illumos: Treat absolute symbols specially

illumos is a descendent of Solaris/OpenSolaris, and treats
symbols with shndx=SHN_ABS and st_value=0 specially, such that
they should be marked imported.  This change adds a special
case for this behavior, wrapped up in a function that #ifdef's
out on other platforms.  With this patch, executables linked
with mold on illumos run; without it, they do not.

The original behavior was spotted by Luqman Aden (@luqmana).
This also patches a small bogon in the third-party `mimalloc`
code.  I've sent that same fix upstream, but so far the
maintainer has not resonded, so replicate here.

Fixes #1183

Signed-off-by: Dan Cross <cross@oxidecomputer.com>

elf/passes.cc

@@ -1783,6 +1783,20 @@ void parse_symbol_version(Context<E> &ctx) {
   });
 }
 
+namespace {
+template <typename E>
+inline bool should_import_absolute_sym(const Symbol<E> *sym) {
+#ifdef __sun
+  // On illumos, symbols with shndx=SHN_ABS and st_value=0 are special
+  // and should be imported.
+  return sym->value == 0;
+#else
+  (void)sym;
+  return false;
+#endif
+}
+} // anonymous namespace
+
 template <typename E>
 void compute_import_export(Context<E> &ctx) {
   Timer t(ctx, "compute_import_export");
@@ -1823,7 +1837,7 @@ void compute_import_export(Context<E> &ctx) {
     for (Symbol<E> *sym : file->get_global_syms()) {
       // If we are using a symbol in a DSO, we need to import it.
       if (sym->file && sym->file->is_dso) {
-        if (!sym->is_absolute()) {
+        if (!sym->is_absolute() || should_import_absolute_sym(sym)) {
           std::scoped_lock lock(sym->mu);
           sym->is_imported = true;
         }

third-party/mimalloc/src/prim/unix/prim.c

@@ -311,7 +311,7 @@ static void* unix_mmap(void* addr, size_t size, size_t try_alignment, int protec
       #elif defined(__sun)
       if (allow_large && _mi_os_use_large_page(size, try_alignment)) {
         struct memcntl_mha cmd = {0};
-        cmd.mha_pagesize = large_os_page_size;
+        cmd.mha_pagesize = _mi_os_large_page_size();
         cmd.mha_cmd = MHA_MAPSIZE_VA;
         if (memcntl((caddr_t)p, size, MC_HAT_ADVISE, (caddr_t)&cmd, 0, 0) == 0) {
           *is_large = true;