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    Subject[patch 02/10] x86/mce: Disable tracing and kprobes on do_machine_check()
    From: Andy Lutomirski <luto@kernel.org>

    do_machine_check() can be raised in almost any context including the most
    fragile ones. Prevent kprobes and tracing.

    Signed-off-by: Andy Lutomirski <luto@kernel.org>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    ---
    arch/x86/include/asm/traps.h | 3 ---
    arch/x86/kernel/cpu/mce/core.c | 12 ++++++++++--
    2 files changed, 10 insertions(+), 5 deletions(-)

    --- a/arch/x86/include/asm/traps.h
    +++ b/arch/x86/include/asm/traps.h
    @@ -88,9 +88,6 @@ dotraplinkage void do_page_fault(struct
    dotraplinkage void do_spurious_interrupt_bug(struct pt_regs *regs, long error_code);
    dotraplinkage void do_coprocessor_error(struct pt_regs *regs, long error_code);
    dotraplinkage void do_alignment_check(struct pt_regs *regs, long error_code);
    -#ifdef CONFIG_X86_MCE
    -dotraplinkage void do_machine_check(struct pt_regs *regs, long error_code);
    -#endif
    dotraplinkage void do_simd_coprocessor_error(struct pt_regs *regs, long error_code);
    #ifdef CONFIG_X86_32
    dotraplinkage void do_iret_error(struct pt_regs *regs, long error_code);
    --- a/arch/x86/kernel/cpu/mce/core.c
    +++ b/arch/x86/kernel/cpu/mce/core.c
    @@ -1213,8 +1213,14 @@ static void __mc_scan_banks(struct mce *
    * On Intel systems this is entered on all CPUs in parallel through
    * MCE broadcast. However some CPUs might be broken beyond repair,
    * so be always careful when synchronizing with others.
    + *
    + * Tracing and kprobes are disabled: if we interrupted a kernel context
    + * with IF=1, we need to minimize stack usage. There are also recursion
    + * issues: if the machine check was due to a failure of the memory
    + * backing the user stack, tracing that reads the user stack will cause
    + * potentially infinite recursion.
    */
    -void do_machine_check(struct pt_regs *regs, long error_code)
    +void notrace do_machine_check(struct pt_regs *regs, long error_code)
    {
    DECLARE_BITMAP(valid_banks, MAX_NR_BANKS);
    DECLARE_BITMAP(toclear, MAX_NR_BANKS);
    @@ -1360,6 +1366,7 @@ void do_machine_check(struct pt_regs *re
    ist_exit(regs);
    }
    EXPORT_SYMBOL_GPL(do_machine_check);
    +NOKPROBE_SYMBOL(do_machine_check);

    #ifndef CONFIG_MEMORY_FAILURE
    int memory_failure(unsigned long pfn, int flags)
    @@ -1892,10 +1899,11 @@ static void unexpected_machine_check(str
    void (*machine_check_vector)(struct pt_regs *, long error_code) =
    unexpected_machine_check;

    -dotraplinkage void do_mce(struct pt_regs *regs, long error_code)
    +dotraplinkage notrace void do_mce(struct pt_regs *regs, long error_code)
    {
    machine_check_vector(regs, error_code);
    }
    +NOKPROBE_SYMBOL(do_mce);

    /*
    * Called for each booted CPU to set up machine checks.
    \
     
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