bpf: Fix updating attached freplace prog to PROG_ARRAY map

The commit f7866c3587337731 ("bpf: Fix null pointer dereference in resolve_prog_type() for BPF_PROG_TYPE_EXT") fixed the following panic, which was caused by updating attached freplace prog to PROG_ARRAY map.

But, it does not support updating attached freplace prog to PROG_ARRAY map.

[309049.036402] BUG: kernel NULL pointer dereference, address: 0000000000000004
[309049.036419] #PF: supervisor read access in kernel mode
[309049.036426] #PF: error_code(0x0000) - not-present page
[309049.036432] PGD 0 P4D 0
[309049.036437] Oops: 0000 [#1] PREEMPT SMP NOPTI
[309049.036444] CPU: 2 PID: 788148 Comm: test_progs Not tainted 6.8.0-31-generic #31-Ubuntu
[309049.036465] Hardware name: VMware, Inc. VMware20,1/440BX Desktop Reference Platform, BIOS VMW201.00V.21805430.B64.2305221830 05/22/2023
[309049.036477] RIP: 0010:bpf_prog_map_compatible+0x2a/0x140
[309049.036488] Code: 0f 1f 44 00 00 55 48 89 e5 41 57 41 56 49 89 fe 41 55 41 54 53 44 8b 6e 04 48 89 f3 41 83 fd 1c 75 0c 48 8b 46 38 48 8b 40 70 <44> 8b 68 04 f6 43 03 01 75 1c 48 8b 43 38 44 0f b6 a0 89 00 00 00
[309049.036505] RSP: 0018:ffffb2e080fd7ce0 EFLAGS: 00010246
[309049.036513] RAX: 0000000000000000 RBX: ffffb2e0807c1000 RCX: 0000000000000000
[309049.036521] RDX: 0000000000000000 RSI: ffffb2e0807c1000 RDI: ffff990290259e00
[309049.036528] RBP: ffffb2e080fd7d08 R08: 0000000000000000 R09: 0000000000000000
[309049.036536] R10: 0000000000000000 R11: 0000000000000000 R12: ffff990290259e00
[309049.036543] R13: 000000000000001c R14: ffff990290259e00 R15: ffff99028e29c400
[309049.036551] FS:  00007b82cbc28140(0000) GS:ffff9903b3f00000(0000) knlGS:0000000000000000
[309049.036559] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[309049.036566] CR2: 0000000000000004 CR3: 0000000101286002 CR4: 00000000003706f0
[309049.036573] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[309049.036581] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[309049.036588] Call Trace:
[309049.036592]  <TASK>
[309049.036597]  ? show_regs+0x6d/0x80
[309049.036604]  ? __die+0x24/0x80
[309049.036619]  ? page_fault_oops+0x99/0x1b0
[309049.036628]  ? do_user_addr_fault+0x2ee/0x6b0
[309049.036634]  ? exc_page_fault+0x83/0x1b0
[309049.036641]  ? asm_exc_page_fault+0x27/0x30
[309049.036649]  ? bpf_prog_map_compatible+0x2a/0x140
[309049.036656]  prog_fd_array_get_ptr+0x2c/0x70
[309049.036664]  bpf_fd_array_map_update_elem+0x37/0x130
[309049.036671]  bpf_map_update_value+0x1d3/0x260
[309049.036677]  map_update_elem+0x1fa/0x360
[309049.036683]  __sys_bpf+0x54c/0xa10

[309049.036689]  __x64_sys_bpf+0x1a/0x30
[309049.036694]  x64_sys_call+0x1936/0x25c0
[309049.036700]  do_syscall_64+0x7f/0x180
[309049.036706]  ? do_syscall_64+0x8c/0x180
[309049.036712]  ? do_syscall_64+0x8c/0x180
[309049.036717]  ? irqentry_exit+0x43/0x50
[309049.036723]  ? common_interrupt+0x54/0xb0
[309049.036729]  entry_SYSCALL_64_after_hwframe+0x73/0x7b

Since commit 1c123c567fb138eb ("bpf: Resolve fext program type when checking map compatibility"), freplace prog can be used as tail-callee of its target prog.

And the commit 3aac1ead5eb6b76f ("bpf: Move prog->aux->linked_prog and trampoline into bpf_link on attach") sets prog->aux->dst_prog as NULL when attach freplace prog to its target.

