From 5d9ef5f83a79f56ddd6230c7e9428525bab0d82c Mon Sep 17 00:00:00 2001
From: Thomas Munro <thomas.munro@gmail.com>
Date: Tue, 27 Aug 2024 08:58:48 +1200
Subject: [PATCH v7] Monkey-patch LLVM code to fix ARM relocation bug.

Supply a new memory manager for RuntimeDyld that avoids overflowing the
jump distance in linked code on large memory machines.  This is the same
Apache v2-licensed code that is normally used inside the LLVM library,
except this copy has been patched by Michael Smith in his proposed fix
https://www.github.com/llvm/llvm-project/pull/71968.

We hereby slurp it into our own source tree, after moving into a new
namespace llvm::backport and making some minor adjustments so that it
can be compiled with older LLVM versions as far back as 12.  It's harder
to make it work on even older LLVM versions, but it doesn't seem likely
that people are really using them so that is not investigated for now.
(We were probably remiss in not disclaiming support for ancient LLVM
releases sooner; starting from PostgreSQL 16 we've been more agressive
about trimming version support to match the trailing end of common
software distributions).

The problem could also have been addressed by switching to JITLink, and
that is the LLVM project's recommended solution as RuntimeDyld is about
to be deprecated.  We'll have to do that soon enough anyway, and then
when the LLVM version support window advances far enough in a few years
we'll be able to delete this code.  Unfortunately that wouldn't work
today for some relevant releases of LLVM where JITLink is missing or
incomplete.

Several other projects have already taken the approach of back-porting
this fix into their fork of LLVM, which is a vote of confidence despite
the lack of commit into LLVM as of today.  We don't have our own copy of
LLVM so we can't do exactly what they've done.  We just pick up the
whole patched class and inject an instance of it into the regular LLVM
code.

The changes that we've had to make to our copy can be seen by diffing
our SectionMemoryManager.{h,cpp} files against the ones in the tree of
the pull request.

The LLVM project hasn't chosen to commit the fix yet, and even it it
did, it wouldn't be back-ported into the releases of LLVM that most of
our users care about, so there is not much point in waiting any longer
for that.  If they make further changes and commit it to LLVM 19 or 20,
we'll still need this for older versions, but we may want to
resynchronize our copy.

This should fix the spate of crash reports we've been receiving lately
from users on large memory ARM systems.

Back-patch to all supported releases.

Co-authored-by: Thomas Munro <thomas.munro@gmail.com>
Co-authored-by: Anthonin Bonnefoy <anthonin.bonnefoy@datadoghq.com>
Reported-by: Anthonin Bonnefoy <anthonin.bonnefoy@datadoghq.com>
Discussion: https://postgr.es/m/CAO6_Xqr63qj%3DSx7HY6ZiiQ6R_JbX%2B-p6sTPwDYwTWZjUmjsYBg%40mail.gmail.com
---
 src/backend/jit/llvm/Makefile                 |   3 +-
 src/backend/jit/llvm/SectionMemoryManager.cpp | 394 ++++++++++++++++++
 src/backend/jit/llvm/llvmjit.c                |   7 +
 src/backend/jit/llvm/llvmjit_wrap.cpp         |  20 +
 src/backend/jit/llvm/meson.build              |   1 +
 src/include/jit/SectionMemoryManager.h        | 227 ++++++++++
 src/include/jit/llvmjit.h                     |   8 +
 src/include/jit/llvmjit_backport.h            |  20 +
 src/tools/pginclude/headerscheck              |   3 +
 9 files changed, 682 insertions(+), 1 deletion(-)
 create mode 100644 src/backend/jit/llvm/SectionMemoryManager.cpp
 create mode 100644 src/include/jit/SectionMemoryManager.h
 create mode 100644 src/include/jit/llvmjit_backport.h

diff --git a/src/backend/jit/llvm/Makefile b/src/backend/jit/llvm/Makefile
index bfe5c207a2b..e8c12060b93 100644
--- a/src/backend/jit/llvm/Makefile
+++ b/src/backend/jit/llvm/Makefile
@@ -47,7 +47,8 @@ OBJS += \
 	llvmjit.o \
 	llvmjit_error.o \
 	llvmjit_inline.o \
-	llvmjit_wrap.o
+	llvmjit_wrap.o \
+	SectionMemoryManager.o
 
