diff mbox series

[v2,bpf-next,04/17] libbpf: mark BPF subprogs with hidden visibility as static for BPF verifier

Message ID 20210416202404.3443623-5-andrii@kernel.org
State New
Headers show
Series BPF static linker: support externs | expand

Commit Message

Andrii Nakryiko April 16, 2021, 8:23 p.m. UTC
Define __hidden helper macro in bpf_helpers.h, which is a short-hand for
__attribute__((visibility("hidden"))). Add libbpf support to mark BPF
subprograms marked with __hidden as static in BTF information to enforce BPF
verifier's static function validation algorithm, which takes more information
(caller's context) into account during a subprogram validation.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 tools/lib/bpf/bpf_helpers.h     |  8 ++++++
 tools/lib/bpf/btf.c             |  5 ----
 tools/lib/bpf/libbpf.c          | 45 ++++++++++++++++++++++++++++++++-
 tools/lib/bpf/libbpf_internal.h |  6 +++++
 4 files changed, 58 insertions(+), 6 deletions(-)

Comments

Yonghong Song April 22, 2021, 5:43 a.m. UTC | #1
On 4/16/21 1:23 PM, Andrii Nakryiko wrote:
> Define __hidden helper macro in bpf_helpers.h, which is a short-hand for

> __attribute__((visibility("hidden"))). Add libbpf support to mark BPF

> subprograms marked with __hidden as static in BTF information to enforce BPF

> verifier's static function validation algorithm, which takes more information

> (caller's context) into account during a subprogram validation.

> 

> Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

> ---

>   tools/lib/bpf/bpf_helpers.h     |  8 ++++++

>   tools/lib/bpf/btf.c             |  5 ----

>   tools/lib/bpf/libbpf.c          | 45 ++++++++++++++++++++++++++++++++-

>   tools/lib/bpf/libbpf_internal.h |  6 +++++

>   4 files changed, 58 insertions(+), 6 deletions(-)

> 

> diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h

> index 75c7581b304c..9720dc0b4605 100644

> --- a/tools/lib/bpf/bpf_helpers.h

> +++ b/tools/lib/bpf/bpf_helpers.h

> @@ -47,6 +47,14 @@

>   #define __weak __attribute__((weak))

>   #endif

>   

> +/*

> + * Use __hidden attribute to mark a non-static BPF subprogram effectively

> + * static for BPF verifier's verification algorithm purposes, allowing more

> + * extensive and permissive BPF verification process, taking into account

> + * subprogram's caller context.

> + */

> +#define __hidden __attribute__((visibility("hidden")))


To prevent potential external __hidden macro definition conflict, how
about

#ifdef __hidden
#undef __hidden
#define __hidden __attribute__((visibility("hidden")))
#endif

> +

>   /* When utilizing vmlinux.h with BPF CO-RE, user BPF programs can't include

>    * any system-level headers (such as stddef.h, linux/version.h, etc), and

>    * commonly-used macros like NULL and KERNEL_VERSION aren't available through

> diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c

> index d30e67e7e1e5..d57e13a13798 100644

> --- a/tools/lib/bpf/btf.c

> +++ b/tools/lib/bpf/btf.c

> @@ -1605,11 +1605,6 @@ static void *btf_add_type_mem(struct btf *btf, size_t add_sz)

>   			      btf->hdr->type_len, UINT_MAX, add_sz);

>   }

>   

> -static __u32 btf_type_info(int kind, int vlen, int kflag)

> -{

> -	return (kflag << 31) | (kind << 24) | vlen;

> -}

> -

>   static void btf_type_inc_vlen(struct btf_type *t)

>   {

>   	t->info = btf_type_info(btf_kind(t), btf_vlen(t) + 1, btf_kflag(t));

> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c

> index 9cc2d45b0080..ce5558d0a61b 100644

> --- a/tools/lib/bpf/libbpf.c

> +++ b/tools/lib/bpf/libbpf.c

> @@ -71,6 +71,7 @@

>   static struct bpf_map *bpf_object__add_map(struct bpf_object *obj);

>   static const struct btf_type *

>   skip_mods_and_typedefs(const struct btf *btf, __u32 id, __u32 *res_id);

> +static bool prog_is_subprog(const struct bpf_object *obj, const struct bpf_program *prog);

>   

>   static int __base_pr(enum libbpf_print_level level, const char *format,

>   		     va_list args)

> @@ -274,6 +275,7 @@ struct bpf_program {

>   	bpf_program_clear_priv_t clear_priv;

