enable core dumps for WSLGd and its children (#280)

* enable core dumps for WSLGd and its children

* misc changes from feedbacks

* more from feedbacks

Co-authored-by: Hideyuki Nagase <[email protected]>

Author: hideyukn88

WSLGd/main.cpp

@@ -18,7 +18,12 @@ constexpr auto c_shareDocsDir = "/usr/share/doc";
 constexpr auto c_shareDocsMount = SHARE_PATH "/doc";
 constexpr auto c_x11RuntimeDir = SHARE_PATH "/.X11-unix";
 constexpr auto c_xdgRuntimeDir = SHARE_PATH "/runtime-dir";
-constexpr auto c_stdErrLogMount = SHARE_PATH "/stderr.log";
+constexpr auto c_stdErrLogFile = SHARE_PATH "/stderr.log";
+
+constexpr auto c_coreDir = SHARE_PATH "/dumps";
+constexpr auto c_corePatternDefault = "core.%e";
+constexpr auto c_corePatternFile = "/proc/sys/kernel/core_pattern";
+constexpr auto c_corePatternEnv = "WSL2_WSLG_CORE_PATTERN";
 
 constexpr auto c_sharedMemoryMountPoint = "/mnt/shared_memory";
 constexpr auto c_sharedMemoryMountPointEnv = "WSL2_SHARED_MEMORY_MOUNT_POINT";
@@ -79,9 +84,9 @@ try {
 
     // Open a file for logging errors and set it to stderr for WSLGd as well as any child process.
     {
-        wil::unique_fd fd_stdErrLog(open(c_stdErrLogMount, (O_RDWR | O_CREAT), (S_IRUSR | S_IRGRP | S_IROTH)));
-        if (fd_stdErrLog && (fd_stdErrLog.get() != STDERR_FILENO)) {
-            dup2(fd_stdErrLog.get(), STDERR_FILENO);
+        wil::unique_fd stdErrLogFd(open(c_stdErrLogFile, (O_RDWR | O_CREAT), (S_IRUSR | S_IRGRP | S_IROTH)));
+        if (stdErrLogFd && (stdErrLogFd.get() != STDERR_FILENO)) {
+            dup2(stdErrLogFd.get(), STDERR_FILENO);
         }
     }
 
@@ -186,6 +191,34 @@ try {
 
     SetupOptionalEnv();
 
+    // "ulimits -c unlimited" for core dumps.
+    struct rlimit limit;
+    limit.rlim_cur = RLIM_INFINITY;
+    limit.rlim_max = RLIM_INFINITY;
+    THROW_LAST_ERROR_IF(setrlimit(RLIMIT_CORE, &limit) < 0);
+
+    // create folder to store core files.
+    std::filesystem::create_directories(c_coreDir);
+    THROW_LAST_ERROR_IF(chmod(c_coreDir, 0777) < 0);
+
+    // update core_pattern.
+    {
+        wil::unique_file corePatternFile(fopen(c_corePatternFile, "w"));
+        if (corePatternFile.get()) {
+            // combine folder path and core pattern.
+            std::string corePatternFullPath(c_coreDir);
+            corePatternFullPath += "/";
+            auto corePattern = getenv(c_corePatternEnv);
+            if (corePattern) {
+                corePatternFullPath += corePattern;
+            } else {
+                corePatternFullPath += c_corePatternDefault; // set to default core_pattern.
+            }
+            // write to core_pattern file.
+            THROW_LAST_ERROR_IF(fprintf(corePatternFile.get(), "%s", corePatternFullPath.c_str()) < 0);
+        }
+    }
+
     // Set shared memory mount point to env when available.
     if (!is_shared_memory_mounted ||
         (setenv(c_sharedMemoryMountPointEnv, c_sharedMemoryMountPoint, true) < 0)) {

WSLGd/precomp.h

@@ -1,6 +1,8 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT license.
 #include <sys/capability.h>
+#include <sys/time.h>
+#include <sys/resource.h>
 #include <sys/prctl.h>
 #include <sys/mount.h>
 #include <sys/socket.h>