The CONFIG_CSD_LOCK_WAIT_DEBUG option enables debugging of hung
smp_call_function*() calls (e.g. when the target CPU gets stuck within
the callback function). Testing this option requires triggering such
hangs.
This patch adds an lkdtm test with a hung smp_call_function_single()
callback, which can be used to test CONFIG_CSD_LOCK_WAIT_DEBUG and NMI
backtraces (as CONFIG_CSD_LOCK_WAIT_DEBUG will attempt an NMI backtrace
of the hung target CPU).
On arm64 using pseudo-NMI, this looks like:
| # mount -t debugfs none /sys/kernel/debug/
| # echo SMP_CALL_LOCKUP > /sys/kernel/debug/provoke-crash/DIRECT
| lkdtm: Performing direct entry SMP_CALL_LOCKUP
| smp: csd: Detected non-responsive CSD lock (#1) on CPU#1, waiting 5000000176 ns for CPU#00 __lkdtm_SMP_CALL_LOCKUP+0x0/0x8(0x0).
| smp: csd: CSD lock (#1) handling this request.
| Sending NMI from CPU 1 to CPUs 0:
| NMI backtrace for cpu 0
| CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.9.0-rc4-00001-gfdfd281212ec #1
| Hardware name: linux,dummy-virt (DT)
| pstate: 60401005 (nZCv daif +PAN -UAO -TCO -DIT +SSBS BTYPE=--)
| pc : __lkdtm_SMP_CALL_LOCKUP+0x0/0x8
| lr : __flush_smp_call_function_queue+0x1b0/0x290
| sp : ffff800080003f30
| pmr_save: 00000060
| x29: ffff800080003f30 x28: ffffa4ce961a4900 x27: 0000000000000000
| x26: fff000003fcfa0c0 x25: ffffa4ce961a4900 x24: ffffa4ce959aa140
| x23: ffffa4ce959aa140 x22: 0000000000000000 x21: ffff800080523c40
| x20: 0000000000000000 x19: 0000000000000000 x18: fff05b31aa323000
| x17: fff05b31aa323000 x16: ffff800080000000 x15: 0000330fc3fe6b2c
| x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000279
| x11: 0000000000000040 x10: fff000000302d0a8 x9 : fff000000302d0a0
| x8 : fff0000003400270 x7 : 0000000000000000 x6 : ffffa4ce9451b810
| x5 : 0000000000000000 x4 : fff05b31aa323000 x3 : ffff800080003f30
| x2 : fff05b31aa323000 x1 : ffffa4ce959aa140 x0 : 0000000000000000
| Call trace:
| __lkdtm_SMP_CALL_LOCKUP+0x0/0x8
| generic_smp_call_function_single_interrupt+0x14/0x20
| ipi_handler+0xb8/0x178
| handle_percpu_devid_irq+0x84/0x130
| generic_handle_domain_irq+0x2c/0x44
| gic_handle_irq+0x118/0x240
| call_on_irq_stack+0x24/0x4c
| do_interrupt_handler+0x80/0x84
| el1_interrupt+0x44/0xc0
| el1h_64_irq_handler+0x18/0x24
| el1h_64_irq+0x78/0x7c
| default_idle_call+0x40/0x60
| do_idle+0x23c/0x2d0
| cpu_startup_entry+0x38/0x3c
| kernel_init+0x0/0x1d8
| start_kernel+0x51c/0x608
| __primary_switched+0x80/0x88
| CPU: 1 PID: 128 Comm: sh Not tainted 6.9.0-rc4-00001-gfdfd281212ec #1
| Hardware name: linux,dummy-virt (DT)
| Call trace:
| dump_backtrace+0x90/0xe8
| show_stack+0x18/0x24
| dump_stack_lvl+0xac/0xe8
| dump_stack+0x18/0x24
| csd_lock_wait_toolong+0x268/0x338
| smp_call_function_single+0x1dc/0x2f0
| lkdtm_SMP_CALL_LOCKUP+0xcc/0xfc
| lkdtm_do_action+0x1c/0x38
| direct_entry+0xbc/0x14c
| full_proxy_write+0x60/0xb4
| vfs_write+0xd0/0x35c
| ksys_write+0x70/0x104
| __arm64_sys_write+0x1c/0x28
| invoke_syscall+0x48/0x114
| el0_svc_common.constprop.0+0x40/0xe0
| do_el0_svc+0x1c/0x28
| el0_svc+0x38/0x108
| el0t_64_sync_handler+0x120/0x12c
| el0t_64_sync+0x1a4/0x1a8
| smp: csd: Continued non-responsive CSD lock (#1) on CPU#1, waiting 10000064272 ns for CPU#00 __lkdtm_SMP_CALL_LOCKUP+0x0/0x8(0x0).
