diff --git a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
--- a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -507,6 +507,32 @@
   return Flags;
 }
 
+/// Return true if one of the default sections
+static bool isDefaultELFSection(const MCSectionELF &S) {
+  for (StringRef prefix :
+       {".bss", ".text", ".data", ".rodata", ".tdata", ".tbss",
+        ".gcc_except_table", ".debug_", ".apple_", ".llvm_", ".eh_frame",
+        ".stack_sizes", ".pseudo_probe"})
+    if (S.getName().startswith(prefix))
+      return true;
+  return false;
+}
+
+/// Return true if the section is compatible with the given flags.
+static bool flagsCompatible(const unsigned OldFlags, const unsigned NewFlags) {
+  // WRITE and EXECINSTR are not compatible
+  if (OldFlags & ELF::SHF_EXECINSTR && NewFlags & ELF::SHF_WRITE)
+    return false;
+  if (OldFlags & ELF::SHF_WRITE && NewFlags & ELF::SHF_EXECINSTR)
+    return false;
+
+  // TLS and non-TLS are not compatible
+  if ((OldFlags & ELF::SHF_TLS) != (NewFlags & ELF::SHF_TLS))
+    return false;
+
+  return true;
+}
+
 static const Comdat *getELFComdat(const GlobalValue *GV) {
   const Comdat *C = GV->getComdat();
   if (!C)
@@ -726,6 +752,28 @@
   assert(Section->getLinkedToSymbol() == LinkedToSym &&
          "Associated symbol mismatch between sections");
 
+  // Update the seen flags of user defined sections, raise an error if invalid
+  // combinations are seen. Don't update flags of standard sections (.text etc).
+  if (Section->getFlags() != Flags && !isDefaultELFSection(*Section)) {
+    if (flagsCompatible(Section->getFlags(), Flags)) {
+      // If all flags are compatible then add any new ones to the section.
+      const auto MergedFlags = Section->getFlags() | Flags;
+      if (MergedFlags != Section->getFlags()) {
+        Section->setFlags(MergedFlags);
+        GO->getContext().diagnose(LoweringDiagnosticInfo(
+            "Symbol " + GO->getName() + ": updating section flags: " +
+                SectionName + " 0x" + utohexstr(MergedFlags),
+            DS_Remark));
+      }
+    } else {
+      GO->getContext().diagnose(LoweringDiagnosticInfo(
+          "Symbol '" + GO->getName() +
+          "' implies incompatible flags for section '" + SectionName +
+          "'. Old: 0x" + utohexstr(Section->getFlags()) + ", New: 0x" +
+          utohexstr(Flags)));
+    }
+  }
+
   if (!getContext().getAsmInfo()->useIntegratedAssembler()) {
     // If we are not using the integrated assembler then this symbol might have
     // been placed in an incompatible mergeable section. Emit an error if this
diff --git a/llvm/test/CodeGen/Generic/elf-incompatible-section-flags.ll b/llvm/test/CodeGen/Generic/elf-incompatible-section-flags.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/CodeGen/Generic/elf-incompatible-section-flags.ll
@@ -0,0 +1,55 @@
+; RUN: not llc -mtriple=aarch64-none-eabi %s -o - 2>&1 | FileCheck %s
+; RUN: not llc -mtriple=aarch64-none-eabi %s -o - 2> /dev/null | FileCheck %s --check-prefix=ASSEMBLY
+
+; User creates globals with SHF_WRITE and SHF_EXECINSTR
+@rw_s1 = global i32 10, section "s1_ax", align 4
+define i32 @fn_s1() section "s1_ax" {
+    entry:
+    ret i32 0
+}
+; CHECK: error: Symbol 'rw_s1' implies incompatible flags for section 's1_ax'. Old: 0x6, New: 0x3
+
+; This is fine; constant can live in SHF_EXECINSTR section
+@ro_s2 = constant i32 10, section "s2_ax", align 4
+define i32 @fn_s2() section "s2_ax" {
+    entry:
+    ret i32 0
+}
+; CHECK-NOT: error: Symbol 'ro_s2' implies incompatible flags for section 's2_ax'.
+; CHECK-NOT: remark: Symbol ro_s2: updating section flags
+; ASSEMBLY: .section s2_ax,"ax"
+; ASSEMBLY: .section s2_ax,"ax"
+
+; This is also fine; constant can live in SHF_WRITE
+@ro_s3 = constant i32 10, section "s3_aw", align 4
+@rw_s3 = global i32 10, section "s3_aw", align 4
+; CHECK-NOT: error: Symbol 'rw_s3' implies incompatible flags for section 's3_aw'.
+; CHECK: remark: Symbol rw_s3: updating section flags: s3_aw 0x3
+; ASSEMBLY:  .section s3_aw,"a"
+
+; This is fine; .text is read only, but the flags shouldn't change
+@ro_text = constant i32 10, section ".text", align 4
+; CHECK-NOT: error: Symbol 'ro_text' implies incompatible flags for section '.text'.
+; CHECK-NOT: remark: Symbol ro_text: updating section flags: .text
+
+; This is fine; .text is read only, but mutable globals are not necessarily written to
+@rw_text = global i32 10, section ".text", align 4
+; CHECK-NOT: error: Symbol 'rw_text' implies incompatible flags for section '.text'. Old: 0x6, New: 0x3
+; CHECK-NOT: remark: Symbol rw_text: updating section flags: .text
+
+; This is fine; .data is writeable, but the flags shouldn't change and constants are allowed
+@ro_data = constant i32 10, section ".data", align 4
+; CHECK-NOT: error: Symbol 'ro_data' implies incompatible flags for section '.data'.
+; CHECK-NOT: remark: Symbol ro_data: updating section flags: .data
+
+; TLS and non-TLS symbols cannot live in the same section
+@tls_var = thread_local global i32 10, section "s4", align 4
+@non_tls_var = global i32 10, section "s4", align 4
+; CHECK: error: Symbol 'non_tls_var' implies incompatible flags for section 's4'. Old: 0x403, New: 0x3
+; CHECK-NOT: remark: Symbol non_tls_var: updating section flags: s4
+
+; TLS and non-TLS symbols cannot live in the same section
+@non_tls_var2 = global i32 10, section "s5", align 4
+@tls_var2 = thread_local global i32 10, section "s5", align 4
+; CHECK: error: Symbol 'tls_var2' implies incompatible flags for section 's5'. Old: 0x3, New: 0x403
+; CHECK-NOT: remark: Symbol tls_var2: updating section flags: s5