Re: [RFC PATCH v4 5/6] uretprobes: invoke return probe handlers

2013-03-05 Thread Anton Arapov 
On Mon, Mar 04, 2013 at 05:51:20PM +0100, Oleg Nesterov wrote:
> On 03/04, Anton Arapov wrote:
> >
> > +static void handle_uretprobe(struct xol_area *area, struct pt_regs *regs)
> > +{
> > +   struct hlist_head *head;
> > +   struct hlist_node *tmp;
> > +   struct return_uprobe_i *ri;
> > +   struct uprobe_task *utask;
> > +   unsigned long orig_ret_vaddr;
> > +
> > +   /* TODO: uretprobe bypass logic */
> > +
> > +   utask = get_utask();
> > +   if (!utask) {
> > +   /* TODO:RFC task is not probed, do we want printk here? */
> > +   return;
> > +   }
> > +   head = >return_uprobes;
> > +   hlist_for_each_entry_safe(ri, tmp, head, hlist) {
> > +   if (ri->uprobe->consumers) {
> > +   instruction_pointer_set(regs, ri->orig_ret_vaddr);
> This doesn't look right if ri->orig_ret_vaddr == area->vaddr. We should
> splice the list and find orig_ret_vaddr in advance.
True, this cycle is buggy. I will rework handle_uretprobe().

> > @@ -1589,8 +1639,11 @@ static void handle_swbp(struct pt_regs *regs)
> >
> > if (!uprobe) {
> > if (is_swbp > 0) {
> > -   /* No matching uprobe; signal SIGTRAP. */
> > -   send_sig(SIGTRAP, current, 0);
> > +   area = get_xol_area();
> > +   if (area && bp_vaddr == area->vaddr)
> > +   handle_uretprobe(area, regs);
> > +   else
> > +   send_sig(SIGTRAP, current, 0);
> 
> Why? We can check bp_vaddr at the start, before find_active_uprobe().
For some reason, I was thinking it is better to hide this logic under
if (!uprobe). Will correct this chunk.

> And I'd suggest to not use area->vaddr directly, imho a trivial helper
> makes sense.
I see the idea behind, with this change it will be more clear and
fragile in case someone change the underneath logic. Will do this.

thank you very much!
Anton.
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Re: [RFC PATCH v4 5/6] uretprobes: invoke return probe handlers

2013-03-05 Thread Anton Arapov 
On Tue, Mar 05, 2013 at 12:33:26PM +0530, Ananth N Mavinakayanahalli wrote:
> On Mon, Mar 04, 2013 at 03:38:12PM +0100, Anton Arapov wrote:
> > 
> > diff --git a/arch/x86/include/asm/uprobes.h b/arch/x86/include/asm/uprobes.h
> > index c353555..fa9d9de 100644
> > --- a/arch/x86/include/asm/uprobes.h
> > +++ b/arch/x86/include/asm/uprobes.h
> > @@ -56,4 +56,9 @@ extern bool arch_uprobe_xol_was_trapped(struct 
> > task_struct *tsk);
> >  extern int  arch_uprobe_exception_notify(struct notifier_block *self, 
> > unsigned long val, void *data);
> >  extern void arch_uprobe_abort_xol(struct arch_uprobe *aup, struct pt_regs 
> > *regs);
> >  extern unsigned long arch_uretprobe_hijack_return_addr(unsigned long 
> > rp_trampoline_vaddr, struct pt_regs *regs);
> > +
> > +static inline unsigned long arch_uretprobe_get_sp(struct pt_regs *regs)
> > +{
> > +   return (unsigned long)regs->sp;
> > +}
> 
> You could use GET_USP() here.
perhaps, which in turn is a helper for user_stack_pointer() :) comment
is valid though.

thanks,
Anton.
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Re: [RFC PATCH v4 5/6] uretprobes: invoke return probe handlers

2013-03-05 Thread Anton Arapov 
On Tue, Mar 05, 2013 at 12:33:26PM +0530, Ananth N Mavinakayanahalli wrote:
 On Mon, Mar 04, 2013 at 03:38:12PM +0100, Anton Arapov wrote:
  
  diff --git a/arch/x86/include/asm/uprobes.h b/arch/x86/include/asm/uprobes.h
  index c353555..fa9d9de 100644
  --- a/arch/x86/include/asm/uprobes.h
  +++ b/arch/x86/include/asm/uprobes.h
  @@ -56,4 +56,9 @@ extern bool arch_uprobe_xol_was_trapped(struct 
  task_struct *tsk);
   extern int  arch_uprobe_exception_notify(struct notifier_block *self, 
  unsigned long val, void *data);
   extern void arch_uprobe_abort_xol(struct arch_uprobe *aup, struct pt_regs 
  *regs);
   extern unsigned long arch_uretprobe_hijack_return_addr(unsigned long 
  rp_trampoline_vaddr, struct pt_regs *regs);
  +
  +static inline unsigned long arch_uretprobe_get_sp(struct pt_regs *regs)
  +{
  +   return (unsigned long)regs-sp;
  +}
 
