linux-kernel - Re: [PATCH] arch/tile: clean up tile-specific PTRACE

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Date:	Fri, 14 Dec 2012 18:26:56 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Chris Metcalf <cmetcalf@...era.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arch/tile: clean up tile-specific PTRACE_SETOPTIONS

On 12/13, Chris Metcalf wrote:
>
> Use the newer idioms for setting PTRACE_O_xxx and PT_TRACE_xxx flags.
> Only set/clear tile-specific flags if the generic routine returns
> success, since otherwise we want to avoid setting any flags at all.
> Atomically update the ptrace flags with the new values.  Eliminate
> the PT_TRACE_MASK_TILE bitmask and just shift PTRACE_O_MASK_TILE.
> Add a BUILD_BUG_ON to avoid overlapping with generic bits.
>
> Signed-off-by: Chris Metcalf <cmetcalf@...era.com>

Acked-by: Oleg Nesterov <oleg@...hat.com>

> ---
>  arch/tile/include/asm/ptrace.h      |    3 +--
>  arch/tile/include/uapi/asm/ptrace.h |    2 +-
>  arch/tile/kernel/ptrace.c           |   10 +++++++---
>  3 files changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/tile/include/asm/ptrace.h b/arch/tile/include/asm/ptrace.h
> index 1a4fd9a..5ce052e 100644
> --- a/arch/tile/include/asm/ptrace.h
> +++ b/arch/tile/include/asm/ptrace.h
> @@ -24,8 +24,7 @@ typedef unsigned long pt_reg_t;
>  #include <uapi/asm/ptrace.h>
>  
>  #define PTRACE_O_MASK_TILE	(PTRACE_O_TRACEMIGRATE)
> -#define PT_TRACE_MIGRATE	0x00080000
> -#define PT_TRACE_MASK_TILE	(PT_TRACE_MIGRATE)
> +#define PT_TRACE_MIGRATE	PT_EVENT_FLAG(PTRACE_EVENT_MIGRATE)
>  
>  /* Flag bits in pt_regs.flags */
>  #define PT_FLAGS_DISABLE_IRQ    1  /* on return to kernel, disable irqs */
> diff --git a/arch/tile/include/uapi/asm/ptrace.h b/arch/tile/include/uapi/asm/ptrace.h
> index 0d22088..7757e19 100644
> --- a/arch/tile/include/uapi/asm/ptrace.h
> +++ b/arch/tile/include/uapi/asm/ptrace.h
> @@ -81,8 +81,8 @@ struct pt_regs {
>  #define PTRACE_SETFPREGS	15
>  
>  /* Support TILE-specific ptrace options, with events starting at 16. */
> -#define PTRACE_O_TRACEMIGRATE	0x00010000
>  #define PTRACE_EVENT_MIGRATE	16
> +#define PTRACE_O_TRACEMIGRATE	(1 << PTRACE_EVENT_MIGRATE)
>  
>  /*
>   * Flag bits in pt_regs.flags that are part of the ptrace API.
> diff --git a/arch/tile/kernel/ptrace.c b/arch/tile/kernel/ptrace.c
> index 64ba102..b32bc3f 100644
> --- a/arch/tile/kernel/ptrace.c
> +++ b/arch/tile/kernel/ptrace.c
> @@ -151,12 +151,16 @@ long arch_ptrace(struct task_struct *child, long request,
>  
>  	case PTRACE_SETOPTIONS:
>  		/* Support TILE-specific ptrace options. */
> -		child->ptrace &= ~PT_TRACE_MASK_TILE;
> +		BUILD_BUG_ON(PTRACE_O_MASK_TILE & PTRACE_O_MASK);
>  		tmp = data & PTRACE_O_MASK_TILE;
>  		data &= ~PTRACE_O_MASK_TILE;
>  		ret = ptrace_request(child, request, addr, data);
> -		if (tmp & PTRACE_O_TRACEMIGRATE)
> -			child->ptrace |= PT_TRACE_MIGRATE;
> +		if (ret == 0) {
> +			unsigned int flags = child->ptrace;
> +			flags &= ~(PTRACE_O_MASK_TILE << PT_OPT_FLAG_SHIFT);
> +			flags |= (tmp << PT_OPT_FLAG_SHIFT);
> +			child->ptrace = flags;
> +		}
>  		break;
>  
>  	default:
> -- 
> 1.7.10.3
> 

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