[PATCH] arm64: fix single step issue in kgdb

[Wei Li]

Because the former mail is in html by my mistake, it is rejected by the mailing list server. I just update the diffstat info and resend it in plain text. There is no difference in patch. Sorry to make you confused, please ignore the former one.




On 2018-04-20 16:21:10，"Daniel Thompson" <daniel.thompson at linaro.org> wrote：
>On Thu, Apr 19, 2018 at 08:23:41PM +0800, Wei Li wrote:
>> From: Wei Li <liwei1412 at 163.com>
>> 
>> In kdb, as the frontend for kgdb, cmd "ss" does not work well. It can only take effects once and the single step exception is reported as oops after a breakpoint triggered in kdb. Then the cmd "go" does not work well either due to this. Refer to the DDI0487C_a_armv8_arm.pdf (D2.12), i set the SPSR.SS=1 every time. It has been verified in qemu.
>> 
>> Signed-off-by: Wei Li <liwei1412 at 163.com>
>> ---
>>  include/asm/debug-monitors.h |    3 +++
>>  kernel/debug-monitors.c      |    4 ++--
>>  kernel/kgdb.c                |    3 ++-
>
>This contains many similar changes to a patch from earlier with the same
>Subject. It is a v2? If so the subject should reflect that (and a
>changelog would be nice).
>
>
>Daniel.
>
>
>>  3 files changed, 7 insertions(+), 3 deletions(-)
>>  
>> diff -uprN linux-4.16.2_org/arch/arm64/include/asm/debug-monitors.h linux-4.16.2_mod/arch/arm64/include/asm/debug-monitors.h
>> --- linux-4.16.2_org/arch/arm64/include/asm/debug-monitors.h    2018-04-12 18:30:01.000000000 +0800
>> +++ linux-4.16.2_mod/arch/arm64/include/asm/debug-monitors.h    2018-04-19 00:19:10.134999268 +0800
>> @@ -135,6 +135,9 @@ static inline int reinstall_suspended_bp
>>  
>>  int aarch32_break_handler(struct pt_regs *regs);
>>  
>> +void set_regs_spsr_ss(struct pt_regs *regs);
>> +void clear_regs_spsr_ss(struct pt_regs *regs);
>> +
>>  #endif    /* __ASSEMBLY */
>>  #endif    /* __KERNEL__ */
>>  #endif    /* __ASM_DEBUG_MONITORS_H */
>> diff -uprN linux-4.16.2_org/arch/arm64/kernel/debug-monitors.c linux-4.16.2_mod/arch/arm64/kernel/debug-monitors.c
>> --- linux-4.16.2_org/arch/arm64/kernel/debug-monitors.c    2018-04-12 18:30:01.000000000 +0800
>> +++ linux-4.16.2_mod/arch/arm64/kernel/debug-monitors.c    2018-04-19 00:19:19.435189356 +0800
>> @@ -150,13 +150,13 @@ postcore_initcall(debug_monitors_init);
>>  /*
>>   * Single step API and exception handling.
>>   */
>> -static void set_regs_spsr_ss(struct pt_regs *regs)
>> +void set_regs_spsr_ss(struct pt_regs *regs)
>>  {
>>      regs->pstate |= DBG_SPSR_SS;
>>  }
>>  NOKPROBE_SYMBOL(set_regs_spsr_ss);
>>  
>> -static void clear_regs_spsr_ss(struct pt_regs *regs)
>> +void clear_regs_spsr_ss(struct pt_regs *regs)
>>  {
>>      regs->pstate &= ~DBG_SPSR_SS;
>>  }
>> diff -uprN linux-4.16.2_org/arch/arm64/kernel/kgdb.c linux-4.16.2_mod/arch/arm64/kernel/kgdb.c
>> --- linux-4.16.2_org/arch/arm64/kernel/kgdb.c    2018-04-12 18:30:01.000000000 +0800
>> +++ linux-4.16.2_mod/arch/arm64/kernel/kgdb.c    2018-04-19 00:19:40.892911795 +0800
>> @@ -221,6 +221,7 @@ int kgdb_arch_handle_exception(int excep
>>          /*
>>           * Enable single step handling
>>           */
>> +        set_regs_spsr_ss(linux_regs);
>>          if (!kernel_active_single_step())
>>              kernel_enable_single_step(linux_regs);
>>          err = 0;
>> @@ -252,7 +253,7 @@ static int kgdb_step_brk_fn(struct pt_re
>>      if (!kgdb_single_step)
>>          return DBG_HOOK_ERROR;
>>  
>> -    kgdb_handle_exception(1, SIGTRAP, 0, regs);
>> +    kgdb_handle_exception(0, SIGTRAP, 0, regs);
>>      return 0;
>>  }
>>  NOKPROBE_SYMBOL(kgdb_step_brk_fn);
>>