[CodeGen][ARM] Bug fix InsertStackProtectors with EH_SJ_LJ #147411

AbhayKanhere · 2025-07-07T22:03:13Z

when exception handling with setjmp/longjmp (exception-mode=eh_sjlj is enabled,
eh_sjlj_callsite intrinsic is inserted in same basic block as the throwing/exception instruction. This fix ensures stack protector insertion code does not split the block and move these apart into different basic blocks.

llvmbot · 2025-07-07T22:03:41Z

@llvm/pr-subscribers-backend-arm

Author: Abhay Kanhere (AbhayKanhere)

Changes

when exception handling with setjmp/longjmp (exception-mode=eh_sjlj is enabled,
eh_sjlj_callsite intrinsic is inserted in same basic block as the throwing/exception instruction. This fix ensures stack protector insertion code does not split the block and move these apart into different basic blocks.

Full diff: https://github.com/llvm/llvm-project/pull/147411.diff

2 Files Affected:

(modified) llvm/lib/CodeGen/StackProtector.cpp (+9-1)
(added) llvm/test/CodeGen/ARM/stack-protector-eh-sjlj.ll (+166)

diff --git a/llvm/lib/CodeGen/StackProtector.cpp b/llvm/lib/CodeGen/StackProtector.cpp
index 5f866eea7d4e7..a2bc69ef5ff4d 100644
--- a/llvm/lib/CodeGen/StackProtector.cpp
+++ b/llvm/lib/CodeGen/StackProtector.cpp
@@ -588,7 +588,14 @@ bool InsertStackProtectors(const TargetMachine *TM, Function *F,
       continue;
     Instruction *CheckLoc = dyn_cast<ReturnInst>(BB.getTerminator());
     if (!CheckLoc && !DisableCheckNoReturn)
-      for (auto &Inst : BB)
+      for (auto &Inst : BB) {
+        if(auto *IB = dyn_cast<IntrinsicInst>(&Inst) )
+           if(IB->getIntrinsicID()==Intrinsic::eh_sjlj_callsite) {
+              // eh_sjlj_callsite has to be in same BB as the
+              // bb terminator. Dont insert within this range.
+              CheckLoc = IB;
+              break;
+           }
         if (auto *CB = dyn_cast<CallBase>(&Inst))
           // Do stack check before noreturn calls that aren't nounwind (e.g:
           // __cxa_throw).
@@ -596,6 +603,7 @@ bool InsertStackProtectors(const TargetMachine *TM, Function *F,
             CheckLoc = CB;
             break;
           }
+      }
 