 # Code generation
 OBJS += \
diff --git a/src/backend/jit/llvm/SectionMemoryManager.cpp b/src/backend/jit/llvm/SectionMemoryManager.cpp
new file mode 100644
index 00000000000..f88ca3412e2
--- /dev/null
+++ b/src/backend/jit/llvm/SectionMemoryManager.cpp
@@ -0,0 +1,394 @@
+/*
+ * This file taken from https://github.com/llvm/llvm-project/pull/71968, with
+ * the name changed to llvm::backport::SectionMemoryManager, so we can support
+ * the ARM memory model on broken LLVM versions.
+ */
+
+//===- SectionMemoryManager.cpp - Memory manager for MCJIT/RtDyld *- C++ -*-==//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the section-based memory manager used by the MCJIT
+// execution engine and RuntimeDyld
+//
+//===----------------------------------------------------------------------===//
+
+#include "jit/llvmjit_backport.h"
+
+#ifdef USE_LLVM_BACKPORT_SECTION_MEMORY_MANAGER
+
+#include "jit/SectionMemoryManager.h"
+#include "llvm/Support/MathExtras.h"
+#include "llvm/Support/Process.h"
+
+namespace llvm {
+namespace backport {
+
+bool SectionMemoryManager::hasSpace(const MemoryGroup &MemGroup,
+                                    uintptr_t Size) const {
+  for (const FreeMemBlock &FreeMB : MemGroup.FreeMem) {
+    if (FreeMB.Free.allocatedSize() >= Size)
+      return true;
+  }
+  return false;
+}
+
+#if LLVM_VERSION_MAJOR < 16
+void SectionMemoryManager::reserveAllocationSpace(uintptr_t CodeSize,
+												  uint32_t CodeAlign_i,
+												  uintptr_t RODataSize,
+												  uint32_t RODataAlign_i,
+												  uintptr_t RWDataSize,
+												  uint32_t RWDataAlign_i) {
+	Align CodeAlign(CodeAlign_i);
+	Align RODataAlign(RODataAlign_i);
+	Align RWDataAlign(RWDataAlign_i);
+#else
+void SectionMemoryManager::reserveAllocationSpace(
+    uintptr_t CodeSize, Align CodeAlign, uintptr_t RODataSize,
+    Align RODataAlign, uintptr_t RWDataSize, Align RWDataAlign) {
+#endif
+  if (CodeSize == 0 && RODataSize == 0 && RWDataSize == 0)
+    return;
+
+  static const size_t PageSize = sys::Process::getPageSizeEstimate();
+
+  // Code alignment needs to be at least the stub alignment - however, we
+  // don't have an easy way to get that here so as a workaround, we assume
+  // it's 8, which is the largest value I observed across all platforms.
+  constexpr uint64_t StubAlign = 8;
+  CodeAlign = Align(std::max(CodeAlign.value(), StubAlign));
+  RODataAlign = Align(std::max(RODataAlign.value(), StubAlign));
+  RWDataAlign = Align(std::max(RWDataAlign.value(), StubAlign));
+
+  // Get space required for each section. Use the same calculation as
+  // allocateSection because we need to be able to satisfy it.
+  uint64_t RequiredCodeSize = alignTo(CodeSize, CodeAlign) + CodeAlign.value();
+  uint64_t RequiredRODataSize =
+      alignTo(RODataSize, RODataAlign) + RODataAlign.value();
+  uint64_t RequiredRWDataSize =
+      alignTo(RWDataSize, RWDataAlign) + RWDataAlign.value();
+
+  if (hasSpace(CodeMem, RequiredCodeSize) &&
+      hasSpace(RODataMem, RequiredRODataSize) &&
+      hasSpace(RWDataMem, RequiredRWDataSize)) {
+    // Sufficient space in contiguous block already available.
+    return;
+  }
+
+  // MemoryManager does not have functions for releasing memory after it's
+  // allocated. Normally it tries to use any excess blocks that were allocated
+  // due to page alignment, but if we have insufficient free memory for the
+  // request this can lead to allocating disparate memory that can violate the
+  // ARM ABI. Clear free memory so only the new allocations are used, but do
+  // not release allocated memory as it may still be in-use.
+  CodeMem.FreeMem.clear();
+  RODataMem.FreeMem.clear();
+  RWDataMem.FreeMem.clear();
+
+  // Round up to the nearest page size. Blocks must be page-aligned.
+  RequiredCodeSize = alignTo(RequiredCodeSize, PageSize);
+  RequiredRODataSize = alignTo(RequiredRODataSize, PageSize);
+  RequiredRWDataSize = alignTo(RequiredRWDataSize, PageSize);
+  uint64_t RequiredSize =
+      RequiredCodeSize + RequiredRODataSize + RequiredRWDataSize;
+
+  std::error_code ec;
+  sys::MemoryBlock MB = MMapper->allocateMappedMemory(
+      AllocationPurpose::RWData, RequiredSize, nullptr,
+      sys::Memory::MF_READ | sys::Memory::MF_WRITE, ec);
+  if (ec) {
+    return;
+  }
+  // CodeMem will arbitrarily own this MemoryBlock to handle cleanup.
+  CodeMem.AllocatedMem.push_back(MB);
+  uintptr_t Addr = (uintptr_t)MB.base();
+  FreeMemBlock FreeMB;
+  FreeMB.PendingPrefixIndex = (unsigned)-1;
+
+  if (CodeSize > 0) {
+    assert(isAddrAligned(CodeAlign, (void *)Addr));
+    FreeMB.Free = sys::MemoryBlock((void *)Addr, RequiredCodeSize);
+    CodeMem.FreeMem.push_back(FreeMB);
+    Addr += RequiredCodeSize;
+  }
+
+  if (RODataSize > 0) {
+    assert(isAddrAligned(RODataAlign, (void *)Addr));
+    FreeMB.Free = sys::MemoryBlock((void *)Addr, RequiredRODataSize);
+    RODataMem.FreeMem.push_back(FreeMB);
+    Addr += RequiredRODataSize;
+  }
+