 You could use GET_USP() here.
perhaps, which in turn is a helper for user_stack_pointer() :) comment
is valid though.

thanks,
Anton.
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Re: [RFC PATCH v4 5/6] uretprobes: invoke return probe handlers

2013-03-05 Thread Anton Arapov 
On Mon, Mar 04, 2013 at 05:51:20PM +0100, Oleg Nesterov wrote:
 On 03/04, Anton Arapov wrote:
 
  +static void handle_uretprobe(struct xol_area *area, struct pt_regs *regs)
  +{
  +   struct hlist_head *head;
  +   struct hlist_node *tmp;
  +   struct return_uprobe_i *ri;
  +   struct uprobe_task *utask;
  +   unsigned long orig_ret_vaddr;
  +
  +   /* TODO: uretprobe bypass logic */
  +
  +   utask = get_utask();
  +   if (!utask) {
  +   /* TODO:RFC task is not probed, do we want printk here? */
  +   return;
  +   }
  +   head = utask-return_uprobes;
  +   hlist_for_each_entry_safe(ri, tmp, head, hlist) {
  +   if (ri-uprobe-consumers) {
  +   instruction_pointer_set(regs, ri-orig_ret_vaddr);
 This doesn't look right if ri-orig_ret_vaddr == area-vaddr. We should
 splice the list and find orig_ret_vaddr in advance.
True, this cycle is buggy. I will rework handle_uretprobe().

  @@ -1589,8 +1639,11 @@ static void handle_swbp(struct pt_regs *regs)
 
  if (!uprobe) {
  if (is_swbp  0) {
  -   /* No matching uprobe; signal SIGTRAP. */
  -   send_sig(SIGTRAP, current, 0);
  +   area = get_xol_area();
  +   if (area  bp_vaddr == area-vaddr)
  +   handle_uretprobe(area, regs);
  +   else
  +   send_sig(SIGTRAP, current, 0);
 
 Why? We can check bp_vaddr at the start, before find_active_uprobe().
For some reason, I was thinking it is better to hide this logic under
if (!uprobe). Will correct this chunk.

 And I'd suggest to not use area-vaddr directly, imho a trivial helper
 makes sense.
I see the idea behind, with this change it will be more clear and
fragile in case someone change the underneath logic. Will do this.

thank you very much!
Anton.
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Re: [RFC PATCH v4 5/6] uretprobes: invoke return probe handlers

2013-03-04 Thread Ananth N Mavinakayanahalli 
On Mon, Mar 04, 2013 at 03:38:12PM +0100, Anton Arapov wrote:
> 
> diff --git a/arch/x86/include/asm/uprobes.h b/arch/x86/include/asm/uprobes.h
> index c353555..fa9d9de 100644
> --- a/arch/x86/include/asm/uprobes.h
> +++ b/arch/x86/include/asm/uprobes.h
> @@ -56,4 +56,9 @@ extern bool arch_uprobe_xol_was_trapped(struct task_struct 
> *tsk);
>  extern int  arch_uprobe_exception_notify(struct notifier_block *self, 
> unsigned long val, void *data);
>  extern void arch_uprobe_abort_xol(struct arch_uprobe *aup, struct pt_regs 
> *regs);
>  extern unsigned long arch_uretprobe_hijack_return_addr(unsigned long 
> rp_trampoline_vaddr, struct pt_regs *regs);
> +
> +static inline unsigned long arch_uretprobe_get_sp(struct pt_regs *regs)
> +{
> + return (unsigned long)regs->sp;
> +}

You could use GET_USP() here.

