From 98aaf4cf086e2492796b11116e69e0ff01093663 Mon Sep 17 00:00:00 2001
From: Christopher Ferris <cferris@google.com>
Date: Fri, 3 May 2019 11:13:17 -0700
Subject: [PATCH] Ignore memory from elf on /memfd:

In ART, some of the maps are /memfd:/jit-cache and it triggers the warning
about unreadable elf files. Do not set the elf from memory not file
flag in this case.

Bug: 131909548

Test: New unit tests pass.
Test: No warnings dumping stacks with this change done.
Change-Id: Ifba5e65da609525ded75430da173c614f6e4801e
---
 libunwindstack/Unwinder.cpp           |  3 ++-
 libunwindstack/tests/UnwinderTest.cpp | 36 +++++++++++++++++++++++++++
 2 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/libunwindstack/Unwinder.cpp b/libunwindstack/Unwinder.cpp
index 26626b5cd..37323dc16 100644
--- a/libunwindstack/Unwinder.cpp
+++ b/libunwindstack/Unwinder.cpp
@@ -25,6 +25,7 @@
 #include <algorithm>
 
 #include <android-base/stringprintf.h>
+#include <android-base/strings.h>
 
 #include <demangle.h>
 
@@ -168,7 +169,7 @@ void Unwinder::Unwind(const std::vector<std::string>* initial_map_names_to_skip,
       // If this elf is memory backed, and there is a valid file, then set
       // an indicator that we couldn't open the file.
       if (!elf_from_memory_not_file_ && map_info->memory_backed_elf && !map_info->name.empty() &&
-          map_info->name[0] != '[') {
+          map_info->name[0] != '[' && !android::base::StartsWith(map_info->name, "/memfd:")) {
         elf_from_memory_not_file_ = true;
       }
       step_pc = regs_->pc();
diff --git a/libunwindstack/tests/UnwinderTest.cpp b/libunwindstack/tests/UnwinderTest.cpp
index f6350216f..30e57a142 100644
--- a/libunwindstack/tests/UnwinderTest.cpp
+++ b/libunwindstack/tests/UnwinderTest.cpp
@@ -126,6 +126,12 @@ class UnwinderTest : public ::testing::Test {
     const auto& info5 = *--maps_->end();
     info5->memory_backed_elf = true;
 
+    elf = new ElfFake(new MemoryFake);
+    elf->FakeSetInterface(new ElfInterfaceFake(nullptr));
+    AddMapInfo(0xc3000, 0xc4000, 0, PROT_READ | PROT_WRITE | PROT_EXEC, "/memfd:/jit-cache", elf);
+    const auto& info6 = *--maps_->end();
+    info6->memory_backed_elf = true;
+
     process_memory_.reset(new MemoryFake);
   }
 
@@ -1234,6 +1240,36 @@ TEST_F(UnwinderTest, elf_from_memory_but_empty_filename) {
   EXPECT_EQ(PROT_READ | PROT_WRITE | PROT_EXEC, frame->map_flags);
 }
 
+TEST_F(UnwinderTest, elf_from_memory_but_from_memfd) {
+  ElfInterfaceFake::FakePushFunctionData(FunctionData("Frame0", 0));
+
+  regs_.set_pc(0xc3050);
+  regs_.set_sp(0x10000);
+  ElfInterfaceFake::FakePushStepData(StepData(0, 0, true));
+
+  Unwinder unwinder(64, maps_.get(), &regs_, process_memory_);
+  unwinder.Unwind();
+  EXPECT_EQ(ERROR_NONE, unwinder.LastErrorCode());
+  EXPECT_FALSE(unwinder.elf_from_memory_not_file());
+
+  ASSERT_EQ(1U, unwinder.NumFrames());
+
+  auto* frame = &unwinder.frames()[0];
+  EXPECT_EQ(0U, frame->num);
+  EXPECT_EQ(0x50U, frame->rel_pc);
+  EXPECT_EQ(0xc3050U, frame->pc);
+  EXPECT_EQ(0x10000U, frame->sp);
+  EXPECT_EQ("Frame0", frame->function_name);
+  EXPECT_EQ(0U, frame->function_offset);
+  EXPECT_EQ("/memfd:/jit-cache", frame->map_name);
+  EXPECT_EQ(0U, frame->map_elf_start_offset);
+  EXPECT_EQ(0U, frame->map_exact_offset);
+  EXPECT_EQ(0xc3000U, frame->map_start);
+  EXPECT_EQ(0xc4000U, frame->map_end);
+  EXPECT_EQ(0U, frame->map_load_bias);
+  EXPECT_EQ(PROT_READ | PROT_WRITE | PROT_EXEC, frame->map_flags);
+}
+
 // Verify format frame code.
 TEST_F(UnwinderTest, format_frame) {
   RegsFake regs_arm(10);