>   

>   	bool load;

> +	bool mark_btf_static;

>   	enum bpf_prog_type type;

>   	enum bpf_attach_type expected_attach_type;

>   	int prog_ifindex;

> @@ -698,6 +700,15 @@ bpf_object__add_programs(struct bpf_object *obj, Elf_Data *sec_data,

>   		if (err)

>   			return err;

>   

> +		/* if function is a global/weak symbol, but has hidden

> +		 * visibility (or any non-default one), mark its BTF FUNC as

> +		 * static to enable more permissive BPF verification mode with

> +		 * more outside context available to BPF verifier

> +		 */

> +		if (GELF_ST_BIND(sym.st_info) != STB_LOCAL

> +		    && GELF_ST_VISIBILITY(sym.st_other) != STV_DEFAULT)


Maybe we should check GELF_ST_VISIBILITY(sym.st_other) == STV_HIDDEN 
instead?

> +			prog->mark_btf_static = true;

> +

>   		nr_progs++;

>   		obj->nr_programs = nr_progs;

>   

> @@ -2618,7 +2629,7 @@ static int bpf_object__sanitize_and_load_btf(struct bpf_object *obj)

>   {

>   	struct btf *kern_btf = obj->btf;

>   	bool btf_mandatory, sanitize;

> -	int err = 0;

> +	int i, err = 0;

>   

>   	if (!obj->btf)

>   		return 0;

> @@ -2632,6 +2643,38 @@ static int bpf_object__sanitize_and_load_btf(struct bpf_object *obj)

>   		return 0;

>   	}

>   

> +	/* Even though some subprogs are global/weak, user might prefer more

> +	 * permissive BPF verification process that BPF verifier performs for

> +	 * static functions, taking into account more context from the caller

> +	 * functions. In such case, they need to mark such subprogs with

> +	 * __attribute__((visibility("hidden"))) and libbpf will adjust

> +	 * corresponding FUNC BTF type to be marked as static and trigger more

> +	 * involved BPF verification process.

> +	 */

> +	for (i = 0; i < obj->nr_programs; i++) {

> +		struct bpf_program *prog = &obj->programs[i];

> +		struct btf_type *t;

> +		const char *name;

> +		int j, n;

> +

> +		if (!prog->mark_btf_static || !prog_is_subprog(obj, prog))

> +			continue;

> +

> +		n = btf__get_nr_types(obj->btf);

> +		for (j = 1; j <= n; j++) {

> +			t = btf_type_by_id(obj->btf, j);

> +			if (!btf_is_func(t) || btf_func_linkage(t) != BTF_FUNC_GLOBAL)

> +				continue;

> +

> +			name = btf__str_by_offset(obj->btf, t->name_off);

> +			if (strcmp(name, prog->name) != 0)

> +				continue;

> +

> +			t->info = btf_type_info(BTF_KIND_FUNC, BTF_FUNC_STATIC, 0);

> +			break;

> +		}

> +	}

> +

>   	sanitize = btf_needs_sanitization(obj);

[...]
Andrii Nakryiko April 22, 2021, 6:09 p.m. UTC | #2
On Wed, Apr 21, 2021 at 10:43 PM Yonghong Song <yhs@fb.com> wrote:
>

>

>

> On 4/16/21 1:23 PM, Andrii Nakryiko wrote:

> > Define __hidden helper macro in bpf_helpers.h, which is a short-hand for

> > __attribute__((visibility("hidden"))). Add libbpf support to mark BPF

> > subprograms marked with __hidden as static in BTF information to enforce BPF

> > verifier's static function validation algorithm, which takes more information

> > (caller's context) into account during a subprogram validation.

> >

> > Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

> > ---

> >   tools/lib/bpf/bpf_helpers.h     |  8 ++++++

> >   tools/lib/bpf/btf.c             |  5 ----

> >   tools/lib/bpf/libbpf.c          | 45 ++++++++++++++++++++++++++++++++-

> >   tools/lib/bpf/libbpf_internal.h |  6 +++++

> >   4 files changed, 58 insertions(+), 6 deletions(-)

> >

> > diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h

> > index 75c7581b304c..9720dc0b4605 100644

> > --- a/tools/lib/bpf/bpf_helpers.h

> > +++ b/tools/lib/bpf/bpf_helpers.h

> > @@ -47,6 +47,14 @@

> >   #define __weak __attribute__((weak))

> >   #endif

> >

> > +/*

> > + * Use __hidden attribute to mark a non-static BPF subprogram effectively

> > + * static for BPF verifier's verification algorithm purposes, allowing more

> > + * extensive and permissive BPF verification process, taking into account

> > + * subprogram's caller context.

