(allocated_size, PROT_READ | PROT_WRITE, MAP_ANONYMOUS, -1, 0);
+      void *new = mmapAnonForLinker(allocated_size);
       if (new) {
           memcpy(new, oc->image, oc->fileSize);
           if (oc->imageMapped) {
diff --git a/rts/linker/elf_got.c b/rts/linker/elf_got.c
index 1aca219f9b..4b014dac50 100644
--- a/rts/linker/elf_got.c
+++ b/rts/linker/elf_got.c
@@ -48,11 +48,8 @@ makeGot(ObjectCode * oc) {
     }
     if(got_slots > 0) {
         oc->info->got_size = got_slots * sizeof(void *);
-         void * mem = mmapForLinker(oc->info->got_size,
-                           PROT_READ | PROT_WRITE,
-                           MAP_ANON | MAP_PRIVATE,
-                           -1, 0);
-        if (mem == MAP_FAILED) {
+        void * mem = mmapAnonForLinker(oc->info->got_size);
+        if (mem == NULL) {
             errorBelch("MAP_FAILED. errno=%d", errno);
             return EXIT_FAILURE;
         }