Messages in this thread | | | Date | Thu, 10 Jan 2013 11:05:01 +0530 | From | Srikar Dronamraju <> | Subject | Re: [PATCH 1/1] uprobes: Teach handler_chain() to filter out the probed task |
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* Oleg Nesterov <oleg@redhat.com> [2012-12-29 18:36:14]:
> Currrently the are 2 problems with pre-filtering: > > 1. It is not possible to add/remove a task (mm) after uprobe_register() > > 2. A forked child inherits all breakpoints and uprobe_consumer can not > control this. > > This patch does the first step to improve the filtering. handler_chain() > removes the breakpoints installed by this uprobe from current->mm if all > handlers return UPROBE_HANDLER_REMOVE. > > Note that handler_chain() relies on ->register_rwsem to avoid the race > with uprobe_register/unregister which can add/del a consumer, or even > remove and then insert the new uprobe at the same address. > > Perhaps we will add uprobe_apply_mm(uprobe, mm, is_register) and teach > copy_mm() to do filter(UPROBE_FILTER_FORK), but I think this change makes > sense anyway. > > Note: instead of checking the retcode from uc->handler, we could add > uc->filter(UPROBE_FILTER_BPHIT). But I think this is not optimal to > call 2 hooks in a row. This buys nothing, and if handler/filter do > something nontrivial they will probably do the same work twice. > > Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
> --- > include/linux/uprobes.h | 3 ++ > kernel/events/uprobes.c | 58 ++++++++++++++++++++++++++++++++++++++-------- > 2 files changed, 51 insertions(+), 10 deletions(-) > > diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h > index c2df693..95d0002 100644 > --- a/include/linux/uprobes.h > +++ b/include/linux/uprobes.h > @@ -35,6 +35,9 @@ struct inode; > # include <asm/uprobes.h> > #endif > > +#define UPROBE_HANDLER_REMOVE 1 > +#define UPROBE_HANDLER_MASK 1 > + > enum uprobe_filter_ctx { > UPROBE_FILTER_REGISTER, > UPROBE_FILTER_UNREGISTER, > diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c > index e2ebb6f..59b6e97 100644 > --- a/kernel/events/uprobes.c > +++ b/kernel/events/uprobes.c > @@ -440,16 +440,6 @@ static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset) > return uprobe; > } > > -static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs) > -{ > - struct uprobe_consumer *uc; > - > - down_read(&uprobe->register_rwsem); > - for (uc = uprobe->consumers; uc; uc = uc->next) > - uc->handler(uc, regs); > - up_read(&uprobe->register_rwsem); > -} > - > static void consumer_add(struct uprobe *uprobe, struct uprobe_consumer *uc) > { > down_write(&uprobe->consumer_rwsem); > @@ -882,6 +872,33 @@ void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consume > put_uprobe(uprobe); > } > > +static int unapply_uprobe(struct uprobe *uprobe, struct mm_struct *mm) > +{ > + struct vm_area_struct *vma; > + int err = 0; > + > + down_read(&mm->mmap_sem); > + for (vma = mm->mmap; vma; vma = vma->vm_next) { > + unsigned long vaddr; > + loff_t offset; > + > + if (!valid_vma(vma, false) || > + vma->vm_file->f_mapping->host != uprobe->inode) > + continue; > + > + offset = (loff_t)vma->vm_pgoff << PAGE_SHIFT; > + if (uprobe->offset < offset || > + uprobe->offset >= offset + vma->vm_end - vma->vm_start) > + continue; > + > + vaddr = offset_to_vaddr(vma, uprobe->offset); > + err |= remove_breakpoint(uprobe, mm, vaddr); > + } > + up_read(&mm->mmap_sem); > + > + return err; > +} > + > static struct rb_node * > find_node_in_range(struct inode *inode, loff_t min, loff_t max) > { > @@ -1435,6 +1452,27 @@ static struct uprobe *find_active_uprobe(unsigned long bp_vaddr, int *is_swbp) > return uprobe; > } > > +static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs) > +{ > + struct uprobe_consumer *uc; > + int remove = UPROBE_HANDLER_REMOVE; > + > + down_read(&uprobe->register_rwsem); > + for (uc = uprobe->consumers; uc; uc = uc->next) { > + int rc = uc->handler(uc, regs); > + > + WARN(rc & ~UPROBE_HANDLER_MASK, > + "bad rc=0x%x from %pf()\n", rc, uc->handler); > + remove &= rc; > + } > + > + if (remove && uprobe->consumers) { > + WARN_ON(!uprobe_is_active(uprobe)); > + unapply_uprobe(uprobe, current->mm); > + } > + up_read(&uprobe->register_rwsem); > +} > + > /* > * Run handler and ask thread to singlestep. > * Ensure all non-fatal signals cannot interrupt thread while it singlesteps. > -- > 1.5.5.1 > >
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