+  if (RWDataSize > 0) {
+    assert(isAddrAligned(RWDataAlign, (void *)Addr));
+    FreeMB.Free = sys::MemoryBlock((void *)Addr, RequiredRWDataSize);
+    RWDataMem.FreeMem.push_back(FreeMB);
+  }
+}
+
+uint8_t *SectionMemoryManager::allocateDataSection(uintptr_t Size,
+                                                   unsigned Alignment,
+                                                   unsigned SectionID,
+                                                   StringRef SectionName,
+                                                   bool IsReadOnly) {
+  if (IsReadOnly)
+    return allocateSection(SectionMemoryManager::AllocationPurpose::ROData,
+                           Size, Alignment);
+  return allocateSection(SectionMemoryManager::AllocationPurpose::RWData, Size,
+                         Alignment);
+}
+
+uint8_t *SectionMemoryManager::allocateCodeSection(uintptr_t Size,
+                                                   unsigned Alignment,
+                                                   unsigned SectionID,
+                                                   StringRef SectionName) {
+  return allocateSection(SectionMemoryManager::AllocationPurpose::Code, Size,
+                         Alignment);
+}
+
+uint8_t *SectionMemoryManager::allocateSection(
+    SectionMemoryManager::AllocationPurpose Purpose, uintptr_t Size,
+    unsigned Alignment) {
+  if (!Alignment)
+    Alignment = 16;
+
+  assert(!(Alignment & (Alignment - 1)) && "Alignment must be a power of two.");
+
+  uintptr_t RequiredSize = Alignment * ((Size + Alignment - 1) / Alignment + 1);
+  uintptr_t Addr = 0;
+
+  MemoryGroup &MemGroup = [&]() -> MemoryGroup & {
+    switch (Purpose) {
+    case AllocationPurpose::Code:
+      return CodeMem;
+    case AllocationPurpose::ROData:
+      return RODataMem;
+    case AllocationPurpose::RWData:
+      return RWDataMem;
+    }
+    llvm_unreachable("Unknown SectionMemoryManager::AllocationPurpose");
+  }();
+
+  // Look in the list of free memory regions and use a block there if one
+  // is available.
+  for (FreeMemBlock &FreeMB : MemGroup.FreeMem) {
+    if (FreeMB.Free.allocatedSize() >= RequiredSize) {
+      Addr = (uintptr_t)FreeMB.Free.base();
+      uintptr_t EndOfBlock = Addr + FreeMB.Free.allocatedSize();
+      // Align the address.
+      Addr = (Addr + Alignment - 1) & ~(uintptr_t)(Alignment - 1);
+
+      if (FreeMB.PendingPrefixIndex == (unsigned)-1) {
+        // The part of the block we're giving out to the user is now pending
+        MemGroup.PendingMem.push_back(sys::MemoryBlock((void *)Addr, Size));
+
+        // Remember this pending block, such that future allocations can just
+        // modify it rather than creating a new one
+        FreeMB.PendingPrefixIndex = MemGroup.PendingMem.size() - 1;
+      } else {
+        sys::MemoryBlock &PendingMB =
+            MemGroup.PendingMem[FreeMB.PendingPrefixIndex];
+        PendingMB = sys::MemoryBlock(PendingMB.base(),
+                                     Addr + Size - (uintptr_t)PendingMB.base());
+      }
+
+      // Remember how much free space is now left in this block
+      FreeMB.Free =
+          sys::MemoryBlock((void *)(Addr + Size), EndOfBlock - Addr - Size);
+      return (uint8_t *)Addr;
+    }
+  }
+
+  // No pre-allocated free block was large enough. Allocate a new memory region.
+  // Note that all sections get allocated as read-write.  The permissions will
+  // be updated later based on memory group.
+  //
+  // FIXME: It would be useful to define a default allocation size (or add
+  // it as a constructor parameter) to minimize the number of allocations.
+  //
+  // FIXME: Initialize the Near member for each memory group to avoid
+  // interleaving.
+  std::error_code ec;
+  sys::MemoryBlock MB = MMapper->allocateMappedMemory(
+      Purpose, RequiredSize, &MemGroup.Near,
+      sys::Memory::MF_READ | sys::Memory::MF_WRITE, ec);
+  if (ec) {
+    // FIXME: Add error propagation to the interface.
+    return nullptr;
+  }
+
+  // Save this address as the basis for our next request
+  MemGroup.Near = MB;
+
+  // Copy the address to all the other groups, if they have not
+  // been initialized.
+  if (CodeMem.Near.base() == nullptr)
+    CodeMem.Near = MB;
+  if (RODataMem.Near.base() == nullptr)
+    RODataMem.Near = MB;
+  if (RWDataMem.Near.base() == nullptr)
+    RWDataMem.Near = MB;
+
+  // Remember that we allocated this memory
+  MemGroup.AllocatedMem.push_back(MB);
+  Addr = (uintptr_t)MB.base();
+  uintptr_t EndOfBlock = Addr + MB.allocatedSize();
+
+  // Align the address.
+  Addr = (Addr + Alignment - 1) & ~(uintptr_t)(Alignment - 1);
+
+  // The part of the block we're giving out to the user is now pending
+  MemGroup.PendingMem.push_back(sys::MemoryBlock((void *)Addr, Size));
+
+  // The allocateMappedMemory may allocate much more memory than we need. In
+  // this case, we store the unused memory as a free memory block.
+  unsigned FreeSize = EndOfBlock - Addr - Size;
