Fix null pointer dereference in RegsArm.

Fix RegsArm::GetPcAdjustment to check for an invalid elf before trying
to read memory.
Modify the tests for this so it crashes without this change.

Also modify the GetPcAdjustment for all different architectures so
that unless the relative pc is too small, it will return the minimum
amount that should be adjusted. This is to handle cases where we still
want to adjust the pc but it's in an invalid elf. Mostly this is for
handling cases when the pc is in jit gdb debug code so that we use the
right unwind information.

Bug: 77233204

Test: Passes unit tests for libbacktrace/libunwindstack.
Change-Id: Id73609adaf3b80a583584441de228156fec3afa7
(cherry picked from commit 6dbc28ece3ab7cadd0087b4dc31ba9a2986545f0)
diff --git a/libunwindstack/tests/RegsTest.cpp b/libunwindstack/tests/RegsTest.cpp
index 3e80733..d15823e 100644
--- a/libunwindstack/tests/RegsTest.cpp
+++ b/libunwindstack/tests/RegsTest.cpp
@@ -94,48 +94,48 @@
 
 TEST_F(RegsTest, rel_pc) {
   RegsArm64 arm64;
-  ASSERT_EQ(4U, arm64.GetPcAdjustment(0x10, elf_.get()));
-  ASSERT_EQ(4U, arm64.GetPcAdjustment(0x4, elf_.get()));
-  ASSERT_EQ(0U, arm64.GetPcAdjustment(0x3, elf_.get()));
-  ASSERT_EQ(0U, arm64.GetPcAdjustment(0x2, elf_.get()));
-  ASSERT_EQ(0U, arm64.GetPcAdjustment(0x1, elf_.get()));
-  ASSERT_EQ(0U, arm64.GetPcAdjustment(0x0, elf_.get()));
+  EXPECT_EQ(4U, arm64.GetPcAdjustment(0x10, elf_.get()));
+  EXPECT_EQ(4U, arm64.GetPcAdjustment(0x4, elf_.get()));
+  EXPECT_EQ(0U, arm64.GetPcAdjustment(0x3, elf_.get()));
+  EXPECT_EQ(0U, arm64.GetPcAdjustment(0x2, elf_.get()));
+  EXPECT_EQ(0U, arm64.GetPcAdjustment(0x1, elf_.get()));
+  EXPECT_EQ(0U, arm64.GetPcAdjustment(0x0, elf_.get()));
 
   RegsX86 x86;
-  ASSERT_EQ(1U, x86.GetPcAdjustment(0x100, elf_.get()));
-  ASSERT_EQ(1U, x86.GetPcAdjustment(0x2, elf_.get()));
-  ASSERT_EQ(1U, x86.GetPcAdjustment(0x1, elf_.get()));
-  ASSERT_EQ(0U, x86.GetPcAdjustment(0x0, elf_.get()));
+  EXPECT_EQ(1U, x86.GetPcAdjustment(0x100, elf_.get()));
+  EXPECT_EQ(1U, x86.GetPcAdjustment(0x2, elf_.get()));
+  EXPECT_EQ(1U, x86.GetPcAdjustment(0x1, elf_.get()));
+  EXPECT_EQ(0U, x86.GetPcAdjustment(0x0, elf_.get()));
 
   RegsX86_64 x86_64;
-  ASSERT_EQ(1U, x86_64.GetPcAdjustment(0x100, elf_.get()));
-  ASSERT_EQ(1U, x86_64.GetPcAdjustment(0x2, elf_.get()));
-  ASSERT_EQ(1U, x86_64.GetPcAdjustment(0x1, elf_.get()));
-  ASSERT_EQ(0U, x86_64.GetPcAdjustment(0x0, elf_.get()));
+  EXPECT_EQ(1U, x86_64.GetPcAdjustment(0x100, elf_.get()));
+  EXPECT_EQ(1U, x86_64.GetPcAdjustment(0x2, elf_.get()));
+  EXPECT_EQ(1U, x86_64.GetPcAdjustment(0x1, elf_.get()));
+  EXPECT_EQ(0U, x86_64.GetPcAdjustment(0x0, elf_.get()));
 