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Re: [RFC PATCH v4 5/6] uretprobes: invoke return probe handlers

2013-03-04 Thread Oleg Nesterov 
On 03/04, Anton Arapov wrote:
>
> +static void handle_uretprobe(struct xol_area *area, struct pt_regs *regs)
> +{
> + struct hlist_head *head;
> + struct hlist_node *tmp;
> + struct return_uprobe_i *ri;
> + struct uprobe_task *utask;
> + unsigned long orig_ret_vaddr;
> +
> + /* TODO: uretprobe bypass logic */
> +
> + utask = get_utask();
> + if (!utask) {
> + /* TODO:RFC task is not probed, do we want printk here? */
> + return;
> + }
> + head = >return_uprobes;
> + hlist_for_each_entry_safe(ri, tmp, head, hlist) {
> + if (ri->uprobe->consumers) {
> + instruction_pointer_set(regs, ri->orig_ret_vaddr);

This doesn't look right if ri->orig_ret_vaddr == area->vaddr. We should
splice the list and find orig_ret_vaddr in advance.

> @@ -1589,8 +1639,11 @@ static void handle_swbp(struct pt_regs *regs)
>
>   if (!uprobe) {
>   if (is_swbp > 0) {
> - /* No matching uprobe; signal SIGTRAP. */
> - send_sig(SIGTRAP, current, 0);
> + area = get_xol_area();
> + if (area && bp_vaddr == area->vaddr)
> + handle_uretprobe(area, regs);
> + else
> + send_sig(SIGTRAP, current, 0);

Why? We can check bp_vaddr at the start, before find_active_uprobe().

And I'd suggest to not use area->vaddr directly, imho a trivial helper
makes sense.

Oleg.

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[RFC PATCH v4 5/6] uretprobes: invoke return probe handlers

2013-03-04 Thread Anton Arapov 
  Uretprobe handlers are invoked when the trampoline is hit, on completion the
trampoline is replaced with the saved return address and the uretprobe instance
deleted.

v4:
 - check, whether utask is not NULL in handle_uretprobe()
   ? do we want a printk() for this case?
 - get rid of area->rp_trampoline_vaddr
 - minor handle_uretprobe() fixups
v3:
 - protected uprobe with refcounter. See put_uprobe() in handle_uretprobe()
that reflects increment in prepare_uretprobe()
v2:
 - get rid of ->return_consumers member from struct uprobe, introduce
rp_handler() in consumer instead

Signed-off-by: Anton Arapov 
---
 arch/x86/include/asm/uprobes.h |  5 
 kernel/events/uprobes.c| 57 --
 2 files changed, 60 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/uprobes.h b/arch/x86/include/asm/uprobes.h
index c353555..fa9d9de 100644
--- a/arch/x86/include/asm/uprobes.h
+++ b/arch/x86/include/asm/uprobes.h
@@ -56,4 +56,9 @@ extern bool arch_uprobe_xol_was_trapped(struct task_struct 
*tsk);
 extern int  arch_uprobe_exception_notify(struct notifier_block *self, unsigned 
long val, void *data);
 extern void arch_uprobe_abort_xol(struct arch_uprobe *aup, struct pt_regs 
*regs);
 extern unsigned long arch_uretprobe_hijack_return_addr(unsigned long 
rp_trampoline_vaddr, struct pt_regs *regs);
+
+static inline unsigned long arch_uretprobe_get_sp(struct pt_regs *regs)
+{
+   return (unsigned long)regs->sp;
+}
 #endif /* _ASM_UPROBES_H */
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 12acc10..e86b6ea 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1574,6 +1574,55 @@ static void handler_chain(struct uprobe *uprobe, struct 
pt_regs *regs)
up_read(>register_rwsem);
 }
 
+static void handler_uretprobe_chain(struct uprobe *uprobe, struct pt_regs 
*regs)
+{
+   struct uprobe_consumer *uc;
+
+   down_read(>register_rwsem);
+   for (uc = uprobe->consumers; uc; uc = uc->next) {
+   if (uc->rp_handler)
+   uc->rp_handler(uc, regs);
+   }
+   up_read(>register_rwsem);
+}
+
+static void handle_uretprobe(struct xol_area *area, struct pt_regs *regs)
+{
+   struct hlist_head *head;
+   struct hlist_node *tmp;
+   struct return_uprobe_i *ri;
+   struct uprobe_task *utask;
+   unsigned long orig_ret_vaddr;
+
+   /* TODO: uretprobe bypass logic */
+
+   utask = get_utask();
+   if (!utask) {
+   /* TODO:RFC task is not probed, do we want printk here? */
+   return;
+   }
+   head = >return_uprobes;
+   hlist_for_each_entry_safe(ri, tmp, head, hlist) {
+   if (ri->uprobe->consumers) {
+   instruction_pointer_set(regs, ri->orig_ret_vaddr);
+   handler_uretprobe_chain(ri->uprobe, regs);
+   }
+
+   orig_ret_vaddr = ri->orig_ret_vaddr;
+   put_uprobe(ri->uprobe);
+   hlist_del(>hlist);
+   kfree(ri);
+
+   if (orig_ret_vaddr != area->vaddr)
+   return;
+   }
+
+   /* TODO: change the message */
+   printk(KERN_ERR "uprobe: no instance found! pid/tgid=%d/%d",
+   current->pid, current->tgid);
+   send_sig(SIGSEGV, current, 0);
+}
+
 /*
  * Run handler and ask thread to singlestep.
  * Ensure all non-fatal signals cannot interrupt thread while it singlesteps.
@@ -1581,6 +1630,7 @@ static void handler_chain(struct uprobe *uprobe, struct 
pt_regs *regs)
 static void handle_swbp(struct pt_regs *regs)
 {
struct uprobe *uprobe;
+   struct xol_area *area;
unsigned long bp_vaddr;
int uninitialized_var(is_swbp);
 