     if (!CheckLoc)
       continue;
diff --git a/llvm/test/CodeGen/ARM/stack-protector-eh-sjlj.ll b/llvm/test/CodeGen/ARM/stack-protector-eh-sjlj.ll
new file mode 100644
index 0000000000000..860d4d468505d
--- /dev/null
+++ b/llvm/test/CodeGen/ARM/stack-protector-eh-sjlj.ll
@@ -0,0 +1,166 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc  -O0 -mtriple=thumbv7s-apple-darwin < %s  | FileCheck %s
+target datalayout = "e-m:o-p:32:32-Fi8-f64:32:64-v64:32:64-v128:32:128-a:0:32-n32-S32"
+
+; Function Attrs: mustprogress noinline optnone ssp
+define ptr @foo() #0 personality ptr @__gxx_personality_sj0 {
+; CHECK-LABEL: foo:
+; CHECK:       Lfunc_begin0:
+; CHECK-NEXT:  @ %bb.0:
+; CHECK-NEXT:    push {r4, r5, r6, r7, lr}
+; CHECK-NEXT:    add r7, sp, #12
+; CHECK-NEXT:    push.w {r8, r10, r11}
+; CHECK-NEXT:    sub.w r4, sp, #64
+; CHECK-NEXT:    bfc r4, #0, #4
+; CHECK-NEXT:    mov sp, r4
+; CHECK-NEXT:    vst1.64 {d8, d9, d10, d11}, [r4:128]!
+; CHECK-NEXT:    vst1.64 {d12, d13, d14, d15}, [r4:128]
+; CHECK-NEXT:    sub sp, #96
+; CHECK-NEXT:    movw r0, :lower16:(L___stack_chk_guard$non_lazy_ptr-(LPC0_2+4))
+; CHECK-NEXT:    movt r0, :upper16:(L___stack_chk_guard$non_lazy_ptr-(LPC0_2+4))
+; CHECK-NEXT:  LPC0_2:
+; CHECK-NEXT:    add r0, pc
+; CHECK-NEXT:    ldr r0, [r0]
+; CHECK-NEXT:    ldr r0, [r0]
+; CHECK-NEXT:    movw r0, :lower16:(L___stack_chk_guard$non_lazy_ptr-(LPC0_3+4))
+; CHECK-NEXT:    movt r0, :upper16:(L___stack_chk_guard$non_lazy_ptr-(LPC0_3+4))
+; CHECK-NEXT:  LPC0_3:
+; CHECK-NEXT:    add r0, pc
+; CHECK-NEXT:    ldr r0, [r0]
+; CHECK-NEXT:    ldr r0, [r0]
+; CHECK-NEXT:    str r0, [sp, #92]
+; CHECK-NEXT:    movw r0, :lower16:(L___gxx_personality_sj0$non_lazy_ptr-(LPC0_4+4))
+; CHECK-NEXT:    movt r0, :upper16:(L___gxx_personality_sj0$non_lazy_ptr-(LPC0_4+4))
+; CHECK-NEXT:  LPC0_4:
+; CHECK-NEXT:    add r0, pc
+; CHECK-NEXT:    ldr r0, [r0]
+; CHECK-NEXT:    str r0, [sp, #36]
+; CHECK-NEXT:    ldr r0, LCPI0_0
+; CHECK-NEXT:  LPC0_0:
+; CHECK-NEXT:    add r0, pc
+; CHECK-NEXT:    str r0, [sp, #40]
+; CHECK-NEXT:    str r7, [sp, #44]
+; CHECK-NEXT:    mov r0, sp
+; CHECK-NEXT:    str r0, [sp, #52]
+; CHECK-NEXT:    ldr r0, LCPI0_1
+; CHECK-NEXT:    orr r0, r0, #1
+; CHECK-NEXT:  LPC0_1:
+; CHECK-NEXT:    add r0, pc
+; CHECK-NEXT:    str r0, [sp, #48]
+; CHECK-NEXT:    add r0, sp, #12
+; CHECK-NEXT:    bl __Unwind_SjLj_Register
+; CHECK-NEXT:    movs r0, #1
+; CHECK-NEXT:    str r0, [sp, #16]
+; CHECK-NEXT:    movw r0, :lower16:(L___stack_chk_guard$non_lazy_ptr-(LPC0_5+4))
+; CHECK-NEXT:    movt r0, :upper16:(L___stack_chk_guard$non_lazy_ptr-(LPC0_5+4))
+; CHECK-NEXT:  LPC0_5:
+; CHECK-NEXT:    add r0, pc
+; CHECK-NEXT:    ldr r0, [r0]
+; CHECK-NEXT:    ldr r0, [r0]
+; CHECK-NEXT:    ldr r1, [sp, #92]
+; CHECK-NEXT:    cmp r0, r1
+; CHECK-NEXT:    bne LBB0_7
+; CHECK-NEXT:  @ %bb.1: @ %SP_return
+; CHECK-NEXT:  Ltmp0:
+; CHECK-NEXT:    movs r2, #0
+; CHECK-NEXT:    mov r0, r2
+; CHECK-NEXT:    mov r1, r2
+; CHECK-NEXT:    blx r2
+; CHECK-NEXT:  Ltmp1:
+; CHECK-NEXT:    b LBB0_2
+; CHECK-NEXT:  LBB0_2:
+; CHECK-NEXT:    movs r0, #2
+; CHECK-NEXT:    str r0, [sp, #16]
+; CHECK-NEXT:    movw r0, :lower16:(L___stack_chk_guard$non_lazy_ptr-(LPC0_6+4))