Then, as for following example:

tailcall_freplace.c:

// SPDX-License-Identifier: GPL-2.0

\#include <linux/bpf.h>
\#include <bpf/bpf_helpers.h>
\#include "bpf_legacy.h"

struct {
	__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
	__uint(max_entries, 1);
	__uint(key_size, sizeof(__u32));
	__uint(value_size, sizeof(__u32));
} jmp_table SEC(".maps");

int count = 0;

__noinline int
subprog(struct __sk_buff *skb)

{
	volatile int ret = 1;

	count++;

	bpf_tail_call_static(skb, &jmp_table, 0);

	return ret;
}

SEC("freplace")
int entry(struct __sk_buff *skb)

{
	return subprog(skb);
}

char __license[] SEC("license") = "GPL";

tc_bpf2bpf.c:

// SPDX-License-Identifier: GPL-2.0

\#include <linux/bpf.h>
\#include <bpf/bpf_helpers.h>
\#include "bpf_legacy.h"

__noinline int
subprog(struct __sk_buff *skb)

{
	volatile int ret = 1;

	return ret;
}

SEC("tc")
int entry(struct __sk_buff *skb)

{
	return subprog(skb);
}

char __license[] SEC("license") = "GPL";

And freplace entry prog's target is the tc subprog.

After loading, the freplace jmp_table's owner type is BPF_PROG_TYPE_SCHED_CLS.

Next, after attaching freplace prog to tc subprog, its prog->aux-> dst_prog is NULL.

Next, when update freplace prog to jmp_table, bpf_prog_map_compatible() returns false because resolve_prog_type() returns BPF_PROG_TYPE_EXT instead of BPF_PROG_TYPE_SCHED_CLS.

With this patch, resolve_prog_type() returns BPF_PROG_TYPE_SCHED_CLS to support updating attached freplace prog to PROG_ARRY map for this example.

Fixes f7866c358733 ("bpf: Fix null pointer dereference in resolve_prog_type() for BPF_PROG_TYPE_EXT")

Cc Toke Høiland-Jørgensen <[email protected]>

Cc Martin KaFai Lau <[email protected]>

Signed-off-by Leon Hwang <[email protected]>

---
  include/linux/bpf_verifier.h | 4 ++--
  1 file changed, 2 insertions(+), 2 deletions(-)

include/linux/bpf_verifier.h +0 -0

index 5cea15c81b8a8..387e034e73d0e 100644

include/linux/bpf_verifier.h +0 -0

  }
 
  static inline bool bpf_prog_check_recur(const struct bpf_prog *prog)

Quoted 7 lines · Leon Hwang

The commit f7866c3587337731 ("bpf: Fix null pointer dereference in

resolve_prog_type() for BPF_PROG_TYPE_EXT") fixed the following panic,

which was caused by updating attached freplace prog to PROG_ARRAY map.

I am confused here. You mentioned that commit f7866c3587337731

fixed the panic below. But looking at commit message:

https://lore.kernel.org/bpf/[email protected]

it does not seem the case.

Quoted 6 lines

But, it does not support updating attached freplace prog to PROG_ARRAY

map.

This seems true since this patch itself intends fixing this issue.

Quoted 78 lines

[309049.036402] BUG: kernel NULL pointer dereference, address: 0000000000000004

 [309049.036419] #PF: supervisor read access in kernel mode

 [309049.036426] #PF: error_code(0x0000) - not-present page

 [309049.036432] PGD 0 P4D 0

 [309049.036437] Oops: 0000 [#1] PREEMPT SMP NOPTI

 [309049.036444] CPU: 2 PID: 788148 Comm: test_progs Not tainted 6.8.0-31-generic #31-Ubuntu

 [309049.036465] Hardware name: VMware, Inc. VMware20,1/440BX Desktop Reference Platform, BIOS VMW201.00V.21805430.B64.2305221830 05/22/2023

 [309049.036477] RIP: 0010:bpf_prog_map_compatible+0x2a/0x140

 [309049.036488] Code: 0f 1f 44 00 00 55 48 89 e5 41 57 41 56 49 89 fe 41 55 41 54 53 44 8b 6e 04 48 89 f3 41 83 fd 1c 75 0c 48 8b 46 38 48 8b 40 70 <44> 8b 68 04 f6 43 03 01 75 1c 48 8b 43 38 44 0f b6 a0 89 00 00 00

 [309049.036505] RSP: 0018:ffffb2e080fd7ce0 EFLAGS: 00010246

 [309049.036513] RAX: 0000000000000000 RBX: ffffb2e0807c1000 RCX: 0000000000000000

