Allow ZX_ERR_NO_RESOURCES with MAP_ALLOWNOMEM on Fuchsia (#89767)

This can occur if the virtual address space is (almost) entirely
mapped or heavily fragmented.

Author: fabio-d

compiler-rt/lib/scudo/standalone/mem_map_fuchsia.cpp

@@ -84,6 +84,13 @@ static zx_handle_t getPlaceholderVmo() {
   return Vmo;
 }
 
+// Checks if MAP_ALLOWNOMEM allows the given error code.
+static bool IsNoMemError(zx_status_t Status) {
+  // Note: _zx_vmar_map returns ZX_ERR_NO_RESOURCES if the VMAR does not contain
+  // a suitable free spot.
+  return Status == ZX_ERR_NO_MEMORY || Status == ZX_ERR_NO_RESOURCES;
+}
+
 MemMapFuchsia::MemMapFuchsia(uptr Base, uptr Capacity)
     : MapAddr(Base), WindowBase(Base), WindowSize(Capacity) {
   // Create the VMO.
@@ -101,7 +108,7 @@ bool MemMapFuchsia::mapImpl(UNUSED uptr Addr, uptr Size, const char *Name,
   // Create the VMO.
   zx_status_t Status = _zx_vmo_create(Size, 0, &Vmo);
   if (UNLIKELY(Status != ZX_OK)) {
-    if (Status != ZX_ERR_NO_MEMORY || !AllowNoMem)
+    if (!IsNoMemError(Status) || !AllowNoMem)
       dieOnError(Status, "zx_vmo_create", Size);
     return false;
   }
@@ -116,7 +123,7 @@ bool MemMapFuchsia::mapImpl(UNUSED uptr Addr, uptr Size, const char *Name,
   Status =
       _zx_vmar_map(_zx_vmar_root_self(), MapFlags, 0, Vmo, 0, Size, &MapAddr);
   if (UNLIKELY(Status != ZX_OK)) {
-    if (Status != ZX_ERR_NO_MEMORY || !AllowNoMem)
+    if (!IsNoMemError(Status) || !AllowNoMem)
       dieOnError(Status, "zx_vmar_map", Size);
 
     Status = _zx_handle_close(Vmo);
@@ -187,7 +194,7 @@ bool MemMapFuchsia::remapImpl(uptr Addr, uptr Size, const char *Name,
       _zx_vmar_map(_zx_vmar_root_self(), MapFlags, Addr - getRootVmarBase(),
                    Vmo, Addr - MapAddr, Size, &MappedAddr);
   if (UNLIKELY(Status != ZX_OK)) {
-    if (Status != ZX_ERR_NO_MEMORY || !AllowNoMem)
+    if (!IsNoMemError(Status) || !AllowNoMem)
       dieOnError(Status, "zx_vmar_map", Size);
     return false;
   }
@@ -227,7 +234,7 @@ bool ReservedMemoryFuchsia::createImpl(UNUSED uptr Addr, uptr Size,
   zx_status_t Status = _zx_vmar_map(_zx_vmar_root_self(), ZX_VM_ALLOW_FAULTS, 0,
                                     getPlaceholderVmo(), 0, Size, &Base);
   if (UNLIKELY(Status != ZX_OK)) {
-    if (Status != ZX_ERR_NO_MEMORY || !AllowNoMem)
+    if (!IsNoMemError(Status) || !AllowNoMem)
       dieOnError(Status, "zx_vmar_map", Size);
     return false;
   }