   RegsMips mips;
-  ASSERT_EQ(8U, mips.GetPcAdjustment(0x10, elf_.get()));
-  ASSERT_EQ(8U, mips.GetPcAdjustment(0x8, elf_.get()));
-  ASSERT_EQ(0U, mips.GetPcAdjustment(0x7, elf_.get()));
-  ASSERT_EQ(0U, mips.GetPcAdjustment(0x6, elf_.get()));
-  ASSERT_EQ(0U, mips.GetPcAdjustment(0x5, elf_.get()));
-  ASSERT_EQ(0U, mips.GetPcAdjustment(0x4, elf_.get()));
-  ASSERT_EQ(0U, mips.GetPcAdjustment(0x3, elf_.get()));
-  ASSERT_EQ(0U, mips.GetPcAdjustment(0x2, elf_.get()));
-  ASSERT_EQ(0U, mips.GetPcAdjustment(0x1, elf_.get()));
-  ASSERT_EQ(0U, mips.GetPcAdjustment(0x0, elf_.get()));
+  EXPECT_EQ(8U, mips.GetPcAdjustment(0x10, elf_.get()));
+  EXPECT_EQ(8U, mips.GetPcAdjustment(0x8, elf_.get()));
+  EXPECT_EQ(0U, mips.GetPcAdjustment(0x7, elf_.get()));
+  EXPECT_EQ(0U, mips.GetPcAdjustment(0x6, elf_.get()));
+  EXPECT_EQ(0U, mips.GetPcAdjustment(0x5, elf_.get()));
+  EXPECT_EQ(0U, mips.GetPcAdjustment(0x4, elf_.get()));
+  EXPECT_EQ(0U, mips.GetPcAdjustment(0x3, elf_.get()));
+  EXPECT_EQ(0U, mips.GetPcAdjustment(0x2, elf_.get()));
+  EXPECT_EQ(0U, mips.GetPcAdjustment(0x1, elf_.get()));
+  EXPECT_EQ(0U, mips.GetPcAdjustment(0x0, elf_.get()));
 
   RegsMips64 mips64;
-  ASSERT_EQ(8U, mips64.GetPcAdjustment(0x10, elf_.get()));
-  ASSERT_EQ(8U, mips64.GetPcAdjustment(0x8, elf_.get()));
-  ASSERT_EQ(0U, mips64.GetPcAdjustment(0x7, elf_.get()));
-  ASSERT_EQ(0U, mips64.GetPcAdjustment(0x6, elf_.get()));
-  ASSERT_EQ(0U, mips64.GetPcAdjustment(0x5, elf_.get()));
-  ASSERT_EQ(0U, mips64.GetPcAdjustment(0x4, elf_.get()));
-  ASSERT_EQ(0U, mips64.GetPcAdjustment(0x3, elf_.get()));
-  ASSERT_EQ(0U, mips64.GetPcAdjustment(0x2, elf_.get()));
-  ASSERT_EQ(0U, mips64.GetPcAdjustment(0x1, elf_.get()));
-  ASSERT_EQ(0U, mips64.GetPcAdjustment(0x0, elf_.get()));
+  EXPECT_EQ(8U, mips64.GetPcAdjustment(0x10, elf_.get()));
+  EXPECT_EQ(8U, mips64.GetPcAdjustment(0x8, elf_.get()));
+  EXPECT_EQ(0U, mips64.GetPcAdjustment(0x7, elf_.get()));
+  EXPECT_EQ(0U, mips64.GetPcAdjustment(0x6, elf_.get()));
+  EXPECT_EQ(0U, mips64.GetPcAdjustment(0x5, elf_.get()));
+  EXPECT_EQ(0U, mips64.GetPcAdjustment(0x4, elf_.get()));
+  EXPECT_EQ(0U, mips64.GetPcAdjustment(0x3, elf_.get()));
+  EXPECT_EQ(0U, mips64.GetPcAdjustment(0x2, elf_.get()));
+  EXPECT_EQ(0U, mips64.GetPcAdjustment(0x1, elf_.get()));
+  EXPECT_EQ(0U, mips64.GetPcAdjustment(0x0, elf_.get()));
 }
 
