This patch enables dumping kfunc prototypes from bpftool. This is useful
b/c with this patch, end users will no longer have to manually define
kfunc prototypes. For the kernel tree, this also means we can drop
kfunc prototypes from:
tools/testing/selftests/bpf/bpf_kfuncs.h
tools/testing/selftests/bpf/bpf_experimental.h
Example usage:
$ make PAHOLE=/home/dxu/dev/pahole/build/pahole -j30 vmlinux
$ ./tools/bpf/bpftool/bpftool btf dump file ./vmlinux format c | rg "__ksym;" | head -3
extern void cgroup_rstat_updated(struct cgroup * cgrp, int cpu) __ksym;
extern void cgroup_rstat_flush(struct cgroup * cgrp) __ksym;
extern struct bpf_key * bpf_lookup_user_key(u32 serial, u64 flags) __ksym;
Note that this patch is only effective after enabling pahole [0]
and kernel [1] changes are merged.
[0]: https://lore.kernel.org/bpf/0f25134ec999e368478c4ca993b3b729c2a03383.1706491733.git.dxu@dxuuu.xyz/
[1]: https://lore.kernel.org/bpf/[email protected]/
Signed-off-by: Daniel Xu <[email protected]>
---
tools/bpf/bpftool/btf.c | 29 +++++++++++++++++++++++++++++
1 file changed, 29 insertions(+)
diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c
index 91fcb75babe3..9ab26ed12733 100644
--- a/tools/bpf/bpftool/btf.c
+++ b/tools/bpf/bpftool/btf.c
@@ -20,6 +20,8 @@
#include "json_writer.h"
#include "main.h"
+#define KFUNC_DECL_TAG "bpf_kfunc"
+
static const char * const btf_kind_str[NR_BTF_KINDS] = {
[BTF_KIND_UNKN] = "UNKNOWN",
[BTF_KIND_INT] = "INT",
@@ -454,6 +456,28 @@ static int dump_btf_raw(const struct btf *btf,
return 0;
}
+static void dump_btf_kfuncs(const struct btf *btf)
+{
+ int cnt = btf__type_cnt(btf);
+ int i;
+
+ for (i = 1; i < cnt; i++) {
+ const struct btf_type *t = btf__type_by_id(btf, i);
+ char kfunc_sig[1024];
+ const char *name;
+
+ if (!btf_is_decl_tag(t))
+ continue;
+
+ name = btf__name_by_offset(btf, t->name_off);
+ if (strncmp(name, KFUNC_DECL_TAG, sizeof(KFUNC_DECL_TAG)))
+ continue;
+
+ btf_dumper_type_only(btf, t->type, kfunc_sig, sizeof(kfunc_sig));
+ printf("extern %s __ksym;\n\n", kfunc_sig);
+ }
+}
+
static void __printf(2, 0) btf_dump_printf(void *ctx,
const char *fmt, va_list args)
{
@@ -476,6 +500,9 @@ static int dump_btf_c(const struct btf *btf,
printf("#ifndef BPF_NO_PRESERVE_ACCESS_INDEX\n");
printf("#pragma clang attribute push (__attribute__((preserve_access_index)), apply_to = record)\n");
printf("#endif\n\n");
+ printf("#ifndef __ksym\n");
+ printf("#define __ksym __attribute__((section(\".ksyms\")))\n");
+ printf("#endif\n\n");
if (root_type_cnt) {
for (i = 0; i < root_type_cnt; i++) {
@@ -491,6 +518,8 @@ static int dump_btf_c(const struct btf *btf,
if (err)
goto done;
}
+
+ dump_btf_kfuncs(btf);
}
printf("#ifndef BPF_NO_PRESERVE_ACCESS_INDEX\n");
--
2.42.1
On Sun, Jan 28, 2024 at 06:35:33PM -0700, Daniel Xu wrote:
> This patch enables dumping kfunc prototypes from bpftool. This is useful
> b/c with this patch, end users will no longer have to manually define
> kfunc prototypes. For the kernel tree, this also means we can drop
> kfunc prototypes from:
>
> tools/testing/selftests/bpf/bpf_kfuncs.h
> tools/testing/selftests/bpf/bpf_experimental.h
>
> Example usage:
>
> $ make PAHOLE=/home/dxu/dev/pahole/build/pahole -j30 vmlinux
>
> $ ./tools/bpf/bpftool/bpftool btf dump file ./vmlinux format c | rg "__ksym;" | head -3
> extern void cgroup_rstat_updated(struct cgroup * cgrp, int cpu) __ksym;
> extern void cgroup_rstat_flush(struct cgroup * cgrp) __ksym;
> extern struct bpf_key * bpf_lookup_user_key(u32 serial, u64 flags) __ksym;
hi,
I'm getting following declaration for bpf_rbtree_add_impl:
extern int bpf_rbtree_add_impl(struct bpf_rb_root * root, struct bpf_rb_node * node, bool (struct bpf_rb_node *, const struct bpf_rb_node *)* less, void * meta__ign, u64 off) __ksym;
and it fails to compile with:
In file included from skeleton/pid_iter.bpf.c:3:
./vmlinux.h:164511:141: error: expected ')'
164511 | extern int bpf_rbtree_add_impl(struct bpf_rb_root * root, struct bpf_rb_node * node, bool (struct bpf_rb_node *, const struct bpf_rb_node *)* less, void * meta__ign, u64 off) __ksym;
| ^
./vmlinux.h:164511:31: note: to match this '('
164511 | extern int bpf_rbtree_add_impl(struct bpf_rb_root * root, struct bpf_rb_node * node, bool (struct bpf_rb_node *, const struct bpf_rb_node *)* less, void * meta__ign, u64 off) __ksym;
looks like the btf_dumper_type_only won't dump function pointer argument
properly.. I guess we should fix that, but looking at the other stuff in
vmlinux.h like *_ops struct we can print function pointers properly, so
perhaps another way around is to use btf_dumper interface instead
jirka
>
> Note that this patch is only effective after enabling pahole [0]
> and kernel [1] changes are merged.
