From 549d3c92d6ee6a45176d26184b772e5233450706 Mon Sep 17 00:00:00 2001
From: Simon Zünd <szuend@chromium.org>
Date: Thu, 17 Sep 2026 05:36:52 +0000
Subject: [PATCH] [profiler] Reject negative --cpu-profiler-sampling-interval values

Change cpu_profiler_sampling_interval from DEFINE_INT to DEFINE_UINT so
negative values passed on the command line are rejected by
TryParseUnsigned and the default sampling interval (1000us) is preserved
instead of triggering a DCHECK in CpuProfile::CheckSubsample.

Also add a DCHECK_GE in CpuProfiler::set_sampling_interval to catch any
internal callers passing negative TimeDeltas.

TAG=agy
CONV=3fcd8b38-1a75-4f2a-b6f0-de9220fcc36a

Fixed: 561926123
Change-Id: If536c94c0f652f7931605ac8dfe2f3542762e4ea
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/8423899
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Simon Zünd <szuend@chromium.org>
Cr-Commit-Position: refs/heads/main@{#109923}
---
diff --git a/src/flags/flag-definitions.h b/src/flags/flag-definitions.h
index 6150a19..547b857 100644
--- a/src/flags/flag-definitions.h
+++ b/src/flags/flag-definitions.h
@@ -3190,8 +3190,8 @@
 DEFINE_IMPLICATION(parallel_compile_tasks_for_lazy, lazy_compile_dispatcher)
 
 // cpu-profiler.cc
-DEFINE_INT(cpu_profiler_sampling_interval, 1000,
-           "CPU profiler sampling interval in microseconds")
+DEFINE_UINT(cpu_profiler_sampling_interval, 1000,
+            "CPU profiler sampling interval in microseconds")
 
 // debugger
 DEFINE_BOOL(simulator_debugger, false,
diff --git a/src/profiler/cpu-profiler.cc b/src/profiler/cpu-profiler.cc
index 5c3955f..0204463 100644
--- a/src/profiler/cpu-profiler.cc
+++ b/src/profiler/cpu-profiler.cc
@@ -570,6 +570,7 @@
 
 void CpuProfiler::set_sampling_interval(base::TimeDelta value) {
   DCHECK(!is_profiling_);
+  DCHECK_GE(value, base::TimeDelta());
   base_sampling_interval_ = value;
 }
 
diff --git a/test/unittests/flags/flag-definitions-unittest.cc b/test/unittests/flags/flag-definitions-unittest.cc
index 2e06620..bfafc52 100644
--- a/test/unittests/flags/flag-definitions-unittest.cc
+++ b/test/unittests/flags/flag-definitions-unittest.cc
@@ -173,6 +173,14 @@
   CHECK_EQ(0, FlagList::SetFlagsFromString(str, strlen(str)));
 }
 
+TEST_F(FlagDefinitionsTest, RejectNegativeUnsignedFlagAndKeepDefault) {
+  int argc = 2;
+  const char* argv[] = {"Test", "--cpu-profiler-sampling-interval=-100"};
+  CHECK_EQ(1, FlagList::SetFlagsFromCommandLine(&argc, const_cast<char**>(argv),
+                                                true));
+  CHECK_EQ(1000u, v8_flags.cpu_profiler_sampling_interval.value());
+}
+
 TEST_F(FlagDefinitionsTest, FlagsRemoveIncomplete) {
   // Test that processed command line arguments are removed, even
   // if the list of arguments ends unexpectedly.

diff --git a/test/unittests/flags/flag-definitions-unittest.cc b/test/unittests/flags/flag-definitions-unittest.cc
index 2e06620..bfafc52 100644
--- a/test/unittests/flags/flag-definitions-unittest.cc
+++ b/test/unittests/flags/flag-definitions-unittest.cc
@@ -173,6 +173,14 @@
   CHECK_EQ(0, FlagList::SetFlagsFromString(str, strlen(str)));
 }
 
+TEST_F(FlagDefinitionsTest, RejectNegativeUnsignedFlagAndKeepDefault) {
+  int argc = 2;
+  const char* argv[] = {"Test", "--cpu-profiler-sampling-interval=-100"};
+  CHECK_EQ(1, FlagList::SetFlagsFromCommandLine(&argc, const_cast<char**>(argv),
+                                                true));
+  CHECK_EQ(1000u, v8_flags.cpu_profiler_sampling_interval.value());
+}
+
 TEST_F(FlagDefinitionsTest, FlagsRemoveIncomplete) {
   // Test that processed command line arguments are removed, even
   // if the list of arguments ends unexpectedly.