[PATCH] RISC-V: Enable IPI CPU Backtrace
From: takakura
Date: Wed Apr 17 2024 - 01:07:29 EST
From: Ryo Takakura <takakura@xxxxxxxxxxxxx>
Add CPU backtrace feature using IPI on riscv.
Currently, riscv doesn't yet support the feature while other
architectures do. As IPI multiplexing allows to handle
multiple IPIs, I think this feature can also be enabled
on riscv by adding IPI.
This patch defines arch_trigger_all_cpu_backtrace() which triggers
the IPI for CPU backtrace.
It will be triggered in the events of oops/panic when options
(oops_all_cpu_backtrace/panic_print) are set accordingly.
Below is the case of oops with the oops_all_cpu_backtrace
enabled.
$ sysctl kernel.oops_all_cpu_backtrace=1
triggering oops shows:
[ 435.716754] NMI backtrace for cpu 3
[ 435.716893] CPU: 3 PID: 621 Comm: in:imklog Tainted: G OE 6.9.0-rc4 #1
[ 435.717086] Hardware name: riscv-virtio,qemu (DT)
[ 435.717182] epc : fallback_scalar_usercopy+0x8/0xdc
[ 435.717300] ra : _copy_to_user+0x32/0x58
[ 435.717391] epc : ffffffff80c33d88 ra : ffffffff80598e3c sp : ff20000000e83b50
[ 435.717544] gp : ffffffff82066bf0 tp : ff60000091fd7000 t0 : 3363303866660000
[ 435.717711] t1 : 000000000000005b t2 : 3363303866666666 s0 : ff20000000e83b60
[ 435.717874] s1 : 00000000000001af a0 : 00007ff74d3df74f a1 : ff60000082cdc800
[ 435.718040] a2 : 000000000000003c a3 : 0000000000000000 a4 : 0000000000000000
[ 435.718196] a5 : 00ffffffffffffc4 a6 : 0000000000000000 a7 : 0000000000000010
[ 435.718333] s2 : ff60000082cdc800 s3 : ffffffff82066910 s4 : 0000000000001df1
[ 435.718475] s5 : ffffffff8206a5b8 s6 : 00007ff74d3df74f s7 : ffffffff8206a5b0
[ 435.718616] s8 : ff60000082cdc800 s9 : ffffffff81e26208 s10: 000000000000003c
[ 435.718760] s11: ffffffff8206a5ad t3 : ff60000082cdc812 t4 : ff60000082cdc812
[ 435.718909] t5 : ff60000082cdc818 t6 : 0000000000040000
[ 435.719019] status: 0000000000040120 badaddr: 0000000000000000 cause: 8000000000000001
[ 435.719191] [<ffffffff80c33d88>] fallback_scalar_usercopy+0x8/0xdc
[ 435.719330] [<ffffffff80094eee>] syslog_print+0x1f4/0x2b2
[ 435.719446] [<ffffffff80095e10>] do_syslog.part.0+0xb0/0x326
[ 435.719594] [<ffffffff8009692e>] do_syslog+0x66/0x88
[ 435.719816] [<ffffffff803a1a80>] kmsg_read+0x44/0x5c
[ 435.720017] [<ffffffff8038ea92>] proc_reg_read+0x7a/0xa8
[ 435.720251] [<ffffffff802fae20>] vfs_read+0x94/0x264
[ 435.720478] [<ffffffff802fb906>] ksys_read+0x64/0xe4
[ 435.720709] [<ffffffff802fb9a6>] __riscv_sys_read+0x20/0x2c
[ 435.720880] [<ffffffff80c43ea2>] do_trap_ecall_u+0x60/0x1d4
[ 435.721236] [<ffffffff80c4f74c>] ret_from_exception+0x0/0x64
Signed-off-by: Ryo Takakura <takakura@xxxxxxxxxxxxx>
---
arch/riscv/include/asm/irq.h | 3 +++
arch/riscv/kernel/smp.c | 16 ++++++++++++++++
2 files changed, 19 insertions(+)
diff --git a/arch/riscv/include/asm/irq.h b/arch/riscv/include/asm/irq.h
index 8e10a94430a2..ed8f76879270 100644
--- a/arch/riscv/include/asm/irq.h
+++ b/arch/riscv/include/asm/irq.h
@@ -12,6 +12,9 @@
#include <asm-generic/irq.h>
+void arch_trigger_cpumask_backtrace(const cpumask_t *mask, int exclude_cpu);
+#define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace
+
void riscv_set_intc_hwnode_fn(struct fwnode_handle *(*fn)(void));
struct fwnode_handle *riscv_get_intc_hwnode(void);
diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
index 45dd4035416e..6e297b9eb641 100644
--- a/arch/riscv/kernel/smp.c
+++ b/arch/riscv/kernel/smp.c
@@ -21,6 +21,7 @@
#include <linux/delay.h>
#include <linux/irq.h>
#include <linux/irq_work.h>
+#include <linux/nmi.h>
#include <asm/tlbflush.h>
#include <asm/cacheflush.h>
@@ -33,6 +34,7 @@ enum ipi_message_type {
IPI_CPU_CRASH_STOP,
IPI_IRQ_WORK,
IPI_TIMER,
+ IPI_CPU_BACKTRACE,
IPI_MAX
};
@@ -136,6 +138,9 @@ static irqreturn_t handle_IPI(int irq, void *data)
tick_receive_broadcast();
break;
#endif
+ case IPI_CPU_BACKTRACE:
+ nmi_cpu_backtrace(get_irq_regs());
+ break;
default:
pr_warn("CPU%d: unhandled IPI%d\n", smp_processor_id(), ipi);
break;
@@ -212,6 +217,7 @@ static const char * const ipi_names[] = {
[IPI_CPU_CRASH_STOP] = "CPU stop (for crash dump) interrupts",
[IPI_IRQ_WORK] = "IRQ work interrupts",
[IPI_TIMER] = "Timer broadcast interrupts",
+ [IPI_CPU_BACKTRACE] = "CPU backtrace interrupts",
};
void show_ipi_stats(struct seq_file *p, int prec)
@@ -332,3 +338,13 @@ void arch_smp_send_reschedule(int cpu)
send_ipi_single(cpu, IPI_RESCHEDULE);
}
EXPORT_SYMBOL_GPL(arch_smp_send_reschedule);
+
+static void riscv_backtrace_ipi(cpumask_t *mask)
+{
+ send_ipi_mask(mask, IPI_CPU_BACKTRACE);
+}
+
+void arch_trigger_cpumask_backtrace(const cpumask_t *mask, int exclude_cpu)
+{
+ nmi_trigger_cpumask_backtrace(mask, exclude_cpu, riscv_backtrace_ipi);
+}
--
2.34.1