> > + */

> > +#define __hidden __attribute__((visibility("hidden")))

>

> To prevent potential external __hidden macro definition conflict, how

> about

>

> #ifdef __hidden

> #undef __hidden

> #define __hidden __attribute__((visibility("hidden")))

> #endif

>


We do force #undef only with __always_inline because of the bad
definition in linux/stddef.h And we check #ifndef for __weak, because
__weak is defined in kernel headers. This is not really the case for
__hidden, the only definition is in
tools/lib/traceevent/event-parse-local.h, which I don't think we
should worry about in BPF context. So I wanted to keep it simple and
fix only if that really causes some real conflicts.

And keep in mind that in BPF code bpf_helpers.h is usually included as
one of the first few headers anyways.


> > +

> >   /* When utilizing vmlinux.h with BPF CO-RE, user BPF programs can't include

> >    * any system-level headers (such as stddef.h, linux/version.h, etc), and

> >    * commonly-used macros like NULL and KERNEL_VERSION aren't available through


[...]

> > @@ -698,6 +700,15 @@ bpf_object__add_programs(struct bpf_object *obj, Elf_Data *sec_data,

> >               if (err)

> >                       return err;

> >

> > +             /* if function is a global/weak symbol, but has hidden

> > +              * visibility (or any non-default one), mark its BTF FUNC as

> > +              * static to enable more permissive BPF verification mode with

> > +              * more outside context available to BPF verifier

> > +              */

> > +             if (GELF_ST_BIND(sym.st_info) != STB_LOCAL

> > +                 && GELF_ST_VISIBILITY(sym.st_other) != STV_DEFAULT)

>

> Maybe we should check GELF_ST_VISIBILITY(sym.st_other) == STV_HIDDEN

> instead?


It felt like only STV_DEFAULT should be "exported", semantically
speaking. Everything else would be treated as if it was static, except
that C rules require that function has to be global. Do you think
there is some danger to do it this way?

Currently static linker doesn't do anything special for STV_INTERNAL
and STV_PROTECTED, so we could just disable those. Do you prefer that?

I just felt that there is no risk of regression if we do this for
non-STV_DEFAULT generically.


>

> > +                     prog->mark_btf_static = true;

> > +

> >               nr_progs++;

> >               obj->nr_programs = nr_progs;

> >


[...]
Yonghong Song April 22, 2021, 11 p.m. UTC | #3
On 4/22/21 11:09 AM, Andrii Nakryiko wrote:
> On Wed, Apr 21, 2021 at 10:43 PM Yonghong Song <yhs@fb.com> wrote:

>>

>>

>>

>> On 4/16/21 1:23 PM, Andrii Nakryiko wrote:

>>> Define __hidden helper macro in bpf_helpers.h, which is a short-hand for

>>> __attribute__((visibility("hidden"))). Add libbpf support to mark BPF

>>> subprograms marked with __hidden as static in BTF information to enforce BPF

>>> verifier's static function validation algorithm, which takes more information

>>> (caller's context) into account during a subprogram validation.

>>>

>>> Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

>>> ---

>>>    tools/lib/bpf/bpf_helpers.h     |  8 ++++++

>>>    tools/lib/bpf/btf.c             |  5 ----

>>>    tools/lib/bpf/libbpf.c          | 45 ++++++++++++++++++++++++++++++++-

>>>    tools/lib/bpf/libbpf_internal.h |  6 +++++

>>>    4 files changed, 58 insertions(+), 6 deletions(-)

>>>

>>> diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h

>>> index 75c7581b304c..9720dc0b4605 100644

>>> --- a/tools/lib/bpf/bpf_helpers.h

>>> +++ b/tools/lib/bpf/bpf_helpers.h

>>> @@ -47,6 +47,14 @@

>>>    #define __weak __attribute__((weak))

>>>    #endif

>>>

>>> +/*

>>> + * Use __hidden attribute to mark a non-static BPF subprogram effectively

>>> + * static for BPF verifier's verification algorithm purposes, allowing more

>>> + * extensive and permissive BPF verification process, taking into account

>>> + * subprogram's caller context.

