From 67649c61853108eb0c29703f6ff0db42e9d69f10 Mon Sep 17 00:00:00 2001
From: Andrew Ermakovich <andrew@resilio.com>
Date: Fri, 21 Apr 2017 18:41:24 +0300
Subject: [PATCH] Fixing breakpad on old linux kernel

Try to read the trace's registers by PTRACE_GETREGS if kernel doesn't support PTRACE_GETREGSET.

Bug:

Change-Id: I881f3a868789747ca217f22a93370c6914881f9a
Reviewed-on: https://chromium-review.googlesource.com/484479
Reviewed-by: Mike Frysinger <vapier@chromium.org>
---
 .../minidump_writer/linux_ptrace_dumper.cc    | 73 +++++++++++--------
 .../minidump_writer/linux_ptrace_dumper.h     |  9 +++
 2 files changed, 53 insertions(+), 29 deletions(-)

diff --git a/src/client/linux/minidump_writer/linux_ptrace_dumper.cc b/src/client/linux/minidump_writer/linux_ptrace_dumper.cc
index 30b8f3dd..f181bf92 100644
--- a/src/client/linux/minidump_writer/linux_ptrace_dumper.cc
+++ b/src/client/linux/minidump_writer/linux_ptrace_dumper.cc
@@ -149,6 +149,46 @@ bool LinuxPtraceDumper::CopyFromProcess(void* dest, pid_t child,
   return true;
 }
 
+bool LinuxPtraceDumper::ReadRegisterSet(ThreadInfo* info, pid_t tid)
+{
+#ifdef PTRACE_GETREGSET
+  struct iovec io;
+  info->GetGeneralPurposeRegisters(&io.iov_base, &io.iov_len);
+  if (sys_ptrace(PTRACE_GETREGSET, tid, (void*)NT_PRSTATUS, (void*)&io) == -1) {
+    return false;
+  }
+
+  info->GetFloatingPointRegisters(&io.iov_base, &io.iov_len);
+  if (sys_ptrace(PTRACE_GETREGSET, tid, (void*)NT_FPREGSET, (void*)&io) == -1) {
+    return false;
+  }
+  return true;
+#else
+  return false;
+#endif
+}
+
+bool LinuxPtraceDumper::ReadRegisters(ThreadInfo* info, pid_t tid) {
+  void* gp_addr;
+  info->GetGeneralPurposeRegisters(&gp_addr, NULL);
+  if (sys_ptrace(PTRACE_GETREGS, tid, NULL, gp_addr) == -1) {
+    return false;
+  }
+
+#if !(defined(__ANDROID__) && defined(__ARM_EABI__))
+  // When running an arm build on an arm64 device, attempting to get the
+  // floating point registers fails. On Android, the floating point registers
+  // aren't written to the cpu context anyway, so just don't get them here.
+  // See http://crbug.com/508324
+  void* fp_addr;
+  info->GetFloatingPointRegisters(&fp_addr, NULL);
+  if (sys_ptrace(PTRACE_GETFPREGS, tid, NULL, fp_addr) == -1) {
+    return false;
+  }
+#endif
+  return true;
+}
+
 // Read thread info from /proc/$pid/status.
 // Fill out the |tgid|, |ppid| and |pid| members of |info|. If unavailable,
 // these members are set to -1. Returns true iff all three members are
@@ -188,37 +228,12 @@ bool LinuxPtraceDumper::GetThreadInfoByIndex(size_t index, ThreadInfo* info) {
   if (info->ppid == -1 || info->tgid == -1)
     return false;
 
-#ifdef PTRACE_GETREGSET
-  struct iovec io;
-  info->GetGeneralPurposeRegisters(&io.iov_base, &io.iov_len);
-  if (sys_ptrace(PTRACE_GETREGSET, tid, (void*)NT_PRSTATUS, (void*)&io) == -1) {
-    return false;
+  if (!ReadRegisterSet(info, tid)) {
+    if (!ReadRegisters(info, tid)) {
+      return false;
+    }
   }
 
-  info->GetFloatingPointRegisters(&io.iov_base, &io.iov_len);
-  if (sys_ptrace(PTRACE_GETREGSET, tid, (void*)NT_FPREGSET, (void*)&io) == -1) {
-    return false;
-  }
-#else  // PTRACE_GETREGSET
-  void* gp_addr;
-  info->GetGeneralPurposeRegisters(&gp_addr, NULL);
-  if (sys_ptrace(PTRACE_GETREGS, tid, NULL, gp_addr) == -1) {
-    return false;
-  }
-
-#if !(defined(__ANDROID__) && defined(__ARM_EABI__))
-  // When running an arm build on an arm64 device, attempting to get the
-  // floating point registers fails. On Android, the floating point registers
-  // aren't written to the cpu context anyway, so just don't get them here.
-  // See http://crbug.com/508324
-  void* fp_addr;
-  info->GetFloatingPointRegisters(&fp_addr, NULL);
-  if (sys_ptrace(PTRACE_GETFPREGS, tid, NULL, fp_addr) == -1) {
-    return false;
-  }
-#endif
-#endif  // PTRACE_GETREGSET
-
 #if defined(__i386)
 #if !defined(bit_FXSAVE)  // e.g. Clang
 #define bit_FXSAVE bit_FXSR
diff --git a/src/client/linux/minidump_writer/linux_ptrace_dumper.h b/src/client/linux/minidump_writer/linux_ptrace_dumper.h
index 2ce834b0..cee58178 100644
--- a/src/client/linux/minidump_writer/linux_ptrace_dumper.h
+++ b/src/client/linux/minidump_writer/linux_ptrace_dumper.h
@@ -85,6 +85,15 @@ class LinuxPtraceDumper : public LinuxDumper {
  private:
   // Set to true if all threads of the crashed process are suspended.
   bool threads_suspended_;
+
+  // Read the tracee's registers on kernel with PTRACE_GETREGSET support.
+  // Returns false if PTRACE_GETREGSET is not defined.
+  // Returns true on success.
+  bool ReadRegisterSet(ThreadInfo* info, pid_t tid);
+
+  // Read the tracee's registers on kernel with PTRACE_GETREGS support.
+  // Returns true on success.
+  bool ReadRegisters(ThreadInfo* info, pid_t tid);
 };
 
 }  // namespace google_breakpad