 [309049.036521] RDX: 0000000000000000 RSI: ffffb2e0807c1000 RDI: ffff990290259e00

 [309049.036528] RBP: ffffb2e080fd7d08 R08: 0000000000000000 R09: 0000000000000000

 [309049.036536] R10: 0000000000000000 R11: 0000000000000000 R12: ffff990290259e00

 [309049.036543] R13: 000000000000001c R14: ffff990290259e00 R15: ffff99028e29c400

 [309049.036551] FS: 00007b82cbc28140(0000) GS:ffff9903b3f00000(0000) knlGS:0000000000000000

 [309049.036559] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

 [309049.036566] CR2: 0000000000000004 CR3: 0000000101286002 CR4: 00000000003706f0

 [309049.036573] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000

 [309049.036581] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

 [309049.036588] Call Trace:

 [309049.036592] <TASK>

 [309049.036597] ? show_regs+0x6d/0x80

 [309049.036604] ? __die+0x24/0x80

 [309049.036619] ? page_fault_oops+0x99/0x1b0

 [309049.036628] ? do_user_addr_fault+0x2ee/0x6b0

 [309049.036634] ? exc_page_fault+0x83/0x1b0

 [309049.036641] ? asm_exc_page_fault+0x27/0x30

 [309049.036649] ? bpf_prog_map_compatible+0x2a/0x140

 [309049.036656] prog_fd_array_get_ptr+0x2c/0x70

 [309049.036664] bpf_fd_array_map_update_elem+0x37/0x130

 [309049.036671] bpf_map_update_value+0x1d3/0x260

 [309049.036677] map_update_elem+0x1fa/0x360

 [309049.036683] __sys_bpf+0x54c/0xa10

 [309049.036689] __x64_sys_bpf+0x1a/0x30

 [309049.036694] x64_sys_call+0x1936/0x25c0

 [309049.036700] do_syscall_64+0x7f/0x180

 [309049.036706] ? do_syscall_64+0x8c/0x180

Quoted 8 lines

 [309049.036712] ? do_syscall_64+0x8c/0x180

 [309049.036717] ? irqentry_exit+0x43/0x50

 [309049.036723] ? common_interrupt+0x54/0xb0

 [309049.036729] entry_SYSCALL_64_after_hwframe+0x73/0x7b

I actually tried your selftest (patch 2/2) without patch 1/1, I got the

following error:

All error logs:

tester_init:PASS:tester_log_buf 0 nsec

process_subtest:PASS:obj_open_mem 0 nsec

process_subtest:PASS:specs_alloc 0 nsec

test_tailcall_freplace:PASS:open fr_skel 0 nsec

test_tailcall_freplace:PASS:open tc_skel 0 nsec

test_tailcall_freplace:PASS:tc_skel entry prog_id 0 nsec

test_tailcall_freplace:PASS:set_attach_target 0 nsec

test_tailcall_freplace:PASS:load fr_skel 0 nsec

test_tailcall_freplace:PASS:attach_freplace 0 nsec

test_tailcall_freplace:PASS:fr_skel entry prog_fd 0 nsec

test_tailcall_freplace:PASS:fr_skel jmp_table map_fd 0 nsec

test_tailcall_freplace:FAIL:update jmp_table unexpected error: -22 (errno 22)

#328/25 tailcalls/tailcall_freplace:FAIL

#328 tailcalls:FAIL

I didn't see kernel panic.

Quoted 8 lines

Since commit 1c123c567fb138eb ("bpf: Resolve fext program type when

checking map compatibility"), freplace prog can be used as tail-callee

of its target prog.

the tailcall target can be a freplace prog.

Quoted 8 lines

And the commit 3aac1ead5eb6b76f ("bpf: Move prog->aux->linked_prog and

trampoline into bpf_link on attach") sets prog->aux->dst_prog as NULL

when attach freplace prog to its target.

when attach -> after attaching

Quoted 40 lines

Then, as for following example:

tailcall_freplace.c:

// SPDX-License-Identifier: GPL-2.0

\#include <linux/bpf.h>

\#include <bpf/bpf_helpers.h>

\#include "bpf_legacy.h"

struct {

__uint(type, BPF_MAP_TYPE_PROG_ARRAY);

__uint(max_entries, 1);

__uint(key_size, sizeof(__u32));

__uint(value_size, sizeof(__u32));

} jmp_table SEC(".maps");

int count = 0;

__noinline int

subprog(struct __sk_buff *skb)

{

volatile int ret = 1;

count++;

bpf_tail_call_static(skb, &jmp_table, 0);

Quoted 4 lines

return ret;

}

This subprog is not needed and could be misleading,

just inline subprog into entry prog, it should be okay.

