[PATCH] kprobes: fix compilation when KPROBE_EVENTS is enabled without kretpobes

[PATCH] kprobes: fix compilation when KPROBE_EVENTS is enabled without kretpobes

[Sven Schnelle]

While implementing kprobes on PA-RISC (without kretprobes) compilation
fails when CONFIG_KPROBE_EVENTS is enabled:

kernel/trace/trace_kprobe.o: in function `trace_kprobe_create':
kernel/trace/trace_kprobe.c:666: undefined reference to `kprobe_on_func_entry'
kernel/trace/trace_kprobe.o: in function `trace_kprobe_on_func_entry':
kernel/trace/trace_kprobe.c:167: undefined reference to `kprobe_on_func_entry'
kernel/trace/trace_kprobe.c:167: undefined reference to `kprobe_on_func_entry'
make: *** [Makefile:1029: vmlinux] Error 1

Given the fact that these functions have no dependencies on kretprobes i think
they should be moved out of the #ifdef CONFIG_KRETPROBES block.

Signed-off-by: Sven Schnelle <svens@stackframe.org>
Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
---
 kernel/kprobes.c | 39 ++++++++++++++++++++-------------------
 1 file changed, 20 insertions(+), 19 deletions(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index c83e54727131..10a7e67fea67 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1819,6 +1819,26 @@ unsigned long __weak arch_deref_entry_point(void *entry)
 	return (unsigned long)entry;
 }
 
+bool __weak arch_kprobe_on_func_entry(unsigned long offset)
+{
+	return !offset;
+}
+
+bool kprobe_on_func_entry(kprobe_opcode_t *addr, const char *sym,
+			  unsigned long offset)
+{
+	kprobe_opcode_t *kp_addr = _kprobe_addr(addr, sym, offset);
+
+	if (IS_ERR(kp_addr))
+		return false;
+
+	if (!kallsyms_lookup_size_offset((unsigned long)kp_addr, NULL, &offset) ||
+					 !arch_kprobe_on_func_entry(offset))
+		return false;
+
+	return true;
+}
+
 #ifdef CONFIG_KRETPROBES
 /*
  * This kprobe pre_handler is registered with every kretprobe. When probe
@@ -1875,25 +1895,6 @@ static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs)
 }
 NOKPROBE_SYMBOL(pre_handler_kretprobe);
 
-bool __weak arch_kprobe_on_func_entry(unsigned long offset)
-{
-	return !offset;
-}
-
-bool kprobe_on_func_entry(kprobe_opcode_t *addr, const char *sym, unsigned long offset)
-{
-	kprobe_opcode_t *kp_addr = _kprobe_addr(addr, sym, offset);
-
-	if (IS_ERR(kp_addr))
-		return false;
-
-	if (!kallsyms_lookup_size_offset((unsigned long)kp_addr, NULL, &offset) ||
-						!arch_kprobe_on_func_entry(offset))
-		return false;
-
-	return true;
-}
-
 int register_kretprobe(struct kretprobe *rp)
 {
 	int ret = 0;
-- 
2.20.1

Re: [PATCH] kprobes: fix compilation when KPROBE_EVENTS is enabled without kretpobes

[Naveen N. Rao]

Sven Schnelle wrote:
> While implementing kprobes on PA-RISC (without kretprobes) compilation
> fails when CONFIG_KPROBE_EVENTS is enabled:

Thanks for working on that! Is there a specific reason kretprobes is not 
being enabled on parisc?

> 
> kernel/trace/trace_kprobe.o: in function `trace_kprobe_create':
> kernel/trace/trace_kprobe.c:666: undefined reference to `kprobe_on_func_entry'
> kernel/trace/trace_kprobe.o: in function `trace_kprobe_on_func_entry':
> kernel/trace/trace_kprobe.c:167: undefined reference to `kprobe_on_func_entry'
> kernel/trace/trace_kprobe.c:167: undefined reference to `kprobe_on_func_entry'
> make: *** [Makefile:1029: vmlinux] Error 1
> 
> Given the fact that these functions have no dependencies on kretprobes i think
> they should be moved out of the #ifdef CONFIG_KRETPROBES block.
> 
> Signed-off-by: Sven Schnelle <svens@stackframe.org>
> Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
> Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Masami Hiramatsu <mhiramat@kernel.org>
> ---
>  kernel/kprobes.c | 39 ++++++++++++++++++++-------------------
>  1 file changed, 20 insertions(+), 19 deletions(-)

These functions were originally added only for kretprobes, but have 
taken on newer uses since then. So, for this patch:
Acked-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>

However, I wonder if we should simply remove CONFIG_KRETPROBES 
altogether. All architectures supporting kprobes today also support 
kretprobes. I don't see why anyone would want to only disable 
kretprobes.


