From d65347d39dd89013a0c46d8206c77e65d6dceda1 Mon Sep 17 00:00:00 2001
From: Idan Horowitz <idan.horowitz@gmail.com>
Date: Thu, 20 Jan 2022 21:10:46 +0200
Subject: [PATCH] Kernel: Make Memory::RingBuffer construction fallible

---
 Kernel/Bus/VirtIO/Console.cpp     |  4 ++--
 Kernel/Bus/VirtIO/ConsolePort.cpp |  4 ++--
 Kernel/Memory/RingBuffer.cpp      | 11 +++++++++--
 Kernel/Memory/RingBuffer.h        |  6 ++++--
 4 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/Kernel/Bus/VirtIO/Console.cpp b/Kernel/Bus/VirtIO/Console.cpp
index de4f2779bc..b46475286e 100644
--- a/Kernel/Bus/VirtIO/Console.cpp
+++ b/Kernel/Bus/VirtIO/Console.cpp
@@ -123,8 +123,8 @@ void Console::handle_queue_update(u16 queue_index)
 
 void Console::setup_multiport()
 {
-    m_control_receive_buffer = make<Memory::RingBuffer>("VirtIOConsole control receive queue"sv, CONTROL_BUFFER_SIZE);
-    m_control_transmit_buffer = make<Memory::RingBuffer>("VirtIOConsole control transmit queue"sv, CONTROL_BUFFER_SIZE);
+    m_control_receive_buffer = Memory::RingBuffer::try_create("VirtIOConsole control receive queue"sv, CONTROL_BUFFER_SIZE).release_value_but_fixme_should_propagate_errors();
+    m_control_transmit_buffer = Memory::RingBuffer::try_create("VirtIOConsole control transmit queue"sv, CONTROL_BUFFER_SIZE).release_value_but_fixme_should_propagate_errors();
 
     auto& queue = get_queue(CONTROL_RECEIVEQ);
     SpinlockLocker queue_lock(queue.lock());
diff --git a/Kernel/Bus/VirtIO/ConsolePort.cpp b/Kernel/Bus/VirtIO/ConsolePort.cpp
index 78149e2380..8545aac8ae 100644
--- a/Kernel/Bus/VirtIO/ConsolePort.cpp
+++ b/Kernel/Bus/VirtIO/ConsolePort.cpp
@@ -17,8 +17,8 @@ ConsolePort::ConsolePort(unsigned port, VirtIO::Console& console)
     , m_console(console)
     , m_port(port)
 {
-    m_receive_buffer = make<Memory::RingBuffer>("VirtIO::ConsolePort Receive"sv, RINGBUFFER_SIZE);
-    m_transmit_buffer = make<Memory::RingBuffer>("VirtIO::ConsolePort Transmit"sv, RINGBUFFER_SIZE);
+    m_receive_buffer = Memory::RingBuffer::try_create("VirtIO::ConsolePort Receive"sv, RINGBUFFER_SIZE).release_value_but_fixme_should_propagate_errors();
+    m_transmit_buffer = Memory::RingBuffer::try_create("VirtIO::ConsolePort Transmit"sv, RINGBUFFER_SIZE).release_value_but_fixme_should_propagate_errors();
     m_receive_queue = m_port == 0 ? 0 : m_port * 2 + 2;
     m_transmit_queue = m_port == 0 ? 1 : m_port * 2 + 3;
 }
diff --git a/Kernel/Memory/RingBuffer.cpp b/Kernel/Memory/RingBuffer.cpp
index 388e4ae1fe..ca0f38602e 100644
--- a/Kernel/Memory/RingBuffer.cpp
+++ b/Kernel/Memory/RingBuffer.cpp
@@ -10,8 +10,15 @@
 
 namespace Kernel::Memory {
 
-RingBuffer::RingBuffer(StringView region_name, size_t capacity)
-    : m_region(MM.allocate_contiguous_kernel_region(page_round_up(capacity).release_value_but_fixme_should_propagate_errors(), region_name, Region::Access::Read | Region::Access::Write).release_value())
+ErrorOr<NonnullOwnPtr<RingBuffer>> RingBuffer::try_create(StringView region_name, size_t capacity)
+{
+    auto region_size = TRY(page_round_up(capacity));
+    auto region = TRY(MM.allocate_contiguous_kernel_region(region_size, region_name, Region::Access::Read | Region::Access::Write));
+    return adopt_nonnull_own_or_enomem(new (nothrow) RingBuffer(move(region), capacity));
+}
+
+RingBuffer::RingBuffer(NonnullOwnPtr<Memory::Region> region, size_t capacity)
+    : m_region(move(region))
     , m_capacity_in_bytes(capacity)
 {
 }
diff --git a/Kernel/Memory/RingBuffer.h b/Kernel/Memory/RingBuffer.h
index 8151fa2490..0e36428e58 100644
--- a/Kernel/Memory/RingBuffer.h
+++ b/Kernel/Memory/RingBuffer.h
@@ -13,7 +13,7 @@ namespace Kernel::Memory {
 
 class RingBuffer {
 public:
-    RingBuffer(StringView region_name, size_t capacity);
+    static ErrorOr<NonnullOwnPtr<RingBuffer>> try_create(StringView region_name, size_t capacity);
 
     bool has_space() const { return m_num_used_bytes < m_capacity_in_bytes; }
     bool copy_data_in(const UserOrKernelBuffer& buffer, size_t offset, size_t length, PhysicalAddress& start_of_copied_data, size_t& bytes_copied);
@@ -29,7 +29,9 @@ public:
     size_t bytes_till_end() const { return (m_capacity_in_bytes - ((m_start_of_used + m_num_used_bytes) % m_capacity_in_bytes)) % m_capacity_in_bytes; };
 
 private:
-    OwnPtr<Memory::Region> m_region;
+    RingBuffer(NonnullOwnPtr<Memory::Region> region, size_t capacity);
+
+    NonnullOwnPtr<Memory::Region> m_region;
     Spinlock m_lock;
     size_t m_start_of_used {};
     size_t m_num_used_bytes {};