From 9d9302bb020e24455412595ee516f123a58c3444 Mon Sep 17 00:00:00 2001
From: Scott Graham <scottmg@chromium.org>
Date: Wed, 30 Sep 2015 17:20:23 -0700
Subject: [PATCH] win: fix VirtualQueryEx on < win10

On Win10, VirtualQueryEx supports querying the x64 part of WOW64
processes. However, on lower OSs it errors past 2/3G. There's no direct
way to retrieve to maximum memory address for processes other than
yourself, but fortunately, VirtualQueryEx sets a distinct error code
when `lpAddress` exceeds the maximum accessible address, so we can just
terminate successfully in that case.

R=mark@chromium.org
BUG=crashpad:20, crashpad:46

Review URL: https://codereview.chromium.org/1376353002 .
---
 util/win/process_info.cc | 22 ++++++++++++++--------
 util/win/process_info.h  |  4 +++-
 2 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/util/win/process_info.cc b/util/win/process_info.cc
index ed5262c7..6d70fa0d 100644
--- a/util/win/process_info.cc
+++ b/util/win/process_info.cc
@@ -16,6 +16,8 @@
 
 #include <winternl.h>
 
+#include <limits>
+
 #include "base/logging.h"
 #include "base/strings/stringprintf.h"
 #include "build/build_config.h"
@@ -253,15 +255,17 @@ bool ReadProcessData(HANDLE process,
   return true;
 }
 
-bool ReadMemoryInfo(HANDLE process, ProcessInfo* process_info) {
+bool ReadMemoryInfo(HANDLE process, bool is_64_bit, ProcessInfo* process_info) {
   DCHECK(process_info->memory_info_.empty());
 
-  SYSTEM_INFO system_info;
-  GetSystemInfo(&system_info);
-  const WinVMAddress min_address =
-      reinterpret_cast<WinVMAddress>(system_info.lpMinimumApplicationAddress);
-  const WinVMAddress max_address =
-      reinterpret_cast<WinVMAddress>(system_info.lpMaximumApplicationAddress);
+  const WinVMAddress min_address = 0;
+  // We can't use GetSystemInfo() to get the address space range for another
+  // process. VirtualQueryEx() will fail with ERROR_INVALID_PARAMETER if the
+  // address is above the highest memory address accessible to the process, so
+  // we just probe the entire potential range (2^32 for x86, or 2^64 for x64).
+  const WinVMAddress max_address = is_64_bit
+                                       ? std::numeric_limits<uint64_t>::max()
+                                       : std::numeric_limits<uint32_t>::max();
   MEMORY_BASIC_INFORMATION memory_basic_information;
   for (WinVMAddress address = min_address; address <= max_address;
        address += memory_basic_information.RegionSize) {
@@ -270,6 +274,8 @@ bool ReadMemoryInfo(HANDLE process, ProcessInfo* process_info) {
                                    &memory_basic_information,
                                    sizeof(memory_basic_information));
     if (result == 0) {
+      if (GetLastError() == ERROR_INVALID_PARAMETER)
+        break;
       PLOG(ERROR) << "VirtualQueryEx";
       return false;
     }
@@ -367,7 +373,7 @@ bool ProcessInfo::Initialize(HANDLE process) {
     return false;
   }
 
-  if (!ReadMemoryInfo(process, this)) {
+  if (!ReadMemoryInfo(process, is_64_bit_, this)) {
     LOG(ERROR) << "ReadMemoryInfo failed";
     return false;
   }
diff --git a/util/win/process_info.h b/util/win/process_info.h
index 5af28bd7..c8bac702 100644
--- a/util/win/process_info.h
+++ b/util/win/process_info.h
@@ -141,7 +141,9 @@ class ProcessInfo {
                               WinVMAddress peb_address_vmaddr,
                               ProcessInfo* process_info);
 
-  friend bool ReadMemoryInfo(HANDLE process, ProcessInfo* process_info);
+  friend bool ReadMemoryInfo(HANDLE process,
+                             bool is_64_bit,
+                             ProcessInfo* process_info);
 
   pid_t process_id_;
   pid_t inherited_from_process_id_;