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Message-ID: <20131112192038.GA7748@redhat.com>
Date: Tue, 12 Nov 2013 20:20:38 +0100
From: Oleg Nesterov <oleg@...hat.com>
To: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@...ibm.com>,
Ingo Molnar <mingo@...e.hu>,
Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
Namhyung Kim <namhyung@...nel.org>,
Steven Rostedt <rostedt@...dmis.org>,
linux-kernel@...r.kernel.org
Subject: [PATCH v2] uprobes: Add uprobe_task->dup_work/dup_addr
On 11/12, Srikar Dronamraju wrote:
>
> Okay, moving to arch_uprobe_task is fine. I probably got confused by
> "First of all it is not really needed,"
OK, this doesn't look good, I agree.
Please see v2 below, I tried to improve the changelog.
> > OK. How about dup_xol_work/dup_xol_vaddr ?
>
> Yes fine with me.
Done.
I added your ack optimistically, please let me know if you think I
should change something else.
Oleg.
---
Subject: [PATCH] uprobes: Add uprobe_task->dup_xol_work/dup_xol_addr
uprobe_task->vaddr is a bit strange. The generic code uses it only
to pass the additional argument to arch_uprobe_pre_xol(), and since
it is always equal to instruction_pointer() this looks even more
strange.
And both utask->vaddr and and utask->autask have the same scope,
they only have the meaning when the task executes the probed insn
out-of-line, so it is safe to reuse both in UTASK_RUNNING state.
This all means that logically ->vaddr belongs to arch_uprobe_task
and we should probably move it there, arch_uprobe_pre_xol() can
record instruction_pointer() itself.
OTOH, it is also used by uprobe_copy_process() and dup_xol_work()
for another purpose, this doesn't look clean and doesn't allow to
move this member into arch_uprobe_task.
This patch adds the union with 2 anonymous structs into uprobe_task.
The first struct is autask + vaddr, this way we "almost" move vaddr
into autask.
The second struct has 2 new members for uprobe_copy_process() paths:
->dup_xol_addr which can be used instead ->vaddr, and ->dup_xol_work
which can be used to avoid kmalloc() and simplify the code.
Note that this union will likely have another member(s), we need
something like "private_data_for_handlers" so that the tracing
handlers could use it to communicate with call_fetch() methods.
Signed-off-by: Oleg Nesterov <oleg@...hat.com>
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Acked-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
---
include/linux/uprobes.h | 21 ++++++++++++++++-----
kernel/events/uprobes.c | 16 ++++------------
2 files changed, 20 insertions(+), 17 deletions(-)
diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
index 319eae7..2225542 100644
--- a/include/linux/uprobes.h
+++ b/include/linux/uprobes.h
@@ -26,6 +26,7 @@
#include <linux/errno.h>
#include <linux/rbtree.h>
+#include <linux/types.h>
struct vm_area_struct;
struct mm_struct;
@@ -72,14 +73,24 @@ enum uprobe_task_state {
*/
struct uprobe_task {
enum uprobe_task_state state;
- struct arch_uprobe_task autask;
- struct return_instance *return_instances;
- unsigned int depth;
- struct uprobe *active_uprobe;
+ union {
+ struct {
+ struct arch_uprobe_task autask;
+ unsigned long vaddr;
+ };
+
+ struct {
+ struct callback_head dup_xol_work;
+ unsigned long dup_xol_addr;
+ };
+ };
+ struct uprobe *active_uprobe;
unsigned long xol_vaddr;
- unsigned long vaddr;
+
+ struct return_instance *return_instances;
+ unsigned int depth;
};
/*
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 24b7d6c..df4ef09 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1403,12 +1403,10 @@ static void uprobe_warn(struct task_struct *t, const char *msg)
static void dup_xol_work(struct callback_head *work)
{
- kfree(work);
-
if (current->flags & PF_EXITING)
return;
- if (!__create_xol_area(current->utask->vaddr))
+ if (!__create_xol_area(current->utask->dup_xol_addr))
uprobe_warn(current, "dup xol area");
}
@@ -1419,7 +1417,6 @@ void uprobe_copy_process(struct task_struct *t, unsigned long flags)
{
struct uprobe_task *utask = current->utask;
struct mm_struct *mm = current->mm;
- struct callback_head *work;
struct xol_area *area;
t->utask = NULL;
@@ -1441,14 +1438,9 @@ void uprobe_copy_process(struct task_struct *t, unsigned long flags)
if (mm == t->mm)
return;
- /* TODO: move it into the union in uprobe_task */
- work = kmalloc(sizeof(*work), GFP_KERNEL);
- if (!work)
- return uprobe_warn(t, "dup xol area");
-
- t->utask->vaddr = area->vaddr;
- init_task_work(work, dup_xol_work);
- task_work_add(t, work, true);
+ t->utask->dup_xol_addr = area->vaddr;
+ init_task_work(&t->utask->dup_xol_work, dup_xol_work);
+ task_work_add(t, &t->utask->dup_xol_work, true);
}
/*
--
1.5.5.1
--
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