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Date: Fri, 10 Feb 2012 18:17:20 +0100
From: Oleg Nesterov <oleg@...hat.com>
To: Denys Vlasenko <vda.linux@...glemail.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Tejun Heo <tj@...nel.org>, Pedro Alves <palves@...hat.com>,
Jan Kratochvil <jan.kratochvil@...hat.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/5] ptrace: simplify PTRACE_foo constants and
PTRACE_SETOPTIONS code
On 02/10, Denys Vlasenko wrote:
>
> Exchange PT_TRACESYSGOOD and PT_PTRACE_CAP bit positions, which makes
> PT_option bits contiguous and therefore makes code in ptrace_setoptions()
> much simpler.
>
> Every PTRACE_O_TRACEevent is defined to (1 << PTRACE_EVENT_event)
> instead of using explicit numeric constants, to ensure we don't
> mess up relationship between bit positions and event ids.
>
> PT_EVENT_FLAG_SHIFT was not particularly useful, PT_OPT_FLAG_SHIFT with
> value of PT_EVENT_FLAG_SHIFT-1 is easier to use.
>
> PT_TRACE_MASK constant is nuked, the only its use is replaced by
> (PTRACE_O_MASK << PT_OPT_FLAG_SHIFT).
>
> Signed-off-by: Denys Vlasenko <vda.linux@...glemail.com>
> Acked-by: Tejun Heo <tj@...nel.org>
Reviewed-by: Oleg Nesterov <oleg@...hat.com>
> ---
> include/linux/ptrace.h | 33 +++++++++++++++------------------
> kernel/ptrace.c | 31 ++++++++-----------------------
> 2 files changed, 23 insertions(+), 41 deletions(-)
>
> diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
> index c2f1f6a..06be6a3 100644
> --- a/include/linux/ptrace.h
> +++ b/include/linux/ptrace.h
> @@ -54,17 +54,6 @@
> /* flags in @data for PTRACE_SEIZE */
> #define PTRACE_SEIZE_DEVEL 0x80000000 /* temp flag for development */
>
> -/* options set using PTRACE_SETOPTIONS */
> -#define PTRACE_O_TRACESYSGOOD 0x00000001
> -#define PTRACE_O_TRACEFORK 0x00000002
> -#define PTRACE_O_TRACEVFORK 0x00000004
> -#define PTRACE_O_TRACECLONE 0x00000008
> -#define PTRACE_O_TRACEEXEC 0x00000010
> -#define PTRACE_O_TRACEVFORKDONE 0x00000020
> -#define PTRACE_O_TRACEEXIT 0x00000040
> -
> -#define PTRACE_O_MASK 0x0000007f
> -
> /* Wait extended result codes for the above trace options. */
> #define PTRACE_EVENT_FORK 1
> #define PTRACE_EVENT_VFORK 2
> @@ -74,6 +63,17 @@
> #define PTRACE_EVENT_EXIT 6
> #define PTRACE_EVENT_STOP 7
>
> +/* options set using PTRACE_SETOPTIONS */
> +#define PTRACE_O_TRACESYSGOOD 1
> +#define PTRACE_O_TRACEFORK (1 << PTRACE_EVENT_FORK)
> +#define PTRACE_O_TRACEVFORK (1 << PTRACE_EVENT_VFORK)
> +#define PTRACE_O_TRACECLONE (1 << PTRACE_EVENT_CLONE)
> +#define PTRACE_O_TRACEEXEC (1 << PTRACE_EVENT_EXEC)
> +#define PTRACE_O_TRACEVFORKDONE (1 << PTRACE_EVENT_VFORK_DONE)
> +#define PTRACE_O_TRACEEXIT (1 << PTRACE_EVENT_EXIT)
> +
> +#define PTRACE_O_MASK 0x0000007f
> +
> #include <asm/ptrace.h>
>
> #ifdef __KERNEL__