>>> + */

>>> +#define __hidden __attribute__((visibility("hidden")))

>>

>> To prevent potential external __hidden macro definition conflict, how

>> about

>>

>> #ifdef __hidden

>> #undef __hidden

>> #define __hidden __attribute__((visibility("hidden")))

>> #endif

>>

> 

> We do force #undef only with __always_inline because of the bad

> definition in linux/stddef.h And we check #ifndef for __weak, because

> __weak is defined in kernel headers. This is not really the case for

> __hidden, the only definition is in

> tools/lib/traceevent/event-parse-local.h, which I don't think we

> should worry about in BPF context. So I wanted to keep it simple and

> fix only if that really causes some real conflicts.

> 

> And keep in mind that in BPF code bpf_helpers.h is usually included as

> one of the first few headers anyways.


That is fine. Conflict of __hidden is a low risk and we can deal with it
later if needed.

> 

> 

>>> +

>>>    /* When utilizing vmlinux.h with BPF CO-RE, user BPF programs can't include

>>>     * any system-level headers (such as stddef.h, linux/version.h, etc), and

>>>     * commonly-used macros like NULL and KERNEL_VERSION aren't available through

> 

> [...]

> 

>>> @@ -698,6 +700,15 @@ bpf_object__add_programs(struct bpf_object *obj, Elf_Data *sec_data,

>>>                if (err)

>>>                        return err;

>>>

>>> +             /* if function is a global/weak symbol, but has hidden

>>> +              * visibility (or any non-default one), mark its BTF FUNC as

>>> +              * static to enable more permissive BPF verification mode with

>>> +              * more outside context available to BPF verifier

>>> +              */

>>> +             if (GELF_ST_BIND(sym.st_info) != STB_LOCAL

>>> +                 && GELF_ST_VISIBILITY(sym.st_other) != STV_DEFAULT)

>>

>> Maybe we should check GELF_ST_VISIBILITY(sym.st_other) == STV_HIDDEN

>> instead?

> 

> It felt like only STV_DEFAULT should be "exported", semantically

> speaking. Everything else would be treated as if it was static, except

> that C rules require that function has to be global. Do you think

> there is some danger to do it this way?

> 

> Currently static linker doesn't do anything special for STV_INTERNAL

> and STV_PROTECTED, so we could just disable those. Do you prefer that?


Yes, let us just deal with STV_DEFAULT and STV_HIDDEN. We already
specialized STV_HIDDEN, so we should not treat STV_INTERNAL/PROTECTED
as what they mean in ELF standard, so let us disable them for now.

> 

> I just felt that there is no risk of regression if we do this for

> non-STV_DEFAULT generically.

> 

> 

>>

>>> +                     prog->mark_btf_static = true;

>>> +

>>>                nr_progs++;

>>>                obj->nr_programs = nr_progs;

>>>

> 

> [...]

>
Andrii Nakryiko April 22, 2021, 11:28 p.m. UTC | #4
On Thu, Apr 22, 2021 at 4:00 PM Yonghong Song <yhs@fb.com> wrote:
>

>

>

> On 4/22/21 11:09 AM, Andrii Nakryiko wrote:

> > On Wed, Apr 21, 2021 at 10:43 PM Yonghong Song <yhs@fb.com> wrote:

> >>

> >>

> >>

> >> On 4/16/21 1:23 PM, Andrii Nakryiko wrote:

> >>> Define __hidden helper macro in bpf_helpers.h, which is a short-hand for

> >>> __attribute__((visibility("hidden"))). Add libbpf support to mark BPF

> >>> subprograms marked with __hidden as static in BTF information to enforce BPF

> >>> verifier's static function validation algorithm, which takes more information

> >>> (caller's context) into account during a subprogram validation.

> >>>

> >>> Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

> >>> ---

> >>>    tools/lib/bpf/bpf_helpers.h     |  8 ++++++

> >>>    tools/lib/bpf/btf.c             |  5 ----

> >>>    tools/lib/bpf/libbpf.c          | 45 ++++++++++++++++++++++++++++++++-

> >>>    tools/lib/bpf/libbpf_internal.h |  6 +++++

> >>>    4 files changed, 58 insertions(+), 6 deletions(-)

> >>>

> >>> diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h

> >>> index 75c7581b304c..9720dc0b4605 100644

> >>> --- a/tools/lib/bpf/bpf_helpers.h

> >>> +++ b/tools/lib/bpf/bpf_helpers.h

> >>> @@ -47,6 +47,14 @@

> >>>    #define __weak __attribute__((weak))

> >>>    #endif

> >>>

> >>> +/*

> >>> + * Use __hidden attribute to mark a non-static BPF subprogram effectively

> >>> + * static for BPF verifier's verification algorithm purposes, allowing more

> >>> + * extensive and permissive BPF verification process, taking into account

> >>> + * subprogram's caller context.

