Revert "Allocate bss section within proper range of other sections"

This reverts commit e019ec94f12268dd92ea5d5204e9e57e7ebf10ca.

This sadly breaks the external interpreter on i386.

For instance, see https://circleci.com/gh/ghc/ghc/10925.

8 files changed, 64 insertions, 77 deletions

diff --git a/rts/linker/Elf.c b/rts/linker/Elf.c
index 0a7ffaec21..fe87aed0b0 100644
--- a/rts/linker/Elf.c
+++ b/rts/linker/Elf.c
@@ -579,7 +579,7 @@ ocVerifyImage_ELF ( ObjectCode* oc )
 /* Figure out what kind of section it is.  Logic derived from
    Figure 1.14 ("Special Sections") of the ELF document
    ("Portable Formats Specification, Version 1.1"). */
-static SectionKind getSectionKind_ELF( Elf_Shdr *hdr, int *is_bss )
+static int getSectionKind_ELF( Elf_Shdr *hdr, int *is_bss )
 {
     *is_bss = false;
 
@@ -681,31 +681,23 @@ ocGetNames_ELF ( ObjectCode* oc )
       StgWord mapped_size = 0, mapped_offset = 0;
       StgWord size = shdr[i].sh_size;
       StgWord offset = shdr[i].sh_offset;
-      StgWord align = shdr[i].sh_addralign;
 
       if (is_bss && size > 0) {
          /* This is a non-empty .bss section.  Allocate zeroed space for
             it, and set its .sh_offset field such that
             ehdrC + .sh_offset == addr_of_zeroed_space.  */
-#if defined(NEED_GOT) || RTS_LINKER_USE_MMAP
-          if (USE_CONTIGUOUS_MMAP || RtsFlags.MiscFlags.linkerAlwaysPic) {
-              /* The space for bss sections is already preallocated */
-              ASSERT(oc->bssBegin != NULL);
-              alloc = SECTION_NOMEM;
-              start =
-                oc->image + roundUpToAlign(oc->bssBegin - oc->image, align);
-              oc->bssBegin = (char*)start + size;
-              ASSERT(oc->bssBegin <= oc->bssEnd);
-          } else {
-              /* Use mmapForLinker to allocate .bss, otherwise the malloced
-               * address might be out of range for sections that are mmaped.
-               */
-              alloc = SECTION_MMAP;
-              start = mmapForLinker(size, MAP_ANONYMOUS, -1, 0);
-              mapped_start = start;
-              mapped_offset = 0;
-              mapped_size = roundUpToPage(size);
-          }
+#if defined(NEED_GOT)
+          /* always use mmap if we use GOT slots.  Otherwise the malloced
+           * address might be out of range for sections that are mmaped.
+           */
+          alloc = SECTION_MMAP;
+          start = mmap(NULL, size,
+                       PROT_READ | PROT_WRITE | PROT_EXEC,
+                       MAP_ANON | MAP_PRIVATE,
+                       -1, 0);
+          mapped_start = start;
+          mapped_offset = 0;
+          mapped_size = roundUpToPage(size);
 #else
           alloc = SECTION_MALLOC;
           start = stgCallocBytes(1, size, "ocGetNames_ELF(BSS)");
@@ -1881,27 +1873,22 @@ int ocRunInit_ELF( ObjectCode *oc )
 
 #if defined(NEED_SYMBOL_EXTRAS)
 
