android-mainline/ANDROID-Revert-perf-core-Use-static_call-to-optimize-perf_guest_info_callbacks.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Will McVicker <willmcvicker@google.com>
Date: Wed, 2 Feb 2022 12:22:56 -0800
Subject: ANDROID: Revert "perf/core: Use static_call to optimize
 perf_guest_info_callbacks"

This reverts commit 87b940a0675e25261f022ac3e53e0dfff9cdb995. When
booting with the Pixel 6, I hit the below CFI failure. An email ([1])
was sent upstream to address this issue.

  Kernel panic - not syncing: CFI failure (target: __static_call_return0+0x0/0x8)
  CPU: 0 PID: 1625 Comm: batterystats-wo Tainted: G        W  OE     5.16.0-mainline #1$
  Hardware name: Raven EVT 1.1 (DT)$
  Call trace:$
   dump_backtrace+0xf0/0x130$
   show_stack+0x1c/0x2c$
   dump_stack_lvl+0x68/0x98$
   panic+0x168/0x420$
   __cfi_check_fail+0x58/0x5c$
   __cfi_slowpath_diag+0x150/0x1a4$
   perf_misc_flags+0x74/0xa4$
   perf_prepare_sample+0x50/0x44c$
   perf_event_output_forward+0x5c/0xcc$
   __perf_event_overflow+0xc8/0x188$
   perf_swevent_event+0x7c/0x10c$
   perf_tp_event+0x168/0x298$
   perf_trace_run_bpf_submit+0x8c/0xdc$
   perf_trace_sched_switch+0x180/0x1cc$
   __schedule+0x850/0x924$
   schedule+0x98/0xe0$
   binder_wait_for_work+0x158/0x368$
   binder_thread_read+0x278/0x243c$
   binder_ioctl_write_read+0x120/0x45c$
   binder_ioctl+0x1ac/0xc34$
   __arm64_sys_ioctl+0xa8/0x118$
   invoke_syscall+0x64/0x178$
   el0_svc_common+0x8c/0x100$
   do_el0_svc+0x28/0xa0$
   el0_svc+0x24/0x84$
   el0t_64_sync_handler+0x88/0xec$
   el0t_64_sync+0x1b4/0x1b8$

[1] https://lore.kernel.org/all/YfrQzoIWyv9lNljh@google.com/

Bug: 217583980
Signed-off-by: Will McVicker <willmcvicker@google.com>
Change-Id: I2951676ca4cce5e55461a71a670b35f9af41ba4e
Signed-off-by: Lee Jones <joneslee@google.com>
---
 include/linux/perf_event.h | 34 ++++++++++++++++++++++++++--------
 kernel/events/core.c       | 15 ---------------
 2 files changed, 26 insertions(+), 23 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1361,22 +1361,40 @@ extern void perf_event_bpf_event(struct bpf_prog *prog,
 
 #ifdef CONFIG_GUEST_PERF_EVENTS
 extern struct perf_guest_info_callbacks __rcu *perf_guest_cbs;
-
-DECLARE_STATIC_CALL(__perf_guest_state, *perf_guest_cbs->state);
-DECLARE_STATIC_CALL(__perf_guest_get_ip, *perf_guest_cbs->get_ip);
-DECLARE_STATIC_CALL(__perf_guest_handle_intel_pt_intr, *perf_guest_cbs->handle_intel_pt_intr);
-
+static inline struct perf_guest_info_callbacks *perf_get_guest_cbs(void)
+{
+	/*
+	 * Callbacks are RCU-protected and must be READ_ONCE to avoid reloading
+	 * the callbacks between a !NULL check and dereferences, to ensure
+	 * pending stores/changes to the callback pointers are visible before a
+	 * non-NULL perf_guest_cbs is visible to readers, and to prevent a
+	 * module from unloading callbacks while readers are active.
+	 */
+	return rcu_dereference(perf_guest_cbs);
+}
 static inline unsigned int perf_guest_state(void)
 {
-	return static_call(__perf_guest_state)();
+	struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
+
+	return guest_cbs ? guest_cbs->state() : 0;
 }
 static inline unsigned long perf_guest_get_ip(void)
 {
-	return static_call(__perf_guest_get_ip)();
+	struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
+
+	/*
+	 * Arbitrarily return '0' in the unlikely scenario that the callbacks
+	 * are unregistered between checking guest state and getting the IP.
+	 */
+	return guest_cbs ? guest_cbs->get_ip() : 0;
 }
 static inline unsigned int perf_guest_handle_intel_pt_intr(void)
 {
-	return static_call(__perf_guest_handle_intel_pt_intr)();
+	struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
+
+	if (guest_cbs && guest_cbs->handle_intel_pt_intr)
+		return guest_cbs->handle_intel_pt_intr();
+	return 0;
 }
 extern void perf_register_guest_info_callbacks(struct perf_guest_info_callbacks *cbs);
 extern void perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks *cbs);
diff --git a/kernel/events/core.c b/kernel/events/core.c
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6769,23 +6769,12 @@ static void perf_pending_task(struct callback_head *head)
 #ifdef CONFIG_GUEST_PERF_EVENTS
 struct perf_guest_info_callbacks __rcu *perf_guest_cbs;
 
-DEFINE_STATIC_CALL_RET0(__perf_guest_state, *perf_guest_cbs->state);
-DEFINE_STATIC_CALL_RET0(__perf_guest_get_ip, *perf_guest_cbs->get_ip);
-DEFINE_STATIC_CALL_RET0(__perf_guest_handle_intel_pt_intr, *perf_guest_cbs->handle_intel_pt_intr);
-
 void perf_register_guest_info_callbacks(struct perf_guest_info_callbacks *cbs)
 {
 	if (WARN_ON_ONCE(rcu_access_pointer(perf_guest_cbs)))
 		return;
 
 	rcu_assign_pointer(perf_guest_cbs, cbs);
-	static_call_update(__perf_guest_state, cbs->state);
-	static_call_update(__perf_guest_get_ip, cbs->get_ip);
-
-	/* Implementing ->handle_intel_pt_intr is optional. */
-	if (cbs->handle_intel_pt_intr)
-		static_call_update(__perf_guest_handle_intel_pt_intr,
-				   cbs->handle_intel_pt_intr);
 }
 EXPORT_SYMBOL_GPL(perf_register_guest_info_callbacks);
 
@@ -6795,10 +6784,6 @@ void perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks *cbs)
 		return;
 
 	rcu_assign_pointer(perf_guest_cbs, NULL);
-	static_call_update(__perf_guest_state, (void *)&__static_call_return0);
-	static_call_update(__perf_guest_get_ip, (void *)&__static_call_return0);
-	static_call_update(__perf_guest_handle_intel_pt_intr,
-			   (void *)&__static_call_return0);
 	synchronize_rcu();
 }
 EXPORT_SYMBOL_GPL(perf_unregister_guest_info_callbacks);