Quoted 100 lines

SEC("freplace")

int entry(struct __sk_buff *skb)

{

return subprog(skb);

}

char __license[] SEC("license") = "GPL";

tc_bpf2bpf.c:

// SPDX-License-Identifier: GPL-2.0

\#include <linux/bpf.h>

\#include <bpf/bpf_helpers.h>

\#include "bpf_legacy.h"

__noinline int

subprog(struct __sk_buff *skb)

{

volatile int ret = 1;

return ret;

}

SEC("tc")

int entry(struct __sk_buff *skb)

{

return subprog(skb);

}

char __license[] SEC("license") = "GPL";

And freplace entry prog's target is the tc subprog.

After loading, the freplace jmp_table's owner type is

BPF_PROG_TYPE_SCHED_CLS.

Next, after attaching freplace prog to tc subprog, its prog->aux->

dst_prog is NULL.

Next, when update freplace prog to jmp_table, bpf_prog_map_compatible()

returns false because resolve_prog_type() returns BPF_PROG_TYPE_EXT instead

of BPF_PROG_TYPE_SCHED_CLS.

With this patch, resolve_prog_type() returns BPF_PROG_TYPE_SCHED_CLS to

support updating attached freplace prog to PROG_ARRY map for this

example.

Fixes f7866c358733 ("bpf: Fix null pointer dereference in resolve_prog_type() for BPF_PROG_TYPE_EXT")

Cc Toke Høiland-Jørgensen <[email protected]>

Cc Martin KaFai Lau <[email protected]>

Signed-off-by Leon Hwang <[email protected]>

---

 include/linux/bpf_verifier.h | 4 ++--

 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h

index 5cea15c81b8a8..387e034e73d0e 100644

--- a/include/linux/bpf_verifier.h

+++ b/include/linux/bpf_verifier.h

@@ -874,8 +874,8 @@ static inline u32 type_flag(u32 type)

/* only use after check_attach_btf_id() */

static inline enum bpf_prog_type resolve_prog_type(const struct bpf_prog *prog)

{

Quoted 8 lines

- return (prog->type == BPF_PROG_TYPE_EXT && prog->aux->dst_prog) ?

- prog->aux->dst_prog->type : prog->type;

+ return prog->type == BPF_PROG_TYPE_EXT ?

+ prog->aux->saved_dst_prog_type : prog->type;

If prog->aux->dst_prog is NULL, is it possible that prog->aux->saved_dst_prog_type

(0, corresponding to BPF_PROG_TYPE_UNSPEC) could be returned? Do we need to do

return (prog->type == BPF_PROG_TYPE_EXT && prog->aux->saved_dst_prog_type) ?

prog->aux->saved_dst_prog_type : prog->type;

Maybe I missed something here?

Quoted 6 lines

}

Quoted 1 line

static inline bool bpf_prog_check_recur(const struct bpf_prog *prog)

Quoted 8 lines · Yonghong Song

Quoted 6 lines · Leon Hwang

The commit f7866c3587337731 ("bpf: Fix null pointer dereference in

resolve_prog_type() for BPF_PROG_TYPE_EXT") fixed the following panic,

which was caused by updating attached freplace prog to PROG_ARRAY map.

Quoted 7 lines

I am confused here. You mentioned that commit f7866c3587337731

fixed the panic below. But looking at commit message:

https://lore.kernel.org/bpf/[email protected]

it does not seem the case.

The commit fixed this panic meanwhile.

This panic seems confusing. I'll remove it in patch v2.

Quoted 38 lines

Quoted 22 lines

---

  include/linux/bpf_verifier.h | 4 ++--

  1 file changed, 2 insertions(+), 2 deletions(-)

  diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h

index 5cea15c81b8a8..387e034e73d0e 100644

--- a/include/linux/bpf_verifier.h

+++ b/include/linux/bpf_verifier.h

@@ -874,8 +874,8 @@ static inline u32 type_flag(u32 type)

/* only use after check_attach_btf_id() */

static inline enum bpf_prog_type resolve_prog_type(const struct bpf_prog *prog)

  {

Quoted 8 lines

- return (prog->type == BPF_PROG_TYPE_EXT && prog->aux->dst_prog) ?

