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    Subject[PATCH 2/5] ptrace: simplify PTRACE_foo constants and PTRACE_SETOPTIONS code
    Date
    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@googlemail.com>
    Acked-by: Tejun Heo <tj@kernel.org>
    ---
    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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