-int ocAllocateExtras_ELF( ObjectCode *oc )
+int ocAllocateSymbolExtras_ELF( ObjectCode *oc )
 {
-  Elf_Ehdr *ehdr = (Elf_Ehdr *) oc->image;
-  Elf_Shdr* shdr = (Elf_Shdr *) ( ((char *)oc->image) + ehdr->e_shoff );
-  Elf_Shdr* symtab = NULL;
-  Elf_Word shnum = elf_shnum(ehdr);
-  int bssSize = 0;
-
-  for (Elf_Word i = 0; i < shnum; ++i) {
-    if(shdr[i].sh_type == SHT_SYMTAB) {
-      symtab = &shdr[i];
-    } else {
-      int isBss = 0;
-      getSectionKind_ELF(&shdr[i], &isBss);
-      if (isBss && shdr[i].sh_size > 0) {
-        bssSize += roundUpToAlign(shdr[i].sh_size, shdr[i].sh_addralign);
-      }
-    }
-  }
+  Elf_Ehdr *ehdr;
+  Elf_Shdr* shdr;
+  Elf_Word i, shnum;
+
+  ehdr = (Elf_Ehdr *) oc->image;
+  shdr = (Elf_Shdr *) ( ((char *)oc->image) + ehdr->e_shoff );
+
+  shnum = elf_shnum(ehdr);
+
+  for( i = 0; i < shnum; i++ )
+    if( shdr[i].sh_type == SHT_SYMTAB )
+      break;
 
-  if (symtab == NULL)
+  if( i == shnum )
   {
     // Not having a symbol table is not in principle a problem.
     // When an object file has no symbols then the 'strip' program
@@ -1911,15 +1898,15 @@ int ocAllocateExtras_ELF( ObjectCode *oc )
     return 1;
   }
 
-  if( symtab->sh_entsize != sizeof( Elf_Sym ) )
+  if( shdr[i].sh_entsize != sizeof( Elf_Sym ) )
   {
     errorBelch( "The entry size (%d) of the symtab isn't %d\n",
-      (int) symtab->sh_entsize, (int) sizeof( Elf_Sym ) );
+      (int) shdr[i].sh_entsize, (int) sizeof( Elf_Sym ) );
 
     return 0;
   }
 
-  return ocAllocateExtras(oc, symtab->sh_size / sizeof( Elf_Sym ), 0, bssSize);
+  return ocAllocateSymbolExtras( oc, shdr[i].sh_size / sizeof( Elf_Sym ), 0 );
 }
 
 #endif /* NEED_SYMBOL_EXTRAS */
diff --git a/rts/linker/Elf.h b/rts/linker/Elf.h
index 30c993b98c..b0d6638e6a 100644
--- a/rts/linker/Elf.h
+++ b/rts/linker/Elf.h
@@ -13,6 +13,6 @@ int ocVerifyImage_ELF    ( ObjectCode* oc );
 int ocGetNames_ELF       ( ObjectCode* oc );
 int ocResolve_ELF        ( ObjectCode* oc );
 int ocRunInit_ELF        ( ObjectCode* oc );
-int ocAllocateExtras_ELF ( ObjectCode *oc );
+int ocAllocateSymbolExtras_ELF( ObjectCode *oc );
 
 #include "EndPrivate.h"
diff --git a/rts/linker/MachO.c b/rts/linker/MachO.c
index 7d5ff32276..ff8ef7a1e4 100644
--- a/rts/linker/MachO.c
+++ b/rts/linker/MachO.c
@@ -186,10 +186,10 @@ resolveImports(
 #if NEED_SYMBOL_EXTRAS
 #if defined(powerpc_HOST_ARCH)
 int
-ocAllocateExtras_MachO(ObjectCode* oc)
+ocAllocateSymbolExtras_MachO(ObjectCode* oc)
 {
 
-    IF_DEBUG(linker, debugBelch("ocAllocateExtras_MachO: start\n"));
+    IF_DEBUG(linker, debugBelch("ocAllocateSymbolExtras_MachO: start\n"));
 
     // Find out the first and last undefined external
     // symbol, so we don't have to allocate too many
@@ -218,31 +218,28 @@ ocAllocateExtras_MachO(ObjectCode* oc)
     }
 
     if (max >= min) {
-        return ocAllocateExtras(oc, max - min + 1, min, 0);
+        return ocAllocateSymbolExtras(oc, max - min + 1, min);
     }
 
-    return ocAllocateExtras(oc, 0, 0, 0);
+    return ocAllocateSymbolExtras(oc,0,0);
 }
 
