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    SubjectRe: [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@googlemail.com>
    > Acked-by: Tejun Heo <tj@kernel.org>

    Reviewed-by: Oleg Nesterov <oleg@redhat.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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