 TEST_F(RegsTest, rel_pc_arm) {
@@ -143,34 +143,36 @@
 
   // Check fence posts.
   elf_->FakeSetLoadBias(0);
-  ASSERT_EQ(2U, arm.GetPcAdjustment(0x5, elf_.get()));
-  ASSERT_EQ(0U, arm.GetPcAdjustment(0x4, elf_.get()));
-  ASSERT_EQ(0U, arm.GetPcAdjustment(0x3, elf_.get()));
-  ASSERT_EQ(0U, arm.GetPcAdjustment(0x2, elf_.get()));
-  ASSERT_EQ(0U, arm.GetPcAdjustment(0x1, elf_.get()));
-  ASSERT_EQ(0U, arm.GetPcAdjustment(0x0, elf_.get()));
+  EXPECT_EQ(2U, arm.GetPcAdjustment(0x5, elf_.get()));
+  EXPECT_EQ(2U, arm.GetPcAdjustment(0x4, elf_.get()));
+  EXPECT_EQ(2U, arm.GetPcAdjustment(0x3, elf_.get()));
+  EXPECT_EQ(2U, arm.GetPcAdjustment(0x2, elf_.get()));
+  EXPECT_EQ(0U, arm.GetPcAdjustment(0x1, elf_.get()));
+  EXPECT_EQ(0U, arm.GetPcAdjustment(0x0, elf_.get()));
 
   elf_->FakeSetLoadBias(0x100);
-  ASSERT_EQ(0U, arm.GetPcAdjustment(0xff, elf_.get()));
-  ASSERT_EQ(2U, arm.GetPcAdjustment(0x105, elf_.get()));
-  ASSERT_EQ(0U, arm.GetPcAdjustment(0x104, elf_.get()));
-  ASSERT_EQ(0U, arm.GetPcAdjustment(0x103, elf_.get()));
-  ASSERT_EQ(0U, arm.GetPcAdjustment(0x102, elf_.get()));
-  ASSERT_EQ(0U, arm.GetPcAdjustment(0x101, elf_.get()));
-  ASSERT_EQ(0U, arm.GetPcAdjustment(0x100, elf_.get()));
+  EXPECT_EQ(0U, arm.GetPcAdjustment(0x1, elf_.get()));
+  EXPECT_EQ(2U, arm.GetPcAdjustment(0x2, elf_.get()));
+  EXPECT_EQ(2U, arm.GetPcAdjustment(0xff, elf_.get()));
+  EXPECT_EQ(2U, arm.GetPcAdjustment(0x105, elf_.get()));
+  EXPECT_EQ(2U, arm.GetPcAdjustment(0x104, elf_.get()));
+  EXPECT_EQ(2U, arm.GetPcAdjustment(0x103, elf_.get()));
+  EXPECT_EQ(2U, arm.GetPcAdjustment(0x102, elf_.get()));
+  EXPECT_EQ(0U, arm.GetPcAdjustment(0x101, elf_.get()));
+  EXPECT_EQ(0U, arm.GetPcAdjustment(0x100, elf_.get()));
 