>
> [0]: https://lore.kernel.org/bpf/0f25134ec999e368478c4ca993b3b729c2a03383.1706491733.git.dxu@dxuuu.xyz/
> [1]: https://lore.kernel.org/bpf/[email protected]/
>
> Signed-off-by: Daniel Xu <[email protected]>
> ---
> tools/bpf/bpftool/btf.c | 29 +++++++++++++++++++++++++++++
> 1 file changed, 29 insertions(+)
>
> diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c
> index 91fcb75babe3..9ab26ed12733 100644
> --- a/tools/bpf/bpftool/btf.c
> +++ b/tools/bpf/bpftool/btf.c
> @@ -20,6 +20,8 @@
> #include "json_writer.h"
> #include "main.h"
>
> +#define KFUNC_DECL_TAG "bpf_kfunc"
> +
> static const char * const btf_kind_str[NR_BTF_KINDS] = {
> [BTF_KIND_UNKN] = "UNKNOWN",
> [BTF_KIND_INT] = "INT",
> @@ -454,6 +456,28 @@ static int dump_btf_raw(const struct btf *btf,
> return 0;
> }
>
> +static void dump_btf_kfuncs(const struct btf *btf)
> +{
> + int cnt = btf__type_cnt(btf);
> + int i;
> +
> + for (i = 1; i < cnt; i++) {
> + const struct btf_type *t = btf__type_by_id(btf, i);
> + char kfunc_sig[1024];
> + const char *name;
> +
> + if (!btf_is_decl_tag(t))
> + continue;
> +
> + name = btf__name_by_offset(btf, t->name_off);
> + if (strncmp(name, KFUNC_DECL_TAG, sizeof(KFUNC_DECL_TAG)))
> + continue;
> +
> + btf_dumper_type_only(btf, t->type, kfunc_sig, sizeof(kfunc_sig));
> + printf("extern %s __ksym;\n\n", kfunc_sig);
> + }
> +}
> +
> static void __printf(2, 0) btf_dump_printf(void *ctx,
> const char *fmt, va_list args)
> {
> @@ -476,6 +500,9 @@ static int dump_btf_c(const struct btf *btf,
> printf("#ifndef BPF_NO_PRESERVE_ACCESS_INDEX\n");
> printf("#pragma clang attribute push (__attribute__((preserve_access_index)), apply_to = record)\n");
> printf("#endif\n\n");
> + printf("#ifndef __ksym\n");
> + printf("#define __ksym __attribute__((section(\".ksyms\")))\n");
> + printf("#endif\n\n");
>
> if (root_type_cnt) {
> for (i = 0; i < root_type_cnt; i++) {
> @@ -491,6 +518,8 @@ static int dump_btf_c(const struct btf *btf,
> if (err)
> goto done;
> }
> +
> + dump_btf_kfuncs(btf);
> }
>
> printf("#ifndef BPF_NO_PRESERVE_ACCESS_INDEX\n");
> --
> 2.42.1
>
Hi Jiri,
On Mon, Jan 29, 2024 at 01:11:17PM +0100, Jiri Olsa wrote:
> On Sun, Jan 28, 2024 at 06:35:33PM -0700, Daniel Xu wrote:
> > This patch enables dumping kfunc prototypes from bpftool. This is useful
> > b/c with this patch, end users will no longer have to manually define
> > kfunc prototypes. For the kernel tree, this also means we can drop
> > kfunc prototypes from:
> >
> > tools/testing/selftests/bpf/bpf_kfuncs.h
> > tools/testing/selftests/bpf/bpf_experimental.h
> >
> > Example usage:
> >
> > $ make PAHOLE=/home/dxu/dev/pahole/build/pahole -j30 vmlinux
> >
> > $ ./tools/bpf/bpftool/bpftool btf dump file ./vmlinux format c | rg "__ksym;" | head -3