- prog->aux->dst_prog->type : prog->type;

+ return prog->type == BPF_PROG_TYPE_EXT ?

+ prog->aux->saved_dst_prog_type : prog->type;

If prog->aux->dst_prog is NULL, is it possible that prog->aux->saved_dst_prog_type

(0, corresponding to BPF_PROG_TYPE_UNSPEC) could be returned? Do we need to do

return (prog->type == BPF_PROG_TYPE_EXT && prog->aux->saved_dst_prog_type) ?

prog->aux->saved_dst_prog_type : prog->type;

Quoted 1 line

Maybe I missed something here?

It seems better to check prog->aux->saved_dst_prog_type. But I don't think so.

prog->aux->saved_dst_prog_type is set in check_attach_btf_id(). And there is no resolve_prog_type() before check_attach_btf_id() in bpf_check().

Therefore, resolve_prog_type() must be called after check_attach_btf_id().

Quoted 27 lines · On 7/25/24 8:27 PM, [email protected] wrote:

Quoted 3 lines · Yonghong Song

On 7/24/24 5:32 PM, Leon Hwang wrote:

The commit f7866c3587337731 ("bpf: Fix null pointer dereference in

resolve_prog_type() for BPF_PROG_TYPE_EXT") fixed the following panic,

which was caused by updating attached freplace prog to PROG_ARRAY map.

Quoted 9 lines

I am confused here. You mentioned that commit f7866c3587337731

fixed the panic below. But looking at commit message:

https://lore.kernel.org/bpf/[email protected]

it does not seem the case.

The commit fixed this panic meanwhile.

This panic seems confusing. I'll remove it in patch v2.

[...]

Quoted 43 lines

---

 include/linux/bpf_verifier.h | 4 ++--

 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h

index 5cea15c81b8a8..387e034e73d0e 100644

--- a/include/linux/bpf_verifier.h

+++ b/include/linux/bpf_verifier.h

@@ -874,8 +874,8 @@ static inline u32 type_flag(u32 type)

/* only use after check_attach_btf_id() */

static inline enum bpf_prog_type resolve_prog_type(const struct bpf_prog *prog)

{

- return (prog->type == BPF_PROG_TYPE_EXT && prog->aux->dst_prog) ?

- prog->aux->dst_prog->type : prog->type;

+ return prog->type == BPF_PROG_TYPE_EXT ?

+ prog->aux->saved_dst_prog_type : prog->type;

Quoted 11 lines

If prog->aux->dst_prog is NULL, is it possible that prog->aux->saved_dst_prog_type

(0, corresponding to BPF_PROG_TYPE_UNSPEC) could be returned? Do we need to do

return (prog->type == BPF_PROG_TYPE_EXT && prog->aux->saved_dst_prog_type) ?

prog->aux->saved_dst_prog_type : prog->type;

Maybe I missed something here?

Quoted 8 lines

It seems better to check prog->aux->saved_dst_prog_type. But I don't think so.

prog->aux->saved_dst_prog_type is set in check_attach_btf_id(). And there is no

resolve_prog_type() before check_attach_btf_id() in bpf_check().

Therefore, resolve_prog_type() must be called after check_attach_btf_id().

In check_attach_btf_id(), I see

if (tgt_prog) {

prog->aux->saved_dst_prog_type = tgt_prog->type;

prog->aux->saved_dst_attach_type = tgt_prog->expected_attach_type;

}

So it is possible prog->aux->saved_dst_prog_type is 0 (default value).

I don't know that if tgt_prog is NULL, whether later resolve_prog_type()

will be called or not. Need more checking here.

