From d384c7815f92d9bd411033f0bc1d92250568b1c4 Mon Sep 17 00:00:00 2001
From: Andreas Kling <awesomekling@gmail.com>
Date: Mon, 15 Apr 2019 23:58:48 +0200
Subject: [PATCH] Kernel: Make it possible to have kmalloc() dump call stacks.

This can be enabled at any time using a sysctl:

    sysctl kmalloc_stacks=1

The stacks will go to the debugger output only.
---
 Kernel/FileSystem/ProcFS.cpp | 5 +++++
 Kernel/FileSystem/ProcFS.h   | 1 +
 Kernel/kmalloc.cpp           | 7 +++++++
 Kernel/kmalloc.h             | 1 +
 4 files changed, 14 insertions(+)

diff --git a/Kernel/FileSystem/ProcFS.cpp b/Kernel/FileSystem/ProcFS.cpp
index 1aaf655101..2cf3c5d5db 100644
--- a/Kernel/FileSystem/ProcFS.cpp
+++ b/Kernel/FileSystem/ProcFS.cpp
@@ -1166,6 +1166,11 @@ ProcFS::ProcFS()
     m_entries[FI_PID_exe] = { "exe", FI_PID_exe, procfs$pid_exe };
     m_entries[FI_PID_cwd] = { "cwd", FI_PID_cwd, procfs$pid_cwd };
     m_entries[FI_PID_fd] = { "fd", FI_PID_fd };
+
+    m_kmalloc_stack_helper.resource() = g_dump_kmalloc_stacks;
+    add_sys_bool("kmalloc_stacks", m_kmalloc_stack_helper, [this] {
+        g_dump_kmalloc_stacks = m_kmalloc_stack_helper.resource();
+    });
 }
 
 ProcFS::ProcFSDirectoryEntry* ProcFS::get_directory_entry(InodeIdentifier identifier) const
diff --git a/Kernel/FileSystem/ProcFS.h b/Kernel/FileSystem/ProcFS.h
index 849cff70a7..e86bf38e21 100644
--- a/Kernel/FileSystem/ProcFS.h
+++ b/Kernel/FileSystem/ProcFS.h
@@ -59,6 +59,7 @@ private:
     mutable Lock m_inodes_lock;
     mutable HashMap<unsigned, ProcFSInode*> m_inodes;
     RetainPtr<ProcFSInode> m_root_inode;
+    Lockable<bool> m_kmalloc_stack_helper;
 };
 
 struct ProcFSInodeCustomData {
diff --git a/Kernel/kmalloc.cpp b/Kernel/kmalloc.cpp
index 9c952bf5cc..e7356efdb4 100644
--- a/Kernel/kmalloc.cpp
+++ b/Kernel/kmalloc.cpp
@@ -9,6 +9,7 @@
 #include <Kernel/i386.h>
 #include <Kernel/Process.h>
 #include <Kernel/Scheduler.h>
+#include <Kernel/KSyms.h>
 #include <AK/Assertions.h>
 
 #define SANITIZE_KMALLOC
@@ -35,6 +36,7 @@ volatile size_t kmalloc_sum_eternal = 0;
 
 dword g_kmalloc_call_count;
 dword g_kfree_call_count;
+bool g_dump_kmalloc_stacks;
 
 static byte* s_next_eternal_ptr;
 static byte* s_end_of_eternal_range;
@@ -95,6 +97,11 @@ void* kmalloc_impl(size_t size)
     InterruptDisabler disabler;
     ++g_kmalloc_call_count;
 
+    if (g_dump_kmalloc_stacks && ksyms_ready) {
+        dbgprintf("kmalloc(%u)\n", size);
+        dump_backtrace(true);
+    }
+
     // We need space for the allocation_t structure at the head of the block.
     size_t real_size = size + sizeof(allocation_t);
 
diff --git a/Kernel/kmalloc.h b/Kernel/kmalloc.h
index 001d22da5a..d490e28ce4 100644
--- a/Kernel/kmalloc.h
+++ b/Kernel/kmalloc.h
@@ -20,6 +20,7 @@ extern volatile size_t kmalloc_sum_eternal;
 extern volatile size_t kmalloc_sum_page_aligned;
 extern dword g_kmalloc_call_count;
 extern dword g_kfree_call_count;
+extern bool g_dump_kmalloc_stacks;
 
 inline void* operator new(size_t, void* p) { return p; }
 inline void* operator new[](size_t, void* p) { return p; }