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SubjectRe: [PATCH 3/7] uprobes: Introduce uprobe_apply()
* Oleg Nesterov <oleg@redhat.com> [2013-02-04 20:02:50]:

> Currently it is not possible to change the filtering constraints after
> uprobe_register(), so a consumer can not, say, start to trace a task/mm
> which was previously filtered out, or remove the no longer needed bp's.
>
> Introduce uprobe_apply() which simply does register_for_each_vma() again
> to consult uprobe_consumer->filter() and install/remove the breakpoints.
> The only complication is that register_for_each_vma() can no longer
> assume that uprobe->consumers should be consulter if is_register == T,
> so we change it to accept "struct uprobe_consumer *new" instead.
>
> Unlike uprobe_register(), uprobe_apply(true) doesn't do "unregister" if
> register_for_each_vma() fails, it is up to caller to handle the error.
>
> Note: we probably need to cleanup the current interface, it is strange
> that uprobe_apply/unregister need inode/offset. We should either change
> uprobe_register() to return "struct uprobe *", or add a private ->uprobe
> member in uprobe_consumer. And in the long term uprobe_apply() should
> take a single argument, uprobe or consumer, even "bool add" should go
> away.
>
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>


Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

> ---
> include/linux/uprobes.h | 6 ++++++
> kernel/events/uprobes.c | 39 +++++++++++++++++++++++++++++++++++----
> 2 files changed, 41 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
> index 95d0002..02b83db 100644
> --- a/include/linux/uprobes.h
> +++ b/include/linux/uprobes.h
> @@ -101,6 +101,7 @@ extern int __weak set_swbp(struct arch_uprobe *aup, struct mm_struct *mm, unsign
> extern int __weak set_orig_insn(struct arch_uprobe *aup, struct mm_struct *mm, unsigned long vaddr);
> extern bool __weak is_swbp_insn(uprobe_opcode_t *insn);
> extern int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *uc);
> +extern int uprobe_apply(struct inode *inode, loff_t offset, struct uprobe_consumer *uc, bool);
> extern void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc);
> extern int uprobe_mmap(struct vm_area_struct *vma);
> extern void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end);
> @@ -124,6 +125,11 @@ uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
> {
> return -ENOSYS;
> }
> +static inline int
> +uprobe_apply(struct inode *inode, loff_t offset, struct uprobe_consumer *uc, bool add)
> +{
> + return -ENOSYS;
> +}
> static inline void
> uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
> {
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index 23340a7..2bcd08e 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -733,8 +733,10 @@ build_map_info(struct address_space *mapping, loff_t offset, bool is_register)
> return curr;
> }
>
> -static int register_for_each_vma(struct uprobe *uprobe, bool is_register)
> +static int
> +register_for_each_vma(struct uprobe *uprobe, struct uprobe_consumer *new)
> {
> + bool is_register = !!new;
> struct map_info *info;
> int err = 0;
>
> @@ -765,7 +767,7 @@ static int register_for_each_vma(struct uprobe *uprobe, bool is_register)
>
> if (is_register) {
> /* consult only the "caller", new consumer. */
> - if (consumer_filter(uprobe->consumers,
> + if (consumer_filter(new,
> UPROBE_FILTER_REGISTER, mm))
> err = install_breakpoint(uprobe, mm, vma, info->vaddr);
> } else if (test_bit(MMF_HAS_UPROBES, &mm->flags)) {
> @@ -788,7 +790,7 @@ static int register_for_each_vma(struct uprobe *uprobe, bool is_register)
> static int __uprobe_register(struct uprobe *uprobe, struct uprobe_consumer *uc)
> {
> consumer_add(uprobe, uc);
> - return register_for_each_vma(uprobe, true);
> + return register_for_each_vma(uprobe, uc);
> }
>
> static void __uprobe_unregister(struct uprobe *uprobe, struct uprobe_consumer *uc)
> @@ -798,7 +800,7 @@ static void __uprobe_unregister(struct uprobe *uprobe, struct uprobe_consumer *u
> if (!consumer_del(uprobe, uc)) /* WARN? */
> return;
>
> - err = register_for_each_vma(uprobe, false);
> + err = register_for_each_vma(uprobe, NULL);
> /* TODO : cant unregister? schedule a worker thread */
> if (!uprobe->consumers && !err)
> delete_uprobe(uprobe);
> @@ -855,6 +857,35 @@ int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *
> EXPORT_SYMBOL_GPL(uprobe_register);
>
> /*
> + * uprobe_apply - unregister a already registered probe.
> + * @inode: the file in which the probe has to be removed.
> + * @offset: offset from the start of the file.
> + * @uc: consumer which wants to add more or remove some breakpoints
> + * @add: add or remove the breakpoints
> + */
> +int uprobe_apply(struct inode *inode, loff_t offset,
> + struct uprobe_consumer *uc, bool add)
> +{
> + struct uprobe *uprobe;
> + struct uprobe_consumer *con;
> + int ret = -ENOENT;
> +
> + uprobe = find_uprobe(inode, offset);
> + if (!uprobe)
> + return ret;
> +
> + down_write(&uprobe->register_rwsem);
> + for (con = uprobe->consumers; con && con != uc ; con = con->next)
> + ;
> + if (con)
> + ret = register_for_each_vma(uprobe, add ? uc : NULL);
> + up_write(&uprobe->register_rwsem);
> + put_uprobe(uprobe);
> +
> + return ret;
> +}
> +
> +/*
> * uprobe_unregister - unregister a already registered probe.
> * @inode: the file in which the probe has to be removed.
> * @offset: offset from the start of the file.
> --
> 1.5.5.1
>

--
Thanks and Regards
Srikar Dronamraju



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