Add a selftest to confirm the issue, which gets -EINVAL when update attached freplace prog to PROG_ARRAY map, has been fixed.

cd tools/testing/selftests/bpf; ./test_progs -t tailcalls 327/25 tailcalls/tailcall_freplace:OK
327 tailcalls:OK
Summary: 1/25 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by Leon Hwang <[email protected]>

---
  .../selftests/bpf/prog_tests/tailcalls.c      | 76 ++++++++++++++++++-
  .../selftests/bpf/progs/tailcall_freplace.c   | 33 ++++++++
  .../testing/selftests/bpf/progs/tc_bpf2bpf.c  | 23 ++++++
  3 files changed, 131 insertions(+), 1 deletion(-)

create mode 100644 tools/testing/selftests/bpf/progs/tailcall_freplace.c create mode 100644 tools/testing/selftests/bpf/progs/tc_bpf2bpf.c

tools/testing/selftests/bpf/prog_tests/tailcalls.c +2 -1

index e01fabb8cc415..f1145601c0005 100644
@@ -5,7 +5,8 @@
  #include "tailcall_poke.skel.h"
  #include "tailcall_bpf2bpf_hierarchy2.skel.h"
  #include "tailcall_bpf2bpf_hierarchy3.skel.h"
-
+#include "tailcall_freplace.skel.h"
+#include "tc_bpf2bpf.skel.h"
 
  /* test_tailcall_1 checks basic functionality by patching multiple locations
   * in a single program for a single tail call slot with nop->jmp, jmp->nop

tools/testing/selftests/bpf/prog_tests/tailcalls.c +8 -0

+ */
+static void test_tailcall_freplace(void)
+{
+	struct tailcall_freplace *fr_skel = NULL;
+	struct tc_bpf2bpf *tc_skel = NULL;
+	struct bpf_link *fr_link = NULL;
+	int prog_fd, map_fd;
+	char buff[128] = {};

tools/testing/selftests/bpf/prog_tests/tailcalls.c +8 -0

+
+	err = bpf_program__set_attach_target(fr_skel->progs.entry,
+					     prog_fd, "subprog");
+	if (!ASSERT_OK(err, "set_attach_target"))
+		goto out;
+
+	err = tailcall_freplace__load(fr_skel);
+	if (!ASSERT_OK(err, "load fr_skel"))

tools/testing/selftests/bpf/prog_tests/tailcalls.c +13 -0

+
+	err = bpf_prog_test_run_opts(prog_fd, &topts);
+	ASSERT_OK(err, "test_run");
+	ASSERT_EQ(topts.retval, 34, "test_run retval");
+
+out:
+	bpf_link__destroy(fr_link);
+	tc_bpf2bpf__destroy(tc_skel);
+	tailcall_freplace__destroy(fr_skel);
+}
+
  void test_tailcalls(void)
  {
  	if (test__start_subtest("tailcall_1"))

@@ -1543,4 +1615,6 @@ void test_tailcalls(void)
  		test_tailcall_bpf2bpf_hierarchy_fentry_entry();
  	test_tailcall_bpf2bpf_hierarchy_2();
  	test_tailcall_bpf2bpf_hierarchy_3();
+	if (test__start_subtest("tailcall_freplace"))
+		test_tailcall_freplace();
  }

tools/testing/selftests/bpf/progs/tailcall_freplace.c new file +0 -0

new file mode 100644
index 0000000000000..80b5fa386ed9c

tools/testing/selftests/bpf/progs/tailcall_freplace.c new file +9 -0

+
+struct {
+	__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
+	__uint(max_entries, 1);
+	__uint(key_size, sizeof(__u32));
+	__uint(value_size, sizeof(__u32));
+} jmp_table SEC(".maps");
+
+int count = 0;

tools/testing/selftests/bpf/progs/tailcall_freplace.c new file +9 -0

+
+SEC("freplace")
+int entry(struct __sk_buff *skb)
+{
+	return subprog(skb);
+}
+
+char __license[] SEC("license") = "GPL";
+

tools/testing/selftests/bpf/progs/tc_bpf2bpf.c new file +23 -0

new file mode 100644
index 0000000000000..4810961554585
@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_legacy.h"
+
+__noinline
+int subprog(struct __sk_buff *skb)
+{
+	volatile int ret = 1;
+
+	asm volatile (""::"r+"(ret));
+	return ret;
+}
+
+SEC("tc")
+int entry(struct __sk_buff *skb)
+{
+	return subprog(skb);
+}
+
+char __license[] SEC("license") = "GPL";
+

Quoted 59 lines · Leon Hwang

Add a selftest to confirm the issue, which gets -EINVAL when update

attached freplace prog to PROG_ARRAY map, has been fixed.

cd tools/testing/selftests/bpf; ./test_progs -t tailcalls

327/25 tailcalls/tailcall_freplace:OK

327 tailcalls:OK

Summary: 1/25 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by Leon Hwang <[email protected]>