+  if (FreeSize > 16) {
+    FreeMemBlock FreeMB;
+    FreeMB.Free = sys::MemoryBlock((void *)(Addr + Size), FreeSize);
+    FreeMB.PendingPrefixIndex = (unsigned)-1;
+    MemGroup.FreeMem.push_back(FreeMB);
+  }
+
+  // Return aligned address
+  return (uint8_t *)Addr;
+}
+
+bool SectionMemoryManager::finalizeMemory(std::string *ErrMsg) {
+  // FIXME: Should in-progress permissions be reverted if an error occurs?
+  std::error_code ec;
+
+  // Make code memory executable.
+  ec = applyMemoryGroupPermissions(CodeMem,
+                                   sys::Memory::MF_READ | sys::Memory::MF_EXEC);
+  if (ec) {
+    if (ErrMsg) {
+      *ErrMsg = ec.message();
+    }
+    return true;
+  }
+
+  // Make read-only data memory read-only.
+  ec = applyMemoryGroupPermissions(RODataMem, sys::Memory::MF_READ);
+  if (ec) {
+    if (ErrMsg) {
+      *ErrMsg = ec.message();
+    }
+    return true;
+  }
+
+  // Read-write data memory already has the correct permissions
+
+  // Some platforms with separate data cache and instruction cache require
+  // explicit cache flush, otherwise JIT code manipulations (like resolved
+  // relocations) will get to the data cache but not to the instruction cache.
+  invalidateInstructionCache();
+
+  return false;
+}
+
+static sys::MemoryBlock trimBlockToPageSize(sys::MemoryBlock M) {
+  static const size_t PageSize = sys::Process::getPageSizeEstimate();
+
+  size_t StartOverlap =
+      (PageSize - ((uintptr_t)M.base() % PageSize)) % PageSize;
+
+  size_t TrimmedSize = M.allocatedSize();
+  TrimmedSize -= StartOverlap;
+  TrimmedSize -= TrimmedSize % PageSize;
+
+  sys::MemoryBlock Trimmed((void *)((uintptr_t)M.base() + StartOverlap),
+                           TrimmedSize);
+
+  assert(((uintptr_t)Trimmed.base() % PageSize) == 0);
+  assert((Trimmed.allocatedSize() % PageSize) == 0);
+  assert(M.base() <= Trimmed.base() &&
+         Trimmed.allocatedSize() <= M.allocatedSize());
+
+  return Trimmed;
+}
+
+std::error_code
+SectionMemoryManager::applyMemoryGroupPermissions(MemoryGroup &MemGroup,
+                                                  unsigned Permissions) {
+  for (sys::MemoryBlock &MB : MemGroup.PendingMem)
+    if (std::error_code EC = MMapper->protectMappedMemory(MB, Permissions))
+      return EC;
+
+  MemGroup.PendingMem.clear();
+
+  // Now go through free blocks and trim any of them that don't span the entire
+  // page because one of the pending blocks may have overlapped it.
+  for (FreeMemBlock &FreeMB : MemGroup.FreeMem) {
+    FreeMB.Free = trimBlockToPageSize(FreeMB.Free);
+    // We cleared the PendingMem list, so all these pointers are now invalid
+    FreeMB.PendingPrefixIndex = (unsigned)-1;
+  }
+
+  // Remove all blocks which are now empty
+  erase_if(MemGroup.FreeMem, [](FreeMemBlock &FreeMB) {
+    return FreeMB.Free.allocatedSize() == 0;
+  });
+
+  return std::error_code();
+}
+
+void SectionMemoryManager::invalidateInstructionCache() {
+  for (sys::MemoryBlock &Block : CodeMem.PendingMem)
+    sys::Memory::InvalidateInstructionCache(Block.base(),
+                                            Block.allocatedSize());
+}
+
+SectionMemoryManager::~SectionMemoryManager() {
+  for (MemoryGroup *Group : {&CodeMem, &RWDataMem, &RODataMem}) {
+    for (sys::MemoryBlock &Block : Group->AllocatedMem)
+      MMapper->releaseMappedMemory(Block);
+  }
+}
+
+SectionMemoryManager::MemoryMapper::~MemoryMapper() = default;
+
+void SectionMemoryManager::anchor() {}
+
+namespace {
+// Trivial implementation of SectionMemoryManager::MemoryMapper that just calls
+// into sys::Memory.
+class DefaultMMapper final : public SectionMemoryManager::MemoryMapper {
+public:
+  sys::MemoryBlock
+  allocateMappedMemory(SectionMemoryManager::AllocationPurpose Purpose,
+                       size_t NumBytes, const sys::MemoryBlock *const NearBlock,
+                       unsigned Flags, std::error_code &EC) override {
+    return sys::Memory::allocateMappedMemory(NumBytes, NearBlock, Flags, EC);
+  }
+
+  std::error_code protectMappedMemory(const sys::MemoryBlock &Block,
+                                      unsigned Flags) override {
+    return sys::Memory::protectMappedMemory(Block, Flags);
+  }
+
+  std::error_code releaseMappedMemory(sys::MemoryBlock &M) override {
+    return sys::Memory::releaseMappedMemory(M);
+  }
+};
+} // namespace
+
+SectionMemoryManager::SectionMemoryManager(MemoryMapper *UnownedMM,
+                                           bool ReserveAlloc)
+    : MMapper(UnownedMM), OwnedMMapper(nullptr),
+      ReserveAllocation(ReserveAlloc) {
+  if (!MMapper) {
+    OwnedMMapper = std::make_unique<DefaultMMapper>();
+    MMapper = OwnedMMapper.get();
+  }
+}
+
+} // namespace backport
+} // namespace llvm
+
+#endif
diff --git a/src/backend/jit/llvm/llvmjit.c b/src/backend/jit/llvm/llvmjit.c
index f346af9c755..72411d0f805 100644
--- a/src/backend/jit/llvm/llvmjit.c
+++ b/src/backend/jit/llvm/llvmjit.c
@@ -34,6 +34,7 @@
 #endif
 
