Kernel: Exclude userspace heap memory from coredumps by default

When a process with a large heap crashes (e.g WebContent), it gets very
cumbersome to dump out a huge amount of memory.

In the vast majority of cases, we're only interested in generating a
nice backtrace from the coredump, so let's have the kernel skip over
userspace heap regions when dumping memory for now.

This is not ideal, and almost a little bit ugly, but it does make
investigating 500 MiB WebContent crashes significantly easier for now.

Kernel/Coredump.cpp

@@ -21,8 +21,15 @@
 #include <LibC/elf.h>
 #include <LibELF/Core.h>
 
+#define INCLUDE_USERSPACE_HEAP_MEMORY_IN_COREDUMPS 0
+
 namespace Kernel {
 
+[[maybe_unused]] static bool looks_like_userspace_heap_region(Memory::Region const& region)
+{
+ return region.name().starts_with("LibJS:"sv) || region.name().starts_with("malloc:"sv);
+}
+
 KResultOr<NonnullOwnPtr<Coredump>> Coredump::try_create(NonnullRefPtr<Process> process, StringView output_path)
 {
  if (!process->is_dumpable()) {
@@ -37,8 +44,16 @@ KResultOr<NonnullOwnPtr<Coredump>> Coredump::try_create(NonnullRefPtr<Process> p
 Coredump::Coredump(NonnullRefPtr<Process> process, NonnullRefPtr<OpenFileDescription> description)
  : m_process(move(process))
  , m_description(move(description))
- , m_num_program_headers(m_process->address_space().region_count() + 1) // +1 for NOTE segment
 {
+ m_num_program_headers = 0;
+ for ([[maybe_unused]] auto& region : m_process->address_space().regions()) {
+#if !INCLUDE_USERSPACE_HEAP_MEMORY_IN_COREDUMPS
+ if (looks_like_userspace_heap_region(*region))
+ continue;
+#endif
+ ++m_num_program_headers;
+ }
+ ++m_num_program_headers; // +1 for NOTE segment
 }
 
 KResultOr<NonnullRefPtr<OpenFileDescription>> Coredump::try_create_target_file(Process const& process, StringView output_path)
@@ -107,6 +122,12 @@ KResult Coredump::write_program_headers(size_t notes_size)
 {
  size_t offset = sizeof(ElfW(Ehdr)) + m_num_program_headers * sizeof(ElfW(Phdr));
  for (auto& region : m_process->address_space().regions()) {
+
+#if !INCLUDE_USERSPACE_HEAP_MEMORY_IN_COREDUMPS
+ if (looks_like_userspace_heap_region(*region))
+ continue;
+#endif
+
  ElfW(Phdr) phdr {};
 
  phdr.p_type = PT_LOAD;
@@ -147,8 +168,12 @@ KResult Coredump::write_program_headers(size_t notes_size)
 KResult Coredump::write_regions()
 {
  for (auto& region : m_process->address_space().regions()) {
- if (region->is_kernel())
+ VERIFY(!region->is_kernel());
+
+#if !INCLUDE_USERSPACE_HEAP_MEMORY_IN_COREDUMPS
+ if (looks_like_userspace_heap_region(*region))
  continue;
+#endif
 
  region->set_readable(true);
  region->remap();
@@ -227,6 +252,12 @@ KResult Coredump::create_notes_regions_data(auto& builder) const
 {
  size_t region_index = 0;
  for (auto& region : m_process->address_space().regions()) {
+
+#if !INCLUDE_USERSPACE_HEAP_MEMORY_IN_COREDUMPS
+ if (looks_like_userspace_heap_region(*region))
+ continue;
+#endif
+
  ELF::Core::MemoryRegionInfo info {};
  info.header.type = ELF::Core::NotesEntryHeader::Type::MemoryRegionInfo;
 

Kernel/Coredump.h

@@ -37,7 +37,7 @@ class Coredump {
 
  NonnullRefPtr<Process> m_process;
  NonnullRefPtr<OpenFileDescription> m_description;
- const size_t m_num_program_headers;
+ size_t m_num_program_headers { 0 };
 };
 
 }