> > extern void cgroup_rstat_updated(struct cgroup * cgrp, int cpu) __ksym;
> > extern void cgroup_rstat_flush(struct cgroup * cgrp) __ksym;
> > extern struct bpf_key * bpf_lookup_user_key(u32 serial, u64 flags) __ksym;
>
> hi,
> I'm getting following declaration for bpf_rbtree_add_impl:
>
> extern int bpf_rbtree_add_impl(struct bpf_rb_root * root, struct bpf_rb_node * node, bool (struct bpf_rb_node *, const struct bpf_rb_node *)* less, void * meta__ign, u64 off) __ksym;
>
> and it fails to compile with:
>
> In file included from skeleton/pid_iter.bpf.c:3:
> ./vmlinux.h:164511:141: error: expected ')'
> 164511 | extern int bpf_rbtree_add_impl(struct bpf_rb_root * root, struct bpf_rb_node * node, bool (struct bpf_rb_node *, const struct bpf_rb_node *)* less, void * meta__ign, u64 off) __ksym;
> | ^
> ./vmlinux.h:164511:31: note: to match this '('
> 164511 | extern int bpf_rbtree_add_impl(struct bpf_rb_root * root, struct bpf_rb_node * node, bool (struct bpf_rb_node *, const struct bpf_rb_node *)* less, void * meta__ign, u64 off) __ksym;
>
> looks like the btf_dumper_type_only won't dump function pointer argument
> properly.. I guess we should fix that, but looking at the other stuff in
> vmlinux.h like *_ops struct we can print function pointers properly, so
> perhaps another way around is to use btf_dumper interface instead
Ah, crap, looks like between all the branch switching I didn't build
vmlinux with kfunc annotations. Having fixed that, I can repro this
build failure.
I'll take a look and see what the best way to fix this is.
Given that end to end the whole flow basically works, should we start
working on merging patches?
Thanks,
Daniel
[..]
On Sun, Jan 28, 2024 at 5:35 PM Daniel Xu <[email protected]> wrote:
>
> This patch enables dumping kfunc prototypes from bpftool. This is useful
> b/c with this patch, end users will no longer have to manually define
> kfunc prototypes. For the kernel tree, this also means we can drop
> kfunc prototypes from:
>
> tools/testing/selftests/bpf/bpf_kfuncs.h
> tools/testing/selftests/bpf/bpf_experimental.h
>
> Example usage:
>
> $ make PAHOLE=/home/dxu/dev/pahole/build/pahole -j30 vmlinux
>
> $ ./tools/bpf/bpftool/bpftool btf dump file ./vmlinux format c | rg "__ksym;" | head -3
> extern void cgroup_rstat_updated(struct cgroup * cgrp, int cpu) __ksym;
> extern void cgroup_rstat_flush(struct cgroup * cgrp) __ksym;
> extern struct bpf_key * bpf_lookup_user_key(u32 serial, u64 flags) __ksym;
>
All kfuncs have to be declared __weak, otherwise it will be impossible
to feature-detect them in BPF code
> Note that this patch is only effective after enabling pahole [0]
> and kernel [1] changes are merged.