 #elif defined(x86_64_HOST_ARCH) || defined(aarch64_HOST_ARCH)
 
 int
-ocAllocateExtras_MachO(ObjectCode* oc)
+ocAllocateSymbolExtras_MachO(ObjectCode* oc)
 {
-    IF_DEBUG(linker, debugBelch("ocAllocateExtras_MachO: start\n"));
+    IF_DEBUG(linker, debugBelch("ocAllocateSymbolExtras_MachO: start\n"));
 
     if (NULL != oc->info->symCmd) {
-        IF_DEBUG(linker,
-            debugBelch("ocAllocateExtras_MachO: allocate %d symbols\n",
-                oc->info->symCmd->nsyms));
-        IF_DEBUG(linker, debugBelch("ocAllocateExtras_MachO: done\n"));
-        return ocAllocateExtras(oc, oc->info->symCmd->nsyms, 0, 0);
+        IF_DEBUG(linker, debugBelch("ocAllocateSymbolExtras_MachO: allocate %d symbols\n", oc->info->symCmd->nsyms));
+        IF_DEBUG(linker, debugBelch("ocAllocateSymbolExtras_MachO: done\n"));
+        return ocAllocateSymbolExtras(oc, oc->info->symCmd->nsyms, 0);
     }
 
-    IF_DEBUG(linker,
-        debugBelch("ocAllocateExtras_MachO: allocated no symbols\n"));
-    IF_DEBUG(linker, debugBelch("ocAllocateExtras_MachO: done\n"));
-    return ocAllocateExtras(oc, 0, 0, 0);
+    IF_DEBUG(linker, debugBelch("ocAllocateSymbolExtras_MachO: allocated no symbols\n"));
+    IF_DEBUG(linker, debugBelch("ocAllocateSymbolExtras_MachO: done\n"));
+    return ocAllocateSymbolExtras(oc,0,0);
 }
 
 #else
diff --git a/rts/linker/MachO.h b/rts/linker/MachO.h
index 4fb58e8668..b495c2b9b1 100644
--- a/rts/linker/MachO.h
+++ b/rts/linker/MachO.h
@@ -13,7 +13,7 @@ int ocGetNames_MachO       ( ObjectCode* oc );
 int ocResolve_MachO        ( ObjectCode* oc );
 int ocRunInit_MachO        ( ObjectCode* oc );
 int machoGetMisalignment( FILE * );
-int ocAllocateExtras_MachO ( ObjectCode* oc );
+int ocAllocateSymbolExtras_MachO ( ObjectCode* oc );
 
 #if defined(powerpc_HOST_ARCH)
 void machoInitSymbolsWithoutUnderscore( void );
diff --git a/rts/linker/PEi386.c b/rts/linker/PEi386.c
index bf642d8b23..ab4583da7c 100644
--- a/rts/linker/PEi386.c
+++ b/rts/linker/PEi386.c
@@ -1777,7 +1777,7 @@ ocGetNames_PEi386 ( ObjectCode* oc )
  * so simply set correct pointer here.
  */
 bool
-ocAllocateExtras_PEi386 ( ObjectCode* oc )
+ocAllocateSymbolExtras_PEi386 ( ObjectCode* oc )
 {
    /* If the ObjectCode was unloaded we don't need a trampoline, it's likely
       an import library so we're discarding it earlier.  */
diff --git a/rts/linker/PEi386.h b/rts/linker/PEi386.h
index 538f132ab5..eb5bec8b78 100644
--- a/rts/linker/PEi386.h
+++ b/rts/linker/PEi386.h
@@ -57,7 +57,7 @@ bool ocRunInit_PEi386     ( ObjectCode *oc );
 bool ocGetNames_PEi386    ( ObjectCode* oc );
 bool ocVerifyImage_PEi386 ( ObjectCode* oc );
 SymbolAddr *lookupSymbol_PEi386(SymbolName *lbl);
-bool ocAllocateExtras_PEi386 ( ObjectCode* oc );
+bool ocAllocateSymbolExtras_PEi386 ( ObjectCode* oc );
 SymbolAddr *lookupSymbolInDLLs ( const SymbolName* lbl );
 /* See Note [mingw-w64 name decoration scheme] */
 /* We use myindex to calculate array addresses, rather than
diff --git a/rts/linker/SymbolExtras.c b/rts/linker/SymbolExtras.c
index a9e4c37967..4c40b10877 100644
--- a/rts/linker/SymbolExtras.c
+++ b/rts/linker/SymbolExtras.c
@@ -31,11 +31,10 @@
 #endif /* RTS_LINKER_USE_MMAP */
 