> @@ -88,13 +88,12 @@
> #define PT_SEIZED 0x00010000 /* SEIZE used, enable new behavior */
> #define PT_PTRACED 0x00000001
> #define PT_DTRACE 0x00000002 /* delayed trace (used on m68k, i386) */
> -#define PT_TRACESYSGOOD 0x00000004
> -#define PT_PTRACE_CAP 0x00000008 /* ptracer can follow suid-exec */
> +#define PT_PTRACE_CAP 0x00000004 /* ptracer can follow suid-exec */
>
> +#define PT_OPT_FLAG_SHIFT 3
> /* PT_TRACE_* event enable flags */
> -#define PT_EVENT_FLAG_SHIFT 4
> -#define PT_EVENT_FLAG(event) (1 << (PT_EVENT_FLAG_SHIFT + (event) - 1))
> -
> +#define PT_EVENT_FLAG(event) (1 << (PT_OPT_FLAG_SHIFT + (event)))
> +#define PT_TRACESYSGOOD PT_EVENT_FLAG(0)
> #define PT_TRACE_FORK PT_EVENT_FLAG(PTRACE_EVENT_FORK)
> #define PT_TRACE_VFORK PT_EVENT_FLAG(PTRACE_EVENT_VFORK)
> #define PT_TRACE_CLONE PT_EVENT_FLAG(PTRACE_EVENT_CLONE)
> @@ -102,8 +101,6 @@
> #define PT_TRACE_VFORK_DONE PT_EVENT_FLAG(PTRACE_EVENT_VFORK_DONE)
> #define PT_TRACE_EXIT PT_EVENT_FLAG(PTRACE_EVENT_EXIT)
>
> -#define PT_TRACE_MASK 0x000003f4
> -
> /* single stepping state bits (used on ARM and PA-RISC) */
> #define PT_SINGLESTEP_BIT 31
> #define PT_SINGLESTEP (1<<PT_SINGLESTEP_BIT)
> diff --git a/kernel/ptrace.c b/kernel/ptrace.c
> index 273f56e..9acd07a 100644
> --- a/kernel/ptrace.c
> +++ b/kernel/ptrace.c
> @@ -262,7 +262,7 @@ static int ptrace_attach(struct task_struct *task, long request,
>
> /*
> * Protect exec's credential calculations against our interference;
> - * interference; SUID, SGID and LSM creds get determined differently
> + * SUID, SGID and LSM creds get determined differently
> * under ptrace.
> */
> retval = -ERESTARTNOINTR;
> @@ -528,31 +528,16 @@ int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long ds
>
> static int ptrace_setoptions(struct task_struct *child, unsigned long data)
> {
> + unsigned flags;
> +
> if (data & ~(unsigned long)PTRACE_O_MASK)
> return -EINVAL;
>
> - child->ptrace &= ~PT_TRACE_MASK;
> -
> - if (data & PTRACE_O_TRACESYSGOOD)
> - child->ptrace |= PT_TRACESYSGOOD;
> -
> - if (data & PTRACE_O_TRACEFORK)
> - child->ptrace |= PT_TRACE_FORK;
> -
> - if (data & PTRACE_O_TRACEVFORK)
> - child->ptrace |= PT_TRACE_VFORK;
> -
> - if (data & PTRACE_O_TRACECLONE)
> - child->ptrace |= PT_TRACE_CLONE;
> -
> - if (data & PTRACE_O_TRACEEXEC)
> - child->ptrace |= PT_TRACE_EXEC;
> -
> - if (data & PTRACE_O_TRACEVFORKDONE)
> - child->ptrace |= PT_TRACE_VFORK_DONE;
> -
> - if (data & PTRACE_O_TRACEEXIT)
> - child->ptrace |= PT_TRACE_EXIT;
> + /* Avoid intermediate state when all opts are cleared */
> + flags = child->ptrace;
> + flags &= ~(PTRACE_O_MASK << PT_OPT_FLAG_SHIFT);
> + flags |= (data << PT_OPT_FLAG_SHIFT);
> + child->ptrace = flags;
>
> return 0;
> }
> --
> 1.7.7.6
>
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