On Mon, Nov 12, 2018 at 02:10:11PM -0800, Stanislav Fomichev wrote:
> On 11/12, Martin Lau wrote:
> > On Fri, Nov 09, 2018 at 08:21:41AM -0800, Stanislav Fomichev wrote:
> > [ ... ]
> > > @@ -1918,23 +2160,20 @@ void *bpf_object__priv(struct bpf_object *obj)
> > > }
> > >
> > > static struct bpf_program *
> > > -__bpf_program__next(struct bpf_program *prev, struct bpf_object *obj)
> > > +__bpf_program__iter(struct bpf_program *p, struct bpf_object *obj, int i)
> > > {
> > > - size_t idx;
> > > + ssize_t idx;
> > >
> > > if (!obj->programs)
> > > return NULL;
> > > - /* First handler */
> > > - if (prev == NULL)
> > > - return &obj->programs[0];
> > >
> > > - if (prev->obj != obj) {
> > > + if (p->obj != obj) {
> > > pr_warning("error: program handler doesn't match object\n");
> > > return NULL;
> > > }
> > >
> > > - idx = (prev - obj->programs) + 1;
> > > - if (idx >= obj->nr_programs)
> > > + idx = (p - obj->programs) + i;
> > > + if (idx >= obj->nr_programs || idx < 0)
> > > return NULL;
> > > return &obj->programs[idx];
> > > }
> > > @@ -1944,8 +2183,29 @@ bpf_program__next(struct bpf_program *prev, struct bpf_object *obj)
> > > {
> > > struct bpf_program *prog = prev;
> > >
> > > + if (prev == NULL)
> > > + return obj->programs;
> > > +
> > This patch breaks the behavior introduced in
> > commit eac7d84519a3 ("tools: libbpf: don't return '.text' as a program for multi-function programs"):
> > "Make bpf_program__next() skip over '.text' section if object file
> > has pseudo calls. The '.text' section is hardly a program in that
> > case, it's more of a storage for code of functions other than main."
> >
> > For example, the userspace could have been doing:
> > prog = bpf_program__next(NULL, obj);
> > bpf_program__set_type(prog, BPF_PROG_TYPE_TRACEPOINT);
> > bpf_object__load(obj);
> >
> > For the bpf_prog.o that has pseudo calls, after this patch in bpf-next,
> > the prog returned by bpf_program__next() could be in ".text" instead of
> > the main bpf program. The next bpf_program__set_type() has
> > no effect to the main program. The following bpf_object__load()
> > will catch user in surprise with the main bpf prog in
> > the wrong BPF_PROG_TYPE.
>
> Will something like the following fix your concern? (plus, assuming the
> same for prev):
>
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -2216,8 +2216,11 @@ bpf_program__next(struct bpf_program *prev, struct bpf_object *obj)
> {
> struct bpf_program *prog = prev;
>
> - if (prev == NULL)
> - return obj->programs;
> + if (prev == NULL) {
> + prog = obj->programs;
> + if (!prog || !bpf_program__is_function_storage(prog, obj))
> + return prog;
> + }
>
> do {
> prog = __bpf_program__iter(prog, obj, 1);
>
> Any suggestions for a better way to do it?
I think that would work. The bpf_program__prev() will need the same
treatment though...
Here is my mostly untested fix to unblock my other dev works. It moves
the very first NULL check back to __bpf_program__iter():
>From de1c89ae1768e756825a6874268b5b1686695c93 Mon Sep 17 00:00:00 2001
From: Martin KaFai Lau <kafai@xxxxxx>
Date: Mon, 12 Nov 2018 14:52:39 -0800
Subject: [PATCH] bpf: libbpf: Fix bpf_program__next() API
This patch restores the behavior in
commit eac7d84519a3 ("tools: libbpf: don't return '.text' as a program for multi-function programs"):
such that bpf_program__next() does not return pseudo programs in ".text".
Fixes: 0c19a9fbc9cd ("libbpf: cleanup after partial failure in bpf_object__pin")
Signed-off-by: Martin KaFai Lau <kafai@xxxxxx>
---
tools/lib/bpf/libbpf.c | 25 +++++++++++--------------
1 file changed, 11 insertions(+), 14 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index e827542ffa3a..a01eb9584e52 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -2193,19 +2193,25 @@ void *bpf_object__priv(struct bpf_object *obj)
}
static struct bpf_program *
-__bpf_program__iter(struct bpf_program *p, struct bpf_object *obj, int i)
+__bpf_program__iter(struct bpf_program *p, struct bpf_object *obj, bool forward)
{
+ size_t nr_programs = obj->nr_programs;
ssize_t idx;
- if (!obj->programs)
+ if (!nr_programs)
return NULL;
+ if (!p)
+ /* Iter from the beginning */
+ return forward ? &obj->programs[0] :
+ &obj->programs[nr_programs - 1];
+
if (p->obj != obj) {
pr_warning("error: program handler doesn't match object\n");
return NULL;
}
- idx = (p - obj->programs) + i;
+ idx = (p - obj->programs) + (forward ? 1 : -1);
if (idx >= obj->nr_programs || idx < 0)
return NULL;
return &obj->programs[idx];
@@ -2216,11 +2222,8 @@ bpf_program__next(struct bpf_program *prev, struct bpf_object *obj)
{
struct bpf_program *prog = prev;
- if (prev == NULL)
- return obj->programs;
-
do {
- prog = __bpf_program__iter(prog, obj, 1);
+ prog = __bpf_program__iter(prog, obj, true);
} while (prog && bpf_program__is_function_storage(prog, obj));
return prog;
@@ -2231,14 +2234,8 @@ bpf_program__prev(struct bpf_program *next, struct bpf_object *obj)
{
struct bpf_program *prog = next;
- if (next == NULL) {
- if (!obj->nr_programs)
- return NULL;
- return obj->programs + obj->nr_programs - 1;
- }
-
do {
- prog = __bpf_program__iter(prog, obj, -1);
+ prog = __bpf_program__iter(prog, obj, false);
} while (prog && bpf_program__is_function_storage(prog, obj));
return prog;
--
2.17.1
>
> > > do {
> > > - prog = __bpf_program__next(prog, obj);
> > > + prog = __bpf_program__iter(prog, obj, 1);
> > > + } while (prog && bpf_program__is_function_storage(prog, obj));
> > > +
> > > + return prog;
> > > +}
> > > +
> > > +struct bpf_program *
> > > +bpf_program__prev(struct bpf_program *next, struct bpf_object *obj)
> > > +{
> > > + struct bpf_program *prog = next;
> > > +
> > > + if (next == NULL) {
> > > + if (!obj->nr_programs)
> > > + return NULL;
> > > + return obj->programs + obj->nr_programs - 1;
> > > + }
> > > +
> > > + do {
> > > + prog = __bpf_program__iter(prog, obj, -1);
> > > } while (prog && bpf_program__is_function_storage(prog, obj));
> > >
> > > return prog;
