[llvm] [OpenMP] Fix stack corruption due to argument mismatch (PR #96386)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-offload

Author: Sushant Gokhale (sushgokh)

<details>
<summary>Changes</summary>

While lowering (#pragma omp target update from), clang's generated .omp_task_entry. is setting up 9 arguments while calling __tgt_target_data_update_nowait_mapper.

At the same time, in __tgt_target_data_update_nowait_mapper, call to targetData<TaskAsyncInfoWrapperTy>() is converted to a sibcall assuming it has the argument count listed in the signature.

AARCH64 asm sequence for this is as follows (removed unrelated insns):

`
.omp_task_entry..108:
  sub   sp, sp, #<!-- -->32
  stp   x29, x30, sp, #<!-- -->16       // 16-byte Folded Spill
  add   x29, sp, #<!-- -->16
  str   x8, sp, #<!-- -->8. // stack canary
  str   xzr, [sp]
  bl   __tgt_target_data_update_nowait_mapper

__tgt_target_data_update_nowait_mapper:
  sub   sp, sp, #<!-- -->32
  stp   x29, x30, sp, #<!-- -->16       // 16-byte Folded Spill
  add   x29, sp, #<!-- -->16
  str   x8, sp, #<!-- -->8 // stack canary
  // Sibcall argument setup
  adrp  x8, :got:_Z16targetDataUpdateP7ident_tR8DeviceTyiPPvS4_PlS5_S4_S4_R11AsyncInfoTyb
  ldr   x8, [x8, :got_lo12:_Z16targetDataUpdateP7ident_tR8DeviceTyiPPvS4_PlS5_S4_S4_R11AsyncInfoTyb]
  stp   x9, x8, x29, #<!-- -->16
  adrp  x8, .L.str.8
  add   x8, x8, :lo12:.L.str.8
  str   x8, x29, #<!-- -->32. <==. This is the insn that erases $fp

  ldp   x29, x30, sp, #<!-- -->16       // 16-byte Folded Reload
  add   sp, sp, #<!-- -->32
  // Sibcall
  b    ZL10targetDataI22TaskAsyncInfoWrapperTyEvP7ident_tliPPvS4_PlS5_S4_S4_PFiS2_R8DeviceTyiS4_S4_S5_S5_S4_S4_R11AsyncInfoTybEPKcSD
`

On AArch64, call to __tgt_target_data_update_nowait_mapper in .omp_task_entry. sets up only single space on stack and this results in ovewriting $fp and subsequent stack corruption. This issue can be credited to discrepancy of __tgt_target_data_update_nowait_mapper signature in openmp/libomptarget/include/omptarget.h taking 13 arguments while clang/lib/CodeGen/CGOpenMPRuntime.cpp and
llvm/include/llvm/Frontend/OpenMP/OMPKinds.def taking only 9 arguments.

This patch modifies __tgt_target_data_update_nowait_mapper signature to match .omp_task_entry usage(and other 2 files mentioned above).

---
Full diff: https://github.com/llvm/llvm-project/pull/96386.diff


2 Files Affected:

- (modified) offload/include/omptarget.h (+1-2) 
- (modified) offload/src/interface.cpp (+1-2) 


``````````diff
diff --git a/offload/include/omptarget.h b/offload/include/omptarget.h
index 323dee41630f2..968589e866334 100644
--- a/offload/include/omptarget.h
+++ b/offload/include/omptarget.h
@@ -388,8 +388,7 @@ void __tgt_target_data_update_mapper(ident_t *Loc, int64_t DeviceId,
 void __tgt_target_data_update_nowait_mapper(
     ident_t *Loc, int64_t DeviceId, int32_t ArgNum, void **ArgsBase,
     void **Args, int64_t *ArgSizes, int64_t *ArgTypes, map_var_info_t *ArgNames,
-    void **ArgMappers, int32_t DepNum, void *DepList, int32_t NoAliasDepNum,
-    void *NoAliasDepList);
+    void **ArgMappers);
 
 // Performs the same actions as data_begin in case ArgNum is non-zero
 // and initiates run of offloaded region on target platform; if ArgNum
diff --git a/offload/src/interface.cpp b/offload/src/interface.cpp
index 763b051cc6d77..27562388c2f11 100644
--- a/offload/src/interface.cpp
+++ b/offload/src/interface.cpp
@@ -207,8 +207,7 @@ EXTERN void __tgt_target_data_update_mapper(ident_t *Loc, int64_t DeviceId,
 EXTERN void __tgt_target_data_update_nowait_mapper(
     ident_t *Loc, int64_t DeviceId, int32_t ArgNum, void **ArgsBase,
     void **Args, int64_t *ArgSizes, int64_t *ArgTypes, map_var_info_t *ArgNames,
-    void **ArgMappers, int32_t DepNum, void *DepList, int32_t NoAliasDepNum,
-    void *NoAliasDepList) {
+    void **ArgMappers) {
   OMPT_IF_BUILT(ReturnAddressSetterRAII RA(__builtin_return_address(0)));
   targetData<TaskAsyncInfoWrapperTy>(
       Loc, DeviceId, ArgNum, ArgsBase, Args, ArgSizes, ArgTypes, ArgNames,

``````````

</details>


https://github.com/llvm/llvm-project/pull/96386