diff mbox series

RISC-V: Add fast call path of crash_kexec()

Message ID 20220515131407.946832-1-xianting.tian@linux.alibaba.com (mailing list archive)
State New
Headers show
Series RISC-V: Add fast call path of crash_kexec() | expand

Commit Message

Xianting Tian May 15, 2022, 1:14 p.m. UTC
Currently, almost all archs (x86, arm64, mips...) support fast call
of crash_kexec() when "regs && kexec_should_crash()" is true. But
RISC-V not, it can only enter crash system via panic(). However panic()
doesn't pass the regs of the real accident scene to crash_kexec(),
it caused we can't get accurate backtrace via gdb,
	$ riscv64-linux-gnu-gdb vmlinux vmcore
	Reading symbols from vmlinux...
	[New LWP 95]
	#0  console_unlock () at kernel/printk/printk.c:2557
	2557                    if (do_cond_resched)
	(gdb) bt
	#0  console_unlock () at kernel/printk/printk.c:2557
	#1  0x0000000000000000 in ?? ()

With the patch we can get the accurate backtrace,
	$ riscv64-linux-gnu-gdb vmlinux vmcore
	Reading symbols from vmlinux...
	[New LWP 95]
	#0  0xffffffe00063a4e0 in test_thread (data=<optimized out>) at drivers/virtio/virtio_mmio.c:806
	806             *(int *)p = 0xdead;
	(gdb)
	(gdb) bt
	#0  0xffffffe00063a4e0 in test_thread (data=<optimized out>) at drivers/virtio/virtio_mmio.c:806
	#1  0x0000000000000000 in ?? ()

Test code to produce NULL address dereference,
	+extern int panic_on_oops;
	+static struct task_struct *k;
	+static int test_thread(void *data) {
	+
	+       void *p = NULL;
	+
	+       while (!panic_on_oops)
	+               msleep(2000);
	+
	+       *(int *)p = 0xdead;
	+
	+       return 0;
	+}
	+
	 static int __init virtio_mmio_init(void)
	 {
	+       k = kthread_run(test_thread, NULL, "test_thread");
	+       if (IS_ERR(k))
	+               pr_err("Couldn't create test kthread\n");
	+
	        return platform_driver_register(&virtio_mmio_driver);
	 }

Signed-off-by: Xianting Tian <xianting.tian@linux.alibaba.com>
---
 arch/riscv/kernel/traps.c | 4 ++++
 1 file changed, 4 insertions(+)

Comments

Guo Ren May 16, 2022, 6:51 a.m. UTC | #1
Great Job, I think it's a fixup, we should add Fix: and Cc: stable@kernel.org

Reviewed-by: Guo Ren <guoren@kernel.org>

On Sun, May 15, 2022 at 9:14 PM Xianting Tian
<xianting.tian@linux.alibaba.com> wrote:
>
> Currently, almost all archs (x86, arm64, mips...) support fast call
> of crash_kexec() when "regs && kexec_should_crash()" is true. But
> RISC-V not, it can only enter crash system via panic(). However panic()
> doesn't pass the regs of the real accident scene to crash_kexec(),
> it caused we can't get accurate backtrace via gdb,
>         $ riscv64-linux-gnu-gdb vmlinux vmcore
>         Reading symbols from vmlinux...
>         [New LWP 95]
>         #0  console_unlock () at kernel/printk/printk.c:2557
>         2557                    if (do_cond_resched)
>         (gdb) bt
>         #0  console_unlock () at kernel/printk/printk.c:2557
>         #1  0x0000000000000000 in ?? ()
>
> With the patch we can get the accurate backtrace,
>         $ riscv64-linux-gnu-gdb vmlinux vmcore
>         Reading symbols from vmlinux...
>         [New LWP 95]
>         #0  0xffffffe00063a4e0 in test_thread (data=<optimized out>) at drivers/virtio/virtio_mmio.c:806
>         806             *(int *)p = 0xdead;
>         (gdb)
>         (gdb) bt
>         #0  0xffffffe00063a4e0 in test_thread (data=<optimized out>) at drivers/virtio/virtio_mmio.c:806
>         #1  0x0000000000000000 in ?? ()
>
> Test code to produce NULL address dereference,
>         +extern int panic_on_oops;
>         +static struct task_struct *k;
>         +static int test_thread(void *data) {
>         +
>         +       void *p = NULL;
>         +
>         +       while (!panic_on_oops)
>         +               msleep(2000);
>         +
>         +       *(int *)p = 0xdead;
>         +
>         +       return 0;
>         +}
>         +
>          static int __init virtio_mmio_init(void)
>          {
>         +       k = kthread_run(test_thread, NULL, "test_thread");
>         +       if (IS_ERR(k))
>         +               pr_err("Couldn't create test kthread\n");
>         +
>                 return platform_driver_register(&virtio_mmio_driver);
>          }
>
> Signed-off-by: Xianting Tian <xianting.tian@linux.alibaba.com>
> ---
>  arch/riscv/kernel/traps.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
> index fe92e119e6a3..e666ebfa2a64 100644
> --- a/arch/riscv/kernel/traps.c
> +++ b/arch/riscv/kernel/traps.c
> @@ -16,6 +16,7 @@
>  #include <linux/mm.h>
>  #include <linux/module.h>
>  #include <linux/irq.h>
> +#include <linux/kexec.h>
>
>  #include <asm/asm-prototypes.h>
>  #include <asm/bug.h>
> @@ -44,6 +45,9 @@ void die(struct pt_regs *regs, const char *str)
>
>         ret = notify_die(DIE_OOPS, str, regs, 0, regs->cause, SIGSEGV);
>
> +       if (regs && kexec_should_crash(current))
> +               crash_kexec(regs);
> +
>         bust_spinlocks(0);
>         add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
>         spin_unlock_irq(&die_lock);
> --
> 2.17.1
>
Xianting Tian May 24, 2022, 1:50 a.m. UTC | #2
just a friendly ping