 #include "jit/llvmjit.h"
+#include "jit/llvmjit_backport.h"
 #include "jit/llvmjit_emit.h"
 #include "miscadmin.h"
 #include "portability/instr_time.h"
@@ -1166,8 +1167,14 @@ llvm_log_jit_error(void *ctx, LLVMErrorRef error)
 static LLVMOrcObjectLayerRef
 llvm_create_object_layer(void *Ctx, LLVMOrcExecutionSessionRef ES, const char *Triple)
 {
+#ifdef USE_LLVM_BACKPORT_SECTION_MEMORY_MANAGER
+	LLVMOrcObjectLayerRef objlayer =
+		LLVMOrcCreateRTDyldObjectLinkingLayerWithSafeSectionMemoryManager(ES);
+#else
 	LLVMOrcObjectLayerRef objlayer =
 		LLVMOrcCreateRTDyldObjectLinkingLayerWithSectionMemoryManager(ES);
+#endif
+
 
 #if defined(HAVE_DECL_LLVMCREATEGDBREGISTRATIONLISTENER) && HAVE_DECL_LLVMCREATEGDBREGISTRATIONLISTENER
 	if (jit_debugging_support)
diff --git a/src/backend/jit/llvm/llvmjit_wrap.cpp b/src/backend/jit/llvm/llvmjit_wrap.cpp
index 7f7623dac64..9e8d63f0122 100644
--- a/src/backend/jit/llvm/llvmjit_wrap.cpp
+++ b/src/backend/jit/llvm/llvmjit_wrap.cpp
@@ -20,6 +20,14 @@ extern "C"
 #include <llvm/IR/Function.h>
 