---

 .../selftests/bpf/prog_tests/tailcalls.c | 76 ++++++++++++++++++-

 .../selftests/bpf/progs/tailcall_freplace.c | 33 ++++++++

 .../testing/selftests/bpf/progs/tc_bpf2bpf.c | 23 ++++++

 3 files changed, 131 insertions(+), 1 deletion(-)

 create mode 100644 tools/testing/selftests/bpf/progs/tailcall_freplace.c

 create mode 100644 tools/testing/selftests/bpf/progs/tc_bpf2bpf.c

diff --git a/tools/testing/selftests/bpf/prog_tests/tailcalls.c b/tools/testing/selftests/bpf/prog_tests/tailcalls.c

index e01fabb8cc415..f1145601c0005 100644

--- a/tools/testing/selftests/bpf/prog_tests/tailcalls.c

+++ b/tools/testing/selftests/bpf/prog_tests/tailcalls.c

@@ -5,7 +5,8 @@

#include "tailcall_poke.skel.h"

#include "tailcall_bpf2bpf_hierarchy2.skel.h"

#include "tailcall_bpf2bpf_hierarchy3.skel.h"

-

+#include "tailcall_freplace.skel.h"

+#include "tc_bpf2bpf.skel.h"

Quoted 1 line

/* test_tailcall_1 checks basic functionality by patching multiple locations

* in a single program for a single tail call slot with nop->jmp, jmp->nop

@@ -1495,6 +1496,77 @@ static void test_tailcall_bpf2bpf_hierarchy_3(void)

RUN_TESTS(tailcall_bpf2bpf_hierarchy3);

Quoted 6 lines

}

Quoted 1 line

+/* test_tailcall_freplace checks that the attached freplace prog is OK to

+ * update to PROG_ARRAY map.

update the prog_array map.

Quoted 30 lines

+ */

+static void test_tailcall_freplace(void)

+{

+ struct tailcall_freplace *fr_skel = NULL;

+ struct tc_bpf2bpf *tc_skel = NULL;

+ struct bpf_link *fr_link = NULL;

+ int prog_fd, map_fd;

+ char buff[128] = {};

+ int err, key;

+

+ LIBBPF_OPTS(bpf_test_run_opts, topts,

+ .data_in = buff,

+ .data_size_in = sizeof(buff),

+ .repeat = 1,

Quoted 8 lines

+ );

+

+ fr_skel = tailcall_freplace__open();

+ if (!ASSERT_OK_PTR(fr_skel, "open fr_skel"))

if (!ASSERT_OK_PTR(fr_skel, "open fr_skel"))

==>

if (!ASSERT_OK_PTR(fr_skel, "tailcall_freplace__open"))

Similar for below other ASSERT_* macros.

Quoted 4 lines

+ goto out;

Let us just do 'return' here.

Quoted 12 lines

+

+ tc_skel = tc_bpf2bpf__open_and_load();

+ if (!ASSERT_OK_PTR(tc_skel, "open tc_skel"))

+ goto out;

+

Quoted 6 lines

+ prog_fd = bpf_program__fd(tc_skel->progs.entry);

+ if (!ASSERT_GE(prog_fd, 0, "tc_skel entry prog_id"))

+ goto out;

ASSERT_GE is not necessary, prog_fd should already be valid.

Quoted 32 lines

+

+ err = bpf_program__set_attach_target(fr_skel->progs.entry,

+ prog_fd, "subprog");

+ if (!ASSERT_OK(err, "set_attach_target"))

+ goto out;

+

+ err = tailcall_freplace__load(fr_skel);

+ if (!ASSERT_OK(err, "load fr_skel"))

+ goto out;

+

+ fr_link = bpf_program__attach_freplace(fr_skel->progs.entry,

+ prog_fd, "subprog");

+ if (!ASSERT_OK_PTR(fr_link, "attach_freplace"))

+ goto out;

+

Quoted 6 lines

+ prog_fd = bpf_program__fd(fr_skel->progs.entry);

+ if (!ASSERT_GE(prog_fd, 0, "fr_skel entry prog_fd"))

+ goto out;

prog_fd is valid here. No need ASSERT_GE.

Quoted 4 lines

+

Quoted 6 lines

+ map_fd = bpf_map__fd(fr_skel->maps.jmp_table);

+ if (!ASSERT_GE(map_fd, 0, "fr_skel jmp_table map_fd"))

+ goto out;

map_fd is valid. No need ASSERT_GE.

