[PATCH] consolidate sys_ptrace()

The sys_ptrace boilerplate code (everything outside the big switch
statement for the arch-specific requests) is shared by most architectures.
This patch moves it to kernel/ptrace.c and leaves the arch-specific code as
arch_ptrace.

Some architectures have a too different ptrace so we have to exclude them.
They continue to keep their implementations.  For sh64 I had to add a
sh64_ptrace wrapper because it does some initialization on the first call.
For um I removed an ifdefed SUBARCH_PTRACE_SPECIAL block, but
SUBARCH_PTRACE_SPECIAL isn't defined anywhere in the tree.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Paul Mackerras <paulus@samba.org>
Acked-by: Ralf Baechle <ralf@linux-mips.org>
Acked-By: David Howells <dhowells@redhat.com>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Acked-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 82 insertions, 0 deletions

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 863eee8bff47..5b8dd98a230e 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -406,3 +406,85 @@ int ptrace_request(struct task_struct *child, long request,
 
         return ret;
 }
+
+#ifndef __ARCH_SYS_PTRACE
+static int ptrace_get_task_struct(long request, long pid,
+                struct task_struct **childp)
+{
+        struct task_struct *child;
+        int ret;
+
+        /*
+         * Callers use child == NULL as an indication to exit early even
+         * when the return value is 0, so make sure it is non-NULL here.
+         */
+        *childp = NULL;
+
+        if (request == PTRACE_TRACEME) {
+                /*
+                 * Are we already being traced?
+                 */
+                if (current->ptrace & PT_PTRACED)
+                        return -EPERM;
+                ret = security_ptrace(current->parent, current);
+                if (ret)
+                        return -EPERM;
+                /*
+                 * Set the ptrace bit in the process ptrace flags.
+                 */
+                current->ptrace |= PT_PTRACED;
+                return 0;
+        }
+
+        /*
+         * You may not mess with init
+         */
+        if (pid == 1)
+                return -EPERM;
+
+        ret = -ESRCH;
+        read_lock(&tasklist_lock);
+        child = find_task_by_pid(pid);
+        if (child)
+                get_task_struct(child);
+        read_unlock(&tasklist_lock);
+        if (!child)
+                return -ESRCH;
+
+        *childp = child;
+        return 0;
+}
+
+asmlinkage long sys_ptrace(long request, long pid, long addr, long data)
+{
+        struct task_struct *child;
+        long ret;
+
+        /*
+         * This lock_kernel fixes a subtle race with suid exec
+         */
+        lock_kernel();
+        ret = ptrace_get_task_struct(request, pid, &child);
+        if (!child)
+                goto out;
+
+        if (request == PTRACE_ATTACH) {
+                ret = ptrace_attach(child);
+                goto out;
+        }
+
+        ret = ptrace_check_attach(child, request == PTRACE_KILL);
+        if (ret < 0)
+                goto out_put_task_struct;
+
+        ret = arch_ptrace(child, request, addr, data);
+        if (ret < 0)
+                goto out_put_task_struct;
+
+ out_put_task_struct:
+        put_task_struct(child);
+ out:
+        unlock_kernel();
+        return ret;
+}
+#endif /* __ARCH_SYS_PTRACE */