linux-kernel - Re: [PATCH v2] arm64/debug: Fix registers on sleeping tasks

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Date:   Thu, 8 Mar 2018 16:19:31 +0000
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Douglas Anderson <dianders@...omium.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>
Cc:     briannorris@...omium.org, evgreen@...omium.org,
        swboyd@...omium.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2] arm64/debug: Fix registers on sleeping tasks

On 05/03/18 23:43, Douglas Anderson wrote:
> This is the equivalent of commit 001bf455d206 ("ARM: 8428/1: kgdb: Fix
> registers on sleeping tasks") but for arm64.  Nuff said.
> 
> ...well, perhaps I could also add that task_pt_regs are userspace
> registers and that's not what kgdb is supposed to be reporting.  We're
> supposed to be reporting kernel registers.
> 
> Signed-off-by: Douglas Anderson <dianders@...omium.org>

I hacked together a (still very immature) kgdb test suite[1] around the 
turn of the year. Whilst its not quite solid enough for me to recommend 
others deploy it except out of curiosity... so I haven't yet started 
yelling about test suite failures except in the privacy of my own head.

However I can confirm that this patch fixes one of the test suite 
failures I haven't had time to blame allocate yet!

So...
Tested-by: Daniel Thompson <daniel.thompson@...aro.org>

BTW is this something that should Cc: stable?


Daniel.

[1] https://github.com/daniel-thompson/kgdbtest


> ---
> 
> Changes in v2:
> - Init cpu_context in one line
> - Explain that task_pt_regs are userspace
> 
>   arch/arm64/kernel/kgdb.c | 21 ++++++++++++++++-----
>   1 file changed, 16 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm64/kernel/kgdb.c b/arch/arm64/kernel/kgdb.c
> index 2122cd187f19..a20de58061a8 100644
> --- a/arch/arm64/kernel/kgdb.c
> +++ b/arch/arm64/kernel/kgdb.c
> @@ -138,14 +138,25 @@ int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
>   void
>   sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *task)
>   {
> -	struct pt_regs *thread_regs;
> +	struct cpu_context *cpu_context = &task->thread.cpu_context;
>   
>   	/* Initialize to zero */
>   	memset((char *)gdb_regs, 0, NUMREGBYTES);
> -	thread_regs = task_pt_regs(task);
> -	memcpy((void *)gdb_regs, (void *)thread_regs->regs, GP_REG_BYTES);
> -	/* Special case for PSTATE (check comments in asm/kgdb.h for details) */
> -	dbg_get_reg(33, gdb_regs + GP_REG_BYTES, thread_regs);
> +
> +	gdb_regs[19] = cpu_context->x19;
> +	gdb_regs[20] = cpu_context->x20;
> +	gdb_regs[21] = cpu_context->x21;
> +	gdb_regs[22] = cpu_context->x22;
> +	gdb_regs[23] = cpu_context->x23;
> +	gdb_regs[24] = cpu_context->x24;
> +	gdb_regs[25] = cpu_context->x25;
> +	gdb_regs[26] = cpu_context->x26;
> +	gdb_regs[27] = cpu_context->x27;
> +	gdb_regs[28] = cpu_context->x28;
> +	gdb_regs[29] = cpu_context->fp;
> +
> +	gdb_regs[31] = cpu_context->sp;
> +	gdb_regs[32] = cpu_context->pc;
>   }
>   
>   void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long pc)
>