@@ -1589,8 +1639,11 @@ static void handle_swbp(struct pt_regs *regs)
 
if (!uprobe) {
if (is_swbp > 0) {
-   /* No matching uprobe; signal SIGTRAP. */
-   send_sig(SIGTRAP, current, 0);
+   area = get_xol_area();
+   if (area && bp_vaddr == area->vaddr)
+   handle_uretprobe(area, regs);
+   else
+   send_sig(SIGTRAP, current, 0);
} else {
/*
 * Either we raced with uprobe_unregister() or we can't
-- 
1.8.1.2

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[RFC PATCH v4 5/6] uretprobes: invoke return probe handlers

2013-03-04 Thread Anton Arapov 
  Uretprobe handlers are invoked when the trampoline is hit, on completion the
trampoline is replaced with the saved return address and the uretprobe instance
deleted.

v4:
 - check, whether utask is not NULL in handle_uretprobe()
   ? do we want a printk() for this case?
 - get rid of area-rp_trampoline_vaddr
 - minor handle_uretprobe() fixups
v3:
 - protected uprobe with refcounter. See put_uprobe() in handle_uretprobe()
that reflects increment in prepare_uretprobe()
v2:
 - get rid of -return_consumers member from struct uprobe, introduce
rp_handler() in consumer instead

Signed-off-by: Anton Arapov an...@redhat.com
---
 arch/x86/include/asm/uprobes.h |  5 
 kernel/events/uprobes.c| 57 --
 2 files changed, 60 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/uprobes.h b/arch/x86/include/asm/uprobes.h
index c353555..fa9d9de 100644
--- a/arch/x86/include/asm/uprobes.h
+++ b/arch/x86/include/asm/uprobes.h
@@ -56,4 +56,9 @@ extern bool arch_uprobe_xol_was_trapped(struct task_struct 
*tsk);
 extern int  arch_uprobe_exception_notify(struct notifier_block *self, unsigned 
long val, void *data);
 extern void arch_uprobe_abort_xol(struct arch_uprobe *aup, struct pt_regs 
*regs);
 extern unsigned long arch_uretprobe_hijack_return_addr(unsigned long 
rp_trampoline_vaddr, struct pt_regs *regs);
+
+static inline unsigned long arch_uretprobe_get_sp(struct pt_regs *regs)
+{
+   return (unsigned long)regs-sp;
+}
 #endif /* _ASM_UPROBES_H */
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 12acc10..e86b6ea 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1574,6 +1574,55 @@ static void handler_chain(struct uprobe *uprobe, struct 
pt_regs *regs)
up_read(uprobe-register_rwsem);
 }
 
