Re: [PATCHv3 bpf-next 4/7] bpf: Add bpf_get_func_ip helper for kprobe programs

[Jiri Olsa <jolsa@redhat.com>]

On Sat, Jul 10, 2021 at 04:55:12PM +0900, Masami Hiramatsu wrote:
> On Wed,  7 Jul 2021 23:47:48 +0200
> Jiri Olsa <jolsa@redhat.com> wrote:
> 
> > Adding bpf_get_func_ip helper for BPF_PROG_TYPE_KPROBE programs,
> > so it's now possible to call bpf_get_func_ip from both kprobe and
> > kretprobe programs.
> > 
> > Taking the caller's address from 'struct kprobe::addr', which is
> > defined for both kprobe and kretprobe.
> > 
> 
> Note that the kp->addr of kretprobe will be the callee function
> address, even if the handler is called when the end of the callee.

yes, that's what we need

> 
> Anyway, this looks good to me.
> 
> Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>

thanks,
jirka

> 
> Thank you,
> 
> > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > ---
> >  include/uapi/linux/bpf.h       |  2 +-
> >  kernel/bpf/verifier.c          |  2 ++
> >  kernel/trace/bpf_trace.c       | 17 +++++++++++++++++
> >  tools/include/uapi/linux/bpf.h |  2 +-
> >  4 files changed, 21 insertions(+), 2 deletions(-)
> > 
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index 83e87ffdbb6e..4894f99a1993 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -4783,7 +4783,7 @@ union bpf_attr {
> >   *
> >   * u64 bpf_get_func_ip(void *ctx)
> >   * 	Description
> > - * 		Get address of the traced function (for tracing programs).
> > + * 		Get address of the traced function (for tracing and kprobe programs).
> >   * 	Return
> >   * 		Address of the traced function.
> >   */
> > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > index f975a3aa9368..79eb9d81a198 100644
> > --- a/kernel/bpf/verifier.c
> > +++ b/kernel/bpf/verifier.c
> > @@ -5979,6 +5979,8 @@ static int has_get_func_ip(struct bpf_verifier_env *env)
> >  			return -ENOTSUPP;
> >  		}
> >  		return 0;
> > +	} else if (type == BPF_PROG_TYPE_KPROBE) {
> > +		return 0;
> >  	}
> >  
> >  	verbose(env, "func %s#%d not supported for program type %d\n",
> > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> > index 9edd3b1a00ad..55acf56b0c3a 100644
> > --- a/kernel/trace/bpf_trace.c
> > +++ b/kernel/trace/bpf_trace.c
> > @@ -17,6 +17,7 @@
> >  #include <linux/error-injection.h>
> >  #include <linux/btf_ids.h>
> >  #include <linux/bpf_lsm.h>
> > +#include <linux/kprobes.h>
> >  
> >  #include <net/bpf_sk_storage.h>
> >  
> > @@ -961,6 +962,20 @@ static const struct bpf_func_proto bpf_get_func_ip_proto_tracing = {
> >  	.arg1_type	= ARG_PTR_TO_CTX,
> >  };
> >  
> > +BPF_CALL_1(bpf_get_func_ip_kprobe, struct pt_regs *, regs)
> > +{
> > +	struct kprobe *kp = kprobe_running();
> > +
> > +	return kp ? (u64) kp->addr : 0;
> > +}
> > +
> > +static const struct bpf_func_proto bpf_get_func_ip_proto_kprobe = {
> > +	.func		= bpf_get_func_ip_kprobe,
> > +	.gpl_only	= true,
> > +	.ret_type	= RET_INTEGER,
> > +	.arg1_type	= ARG_PTR_TO_CTX,
> > +};
> > +
> >  const struct bpf_func_proto *
> >  bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
> >  {
> > @@ -1092,6 +1107,8 @@ kprobe_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
> >  	case BPF_FUNC_override_return:
> >  		return &bpf_override_return_proto;
> >  #endif
> > +	case BPF_FUNC_get_func_ip:
> > +		return &bpf_get_func_ip_proto_kprobe;
> >  	default:
> >  		return bpf_tracing_func_proto(func_id, prog);
> >  	}
> > diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> > index 83e87ffdbb6e..4894f99a1993 100644
> > --- a/tools/include/uapi/linux/bpf.h
> > +++ b/tools/include/uapi/linux/bpf.h
> > @@ -4783,7 +4783,7 @@ union bpf_attr {
> >   *
> >   * u64 bpf_get_func_ip(void *ctx)
> >   * 	Description
> > - * 		Get address of the traced function (for tracing programs).
> > + * 		Get address of the traced function (for tracing and kprobe programs).
> >   * 	Return
> >   * 		Address of the traced function.
> >   */
> > -- 
> > 2.31.1
> > 
> 
> 
> -- 
> Masami Hiramatsu <mhiramat@kernel.org>
>