From 74ee491b842e1f1a4df75f81e980957ff194c5b0 Mon Sep 17 00:00:00 2001
From: Brian Gianforcaro <bgianf@serenityos.org>
Date: Mon, 29 Nov 2021 03:01:24 -0800
Subject: [PATCH] Kernel: Handle string format errors in SlabAllocator stats
 :^)

Switch to KString::formatted and fix API so we can propagate errors.
---
 Kernel/GlobalProcessExposed.cpp | 16 ++++++++++------
 Kernel/Heap/SlabAllocator.cpp   | 24 ++++++++++++++----------
 Kernel/Heap/SlabAllocator.h     |  2 +-
 3 files changed, 25 insertions(+), 17 deletions(-)

diff --git a/Kernel/GlobalProcessExposed.cpp b/Kernel/GlobalProcessExposed.cpp
index 2bed0a83ae..2733e9537c 100644
--- a/Kernel/GlobalProcessExposed.cpp
+++ b/Kernel/GlobalProcessExposed.cpp
@@ -412,11 +412,14 @@ private:
         json.add("super_physical_available", system_memory.super_physical_pages - system_memory.super_physical_pages_used);
         json.add("kmalloc_call_count", stats.kmalloc_call_count);
         json.add("kfree_call_count", stats.kfree_call_count);
-        slab_alloc_stats([&json](size_t slab_size, size_t num_allocated, size_t num_free) {
-            auto prefix = String::formatted("slab_{}", slab_size);
-            json.add(String::formatted("{}_num_allocated", prefix), num_allocated);
-            json.add(String::formatted("{}_num_free", prefix), num_free);
-        });
+        TRY(slab_alloc_stats([&json](size_t slab_size, size_t num_allocated, size_t num_free) -> ErrorOr<void> {
+            auto prefix = TRY(KString::formatted("slab_{}", slab_size));
+            auto formatted_num_allocated = TRY(KString::formatted("{}_num_allocated", prefix));
+            auto formatted_num_free = TRY(KString::formatted("{}_num_free", prefix));
+            json.add(formatted_num_allocated->view(), num_allocated);
+            json.add(formatted_num_free->view(), num_free);
+            return {};
+        }));
         json.finish();
         return {};
     }
@@ -952,7 +955,8 @@ ErrorOr<void> ProcFSRootDirectory::traverse_as_directory(FileSystemID fsid, Func
             VERIFY(!(process.pid() < 0));
             u64 process_id = (u64)process.pid().value();
             InodeIdentifier identifier = { fsid, static_cast<InodeIndex>(process_id << 36) };
-            TRY(callback({ String::formatted("{:d}", process.pid().value()), identifier, 0 }));
+            auto process_id_string = TRY(KString::formatted("{:d}", process_id));
+            TRY(callback({ process_id_string->view(), identifier, 0 }));
         }
         return {};
     });
diff --git a/Kernel/Heap/SlabAllocator.cpp b/Kernel/Heap/SlabAllocator.cpp
index 179cdcc0b8..ed9e83449b 100644
--- a/Kernel/Heap/SlabAllocator.cpp
+++ b/Kernel/Heap/SlabAllocator.cpp
@@ -116,13 +116,14 @@ static_assert(sizeof(Memory::Region) <= s_slab_allocator_128.slab_size());
 #endif
 
 template<typename Callback>
-void for_each_allocator(Callback callback)
+ErrorOr<void> for_each_allocator(Callback callback)
 {
-    callback(s_slab_allocator_16);
-    callback(s_slab_allocator_32);
-    callback(s_slab_allocator_64);
-    callback(s_slab_allocator_128);
-    callback(s_slab_allocator_256);
+    TRY(callback(s_slab_allocator_16));
+    TRY(callback(s_slab_allocator_32));
+    TRY(callback(s_slab_allocator_64));
+    TRY(callback(s_slab_allocator_128));
+    TRY(callback(s_slab_allocator_256));
+    return {};
 }
 
 UNMAP_AFTER_INIT void slab_alloc_init()
@@ -164,13 +165,16 @@ void slab_dealloc(void* ptr, size_t slab_size)
     VERIFY_NOT_REACHED();
 }
 
-void slab_alloc_stats(Function<void(size_t slab_size, size_t allocated, size_t free)> callback)
+ErrorOr<void> slab_alloc_stats(Function<ErrorOr<void>(size_t slab_size, size_t allocated, size_t free)> callback)
 {
-    for_each_allocator([&](auto& allocator) {
+    TRY(for_each_allocator([&](auto& allocator) -> ErrorOr<void> {
         auto num_allocated = allocator.num_allocated();
         auto num_free = allocator.slab_count() - num_allocated;
-        callback(allocator.slab_size(), num_allocated, num_free);
-    });
+        TRY(callback(allocator.slab_size(), num_allocated, num_free));
+        return {};
+    }));
+
+    return {};
 }
 
 }
diff --git a/Kernel/Heap/SlabAllocator.h b/Kernel/Heap/SlabAllocator.h
index 5650d428c1..81d0612fb4 100644
--- a/Kernel/Heap/SlabAllocator.h
+++ b/Kernel/Heap/SlabAllocator.h
@@ -17,7 +17,7 @@ namespace Kernel {
 void* slab_alloc(size_t slab_size);
 void slab_dealloc(void*, size_t slab_size);
 void slab_alloc_init();
-void slab_alloc_stats(Function<void(size_t slab_size, size_t allocated, size_t free)>);
+ErrorOr<void> slab_alloc_stats(Function<ErrorOr<void>(size_t slab_size, size_t allocated, size_t free)>);
 
 #define MAKE_SLAB_ALLOCATED(type)                                            \
 public:                                                                      \