[Lldb-commits] [PATCH] D12138: On Linux, clear the signal mask of the launched inferior

[Yacine Belkadi via lldb-commits]

ybelkadi created this revision.
ybelkadi added reviewers: labath, ovyalov.
ybelkadi added a subscriber: lldb-commits.

Due to fork()/execve(), the launched inferior inherits the signal mask of its 
parent (lldb-server). But because lldb-server modifies its signal mask (It 
blocks SIGCHLD, for example), the inferior starts with some signals being 
initially blocked.

One consequence is that TestCallThatRestarts.ExprCommandThatRestartsTestCase 
(test/expression_command/call-restarts) fails because sigchld_handler() in 
lotta-signals.c is not called, due to the SIGCHLD signal being blocked.

To prevent the signal masking done by lldb-server from affecting the created 
inferior, the signal mask of the inferior is now cleared before the execve().

http://reviews.llvm.org/D12138

Files:
  source/Plugins/Process/Linux/NativeProcessLinux.cpp

Index: source/Plugins/Process/Linux/NativeProcessLinux.cpp
===================================================================
--- source/Plugins/Process/Linux/NativeProcessLinux.cpp
+++ source/Plugins/Process/Linux/NativeProcessLinux.cpp
@@ -554,7 +554,8 @@
         eDupStderrFailed,
         eChdirFailed,
         eExecFailed,
-        eSetGidFailed
+        eSetGidFailed,
+        eSetSigMaskFailed
     };
 
     // Child process.
@@ -629,6 +630,12 @@
             }
         }
 
+        // Clear the signal mask to prevent the child from being affected by
+        // any masking done by the parent.
+        sigset_t set;
+        if (sigemptyset(&set) != 0 || pthread_sigmask(SIG_SETMASK, &set, 
nullptr) != 0)
+            exit(eSetSigMaskFailed);
+
         // Execute.  We should never return...
         execve(argv[0],
                const_cast<char *const *>(argv),
@@ -686,6 +693,9 @@
             case eSetGidFailed:
                 error.SetErrorString("Child setgid failed.");
                 break;
+            case eSetSigMaskFailed:
+                error.SetErrorString("Child failed to set signal mask.");
+                break;
             default:
                 error.SetErrorString("Child returned unknown exit status.");
                 break;



Index: source/Plugins/Process/Linux/NativeProcessLinux.cpp
===================================================================
--- source/Plugins/Process/Linux/NativeProcessLinux.cpp
+++ source/Plugins/Process/Linux/NativeProcessLinux.cpp
@@ -554,7 +554,8 @@
         eDupStderrFailed,
         eChdirFailed,
         eExecFailed,
-        eSetGidFailed
+        eSetGidFailed,
+        eSetSigMaskFailed
     };
 
     // Child process.
@@ -629,6 +630,12 @@
             }
         }
 
+        // Clear the signal mask to prevent the child from being affected by
+        // any masking done by the parent.
+        sigset_t set;
+        if (sigemptyset(&set) != 0 || pthread_sigmask(SIG_SETMASK, &set, nullptr) != 0)
+            exit(eSetSigMaskFailed);
+
         // Execute.  We should never return...
         execve(argv[0],
                const_cast<char *const *>(argv),
@@ -686,6 +693,9 @@
             case eSetGidFailed:
                 error.SetErrorString("Child setgid failed.");
                 break;
+            case eSetSigMaskFailed:
+                error.SetErrorString("Child failed to set signal mask.");
+                break;
             default:
                 error.SetErrorString("Child returned unknown exit status.");
                 break;

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