| smp: csd: CSD lock (#1) handling this request.
| smp: csd: Continued non-responsive CSD lock (#1) on CPU#1, waiting 15000064384 ns for CPU#00 __lkdtm_SMP_CALL_LOCKUP+0x0/0x8(0x0).
| smp: csd: CSD lock (#1) handling this request.
Signed-off-by: Mark Rutland <[email protected]>
Acked-by: Paul E. McKenney <[email protected]>
Cc: Kees Cook <[email protected]>
---
drivers/misc/lkdtm/bugs.c | 30 +++++++++++++++++++++++++
tools/testing/selftests/lkdtm/tests.txt | 1 +
2 files changed, 31 insertions(+)
Since v1 [1]:
* Rename option CSDLOCKUP -> SMP_CALL_LOCKUP
* Add entry to tests.txt
* Fix typo in commit message
* Add Paul's Acked-by tag
[1] https://lore.kernel.org/lkml/[email protected]/
diff --git a/drivers/misc/lkdtm/bugs.c b/drivers/misc/lkdtm/bugs.c
index 5178c02b21eba..62ba015254797 100644
--- a/drivers/misc/lkdtm/bugs.c
+++ b/drivers/misc/lkdtm/bugs.c
@@ -286,6 +286,35 @@ static void lkdtm_HARDLOCKUP(void)
cpu_relax();
}
+static void __lkdtm_SMP_CALL_LOCKUP(void *unused)
+{
+ for (;;)
+ cpu_relax();
+}
+
+static void lkdtm_SMP_CALL_LOCKUP(void)
+{
+ unsigned int cpu, target;
+
+ cpus_read_lock();
+
+ cpu = get_cpu();
+ target = cpumask_any_but(cpu_online_mask, cpu);
+
+ if (target >= nr_cpu_ids) {
+ pr_err("FAIL: no other online CPUs\n");
+ goto out_put_cpus;
+ }
+
+ smp_call_function_single(target, __lkdtm_SMP_CALL_LOCKUP, NULL, 1);
+
+ pr_err("FAIL: did not hang\n");
+
+out_put_cpus:
+ put_cpu();
+ cpus_read_unlock();
+}
+
static void lkdtm_SPINLOCKUP(void)
{
/* Must be called twice to trigger. */
@@ -680,6 +709,7 @@ static struct crashtype crashtypes[] = {
CRASHTYPE(UNALIGNED_LOAD_STORE_WRITE),
CRASHTYPE(SOFTLOCKUP),
CRASHTYPE(HARDLOCKUP),
+ CRASHTYPE(SMP_CALL_LOCKUP),
CRASHTYPE(SPINLOCKUP),
CRASHTYPE(HUNG_TASK),
CRASHTYPE(OVERFLOW_SIGNED),
diff --git a/tools/testing/selftests/lkdtm/tests.txt b/tools/testing/selftests/lkdtm/tests.txt
index 368973f05250f..cff124c1eddd3 100644
--- a/tools/testing/selftests/lkdtm/tests.txt
+++ b/tools/testing/selftests/lkdtm/tests.txt
@@ -31,6 +31,7 @@ SLAB_FREE_CROSS
SLAB_FREE_PAGE
#SOFTLOCKUP Hangs the system
#HARDLOCKUP Hangs the system
+#SMP_CALL_LOCKUP Hangs the system
#SPINLOCKUP Hangs the system
#HUNG_TASK Hangs the system
EXEC_DATA
--
2.30.2