   // Check thumb instructions handling.
   elf_->FakeSetLoadBias(0);
   memory_->SetData32(0x2000, 0);
-  ASSERT_EQ(2U, arm.GetPcAdjustment(0x2005, elf_.get()));
+  EXPECT_EQ(2U, arm.GetPcAdjustment(0x2005, elf_.get()));
   memory_->SetData32(0x2000, 0xe000f000);
-  ASSERT_EQ(4U, arm.GetPcAdjustment(0x2005, elf_.get()));
+  EXPECT_EQ(4U, arm.GetPcAdjustment(0x2005, elf_.get()));
 
   elf_->FakeSetLoadBias(0x400);
   memory_->SetData32(0x2100, 0);
-  ASSERT_EQ(2U, arm.GetPcAdjustment(0x2505, elf_.get()));
+  EXPECT_EQ(2U, arm.GetPcAdjustment(0x2505, elf_.get()));
   memory_->SetData32(0x2100, 0xf111f111);
-  ASSERT_EQ(4U, arm.GetPcAdjustment(0x2505, elf_.get()));
+  EXPECT_EQ(4U, arm.GetPcAdjustment(0x2505, elf_.get()));
 }
 
 TEST_F(RegsTest, elf_invalid) {
@@ -181,32 +183,33 @@
   RegsMips regs_mips;
   RegsMips64 regs_mips64;
   MapInfo map_info(0x1000, 0x2000);
-  Elf* invalid_elf = new Elf(new MemoryFake);
+  Elf* invalid_elf = new Elf(nullptr);
   map_info.elf.reset(invalid_elf);
 
   regs_arm.set_pc(0x1500);
   EXPECT_EQ(0x500U, invalid_elf->GetRelPc(regs_arm.pc(), &map_info));
-  EXPECT_EQ(4U, regs_arm.GetPcAdjustment(0x500U, invalid_elf));
+  EXPECT_EQ(2U, regs_arm.GetPcAdjustment(0x500U, invalid_elf));
+  EXPECT_EQ(2U, regs_arm.GetPcAdjustment(0x511U, invalid_elf));
 
   regs_arm64.set_pc(0x1600);
   EXPECT_EQ(0x600U, invalid_elf->GetRelPc(regs_arm64.pc(), &map_info));
-  EXPECT_EQ(0U, regs_arm64.GetPcAdjustment(0x600U, invalid_elf));
+  EXPECT_EQ(4U, regs_arm64.GetPcAdjustment(0x600U, invalid_elf));
 
   regs_x86.set_pc(0x1700);
   EXPECT_EQ(0x700U, invalid_elf->GetRelPc(regs_x86.pc(), &map_info));
-  EXPECT_EQ(0U, regs_x86.GetPcAdjustment(0x700U, invalid_elf));
+  EXPECT_EQ(1U, regs_x86.GetPcAdjustment(0x700U, invalid_elf));
 
   regs_x86_64.set_pc(0x1800);
   EXPECT_EQ(0x800U, invalid_elf->GetRelPc(regs_x86_64.pc(), &map_info));
-  EXPECT_EQ(0U, regs_x86_64.GetPcAdjustment(0x800U, invalid_elf));
+  EXPECT_EQ(1U, regs_x86_64.GetPcAdjustment(0x800U, invalid_elf));
 
   regs_mips.set_pc(0x1900);
   EXPECT_EQ(0x900U, invalid_elf->GetRelPc(regs_mips.pc(), &map_info));
-  EXPECT_EQ(0U, regs_mips.GetPcAdjustment(0x900U, invalid_elf));
+  EXPECT_EQ(8U, regs_mips.GetPcAdjustment(0x900U, invalid_elf));
 
   regs_mips64.set_pc(0x1a00);
   EXPECT_EQ(0xa00U, invalid_elf->GetRelPc(regs_mips64.pc(), &map_info));
-  EXPECT_EQ(0U, regs_mips64.GetPcAdjustment(0xa00U, invalid_elf));
+  EXPECT_EQ(8U, regs_mips64.GetPcAdjustment(0xa00U, invalid_elf));
 }
 
 TEST_F(RegsTest, arm_verify_sp_pc) {