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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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