 #include "jit/llvmjit.h"
+#include "jit/llvmjit_backport.h"
+
+#ifdef USE_LLVM_BACKPORT_SECTION_MEMORY_MANAGER
+#include <llvm/ExecutionEngine/Orc/RTDyldObjectLinkingLayer.h>
+#include <llvm/ExecutionEngine/SectionMemoryManager.h>
+#include "jit/SectionMemoryManager.h"
+#include <llvm/Support/CBindingWrapping.h>
+#endif
 
 
 /*
@@ -37,3 +45,15 @@ LLVMGetFunctionType(LLVMValueRef r)
 {
 	return llvm::wrap(llvm::unwrap<llvm::Function>(r)->getFunctionType());
 }
+
+#ifdef USE_LLVM_BACKPORT_SECTION_MEMORY_MANAGER
+DEFINE_SIMPLE_CONVERSION_FUNCTIONS(llvm::orc::ExecutionSession, LLVMOrcExecutionSessionRef)
+DEFINE_SIMPLE_CONVERSION_FUNCTIONS(llvm::orc::ObjectLayer, LLVMOrcObjectLayerRef);
+
+LLVMOrcObjectLayerRef
+LLVMOrcCreateRTDyldObjectLinkingLayerWithSafeSectionMemoryManager(LLVMOrcExecutionSessionRef ES)
+{
+	return wrap(new llvm::orc::RTDyldObjectLinkingLayer(
+		*unwrap(ES), [] { return std::make_unique<llvm::backport::SectionMemoryManager>(nullptr, true); }));
+}
+#endif
diff --git a/src/backend/jit/llvm/meson.build b/src/backend/jit/llvm/meson.build
index c1b6a9363eb..ce49043f1d0 100644
--- a/src/backend/jit/llvm/meson.build
+++ b/src/backend/jit/llvm/meson.build
@@ -14,6 +14,7 @@ llvmjit_sources += files(
   'llvmjit_error.cpp',
   'llvmjit_inline.cpp',
   'llvmjit_wrap.cpp',
+  'SectionMemoryManager.cpp',
 )
 
