[compiler-rt] Allow ZX_ERR_NO_RESOURCES with MAP_ALLOWNOMEM on Fuchsia (PR #89767)

[Fabio D'Urso via llvm-commits]

https://github.com/fabio-d created https://github.com/llvm/llvm-project/pull/89767

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


>From 1d50314ddd99e2fbeb99982e106e28f6b216fe02 Mon Sep 17 00:00:00 2001
From: Fabio D'Urso <fdurso at google.com>
Date: Tue, 23 Apr 2024 14:50:44 +0200
Subject: [PATCH] Allow ZX_ERR_NO_RESOURCES with MAP_ALLOWNOMEM on Fuchsia

This can occur if the virtual address space is (almost) entirely
mapped or heavily fragmented.
---
 .../lib/scudo/standalone/mem_map_fuchsia.cpp      | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/compiler-rt/lib/scudo/standalone/mem_map_fuchsia.cpp b/compiler-rt/lib/scudo/standalone/mem_map_fuchsia.cpp
index 28e5a11a37f257..5f3c8b81c07b31 100644
--- a/compiler-rt/lib/scudo/standalone/mem_map_fuchsia.cpp
+++ b/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;
   }