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    Subject[RESEND PATCH V5 1/2] RISC-V: Fixup fast call of crash_kexec()
    Date
    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@kernel.org>
    Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
    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 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);
    +
    bust_spinlocks(0);
    add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
    spin_unlock_irq(&die_lock);
    --
    2.17.1
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