[PATCH v6 0/3] AArch64: KGDB support

[vijay.kilari@gmail.com (Vijay Kilari)]

On Wed, Jan 22, 2014 at 10:01 AM, Vijay Kilari <vijay.kilari@gmail.com> wrote:
> On Wed, Jan 22, 2014 at 12:06 AM, Will Deacon <will.deacon@arm.com> wrote:
>> On Tue, Jan 21, 2014 at 02:10:14PM +0000, Vijay Kilari wrote:
>>> Hi Will,
>>
>> Hello Vijay,
>>
>>> On Mon, Jan 20, 2014 at 3:53 PM, Will Deacon <will.deacon@arm.com> wrote:
>>> > Well, the warnings are one thing but the 100 miles of backtrace output that
>>> > appear on every boot (and I think end in an oops) are probably more
>>> > important to fix. Please enable CONFIG_KGDB_TESTS and
>>> > CONFIG_KGDB_TESTS_ON_BOOT and take a look.
>>> >
>>>
>>> I could manage to run KGDB boot tests if I run from sysfs after complete boot
>>>
>>> echo V1F1000 > /sys/module/kgdbts/parameters/kgdbts
>>>
>>> Here the value of PSTATE is 80000145, which means PSTATE.D is unmasked
>>> hence it works fine.
>>>
>>> If I run during boot by enabling CONFIG_KGDB_TESTS_ON_BOOT,
>>> the step debug test fail because value of PSTATE is 80000345.
>>> If I force PSTATE.D to 0, it works fine
>>>
>>> In debug_monitors.c file, only PSTATE.SS & MDSCR.KDE/MDE is managed
>>> but not PSTATE.D
>>>
>>> Can you please let me know if where PSTATE.D is managed in arm64?
>>
>> That's a good point: I think we wait until our first exception before they
>> are unmasked. Perhaps we should:
>>
>>  (1) Move local_dbg_{save,restore} from debug-monitors.h into irqflags.h

local_dbg_save is setting bit #8 it should be bit #9?

#define local_dbg_save(flags)
         \
        do {
         \
                typecheck(unsigned long, flags);
         \
                asm volatile(
         \
                "mrs    %0, daif                        //
local_dbg_save\n"    \
                "msr    daifset, #8"
         \
                : "=r" (flags) : : "memory");
         \
        } while (0)


>>  (2) Add local_dbg_enable/local_dbg_disable macros
>>  (3) Add a call to local_dbg_enable in the clear_os_lock function after the
>>      isb().
>>
>> Does that work for you?
>
> Yes, only after first exception occurs the PSTATE.D is unmasked.
>
> I have patched (temp) as below and now KGDB boot tests pass
>
> diff --git a/arch/arm64/include/asm/debug-monitors.h
> b/arch/arm64/include/asm/debug-monitors.h
> index aff3a76..ea2bc46 100644
> --- a/arch/arm64/include/asm/debug-monitors.h
> +++ b/arch/arm64/include/asm/debug-monitors.h
> @@ -64,6 +111,24 @@ struct task_struct;
>
>  #define DBG_ARCH_ID_RESERVED   0       /* In case of ptrace ABI updates. */
>
> +#define local_dbg_enable()
>          \
> +       do {
>          \
> +               asm volatile(
>          \
> +               "msr    daifclr, #9             //
> arch_local_irq_disable"      \
> +               :
>          \
> +               :
>          \
> +               : "memory");
>          \
> +       } while (0)
> +
> +#define local_dbg_disable()
>          \
> +       do {
>          \
> +               asm volatile(
>          \
> +               "msr    daifset, #9             //
> arch_local_irq_disable"      \
> +               :
>          \
> +               :
>          \
> +               : "memory");
>          \
> +       } while (0)
> +
>  struct step_hook {
>         struct list_head node;
>         int (*fn)(struct pt_regs *regs, unsigned int insn, unsigned long addr);
>
> diff --git a/arch/arm64/kernel/debug-monitors.c
> b/arch/arm64/kernel/debug-monitors.c
> index f8b90c0..d0e55f7 100644
> --- a/arch/arm64/kernel/debug-monitors.c
> +++ b/arch/arm64/kernel/debug-monitors.c
> @@ -139,6 +142,7 @@ static void clear_os_lock(void *unused)
>  {
>         asm volatile("msr oslar_el1, %0" : : "r" (0));
>         isb();
> +       local_dbg_enable();
>  }
>
>
> boot test:
>
> [32927.161317] msgmni has been set to 1870
> [32927.212747] alg: No test for stdrng (krng)
> [32927.213953] Key type asymmetric registered
> [32927.214899] Asymmetric key parser 'x509' registered
> [32927.220029] Block layer SCSI generic (bsg) driver version 0.4
> loaded (major 253)
> [32927.225824] io scheduler noop registered
> [32927.226764] io scheduler deadline registered
> [32927.230714] io scheduler cfq registered (default)
> [32927.237895] Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled
> [32927.266066] kgdb: Registered I/O driver kgdbts.
> [32927.266419] kgdb: Waiting for connection from remote gdb...
> [32927.268598] kgdbts:RUN plant and detach test
> [32927.270683] kgdbts:RUN sw breakpoint test
> [32927.287659] kgdbts:RUN bad memory access test
> [32927.290322] kgdbts:RUN singlestep test 1000 iterations
> [32927.330342] kgdbts:RUN singlestep [0/1000]
> [32931.286356] kgdbts:RUN singlestep [100/1000]
> [32935.242536] kgdbts:RUN singlestep [200/1000]
> [32939.205392] kgdbts:RUN singlestep [300/1000]
> [32943.169522] kgdbts:RUN singlestep [400/1000]
> [32947.231868] kgdbts:RUN singlestep [500/1000]
> [32951.188008] kgdbts:RUN singlestep [600/1000]
> [32955.332243] kgdbts:RUN singlestep [700/1000]
> [32959.467109] kgdbts:RUN singlestep [800/1000]
> [32963.430888] kgdbts:RUN singlestep [900/1000]
> [32967.346992] kgdbts:RUN do_fork for 100 breakpoints
>
> kgdb test using sysfs:
>
> ~ # echo V1F1000 > /sys/module/kgdbts/parameters/kgdbts
> [33231.554237] kgdb: Registered I/O driver kgdbts.
> [33231.554677] kgdbts:RUN plant and detach test
> [33231.557072] kgdbts:RUN sw breakpoint test
> [33231.576980] kgdbts:RUN bad memory access test
> [33231.580022] kgdbts:RUN singlestep test 1000 iterations
> [33231.627056] kgdbts:RUN singlestep [0/1000]
> [33235.954027] kgdbts:RUN singlestep [100/1000]
> [33240.429086] kgdbts:RUN singlestep [200/1000]
> [33244.687118] kgdbts:RUN singlestep [300/1000]
> [33248.945191] kgdbts:RUN singlestep [400/1000]
> [33253.203751] kgdbts:RUN singlestep [500/1000]
> [33257.462019] kgdbts:RUN singlestep [600/1000]
> [33261.817809] kgdbts:RUN singlestep [700/1000]
> [33266.081268] kgdbts:RUN singlestep [800/1000]
> [33270.339813] kgdbts:RUN singlestep [900/1000]
> [33274.712404] kgdbts:RUN do_fork for 1000 breakpoints
> ~ #
>
> This works for me. Should I patch it or will you send a patch for this?
>
> PS: cc to mailing list missed
>>
>> Will