- Naveen

Re: [PATCH] kprobes: fix compilation when KPROBE_EVENTS is enabled without kretpobes

[Sven Schnelle]

Hi Naveen,

On Sat, Apr 06, 2019 at 10:52:47PM +0530, Naveen N. Rao wrote:
> Sven Schnelle wrote:
> > While implementing kprobes on PA-RISC (without kretprobes) compilation
> > fails when CONFIG_KPROBE_EVENTS is enabled:
> 
> Thanks for working on that! Is there a specific reason kretprobes is not
> being enabled on parisc?

Reason is that i just started to add kprobes support to PA-RISC. I'm planning
doing kretprobes as a second step and have separate patches for kprobe and
kretprobe to keep things small.

Regards
Sven

Re: [PATCH] kprobes: fix compilation when KPROBE_EVENTS is enabled without kretpobes

[Masami Hiramatsu]

On Sat,  6 Apr 2019 17:55:43 +0200
Sven Schnelle <svens@stackframe.org> wrote:

> While implementing kprobes on PA-RISC (without kretprobes) compilation
> fails when CONFIG_KPROBE_EVENTS is enabled:
> 
> kernel/trace/trace_kprobe.o: in function `trace_kprobe_create':
> kernel/trace/trace_kprobe.c:666: undefined reference to `kprobe_on_func_entry'
> kernel/trace/trace_kprobe.o: in function `trace_kprobe_on_func_entry':
> kernel/trace/trace_kprobe.c:167: undefined reference to `kprobe_on_func_entry'
> kernel/trace/trace_kprobe.c:167: undefined reference to `kprobe_on_func_entry'
> make: *** [Makefile:1029: vmlinux] Error 1
> 
> Given the fact that these functions have no dependencies on kretprobes i think
> they should be moved out of the #ifdef CONFIG_KRETPROBES block.

Ah, I got it. Yes, this function had been introduced for kretprobe (because
kretprobe must be the entry of functions) but is used for kprobe_event and
bpf now.

It should be moved out of CONFIG_KPROBE_EVENTS.

Acked-by: Masami Hiramatsu <mhiramat@kernel.org>

Thank you,

> 
> Signed-off-by: Sven Schnelle <svens@stackframe.org>
> Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
> Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Masami Hiramatsu <mhiramat@kernel.org>
> ---
>  kernel/kprobes.c | 39 ++++++++++++++++++++-------------------
>  1 file changed, 20 insertions(+), 19 deletions(-)
> 
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index c83e54727131..10a7e67fea67 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -1819,6 +1819,26 @@ unsigned long __weak arch_deref_entry_point(void *entry)
>  	return (unsigned long)entry;
>  }
>  
> +bool __weak arch_kprobe_on_func_entry(unsigned long offset)
> +{
> +	return !offset;
> +}
> +
> +bool kprobe_on_func_entry(kprobe_opcode_t *addr, const char *sym,
> +			  unsigned long offset)
> +{
> +	kprobe_opcode_t *kp_addr = _kprobe_addr(addr, sym, offset);
> +
> +	if (IS_ERR(kp_addr))
> +		return false;
> +
> +	if (!kallsyms_lookup_size_offset((unsigned long)kp_addr, NULL, &offset) ||
> +					 !arch_kprobe_on_func_entry(offset))
> +		return false;
> +
> +	return true;
> +}
> +
>  #ifdef CONFIG_KRETPROBES
>  /*
>   * This kprobe pre_handler is registered with every kretprobe. When probe
> @@ -1875,25 +1895,6 @@ static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs)
>  }
>  NOKPROBE_SYMBOL(pre_handler_kretprobe);
>  
> -bool __weak arch_kprobe_on_func_entry(unsigned long offset)
> -{
> -	return !offset;
> -}
> -
> -bool kprobe_on_func_entry(kprobe_opcode_t *addr, const char *sym, unsigned long offset)
> -{
> -	kprobe_opcode_t *kp_addr = _kprobe_addr(addr, sym, offset);
> -
> -	if (IS_ERR(kp_addr))
> -		return false;
> -
> -	if (!kallsyms_lookup_size_offset((unsigned long)kp_addr, NULL, &offset) ||
> -						!arch_kprobe_on_func_entry(offset))
> -		return false;
> -
> -	return true;
> -}
> -
>  int register_kretprobe(struct kretprobe *rp)
>  {
>  	int ret = 0;
> -- 
> 2.20.1
> 


-- 
Masami Hiramatsu <mhiramat@kernel.org>