[PATCH v3] RISC-V: Add fixup to support fast call of crash_kexec()
Guo Ren
guoren at kernel.org
Fri Jun 17 00:13:34 PDT 2022
Hi Xianting,
On Fri, Jun 17, 2022 at 2:40 PM Xianting Tian
<xianting.tian at linux.alibaba.com> wrote:
>
> Hi Palmer
>
> Will you apply this patch for 5.19?
Maybe we could update tile with [PATCH v3] RISC-V: Fixup fast call of
crash_kexec() for a V4.
It's a fixup not feature, that would mislead maintainer. And add
"Reviewed-by: Kefeng Wang".
>
> thanks
>
> 在 2022/6/7 上午9:46, Xianting Tian 写道:
> >
> > 在 2022/6/7 上午9:21, Kefeng Wang 写道:
> >>
> >> On 2022/6/6 20:37, Xianting Tian 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;
> >>>
> >>> Fixes: 76d2a0493a17 ("RISC-V: Init and Halt Code")
> >>> Reviewed-by: Guo Ren <guoren at kernel.org>
> >>> Signed-off-by: Xianting Tian <xianting.tian at linux.alibaba.com>
> >>> ---
> >>> Changes from v1:
> >>> - simplify the commit message
> >>> Changes from v2:
> >>> - add fixup in title
> >>> ---
> >>> 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 b40426509244..39d0f8bba4b4 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);
> >>> +
> >>
> >> It seems that the regs won't be null, right? except that,
> >
> > Autually both regs won't be null, But if it is triggered by panic() ,
> > the regs are got via riscv_crash_save_regs(), which are the regs of
> > that moment, but not the real accident scene.
> >
> >>
> >> Reviewed-by: Kefeng Wang <wangkefeng.wang at huawei.com>
> >>
> >>> bust_spinlocks(0);
> >>> add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
> >>> spin_unlock_irq(&die_lock);
--
Best Regards
Guo Ren
ML: https://lore.kernel.org/linux-csky/
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