> >>> + */

> >>> +#define __hidden __attribute__((visibility("hidden")))

> >>

> >> To prevent potential external __hidden macro definition conflict, how

> >> about

> >>

> >> #ifdef __hidden

> >> #undef __hidden

> >> #define __hidden __attribute__((visibility("hidden")))

> >> #endif

> >>

> >

> > We do force #undef only with __always_inline because of the bad

> > definition in linux/stddef.h And we check #ifndef for __weak, because

> > __weak is defined in kernel headers. This is not really the case for

> > __hidden, the only definition is in

> > tools/lib/traceevent/event-parse-local.h, which I don't think we

> > should worry about in BPF context. So I wanted to keep it simple and

> > fix only if that really causes some real conflicts.

> >

> > And keep in mind that in BPF code bpf_helpers.h is usually included as

> > one of the first few headers anyways.

>

> That is fine. Conflict of __hidden is a low risk and we can deal with it

> later if needed.

>

> >

> >

> >>> +

> >>>    /* When utilizing vmlinux.h with BPF CO-RE, user BPF programs can't include

> >>>     * any system-level headers (such as stddef.h, linux/version.h, etc), and

> >>>     * commonly-used macros like NULL and KERNEL_VERSION aren't available through

> >

> > [...]

> >

> >>> @@ -698,6 +700,15 @@ bpf_object__add_programs(struct bpf_object *obj, Elf_Data *sec_data,

> >>>                if (err)

> >>>                        return err;

> >>>

> >>> +             /* if function is a global/weak symbol, but has hidden

> >>> +              * visibility (or any non-default one), mark its BTF FUNC as

> >>> +              * static to enable more permissive BPF verification mode with

> >>> +              * more outside context available to BPF verifier

> >>> +              */

> >>> +             if (GELF_ST_BIND(sym.st_info) != STB_LOCAL

> >>> +                 && GELF_ST_VISIBILITY(sym.st_other) != STV_DEFAULT)

> >>

> >> Maybe we should check GELF_ST_VISIBILITY(sym.st_other) == STV_HIDDEN

> >> instead?

> >

> > It felt like only STV_DEFAULT should be "exported", semantically

> > speaking. Everything else would be treated as if it was static, except

> > that C rules require that function has to be global. Do you think

> > there is some danger to do it this way?

> >

> > Currently static linker doesn't do anything special for STV_INTERNAL

> > and STV_PROTECTED, so we could just disable those. Do you prefer that?

>

> Yes, let us just deal with STV_DEFAULT and STV_HIDDEN. We already

> specialized STV_HIDDEN, so we should not treat STV_INTERNAL/PROTECTED

> as what they mean in ELF standard, so let us disable them for now.


Yep, will do

>

> >

> > I just felt that there is no risk of regression if we do this for

> > non-STV_DEFAULT generically.

> >

> >

> >>

> >>> +                     prog->mark_btf_static = true;

> >>> +

> >>>                nr_progs++;

> >>>                obj->nr_programs = nr_progs;

> >>>

> >

> > [...]

> >
diff mbox series

Patch

diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h
index 75c7581b304c..9720dc0b4605 100644
--- a/tools/lib/bpf/bpf_helpers.h
+++ b/tools/lib/bpf/bpf_helpers.h
@@ -47,6 +47,14 @@ 
 #define __weak __attribute__((weak))
 #endif
 
+/*
+ * Use __hidden attribute to mark a non-static BPF subprogram effectively
+ * static for BPF verifier's verification algorithm purposes, allowing more
+ * extensive and permissive BPF verification process, taking into account
+ * subprogram's caller context.
+ */
+#define __hidden __attribute__((visibility("hidden")))
+
 /* When utilizing vmlinux.h with BPF CO-RE, user BPF programs can't include
  * any system-level headers (such as stddef.h, linux/version.h, etc), and
  * commonly-used macros like NULL and KERNEL_VERSION aren't available through
diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index d30e67e7e1e5..d57e13a13798 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -1605,11 +1605,6 @@  static void *btf_add_type_mem(struct btf *btf, size_t add_sz)
 			      btf->hdr->type_len, UINT_MAX, add_sz);
 }
 
