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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@redhat.com>
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
This commit is contained in:
Oleg Nesterov 2013-11-08 18:52:21 +01:00
parent caea6cf521
commit 3247343118
2 changed files with 20 additions and 17 deletions
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21
include/linux/uprobes.h
View File

@ -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;
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;
struct return_instance *return_instances;
unsigned int depth;
struct uprobe *active_uprobe;
unsigned long xol_vaddr;
unsigned long vaddr;
};
/*

16
kernel/events/uprobes.c
View File

@ -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);
}
/*