+static void handler_uretprobe_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) {
+   if (uc-rp_handler)
+   uc-rp_handler(uc, regs);
+   }
+   up_read(uprobe-register_rwsem);
+}
+
+static void handle_uretprobe(struct xol_area *area, struct pt_regs *regs)
+{
+   struct hlist_head *head;
+   struct hlist_node *tmp;
+   struct return_uprobe_i *ri;
+   struct uprobe_task *utask;
+   unsigned long orig_ret_vaddr;
+
+   /* TODO: uretprobe bypass logic */
+
+   utask = get_utask();
+   if (!utask) {
+   /* TODO:RFC task is not probed, do we want printk here? */
+   return;
+   }
+   head = utask-return_uprobes;
+   hlist_for_each_entry_safe(ri, tmp, head, hlist) {
+   if (ri-uprobe-consumers) {
+   instruction_pointer_set(regs, ri-orig_ret_vaddr);
+   handler_uretprobe_chain(ri-uprobe, regs);
+   }
+
+   orig_ret_vaddr = ri-orig_ret_vaddr;
+   put_uprobe(ri-uprobe);
+   hlist_del(ri-hlist);
+   kfree(ri);
+
+   if (orig_ret_vaddr != area-vaddr)
+   return;
+   }
+
+   /* TODO: change the message */
+   printk(KERN_ERR uprobe: no instance found! pid/tgid=%d/%d,
+   current-pid, current-tgid);
+   send_sig(SIGSEGV, current, 0);
+}
+
 /*
  * Run handler and ask thread to singlestep.
  * Ensure all non-fatal signals cannot interrupt thread while it singlesteps.
@@ -1581,6 +1630,7 @@ static void handler_chain(struct uprobe *uprobe, struct 
pt_regs *regs)
 static void handle_swbp(struct pt_regs *regs)
 {
struct uprobe *uprobe;
+   struct xol_area *area;
unsigned long bp_vaddr;
int uninitialized_var(is_swbp);
 
@@ -1589,8 +1639,11 @@ static void handle_swbp(struct pt_regs *regs)
 
if (!uprobe) {
if (is_swbp  0) {
-   /* No matching uprobe; signal SIGTRAP. */
-   send_sig(SIGTRAP, current, 0);
+   area = get_xol_area();
+   if (area  bp_vaddr == area-vaddr)
+   handle_uretprobe(area, regs);
+   else
+   send_sig(SIGTRAP, current, 0);
} else {
/*
 * Either we raced with uprobe_unregister() or we can't
-- 
1.8.1.2

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Re: [RFC PATCH v4 5/6] uretprobes: invoke return probe handlers

2013-03-04 Thread Oleg Nesterov 
On 03/04, Anton Arapov wrote:

 +static void handle_uretprobe(struct xol_area *area, struct pt_regs *regs)
 +{
 + struct hlist_head *head;
 + struct hlist_node *tmp;
 + struct return_uprobe_i *ri;
 + struct uprobe_task *utask;
 + unsigned long orig_ret_vaddr;
 +
 + /* TODO: uretprobe bypass logic */
 +
 + utask = get_utask();
 + if (!utask) {
 + /* TODO:RFC task is not probed, do we want printk here? */
 + return;
 + }
 + head = utask-return_uprobes;
 + hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 + if (ri-uprobe-consumers) {
 + instruction_pointer_set(regs, ri-orig_ret_vaddr);

This doesn't look right if ri-orig_ret_vaddr == area-vaddr. We should
splice the list and find orig_ret_vaddr in advance.

 @@ -1589,8 +1639,11 @@ static void handle_swbp(struct pt_regs *regs)

   if (!uprobe) {
   if (is_swbp  0) {
 - /* No matching uprobe; signal SIGTRAP. */
 - send_sig(SIGTRAP, current, 0);
 + area = get_xol_area();
 + if (area  bp_vaddr == area-vaddr)
 + handle_uretprobe(area, regs);
 + else
 + send_sig(SIGTRAP, current, 0);

Why? We can check bp_vaddr at the start, before find_active_uprobe().

And I'd suggest to not use area-vaddr directly, imho a trivial helper
makes sense.

Oleg.

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Re: [RFC PATCH v4 5/6] uretprobes: invoke return probe handlers

2013-03-04 Thread Ananth N Mavinakayanahalli 
On Mon, Mar 04, 2013 at 03:38:12PM +0100, Anton Arapov wrote:
 
 diff --git a/arch/x86/include/asm/uprobes.h b/arch/x86/include/asm/uprobes.h
 index c353555..fa9d9de 100644
 --- a/arch/x86/include/asm/uprobes.h
 +++ b/arch/x86/include/asm/uprobes.h
 @@ -56,4 +56,9 @@ extern bool arch_uprobe_xol_was_trapped(struct task_struct 
 *tsk);
  extern int  arch_uprobe_exception_notify(struct notifier_block *self, 
 unsigned long val, void *data);
  extern void arch_uprobe_abort_xol(struct arch_uprobe *aup, struct pt_regs 
 *regs);
  extern unsigned long arch_uretprobe_hijack_return_addr(unsigned long 
 rp_trampoline_vaddr, struct pt_regs *regs);
 +
 +static inline unsigned long arch_uretprobe_get_sp(struct pt_regs *regs)
 +{
 + return (unsigned long)regs-sp;
 +}

You could use GET_USP() here.

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