-static __u32 btf_type_info(int kind, int vlen, int kflag)
-{
-	return (kflag << 31) | (kind << 24) | vlen;
-}
-
 static void btf_type_inc_vlen(struct btf_type *t)
 {
 	t->info = btf_type_info(btf_kind(t), btf_vlen(t) + 1, btf_kflag(t));
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 9cc2d45b0080..ce5558d0a61b 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -71,6 +71,7 @@ 
 static struct bpf_map *bpf_object__add_map(struct bpf_object *obj);
 static const struct btf_type *
 skip_mods_and_typedefs(const struct btf *btf, __u32 id, __u32 *res_id);
+static bool prog_is_subprog(const struct bpf_object *obj, const struct bpf_program *prog);
 
 static int __base_pr(enum libbpf_print_level level, const char *format,
 		     va_list args)
@@ -274,6 +275,7 @@  struct bpf_program {
 	bpf_program_clear_priv_t clear_priv;
 
 	bool load;
+	bool mark_btf_static;
 	enum bpf_prog_type type;
 	enum bpf_attach_type expected_attach_type;
 	int prog_ifindex;
@@ -698,6 +700,15 @@  bpf_object__add_programs(struct bpf_object *obj, Elf_Data *sec_data,
 		if (err)
 			return err;
 
+		/* if function is a global/weak symbol, but has hidden
+		 * visibility (or any non-default one), mark its BTF FUNC as
+		 * static to enable more permissive BPF verification mode with
+		 * more outside context available to BPF verifier
+		 */
+		if (GELF_ST_BIND(sym.st_info) != STB_LOCAL
+		    && GELF_ST_VISIBILITY(sym.st_other) != STV_DEFAULT)
+			prog->mark_btf_static = true;
+
 		nr_progs++;
 		obj->nr_programs = nr_progs;
 
@@ -2618,7 +2629,7 @@  static int bpf_object__sanitize_and_load_btf(struct bpf_object *obj)
 {
 	struct btf *kern_btf = obj->btf;
 	bool btf_mandatory, sanitize;
-	int err = 0;
+	int i, err = 0;
 
 	if (!obj->btf)
 		return 0;
@@ -2632,6 +2643,38 @@  static int bpf_object__sanitize_and_load_btf(struct bpf_object *obj)
 		return 0;
 	}
 
+	/* Even though some subprogs are global/weak, user might prefer more
+	 * permissive BPF verification process that BPF verifier performs for
+	 * static functions, taking into account more context from the caller
+	 * functions. In such case, they need to mark such subprogs with
+	 * __attribute__((visibility("hidden"))) and libbpf will adjust
+	 * corresponding FUNC BTF type to be marked as static and trigger more
+	 * involved BPF verification process.
+	 */
+	for (i = 0; i < obj->nr_programs; i++) {
+		struct bpf_program *prog = &obj->programs[i];
+		struct btf_type *t;
+		const char *name;
+		int j, n;
+
+		if (!prog->mark_btf_static || !prog_is_subprog(obj, prog))
+			continue;
+
+		n = btf__get_nr_types(obj->btf);
+		for (j = 1; j <= n; j++) {
+			t = btf_type_by_id(obj->btf, j);
+			if (!btf_is_func(t) || btf_func_linkage(t) != BTF_FUNC_GLOBAL)
+				continue;
+
+			name = btf__str_by_offset(obj->btf, t->name_off);
+			if (strcmp(name, prog->name) != 0)
+				continue;
+
+			t->info = btf_type_info(BTF_KIND_FUNC, BTF_FUNC_STATIC, 0);
+			break;
+		}
+	}
+
 	sanitize = btf_needs_sanitization(obj);
 	if (sanitize) {
 		const void *raw_data;
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 6017902c687e..92b7eae10c6d 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -19,6 +19,7 @@ 
 #pragma GCC poison reallocarray
 
 #include "libbpf.h"
+#include "btf.h"
 
 #ifndef EM_BPF
 #define EM_BPF 247
@@ -132,6 +133,11 @@  struct btf_type;
 
 struct btf_type *btf_type_by_id(struct btf *btf, __u32 type_id);
 
+static inline __u32 btf_type_info(int kind, int vlen, int kflag)
+{
+	return (kflag << 31) | (kind << 24) | vlen;
+}
+
 void *libbpf_add_mem(void **data, size_t *cap_cnt, size_t elem_sz,
 		     size_t cur_cnt, size_t max_cnt, size_t add_cnt);
 int libbpf_ensure_mem(void **data, size_t *cap_cnt, size_t elem_sz, size_t need_cnt);