 # Code generation
diff --git a/src/include/jit/SectionMemoryManager.h b/src/include/jit/SectionMemoryManager.h
new file mode 100644
index 00000000000..d644ff921dc
--- /dev/null
+++ b/src/include/jit/SectionMemoryManager.h
@@ -0,0 +1,227 @@
+/*
+ * This file taken from https://github.com/llvm/llvm-project/pull/71968, with
+ * the name changed to llvm::backport::SectionMemoryManager, so we can support
+ * the ARM memory model on broken LLVM versions.
+ */
+
+//===- SectionMemoryManager.h - Memory manager for MCJIT/RtDyld -*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains the declaration of a section-based memory manager used by
+// the MCJIT execution engine and RuntimeDyld.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_EXECUTIONENGINE_BACKPORT_SECTIONMEMORYMANAGER_H
+#define LLVM_EXECUTIONENGINE_BACKPORT_SECTIONMEMORYMANAGER_H
+
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ExecutionEngine/RTDyldMemoryManager.h"
+#include "llvm/Support/Alignment.h"
+#include "llvm/Support/Memory.h"
+#include <cstdint>
+#include <string>
+#include <system_error>
+
+namespace llvm {
+namespace backport {
+
+/// This is a simple memory manager which implements the methods called by
+/// the RuntimeDyld class to allocate memory for section-based loading of
+/// objects, usually those generated by the MCJIT execution engine.
+///
+/// This memory manager allocates all section memory as read-write.  The
+/// RuntimeDyld will copy JITed section memory into these allocated blocks
+/// and perform any necessary linking and relocations.
+///
+/// Any client using this memory manager MUST ensure that section-specific
+/// page permissions have been applied before attempting to execute functions
+/// in the JITed object.  Permissions can be applied either by calling
+/// MCJIT::finalizeObject or by calling SectionMemoryManager::finalizeMemory
+/// directly.  Clients of MCJIT should call MCJIT::finalizeObject.
+class SectionMemoryManager : public RTDyldMemoryManager {
+public:
+  /// This enum describes the various reasons to allocate pages from
+  /// allocateMappedMemory.
+  enum class AllocationPurpose {
+    Code,
+    ROData,
+    RWData,
+  };
+
+  /// Implementations of this interface are used by SectionMemoryManager to
+  /// request pages from the operating system.
+  class MemoryMapper {
+  public:
+    /// This method attempts to allocate \p NumBytes bytes of virtual memory for
+    /// \p Purpose.  \p NearBlock may point to an existing allocation, in which
+    /// case an attempt is made to allocate more memory near the existing block.
+    /// The actual allocated address is not guaranteed to be near the requested
+    /// address.  \p Flags is used to set the initial protection flags for the
+    /// block of the memory.  \p EC [out] returns an object describing any error
+    /// that occurs.
+    ///
+    /// This method may allocate more than the number of bytes requested.  The
+    /// actual number of bytes allocated is indicated in the returned
+    /// MemoryBlock.
+    ///
+    /// The start of the allocated block must be aligned with the system
+    /// allocation granularity (64K on Windows, page size on Linux).  If the
+    /// address following \p NearBlock is not so aligned, it will be rounded up
+    /// to the next allocation granularity boundary.
+    ///
+    /// \r a non-null MemoryBlock if the function was successful, otherwise a
+    /// null MemoryBlock with \p EC describing the error.
+    virtual sys::MemoryBlock
+    allocateMappedMemory(AllocationPurpose Purpose, size_t NumBytes,
+                         const sys::MemoryBlock *const NearBlock,
+                         unsigned Flags, std::error_code &EC) = 0;
+
+    /// This method sets the protection flags for a block of memory to the state
+    /// specified by \p Flags.  The behavior is not specified if the memory was
+    /// not allocated using the allocateMappedMemory method.
+    /// \p Block describes the memory block to be protected.
+    /// \p Flags specifies the new protection state to be assigned to the block.
+    ///
+    /// If \p Flags is MF_WRITE, the actual behavior varies with the operating
+    /// system (i.e. MF_READ | MF_WRITE on Windows) and the target architecture
+    /// (i.e. MF_WRITE -> MF_READ | MF_WRITE on i386).
+    ///
+    /// \r error_success if the function was successful, or an error_code
+    /// describing the failure if an error occurred.
+    virtual std::error_code protectMappedMemory(const sys::MemoryBlock &Block,
+                                                unsigned Flags) = 0;
+
+    /// This method releases a block of memory that was allocated with the
+    /// allocateMappedMemory method. It should not be used to release any memory
+    /// block allocated any other way.
+    /// \p Block describes the memory to be released.
+    ///
+    /// \r error_success if the function was successful, or an error_code
+    /// describing the failure if an error occurred.
+    virtual std::error_code releaseMappedMemory(sys::MemoryBlock &M) = 0;
+
+    virtual ~MemoryMapper();
+  };
+
+  /// Creates a SectionMemoryManager instance with \p MM as the associated
+  /// memory mapper.  If \p MM is nullptr then a default memory mapper is used
+  /// that directly calls into the operating system.
+  ///
+  /// If \p ReserveAlloc is true all memory will be pre-allocated, and any
+  /// attempts to allocate beyond pre-allocated memory will fail.
+  SectionMemoryManager(MemoryMapper *MM = nullptr, bool ReserveAlloc = false);
+  SectionMemoryManager(const SectionMemoryManager &) = delete;
+  void operator=(const SectionMemoryManager &) = delete;
+  ~SectionMemoryManager() override;
+
+  /// Enable reserveAllocationSpace when requested.
+  bool needsToReserveAllocationSpace() override { return ReserveAllocation; }
+
+  /// Implements allocating all memory in a single block. This is required to
+  /// limit memory offsets to fit the ARM ABI; large memory systems may
+  /// otherwise allocate separate sections too far apart.
+#if LLVM_VERSION_MAJOR < 16
+  virtual void reserveAllocationSpace(uintptr_t CodeSize, uint32_t CodeAlign,
+                                      uintptr_t RODataSize,
+                                      uint32_t RODataAlign,
+                                      uintptr_t RWDataSize,
+                                      uint32_t RWDataAlign) override;
+#else
+  void reserveAllocationSpace(uintptr_t CodeSize, Align CodeAlign,
+                              uintptr_t RODataSize, Align RODataAlign,
+                              uintptr_t RWDataSize, Align RWDataAlign) override;
+#endif
+
+  /// Allocates a memory block of (at least) the given size suitable for
+  /// executable code.
+  ///
+  /// The value of \p Alignment must be a power of two.  If \p Alignment is zero
+  /// a default alignment of 16 will be used.
+  uint8_t *allocateCodeSection(uintptr_t Size, unsigned Alignment,
+                               unsigned SectionID,
+                               StringRef SectionName) override;
+
+  /// Allocates a memory block of (at least) the given size suitable for
+  /// executable code.
+  ///
+  /// The value of \p Alignment must be a power of two.  If \p Alignment is zero
+  /// a default alignment of 16 will be used.
+  uint8_t *allocateDataSection(uintptr_t Size, unsigned Alignment,
+                               unsigned SectionID, StringRef SectionName,
+                               bool isReadOnly) override;
+
+  /// Update section-specific memory permissions and other attributes.
+  ///
+  /// This method is called when object loading is complete and section page
+  /// permissions can be applied.  It is up to the memory manager implementation
+  /// to decide whether or not to act on this method.  The memory manager will
+  /// typically allocate all sections as read-write and then apply specific
+  /// permissions when this method is called.  Code sections cannot be executed
+  /// until this function has been called.  In addition, any cache coherency
+  /// operations needed to reliably use the memory are also performed.
+  ///
+  /// \returns true if an error occurred, false otherwise.
+  bool finalizeMemory(std::string *ErrMsg = nullptr) override;
+
+  /// Invalidate instruction cache for code sections.
+  ///
+  /// Some platforms with separate data cache and instruction cache require
+  /// explicit cache flush, otherwise JIT code manipulations (like resolved
+  /// relocations) will get to the data cache but not to the instruction cache.
+  ///
+  /// This method is called from finalizeMemory.
+  virtual void invalidateInstructionCache();
+
+private:
+  struct FreeMemBlock {
+    // The actual block of free memory
+    sys::MemoryBlock Free;
+    // If there is a pending allocation from the same reservation right before
+    // this block, store it's index in PendingMem, to be able to update the
+    // pending region if part of this block is allocated, rather than having to
+    // create a new one
+    unsigned PendingPrefixIndex;
+  };
+
+  struct MemoryGroup {
+    // PendingMem contains all blocks of memory (subblocks of AllocatedMem)
+    // which have not yet had their permissions applied, but have been given
+    // out to the user. FreeMem contains all block of memory, which have
+    // neither had their permissions applied, nor been given out to the user.
+    SmallVector<sys::MemoryBlock, 16> PendingMem;
+    SmallVector<FreeMemBlock, 16> FreeMem;
+
+    // All memory blocks that have been requested from the system
+    SmallVector<sys::MemoryBlock, 16> AllocatedMem;
+
+    sys::MemoryBlock Near;
+  };
+
+  uint8_t *allocateSection(AllocationPurpose Purpose, uintptr_t Size,
+                           unsigned Alignment);
+
+  std::error_code applyMemoryGroupPermissions(MemoryGroup &MemGroup,
+                                              unsigned Permissions);
+
+  bool hasSpace(const MemoryGroup &MemGroup, uintptr_t Size) const;
+
+  void anchor() override;
+
+  MemoryGroup CodeMem;
+  MemoryGroup RWDataMem;
+  MemoryGroup RODataMem;
+  MemoryMapper *MMapper;
+  std::unique_ptr<MemoryMapper> OwnedMMapper;
+  bool ReserveAllocation;
+};
+
+} // end namespace backport
+} // end namespace llvm
+
+#endif // LLVM_EXECUTIONENGINE_BACKPORT_SECTIONMEMORYMANAGER_H
diff --git a/src/include/jit/llvmjit.h b/src/include/jit/llvmjit.h
index 420775b1899..dc0d86f4c1d 100644
--- a/src/include/jit/llvmjit.h
+++ b/src/include/jit/llvmjit.h
@@ -17,7 +17,12 @@
  */
 #ifdef USE_LLVM
 