+; CHECK-NEXT:    movt r0, :upper16:(L___stack_chk_guard$non_lazy_ptr-(LPC0_6+4))
+; CHECK-NEXT:  LPC0_6:
+; CHECK-NEXT:    add r0, pc
+; CHECK-NEXT:    ldr r0, [r0]
+; CHECK-NEXT:    ldr r0, [r0]
+; CHECK-NEXT:    ldr r1, [sp, #92]
+; CHECK-NEXT:    cmp r0, r1
+; CHECK-NEXT:    bne LBB0_7
+; CHECK-NEXT:  @ %bb.3: @ %SP_return2
+; CHECK-NEXT:  Ltmp2:
+; CHECK-NEXT:    movs r3, #0
+; CHECK-NEXT:    mov r0, r3
+; CHECK-NEXT:    mov r1, r3
+; CHECK-NEXT:    mov r2, r3
+; CHECK-NEXT:    blx r3
+; CHECK-NEXT:  Ltmp3:
+; CHECK-NEXT:    b LBB0_6
+; CHECK-NEXT:  LBB0_4:
+; CHECK-NEXT:  Ltmp4:
+; CHECK-NEXT:    ldr r0, [sp, #20]
+; CHECK-NEXT:    ldr r0, [sp, #24]
+; CHECK-NEXT:    add r0, sp, #12
+; CHECK-NEXT:    bl __Unwind_SjLj_Unregister
+; CHECK-NEXT:    movw r0, :lower16:(L___stack_chk_guard$non_lazy_ptr-(LPC0_7+4))
+; CHECK-NEXT:    movt r0, :upper16:(L___stack_chk_guard$non_lazy_ptr-(LPC0_7+4))
+; CHECK-NEXT:  LPC0_7:
+; CHECK-NEXT:    add r0, pc
+; CHECK-NEXT:    ldr r0, [r0]
+; CHECK-NEXT:    ldr r0, [r0]
+; CHECK-NEXT:    ldr r1, [sp, #92]
+; CHECK-NEXT:    cmp r0, r1
+; CHECK-NEXT:    bne LBB0_7
+; CHECK-NEXT:  @ %bb.5: @ %SP_return3
+; CHECK-NEXT:    movs r0, #0
+; CHECK-NEXT:    add r4, sp, #96
+; CHECK-NEXT:    vld1.64 {d8, d9, d10, d11}, [r4:128]!
+; CHECK-NEXT:    vld1.64 {d12, d13, d14, d15}, [r4:128]
+; CHECK-NEXT:    sub.w r4, r7, #24
+; CHECK-NEXT:    mov sp, r4
+; CHECK-NEXT:    pop.w {r8, r10, r11}
+; CHECK-NEXT:    pop {r4, r5, r6, r7, pc}
+; CHECK-NEXT:  LBB0_6:
+; CHECK-NEXT:    trap
+; CHECK-NEXT:  LBB0_7: @ %CallStackCheckFailBlk
+; CHECK-NEXT:    bl ___stack_chk_fail
+; CHECK-NEXT:  LBB0_8:
+; CHECK-NEXT:    ldr r0, [sp, #16]
+; CHECK-NEXT:    str r0, [sp, #8] @ 4-byte Spill
+; CHECK-NEXT:    cmp r0, #2
+; CHECK-NEXT:    bhi LBB0_12
+; CHECK-NEXT:  @ %bb.9:
+; CHECK-NEXT:    ldr r1, [sp, #8] @ 4-byte Reload
+; CHECK-NEXT:  LCPI0_2:
+; CHECK-NEXT:    tbb [pc, r1]
+; CHECK-NEXT:  @ %bb.10:
+; CHECK-NEXT:  LJTI0_0:
+; CHECK-NEXT:    .data_region jt8
+; CHECK-NEXT:    .byte (LBB0_11-(LCPI0_2+4))/2
+; CHECK-NEXT:    .byte (LBB0_11-(LCPI0_2+4))/2
+; CHECK-NEXT:    .end_data_region
+; CHECK-NEXT:    .p2align 1
+; CHECK-NEXT:  LBB0_11:
+; CHECK-NEXT:    b LBB0_4
+; CHECK-NEXT:  LBB0_12:
+; CHECK-NEXT:    trap
+; CHECK-NEXT:    .p2align 2
+; CHECK-NEXT:  @ %bb.13:
+  %1 = alloca [14 x i8], align 16
+  %2 = invoke i32 null(ptr noundef null, ptr noundef null) #1
+          to label %3 unwind label %4
+
+3:                                                ; preds = %0
+  invoke void null(ptr null, ptr null, ptr null) #2
+          to label %6 unwind label %4
+
+4:                                                ; preds = %3, %0
+  %5 = landingpad { ptr, i32 }
+          cleanup
+  ret ptr null
+
+6:                                                ; preds = %3
+  unreachable
+}
+
+declare i32 @__gxx_personality_sj0(...)
+
+; uselistorder directives
+uselistorder ptr null, { 2, 3, 4, 5, 0, 6, 7, 1, 8, 9 }
+
+attributes #0 = { mustprogress ssp "frame-pointer"="all" "no-builtin-calloc" "no-builtin-stpcpy" "no-trapping-math"="true" "stack-protector-buffer-size"="8" }
+attributes #1 = { "no-builtin-calloc" "no-builtin-stpcpy" }
+attributes #2 = { noreturn }