在 2022/5/15 下午9:14, Xianting Tian 写道:
> Currently, almost all archs (x86, arm64, mips...) support fast call
> of crash_kexec() when "regs && kexec_should_crash()" is true. But
> RISC-V not, it can only enter crash system via panic(). However panic()
> doesn't pass the regs of the real accident scene to crash_kexec(),
> it caused we can't get accurate backtrace via gdb,
> 	$ riscv64-linux-gnu-gdb vmlinux vmcore
> 	Reading symbols from vmlinux...
> 	[New LWP 95]
> 	#0  console_unlock () at kernel/printk/printk.c:2557
> 	2557                    if (do_cond_resched)
> 	(gdb) bt
> 	#0  console_unlock () at kernel/printk/printk.c:2557
> 	#1  0x0000000000000000 in ?? ()
>
> With the patch we can get the accurate backtrace,
> 	$ riscv64-linux-gnu-gdb vmlinux vmcore
> 	Reading symbols from vmlinux...
> 	[New LWP 95]
> 	#0  0xffffffe00063a4e0 in test_thread (data=<optimized out>) at drivers/virtio/virtio_mmio.c:806
> 	806             *(int *)p = 0xdead;
> 	(gdb)
> 	(gdb) bt
> 	#0  0xffffffe00063a4e0 in test_thread (data=<optimized out>) at drivers/virtio/virtio_mmio.c:806
> 	#1  0x0000000000000000 in ?? ()
>
> Test code to produce NULL address dereference,
> 	+extern int panic_on_oops;
> 	+static struct task_struct *k;
> 	+static int test_thread(void *data) {
> 	+
> 	+       void *p = NULL;
> 	+
> 	+       while (!panic_on_oops)
> 	+               msleep(2000);
> 	+
> 	+       *(int *)p = 0xdead;
> 	+
> 	+       return 0;
> 	+}
> 	+
> 	 static int __init virtio_mmio_init(void)
> 	 {
> 	+       k = kthread_run(test_thread, NULL, "test_thread");
> 	+       if (IS_ERR(k))
> 	+               pr_err("Couldn't create test kthread\n");
> 	+
> 	        return platform_driver_register(&virtio_mmio_driver);
> 	 }
>
> Signed-off-by: Xianting Tian <xianting.tian@linux.alibaba.com>
> ---
>   arch/riscv/kernel/traps.c | 4 ++++
>   1 file changed, 4 insertions(+)
>
> diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
> index fe92e119e6a3..e666ebfa2a64 100644
> --- a/arch/riscv/kernel/traps.c
> +++ b/arch/riscv/kernel/traps.c
> @@ -16,6 +16,7 @@
>   #include <linux/mm.h>
>   #include <linux/module.h>
>   #include <linux/irq.h>
> +#include <linux/kexec.h>
>   
>   #include <asm/asm-prototypes.h>
>   #include <asm/bug.h>
> @@ -44,6 +45,9 @@ void die(struct pt_regs *regs, const char *str)
>   
>   	ret = notify_die(DIE_OOPS, str, regs, 0, regs->cause, SIGSEGV);
>   
> +	if (regs && kexec_should_crash(current))
> +		crash_kexec(regs);
> +
>   	bust_spinlocks(0);
>   	add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
>   	spin_unlock_irq(&die_lock);
diff mbox series

Patch

diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index fe92e119e6a3..e666ebfa2a64 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -16,6 +16,7 @@ 
 #include <linux/mm.h>
 #include <linux/module.h>
 #include <linux/irq.h>
+#include <linux/kexec.h>
 
 #include <asm/asm-prototypes.h>
 #include <asm/bug.h>
@@ -44,6 +45,9 @@  void die(struct pt_regs *regs, const char *str)
 
 	ret = notify_die(DIE_OOPS, str, regs, 0, regs->cause, SIGSEGV);
 
+	if (regs && kexec_should_crash(current))
+		crash_kexec(regs);
+
 	bust_spinlocks(0);
 	add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
 	spin_unlock_irq(&die_lock);