From 97483928ccc8b979466f504e08ecb67ed0f6f711 Mon Sep 17 00:00:00 2001
From: Tobias Sargeant <tobiasjs@google.com>
Date: Tue, 21 Mar 2017 22:43:34 +0000
Subject: Don't generate minidump if crash thread doesn't ref principal
 mapping.

If the crashing thread doesn't reference the principal mapping we can
assume that not only is that thread uninteresting from a debugging
perspective, the whole crash is uninteresting. In that case we should
not generate a minidump at all.

BUG=703599

Change-Id: Ia25bbb8adb79d04dcaf3992c3d2474f3b9b1f796
Reviewed-on: https://chromium-review.googlesource.com/457338
Reviewed-by: Robert Sesek <rsesek@chromium.org>
---
 .../linux/minidump_writer/minidump_writer.cc       | 56 +++++++++++++++++++---
 1 file changed, 49 insertions(+), 7 deletions(-)

(limited to 'src/client/linux/minidump_writer/minidump_writer.cc')

diff --git a/src/client/linux/minidump_writer/minidump_writer.cc b/src/client/linux/minidump_writer/minidump_writer.cc
index 5c2a339e..d11ba6e5 100644
--- a/src/client/linux/minidump_writer/minidump_writer.cc
+++ b/src/client/linux/minidump_writer/minidump_writer.cc
@@ -147,6 +147,7 @@ class MinidumpWriter {
         skip_stacks_if_mapping_unreferenced_(
             skip_stacks_if_mapping_unreferenced),
         principal_mapping_address_(principal_mapping_address),
+        principal_mapping_(nullptr),
     sanitize_stacks_(sanitize_stacks) {
     // Assert there should be either a valid fd or a valid path, not both.
     assert(fd_ != -1 || minidump_path);
@@ -157,12 +158,22 @@ class MinidumpWriter {
     if (!dumper_->Init())
       return false;
 
+    if (!dumper_->ThreadsSuspend() || !dumper_->LateInit())
+      return false;
+
+    if (skip_stacks_if_mapping_unreferenced_) {
+      principal_mapping_ =
+          dumper_->FindMappingNoBias(principal_mapping_address_);
+      if (!CrashingThreadReferencesPrincipalMapping())
+        return false;
+    }
+
     if (fd_ != -1)
       minidump_writer_.SetFile(fd_);
     else if (!minidump_writer_.Open(path_))
       return false;
 
-    return dumper_->ThreadsSuspend() && dumper_->LateInit();
+    return true;
   }
 
   ~MinidumpWriter() {
@@ -173,6 +184,38 @@ class MinidumpWriter {
     dumper_->ThreadsResume();
   }
 
+  bool CrashingThreadReferencesPrincipalMapping() {
+    if (!ucontext_ || !principal_mapping_)
+      return false;
+
+    const uintptr_t low_addr =
+        principal_mapping_->system_mapping_info.start_addr;
+    const uintptr_t high_addr =
+        principal_mapping_->system_mapping_info.end_addr;
+
+    const uintptr_t stack_pointer = UContextReader::GetStackPointer(ucontext_);
+    const uintptr_t pc = UContextReader::GetInstructionPointer(ucontext_);
+
+    if (pc >= low_addr && pc < high_addr)
+      return true;
+
+    uint8_t* stack_copy;
+    const void* stack;
+    size_t stack_len;
+
+    if (!dumper_->GetStackInfo(&stack, &stack_len, stack_pointer))
+      return false;
+
+    stack_copy = reinterpret_cast<uint8_t*>(Alloc(stack_len));
+    dumper_->CopyFromProcess(stack_copy, GetCrashThread(), stack, stack_len);
+
+    uintptr_t stack_pointer_offset =
+        stack_pointer - reinterpret_cast<uintptr_t>(stack);
+
+    return dumper_->StackHasPointerToMapping(
+        stack_copy, stack_len, stack_pointer_offset, *principal_mapping_);
+  }
+
   bool Dump() {
     // A minidump file contains a number of tagged streams. This is the number
     // of stream which we write.
@@ -302,17 +345,15 @@ class MinidumpWriter {
       uintptr_t stack_pointer_offset =
           stack_pointer - reinterpret_cast<uintptr_t>(stack);
       if (skip_stacks_if_mapping_unreferenced_) {
-        const MappingInfo* principal_mapping =
-            dumper_->FindMappingNoBias(principal_mapping_address_);
-        if (!principal_mapping) {
+        if (!principal_mapping_) {
           return true;
         }
-        uintptr_t low_addr = principal_mapping->system_mapping_info.start_addr;
-        uintptr_t high_addr = principal_mapping->system_mapping_info.end_addr;
+        uintptr_t low_addr = principal_mapping_->system_mapping_info.start_addr;
+        uintptr_t high_addr = principal_mapping_->system_mapping_info.end_addr;
         if ((pc < low_addr || pc > high_addr) &&
             !dumper_->StackHasPointerToMapping(*stack_copy, stack_len,
                                                stack_pointer_offset,
-                                               *principal_mapping)) {
+                                               *principal_mapping_)) {
           return true;
         }
       }
@@ -1303,6 +1344,7 @@ class MinidumpWriter {
   // mapping containing principal_mapping_address_.
   bool skip_stacks_if_mapping_unreferenced_;
   uintptr_t principal_mapping_address_;
+  const MappingInfo* principal_mapping_;
   // If true, apply stack sanitization to stored stack data.
   bool sanitize_stacks_;
 };
-- 
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