If the pc is set to zero, the unwind is done.

Bug: 68047085

Test: Ran new unit tests, verified new unwinder does not show an
Test: extra pc zero frame for arm 32 bit processes.
Change-Id: Ic6532e56fbb786a8b7d41638abae777c2d0f1d59

4 files changed, 61 insertions, 4 deletions

diff --git a/libunwindstack/DwarfSection.cpp b/libunwindstack/DwarfSection.cpp
index 8b30b76..b8164c5 100644
--- a/libunwindstack/DwarfSection.cpp
+++ b/libunwindstack/DwarfSection.cpp
@@ -225,11 +225,13 @@ bool DwarfSectionImpl<AddressType>::Eval(const DwarfCie* cie, Memory* regular_me
   // Find the return address location.
   if (return_address_undefined) {
     cur_regs->set_pc(0);
-    *finished = true;
   } else {
     cur_regs->set_pc((*cur_regs)[cie->return_address_register]);
-    *finished = false;
   }
+
+  // If the pc was set to zero, consider this the final frame.
+  *finished = (cur_regs->pc() == 0) ? true : false;
+
   cur_regs->set_sp(cfa);
   // Return false if the unwind is not finished or the cfa and pc didn't change.
   return *finished || prev_cfa != cfa || prev_pc != cur_regs->pc();
diff --git a/libunwindstack/ElfInterfaceArm.cpp b/libunwindstack/ElfInterfaceArm.cpp
index 30a1532..170a5cd 100644
--- a/libunwindstack/ElfInterfaceArm.cpp
+++ b/libunwindstack/ElfInterfaceArm.cpp
@@ -121,8 +121,10 @@ bool ElfInterfaceArm::StepExidx(uint64_t pc, Regs* regs, Memory* process_memory,
     }
     regs_arm->set_sp(arm.cfa());
     (*regs_arm)[ARM_REG_SP] = regs_arm->sp();
-    *finished = false;
     return_value = true;
+
+    // If the pc was set to zero, consider this the final frame.
+    *finished = (regs_arm->pc() == 0) ? true : false;
   }
 
   if (arm.status() == ARM_STATUS_NO_UNWIND) {
diff --git a/libunwindstack/tests/DwarfSectionImplTest.cpp b/libunwindstack/tests/DwarfSectionImplTest.cpp
index c701a29..7e85bbb 100644
--- a/libunwindstack/tests/DwarfSectionImplTest.cpp
+++ b/libunwindstack/tests/DwarfSectionImplTest.cpp
@@ -340,6 +340,23 @@ TYPED_TEST_P(DwarfSectionImplTest, Eval_return_address_undefined) {
   EXPECT_EQ(0x10U, regs.sp());
 }
 
+TYPED_TEST_P(DwarfSectionImplTest, Eval_pc_zero) {
+  DwarfCie cie{.return_address_register = 5};
+  RegsImplFake<TypeParam> regs(10, 9);
+  dwarf_loc_regs_t loc_regs;
+
+  regs.set_pc(0x100);
+  regs.set_sp(0x2000);
+  regs[5] = 0;
+  regs[8] = 0x10;
+  loc_regs[CFA_REG] = DwarfLocation{DWARF_LOCATION_REGISTER, {8, 0}};
+  bool finished;
+  ASSERT_TRUE(this->section_->Eval(&cie, &this->memory_, loc_regs, &regs, &finished));
+  EXPECT_TRUE(finished);
+  EXPECT_EQ(0U, regs.pc());
+  EXPECT_EQ(0x10U, regs.sp());
+}
+
 TYPED_TEST_P(DwarfSectionImplTest, Eval_return_address) {
   DwarfCie cie{.return_address_register = 5};
   RegsImplFake<TypeParam> regs(10, 9);
@@ -854,7 +871,7 @@ REGISTER_TYPED_TEST_CASE_P(
     Eval_cfa_expr_is_register, Eval_cfa_expr, Eval_cfa_val_expr, Eval_bad_regs, Eval_no_cfa,
     Eval_cfa_bad, Eval_cfa_register_prev, Eval_cfa_register_from_value, Eval_double_indirection,
     Eval_invalid_register, Eval_different_reg_locations, Eval_return_address_undefined,
-    Eval_return_address, Eval_ignore_large_reg_loc, Eval_reg_expr, Eval_reg_val_expr,
+    Eval_pc_zero, Eval_return_address, Eval_ignore_large_reg_loc, Eval_reg_expr, Eval_reg_val_expr,
     Eval_same_cfa_same_pc, GetCie_fail_should_not_cache, GetCie_32_version_check,
     GetCie_negative_data_alignment_factor, GetCie_64_no_augment, GetCie_augment, GetCie_version_3,
     GetCie_version_4, GetFdeFromOffset_fail_should_not_cache, GetFdeFromOffset_32_no_augment,
diff --git a/libunwindstack/tests/ElfInterfaceArmTest.cpp b/libunwindstack/tests/ElfInterfaceArmTest.cpp
index feb24ce..4b621c9 100644
--- a/libunwindstack/tests/ElfInterfaceArmTest.cpp
+++ b/libunwindstack/tests/ElfInterfaceArmTest.cpp
@@ -401,4 +401,40 @@ TEST_F(ElfInterfaceArmTest, StepExidx_refuse_unwind) {
   ASSERT_EQ(0x1234U, regs.pc());
 }
 
+TEST_F(ElfInterfaceArmTest, StepExidx_pc_zero) {
+  ElfInterfaceArmFake interface(&memory_);
+
+  interface.FakeSetStartOffset(0x1000);
+  interface.FakeSetTotalEntries(1);
+  memory_.SetData32(0x1000, 0x6000);
+  // Set the pc using a pop r15 command.
+  memory_.SetData32(0x1004, 0x808800b0);
+
+  // pc value of zero.
+  process_memory_.SetData32(0x10000, 0);
+
+  RegsArm regs;
+  regs[ARM_REG_SP] = 0x10000;
+  regs[ARM_REG_LR] = 0x20000;
+  regs.set_sp(regs[ARM_REG_SP]);
+  regs.set_pc(0x1234);
+
+  bool finished;
+  ASSERT_TRUE(interface.StepExidx(0x7000, &regs, &process_memory_, &finished));
+  ASSERT_TRUE(finished);
+  ASSERT_EQ(0U, regs.pc());
+
+  // Now set the pc from the lr register (pop r14).
+  memory_.SetData32(0x1004, 0x808400b0);
+
+  regs[ARM_REG_SP] = 0x10000;
+  regs[ARM_REG_LR] = 0x20000;
+  regs.set_sp(regs[ARM_REG_SP]);
+  regs.set_pc(0x1234);
+
+  ASSERT_TRUE(interface.StepExidx(0x7000, &regs, &process_memory_, &finished));
+  ASSERT_TRUE(finished);
+  ASSERT_EQ(0U, regs.pc());
+}
+
 }  // namespace unwindstack