From 63daf69e1783f04f741398b678540e6723675264 Mon Sep 17 00:00:00 2001
From: Ruihan Li <lrh2000@pku.edu.cn>
Date: Thu, 22 May 2025 20:32:23 +0800
Subject: [PATCH] Fix incorrect types in `sys_getcpu`

---
 kernel/src/syscall/getcpu.rs | 29 ++++++++++++++++------------
 test/apps/getcpu/getcpu.c    | 37 ++++++++++++++++++++----------------
 test/apps/scripts/process.sh |  1 +
 3 files changed, 39 insertions(+), 28 deletions(-)

diff --git a/kernel/src/syscall/getcpu.rs b/kernel/src/syscall/getcpu.rs
index da285391..fd499d1b 100644
--- a/kernel/src/syscall/getcpu.rs
+++ b/kernel/src/syscall/getcpu.rs
@@ -1,27 +1,32 @@
 // SPDX-License-Identifier: MPL-2.0
 
-use ostd::{cpu::PinCurrentCpu, task::disable_preempt};
+use ostd::cpu::CpuId;
 
 use super::SyscallReturn;
 use crate::prelude::*;
 
 pub fn sys_getcpu(cpu: Vaddr, node: Vaddr, _tcache: Vaddr, ctx: &Context) -> Result<SyscallReturn> {
-    // The third argument tcache is unused after Linux 2.6.24 so we ignore it
-    let preempt_guard = disable_preempt();
-    let cpuid = preempt_guard.current_cpu();
-    drop(preempt_guard);
+    // The third argument `tcache` is unused since Linux 2.6.24, so we ignore it.
+
+    // The system call itself is inherently racy, so using `current_racy` here should be fine.
+    let current_cpu = CpuId::current_racy().as_usize() as u32;
+    // TODO: Support NUMA.
+    let current_node = 0u32;
+
     debug!(
-        "getcpu: cpuid = {}, total_cpus = {}",
-        cpuid.as_usize(),
-        ostd::cpu::num_cpus()
+        "[sys_getcpu]: cpu = {} (total {}), node = {}",
+        current_cpu,
+        ostd::cpu::num_cpus(),
+        current_node,
     );
-    // Since cpu and node can be NULL, we need to check them before writing
+
+    // `cpu` and `node` can be NULL, so we need to check before writing.
     if cpu != 0 {
-        ctx.user_space()
-            .write_val::<usize>(cpu, &cpuid.as_usize())?;
+        ctx.user_space().write_val(cpu, &current_cpu)?;
     }
     if node != 0 {
-        ctx.user_space().write_val::<usize>(node, &0)?; // TODO: NUMA is not supported
+        ctx.user_space().write_val(node, &current_node)?;
     }
+
     Ok(SyscallReturn::Return(0))
 }
diff --git a/test/apps/getcpu/getcpu.c b/test/apps/getcpu/getcpu.c
index 0944f59b..86f9c458 100644
--- a/test/apps/getcpu/getcpu.c
+++ b/test/apps/getcpu/getcpu.c
@@ -1,24 +1,29 @@
 // SPDX-License-Identifier: MPL-2.0
 
-#define _GNU_SOURCE
-#include <stdio.h>
-#include <stdlib.h>
-#include <unistd.h>
+#include "../network/test.h"
+
 #include <sys/syscall.h>
+#include <unistd.h>
 
-int main()
+FN_TEST(getcpu)
 {
-	unsigned int cpu, node;
+	struct int_pair {
+		unsigned int first;
+		unsigned int second;
+	};
 
-	// Directly test the getcpu syscall because glibc's getcpu() may not
-	// use the getcpu syscall to retrieve CPU info
-	long ret = syscall(SYS_getcpu, &cpu, &node, NULL);
-	if (ret != 0) {
-		perror("syscall getcpu");
-		exit(EXIT_FAILURE);
-	}
+	struct int_pair cpu = { .first = 0xdeadbeef, .second = 0xbeefdead };
+	struct int_pair node = { .first = 0xbeefdead, .second = 0xdeadbeef };
 
-	printf("getcpu syscall: cpu = %u, node = %u\n", cpu, node);
+	// Use `syscall()` here because `getcpu()` from glibc may not use
+	// the system call to retrieve CPU information.
+	TEST_SUCC(syscall(SYS_getcpu, NULL, NULL));
 
-	return 0;
-}
\ No newline at end of file
+	// Our CI has a maximum of 4 CPUs, and NUMA support is not yet
+	// available. Update these conditions if we have more than 4 CPUs
+	// or if NUMA support is added.
+	TEST_RES(syscall(SYS_getcpu, &cpu, &node),
+		 cpu.first < 4 && cpu.second == 0xbeefdead && node.first == 0 &&
+			 node.second == 0xdeadbeef);
+}
+END_TEST()
diff --git a/test/apps/scripts/process.sh b/test/apps/scripts/process.sh
index 1cb30771..235a18df 100755
--- a/test/apps/scripts/process.sh
+++ b/test/apps/scripts/process.sh
@@ -21,6 +21,7 @@ exit/exit_procfs
 eventfd2/eventfd2
 fork/fork
 fork_c/fork
+getcpu/getcpu
 getpid/getpid
 hello_pie/hello
 hello_world/hello_world