From f84a0134072cfd50496a98b125f7290484a8f51c Mon Sep 17 00:00:00 2001
From: Jamie Liu <jamieliu@google.com>
Date: Fri, 10 May 2024 15:35:45 -0700
Subject: [PATCH] procfs: add topology-related x86 cpuinfo fields

Linux prints these fields when the kernel is built with support for multiple
processors/cores (CONFIG_SMP), in
arch/x86/kernel/cpu/proc.c:show_cpuinfo_core().

Fixes #10205

PiperOrigin-RevId: 632621375
---
 pkg/cpuid/cpuid_amd64.go        | 8 +++++++-
 pkg/cpuid/cpuid_arm64.go        | 2 +-
 pkg/sentry/fsimpl/proc/tasks.go | 2 +-
 test/syscalls/linux/proc.cc     | 6 ++++++
 4 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/pkg/cpuid/cpuid_amd64.go b/pkg/cpuid/cpuid_amd64.go
index 178428d44..f444210cd 100644
--- a/pkg/cpuid/cpuid_amd64.go
+++ b/pkg/cpuid/cpuid_amd64.go
@@ -309,7 +309,7 @@ func (fs FeatureSet) HasFeature(feature Feature) bool {
 // WriteCPUInfoTo is to generate a section of one cpu in /proc/cpuinfo. This is
 // a minimal /proc/cpuinfo, it is missing some fields like "microcode" that are
 // not always printed in Linux. The bogomips field is simply made up.
-func (fs FeatureSet) WriteCPUInfoTo(cpu uint, w io.Writer) {
+func (fs FeatureSet) WriteCPUInfoTo(cpu, numCPU uint, w io.Writer) {
 	// Avoid many redundant calls here, since this can occasionally appear
 	// in the hot path. Read all basic information up front, see above.
 	ax, _, _, _ := fs.query(featureInfo)
@@ -322,6 +322,12 @@ func (fs FeatureSet) WriteCPUInfoTo(cpu uint, w io.Writer) {
 	fmt.Fprintf(w, "model name\t: %s\n", "unknown") // Unknown for now.
 	fmt.Fprintf(w, "stepping\t: %s\n", "unknown")   // Unknown for now.
 	fmt.Fprintf(w, "cpu MHz\t\t: %.3f\n", cpuFreqMHz)
+	fmt.Fprintf(w, "physical id\t: 0\n") // Pretend all CPUs are in the same socket.
+	fmt.Fprintf(w, "siblings\t: %d\n", numCPU)
+	fmt.Fprintf(w, "core id\t\t: %d\n", cpu)
+	fmt.Fprintf(w, "cpu cores\t: %d\n", numCPU) // Pretend each CPU is a distinct core (rather than a hyperthread).
+	fmt.Fprintf(w, "apicid\t\t: %d\n", cpu)
+	fmt.Fprintf(w, "initial apicid\t: %d\n", cpu)
 	fmt.Fprintf(w, "fpu\t\t: yes\n")
 	fmt.Fprintf(w, "fpu_exception\t: yes\n")
 	fmt.Fprintf(w, "cpuid level\t: %d\n", uint32(xSaveInfo)) // Same as ax in vendorID.
diff --git a/pkg/cpuid/cpuid_arm64.go b/pkg/cpuid/cpuid_arm64.go
index 7a22e98b3..964f33acb 100644
--- a/pkg/cpuid/cpuid_arm64.go
+++ b/pkg/cpuid/cpuid_arm64.go
@@ -92,7 +92,7 @@ func (fs FeatureSet) HasFeature(feature Feature) bool {
 
 // WriteCPUInfoTo is to generate a section of one cpu in /proc/cpuinfo. This is
 // a minimal /proc/cpuinfo, and the bogomips field is simply made up.
-func (fs FeatureSet) WriteCPUInfoTo(cpu uint, w io.Writer) {
+func (fs FeatureSet) WriteCPUInfoTo(cpu, numCPU uint, w io.Writer) {
 	fmt.Fprintf(w, "processor\t: %d\n", cpu)
 	fmt.Fprintf(w, "BogoMIPS\t: %.02f\n", fs.cpuFreqMHz) // It's bogus anyway.
 	fmt.Fprintf(w, "Features\t\t: %s\n", fs.FlagString())
diff --git a/pkg/sentry/fsimpl/proc/tasks.go b/pkg/sentry/fsimpl/proc/tasks.go
index b3239f8bd..36cc34d65 100644
--- a/pkg/sentry/fsimpl/proc/tasks.go
+++ b/pkg/sentry/fsimpl/proc/tasks.go
@@ -266,7 +266,7 @@ func cpuInfoData(k *kernel.Kernel) string {
 	features := k.FeatureSet()
 	var buf bytes.Buffer
 	for i, max := uint(0), k.ApplicationCores(); i < max; i++ {
-		features.WriteCPUInfoTo(i, &buf)
+		features.WriteCPUInfoTo(i, max, &buf)
 	}
 	return buf.String()
 }
diff --git a/test/syscalls/linux/proc.cc b/test/syscalls/linux/proc.cc
index 59ffe0a4c..cf77088df 100644
--- a/test/syscalls/linux/proc.cc
+++ b/test/syscalls/linux/proc.cc
@@ -131,6 +131,12 @@ static const char* required_fields[] = {
     "model name",
     "stepping",
     "cpu MHz",
+    "physical id",
+    "siblings",
+    "core id",
+    "cpu cores",
+    "apicid\t\t:",
+    "initial apicid",
     "fpu\t\t:",
     "fpu_exception",
     "cpuid level",