+#include "jit/llvmjit_backport.h"
+
 #include <llvm-c/Types.h>
+#ifdef USE_LLVM_BACKPORT_SECTION_MEMORY_MANAGER
+#include <llvm-c/OrcEE.h>
+#endif
 
 
 /*
@@ -135,6 +140,9 @@ extern LLVMValueRef slot_compile_deform(struct LLVMJitContext *context, TupleDes
  */
 extern LLVMTypeRef LLVMGetFunctionReturnType(LLVMValueRef r);
 extern LLVMTypeRef LLVMGetFunctionType(LLVMValueRef r);
+#ifdef USE_LLVM_BACKPORT_SECTION_MEMORY_MANAGER
+extern LLVMOrcObjectLayerRef LLVMOrcCreateRTDyldObjectLinkingLayerWithSafeSectionMemoryManager(LLVMOrcExecutionSessionRef ES);
+#endif
 
 #ifdef __cplusplus
 } /* extern "C" */
diff --git a/src/include/jit/llvmjit_backport.h b/src/include/jit/llvmjit_backport.h
new file mode 100644
index 00000000000..10b7b5cae87
--- /dev/null
+++ b/src/include/jit/llvmjit_backport.h
@@ -0,0 +1,20 @@
+/*
+ * A small header than can be included by backported LLVM code or PostgreSQL
+ * code, to control conditional compilation.
+ */
+#ifndef LLVMJIT_BACKPORT_H
+#define LLVMJIT_BACKPORT_H
+
+#include <llvm/Config/llvm-config.h>
+
+/*
+ * LLVM RuntimeDyld can produce code that crashes on larger memory ARM systems,
+ * due to memory placement.  As a workaround, we supply an alternative memory
+ * manager class from https://github.com/llvm/llvm-project/pull/71968, but
+ * we've only backported it as far as LLVM 12.
+ */
+#if defined(__aarch64__) && LLVM_VERSION_MAJOR > 11
+#define USE_LLVM_BACKPORT_SECTION_MEMORY_MANAGER
+#endif
+
+#endif
diff --git a/src/tools/pginclude/headerscheck b/src/tools/pginclude/headerscheck
index 3fc737d2cc1..fb91b5760c4 100755
--- a/src/tools/pginclude/headerscheck
+++ b/src/tools/pginclude/headerscheck
@@ -168,6 +168,9 @@ do
 	# This produces a "no previous prototype" warning.
 	! $cplusplus && test "$f" = src/include/storage/checksum_impl.h && continue
 
+	# SectionMemoryManager.h is C++
+	test "$f" = src/include/jit/SectionMemoryManager.h && continue
+
 	# ppport.h is not under our control, so we can't make it standalone.
 	test "$f" = src/pl/plperl/ppport.h && continue
 
-- 
2.46.2