github-actions · 2025-07-07T22:05:43Z

✅ With the latest revision this PR passed the C/C++ code formatter.

AbhayKanhere · 2025-07-07T22:06:00Z

@nickdesaulniers @jroelofs

llvm/lib/CodeGen/StackProtector.cpp

jroelofs · 2025-07-07T22:24:56Z

llvm/lib/CodeGen/StackProtector.cpp

The clang-format bot is complaining about the spacing of things here. You should apply the diff it gave you in this comment: #147411 (comment)

Un-resolving. There is still some spacing weirdness. You should copy the diff, and apply it with pbpaste | patch -p1 from the top-level of the llvm repo.

ok. I took the diff and applied patch -p0 -- format did not complain this time. let me try what you suggest. thanks!

llvm/test/CodeGen/ARM/stack-protector-eh-sjlj.ll

Some armv7s targets use setjmp longjmp exception handling. In this, form a llvm.eh.sjlj.callsite() intrinsic is inserted in each BB with exception exit. This information is then recorded in a callsite table, and used when emitExceptionTables() is called later. When stackprotectors are enabled on this target, StackProtector pass ends up splitting the basic block with this intrinsic, thereby removing information needed by emitExceptionTable call later. This fix ensures the eh.sjlj.callsite remains in same basic block as block terminator instruction.

when exception handling with setjmp/longjmp (exception-mode=eh_sjlj is enabled, eh_sjlj_callsite intrinsic is inserted in same basic block as the throwing/exception instruction. This fix ensures stack protector insertion code does not split the block and move these apart into different basic blocks.

llvmbot added backend:ARM llvm:codegen labels Jul 7, 2025

jroelofs requested review from aemerson, fhahn and nickdesaulniers July 7, 2025 22:22

jroelofs reviewed Jul 7, 2025

View reviewed changes

AbhayKanhere force-pushed the dev/abhay/ehsjlj-stackprotect-bug branch from 4348e3d to 0df6e25 Compare July 9, 2025 00:20

AbhayKanhere force-pushed the dev/abhay/ehsjlj-stackprotect-bug branch 4 times, most recently from 84ec35d to 0ce39a2 Compare July 16, 2025 21:04

AbhayKanhere requested a review from jroelofs July 16, 2025 21:26

jroelofs approved these changes Jul 16, 2025

View reviewed changes

AbhayKanhere force-pushed the dev/abhay/ehsjlj-stackprotect-bug branch from 0ce39a2 to ec9293e Compare July 17, 2025 16:40

AbhayKanhere added 2 commits July 17, 2025 09:42

fix form

d3ad6e6

combined two ifs

7b36326

jroelofs merged commit 33c9445 into llvm:main Jul 24, 2025
9 checks passed

Un1q32 mentioned this pull request Sep 4, 2025

Clang crash when targetting 32 bit iOS with some ObjC++ when stack protector enabled #118175

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[CodeGen][ARM] Bug fix InsertStackProtectors with EH_SJ_LJ #147411

[CodeGen][ARM] Bug fix InsertStackProtectors with EH_SJ_LJ #147411

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[CodeGen][ARM] Bug fix InsertStackProtectors with EH_SJ_LJ #147411

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