 /*
-  ocAllocateExtras
+  ocAllocateSymbolExtras
 
   Allocate additional space at the end of the object file image to make room
-  for jump islands (powerpc, x86_64, arm), GOT entries (x86_64) and
-  bss sections.
+  for jump islands (powerpc, x86_64, arm) and GOT entries (x86_64).
 
   PowerPC relative branch instructions have a 24 bit displacement field.
   As PPC code is always 4-byte-aligned, this yields a +-32MB range.
@@ -50,11 +49,12 @@
   filled in by makeSymbolExtra below.
 */
 
-int ocAllocateExtras(ObjectCode* oc, int count, int first, int bssSize)
+int ocAllocateSymbolExtras( ObjectCode* oc, int count, int first )
 {
+  size_t n;
   void* oldImage = oc->image;
 
-  if (count > 0 || bssSize > 0) {
+  if (count > 0) {
     if (!RTS_LINKER_USE_MMAP) {
 
       // round up to the nearest 4
@@ -65,15 +65,16 @@ int ocAllocateExtras(ObjectCode* oc, int count, int first, int bssSize)
       oc->image = stgReallocBytes( oc->image,
                                misalignment +
                                aligned + sizeof (SymbolExtra) * count,
-                               "ocAllocateExtras" );
+                               "ocAllocateSymbolExtras" );
       oc->image += misalignment;
 
       oc->symbol_extras = (SymbolExtra *) (oc->image + aligned);
     } else if (USE_CONTIGUOUS_MMAP || RtsFlags.MiscFlags.linkerAlwaysPic) {
-      /* Keep image, bssExtras and symbol_extras contiguous */
-      size_t n = roundUpToPage(oc->fileSize);
-      bssSize = roundUpToAlign(bssSize, 8);
-      size_t allocated_size = n + bssSize + (sizeof(SymbolExtra) * count);
+      n = roundUpToPage(oc->fileSize);
+
+      /* Keep image and symbol_extras contiguous */
+
+      size_t allocated_size = n + (sizeof(SymbolExtra) * count);
       void *new = mmapForLinker(allocated_size, MAP_ANONYMOUS, -1, 0);
       if (new) {
           memcpy(new, oc->image, oc->fileSize);
@@ -82,10 +83,12 @@ int ocAllocateExtras(ObjectCode* oc, int count, int first, int bssSize)
           }
           oc->image = new;
           oc->imageMapped = true;
-          oc->fileSize = allocated_size;
-          oc->symbol_extras = (SymbolExtra *) (oc->image + n + bssSize);
-          oc->bssBegin = oc->image + n;
-          oc->bssEnd = oc->image + n + bssSize;
+          oc->fileSize = n + (sizeof(SymbolExtra) * count);
+          oc->symbol_extras = (SymbolExtra *) (oc->image + n);
+          if (mprotect(new, allocated_size,
+                       PROT_READ | PROT_WRITE | PROT_EXEC) != 0) {
+            sysErrorBelch("unable to protect memory");
+          }
       }
       else {
           oc->symbol_extras = NULL;
diff --git a/rts/linker/SymbolExtras.h b/rts/linker/SymbolExtras.h
index af828e66fa..4974c06e7d 100644
--- a/rts/linker/SymbolExtras.h
+++ b/rts/linker/SymbolExtras.h
@@ -7,7 +7,7 @@
 
 #if defined(NEED_SYMBOL_EXTRAS)
 
-int ocAllocateExtras(ObjectCode* oc, int count, int first, int bssSize);
+int ocAllocateSymbolExtras( ObjectCode* oc, int count, int first );
 
 #if defined(arm_HOST_ARCH)
 SymbolExtra* makeArmSymbolExtra( ObjectCode const* oc,