From a6c4e84ac88ea3030e0e3a9921fa8473b3e4f41a Mon Sep 17 00:00:00 2001
From: Max Wipfli <mail@maxwipfli.ch>
Date: Sun, 18 Jul 2021 15:03:34 +0200
Subject: [PATCH] Kernel: Add .profile extension to perfcore files

This adds a ".profile" extension to perfcore files written by the
Kernel. Also, the process name is now visible in the perfcore filename.

Furthermore, this patch adds error handling for the case where the
filename generated by the Kernel is already taken. In that case, a digit
will be added to the filename (before the extension).

This also adds some more error logging to dump_perfcore().
---
 Kernel/Process.cpp | 29 ++++++++++++++++++++++-------
 1 file changed, 22 insertions(+), 7 deletions(-)

diff --git a/Kernel/Process.cpp b/Kernel/Process.cpp
index 7d667a729c..57686035ce 100644
--- a/Kernel/Process.cpp
+++ b/Kernel/Process.cpp
@@ -533,21 +533,36 @@ bool Process::dump_perfcore()
     VERIFY(is_dumpable());
     VERIFY(m_perf_event_buffer);
     dbgln("Generating perfcore for pid: {}", pid().value());
-    auto description_or_error = VirtualFileSystem::the().open(String::formatted("perfcore.{}", pid().value()), O_CREAT | O_EXCL, 0400, current_directory(), UidAndGid { uid(), gid() });
-    if (description_or_error.is_error())
+
+    // Try to generate a filename which isn't already used.
+    auto base_filename = String::formatted("{}_{}", name(), pid().value());
+    auto description_or_error = VirtualFileSystem::the().open(String::formatted("{}.profile", base_filename), O_CREAT | O_EXCL, 0400, current_directory(), UidAndGid { uid(), gid() });
+    for (size_t attempt = 1; attempt < 10 && description_or_error.is_error(); ++attempt)
+        description_or_error = VirtualFileSystem::the().open(String::formatted("{}.{}.profile", base_filename, attempt), O_CREAT | O_EXCL, 0400, current_directory(), UidAndGid { uid(), gid() });
+    if (description_or_error.is_error()) {
+        dbgln("Failed to generate perfcore for pid {}: Could not generate filename for the perfcore file.", pid().value());
         return false;
-    auto& description = description_or_error.value();
+    }
+
+    auto& description = *description_or_error.value();
     KBufferBuilder builder;
-    if (!m_perf_event_buffer->to_json(builder))
+    if (!m_perf_event_buffer->to_json(builder)) {
+        dbgln("Failed to generate perfcore for pid {}: Could not serialize performance events to JSON.", pid().value());
         return false;
+    }
 
     auto json = builder.build();
-    if (!json)
+    if (!json) {
+        dbgln("Failed to generate perfcore for pid {}: Could not allocate buffer.", pid().value());
         return false;
+    }
     auto json_buffer = UserOrKernelBuffer::for_kernel_buffer(json->data());
-    if (description->write(json_buffer, json->size()).is_error())
+    if (description.write(json_buffer, json->size()).is_error()) {
         return false;
-    dbgln("Wrote perfcore to {}", description->absolute_path());
+        dbgln("Failed to generate perfcore for pid {}: Cound not write to perfcore file.", pid().value());
+    }
+
+    dbgln("Wrote perfcore for pid {} to {}", pid().value(), description.absolute_path());
     return true;
 }