Re: [RESEND PATCH v2] RISC-V: Add fast call path of crash_kexec()

[tianxianting]

在 2022/7/22 上午8:11, Palmer Dabbelt 写道:
> On Mon, 06 Jun 2022 01:23:08 PDT (-0700), 
> xianting.tian@xxxxxxxxxxxxxxxxx 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/test_crash.c:81
> >     81             *(int *)p = 0xdead;
> >     (gdb)
> >     (gdb) bt
> >     #0  0xffffffe00064d5c0 in test_thread (data=<optimized out>) at 
> > drivers/test_crash.c:81
> >     #1  0x0000000000000000 in ?? ()
> >
> > Test code to produce NULL address dereference in test_crash.c,
> >     void *p = NULL;
> >     *(int *)p = 0xdead;
> >
> > Reviewed-by: Guo Ren <guoren@xxxxxxxxxx>
> > Tested-by: Xianting Tian <xianting.tian@xxxxxxxxxxxxxxxxx>
> > Signed-off-by: Xianting Tian <xianting.tian@xxxxxxxxxxxxxxxxx>
> > ---
> > Changes from v1:
> > - simplify the commit message
> > ---
> >  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);
>
> Thanks, this is on for-next.

Palmer, thanks for the reply,

Last week, I commit a series of 
patches(https://lkml.org/lkml/2022/7/17/64 
<https://lkml.org/lkml/2022/7/17/64>), which contains this one.

This series of patches worked with crash-utility for RISCV64, Could you 
please review it?

We expect 5.19 could support crash-utility, it is a good functionality.

crash-utility patches for RISCV64:

https://lore.kernel.org/all/20220718025346.411758-1-xianting.tian@xxxxxxxxxxxxxxxxx/ 
<https://lore.kernel.org/all/20220718025346.411758-1-xianting.tian@xxxxxxxxxxxxxxxxx/>