>
> [0]: https://lore.kernel.org/bpf/0f25134ec999e368478c4ca993b3b729c2a033831706491733.git.dxu@dxuuu.xyz/
> [1]: https://lore.kernel.org/bpf/[email protected]/
>
> Signed-off-by: Daniel Xu <[email protected]>
> ---
> tools/bpf/bpftool/btf.c | 29 +++++++++++++++++++++++++++++
> 1 file changed, 29 insertions(+)
>
> diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c
> index 91fcb75babe3..9ab26ed12733 100644
> --- a/tools/bpf/bpftool/btf.c
> +++ b/tools/bpf/bpftool/btf.c
> @@ -20,6 +20,8 @@
> #include "json_writer.h"
> #include "main.h"
>
> +#define KFUNC_DECL_TAG "bpf_kfunc"
> +
> static const char * const btf_kind_str[NR_BTF_KINDS] = {
> [BTF_KIND_UNKN] = "UNKNOWN",
> [BTF_KIND_INT] = "INT",
> @@ -454,6 +456,28 @@ static int dump_btf_raw(const struct btf *btf,
> return 0;
> }
>
> +static void dump_btf_kfuncs(const struct btf *btf)
> +{
> + int cnt = btf__type_cnt(btf);
> + int i;
> +
> + for (i = 1; i < cnt; i++) {
> + const struct btf_type *t = btf__type_by_id(btf, i);
> + char kfunc_sig[1024];
> + const char *name;
> +
> + if (!btf_is_decl_tag(t))
> + continue;
> +
> + name = btf__name_by_offset(btf, t->name_off);
> + if (strncmp(name, KFUNC_DECL_TAG, sizeof(KFUNC_DECL_TAG)))
> + continue;
> +
> + btf_dumper_type_only(btf, t->type, kfunc_sig, sizeof(kfunc_sig));
> + printf("extern %s __ksym;\n\n", kfunc_sig);
> + }
> +}
> +
> static void __printf(2, 0) btf_dump_printf(void *ctx,
> const char *fmt, va_list args)
> {
> @@ -476,6 +500,9 @@ static int dump_btf_c(const struct btf *btf,
> printf("#ifndef BPF_NO_PRESERVE_ACCESS_INDEX\n");
> printf("#pragma clang attribute push (__attribute__((preserve_access_index)), apply_to = record)\n");
> printf("#endif\n\n");
> + printf("#ifndef __ksym\n");
> + printf("#define __ksym __attribute__((section(\".ksyms\")))\n");
> + printf("#endif\n\n");
>
> if (root_type_cnt) {
> for (i = 0; i < root_type_cnt; i++) {
> @@ -491,6 +518,8 @@ static int dump_btf_c(const struct btf *btf,
> if (err)
> goto done;
> }
> +
> + dump_btf_kfuncs(btf);
> }
>
> printf("#ifndef BPF_NO_PRESERVE_ACCESS_INDEX\n");
> --
> 2.42.1
>
On Mon, Jan 29, 2024 at 09:13:13AM -0700, Daniel Xu wrote:
> Hi Jiri,
>
> On Mon, Jan 29, 2024 at 01:11:17PM +0100, Jiri Olsa wrote:
> > On Sun, Jan 28, 2024 at 06:35:33PM -0700, Daniel Xu wrote:
> > > This patch enables dumping kfunc prototypes from bpftool. This is useful
> > > b/c with this patch, end users will no longer have to manually define
> > > kfunc prototypes. For the kernel tree, this also means we can drop
> > > kfunc prototypes from:
> > >
> > > tools/testing/selftests/bpf/bpf_kfuncs.h
> > > tools/testing/selftests/bpf/bpf_experimental.h
> > >
> > > Example usage:
> > >
> > > $ make PAHOLE=/home/dxu/dev/pahole/build/pahole -j30 vmlinux
> > >
> > > $ ./tools/bpf/bpftool/bpftool btf dump file ./vmlinux format c | rg "__ksym;" | head -3
> > > extern void cgroup_rstat_updated(struct cgroup * cgrp, int cpu) __ksym;
> > > extern void cgroup_rstat_flush(struct cgroup * cgrp) __ksym;
> > > extern struct bpf_key * bpf_lookup_user_key(u32 serial, u64 flags) __ksym;
> >
> > hi,
> > I'm getting following declaration for bpf_rbtree_add_impl:
> >
> > extern int bpf_rbtree_add_impl(struct bpf_rb_root * root, struct bpf_rb_node * node, bool (struct bpf_rb_node *, const struct bpf_rb_node *)* less, void * meta__ign, u64 off) __ksym;
> >
> > and it fails to compile with:
> >
> > In file included from skeleton/pid_iter.bpf.c:3:
> > ./vmlinux.h:164511:141: error: expected ')'
> > 164511 | extern int bpf_rbtree_add_impl(struct bpf_rb_root * root, struct bpf_rb_node * node, bool (struct bpf_rb_node *, const struct bpf_rb_node *)* less, void * meta__ign, u64 off) __ksym;
> > | ^
> > ./vmlinux.h:164511:31: note: to match this '('
> > 164511 | extern int bpf_rbtree_add_impl(struct bpf_rb_root * root, struct bpf_rb_node * node, bool (struct bpf_rb_node *, const struct bpf_rb_node *)* less, void * meta__ign, u64 off) __ksym;
> >
> > looks like the btf_dumper_type_only won't dump function pointer argument
> > properly.. I guess we should fix that, but looking at the other stuff in
> > vmlinux.h like *_ops struct we can print function pointers properly, so
> > perhaps another way around is to use btf_dumper interface instead
>
> Ah, crap, looks like between all the branch switching I didn't build
> vmlinux with kfunc annotations. Having fixed that, I can repro this
> build failure.
>
> I'll take a look and see what the best way to fix this is.
>
> Given that end to end the whole flow basically works, should we start
> working on merging patches?
yes, the flow looks good to me.. will check the rest of the patches
jirka