Quoted 14 lines

+

+ key = 0;

+ err = bpf_map_update_elem(map_fd, &key, &prog_fd, BPF_ANY);

+ if (!ASSERT_OK(err, "update jmp_table"))

+ goto out;

+

Quoted 6 lines

+ prog_fd = bpf_program__fd(tc_skel->progs.entry);

+ if (!ASSERT_GE(prog_fd, 0, "prog_fd"))

+ goto out;

prog_fd is valid here.

Quoted 60 lines

+

+ err = bpf_prog_test_run_opts(prog_fd, &topts);

+ ASSERT_OK(err, "test_run");

+ ASSERT_EQ(topts.retval, 34, "test_run retval");

+

+out:

+ bpf_link__destroy(fr_link);

+ tc_bpf2bpf__destroy(tc_skel);

+ tailcall_freplace__destroy(fr_skel);

+}

+

void test_tailcalls(void)

{

if (test__start_subtest("tailcall_1"))

@@ -1543,4 +1615,6 @@ void test_tailcalls(void)

test_tailcall_bpf2bpf_hierarchy_fentry_entry();

test_tailcall_bpf2bpf_hierarchy_2();

test_tailcall_bpf2bpf_hierarchy_3();

+ if (test__start_subtest("tailcall_freplace"))

+ test_tailcall_freplace();

}

diff --git a/tools/testing/selftests/bpf/progs/tailcall_freplace.c b/tools/testing/selftests/bpf/progs/tailcall_freplace.c

new file mode 100644

index 0000000000000..80b5fa386ed9c

--- /dev/null

+++ b/tools/testing/selftests/bpf/progs/tailcall_freplace.c

@@ -0,0 +1,33 @@

+// SPDX-License-Identifier: GPL-2.0

+

Quoted 6 lines

+#include <linux/bpf.h>

+#include <bpf/bpf_helpers.h>

+#include "bpf_legacy.h"

bpf_legacy.h is not needed.

Quoted 32 lines

+

+struct {

+ __uint(type, BPF_MAP_TYPE_PROG_ARRAY);

+ __uint(max_entries, 1);

+ __uint(key_size, sizeof(__u32));

+ __uint(value_size, sizeof(__u32));

+} jmp_table SEC(".maps");

+

+int count = 0;

+

+__noinline

+int subprog(struct __sk_buff *skb)

+{

+ count++;

+

Quoted 8 lines

+ bpf_tail_call_static(skb, &jmp_table, 0);

+

+ return count;

+}

subprog() can be inlined into entry(). This

can avoid confusing vs. tc_bpf2bpf.c.

Better if you can differentiate two 'entry()' function

names, e.g., entry_freplace(), entry_tc(), it can make

it easy for people to understand your change in tailcalls.c.

Quoted 78 lines

+

+SEC("freplace")

+int entry(struct __sk_buff *skb)

+{

+ return subprog(skb);

+}

+

+char __license[] SEC("license") = "GPL";

+

diff --git a/tools/testing/selftests/bpf/progs/tc_bpf2bpf.c b/tools/testing/selftests/bpf/progs/tc_bpf2bpf.c

new file mode 100644

index 0000000000000..4810961554585

--- /dev/null

+++ b/tools/testing/selftests/bpf/progs/tc_bpf2bpf.c

@@ -0,0 +1,23 @@

+// SPDX-License-Identifier: GPL-2.0

+

+#include <linux/bpf.h>

+#include <bpf/bpf_helpers.h>

+#include "bpf_legacy.h"

+

+__noinline

+int subprog(struct __sk_buff *skb)

+{

+ volatile int ret = 1;

+

+ asm volatile (""::"r+"(ret));

+ return ret;

+}

+

+SEC("tc")

+int entry(struct __sk_buff *skb)

+{

+ return subprog(skb);

+}

+

+char __license[] SEC("license") = "GPL";

+

Add a selftest to confirm the issue, which gets -EINVAL when update attached freplace prog to PROG_ARRAY map, has been fixed.

cd tools/testing/selftests/bpf; ./test_progs -t tailcalls 327/25 tailcalls/tailcall_freplace:OK
327 tailcalls:OK
Summary: 1/25 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by Leon Hwang <[email protected]>

---
  .../selftests/bpf/prog_tests/tailcalls.c      | 76 ++++++++++++++++++-
  .../selftests/bpf/progs/tailcall_freplace.c   | 33 ++++++++
  .../testing/selftests/bpf/progs/tc_bpf2bpf.c  | 23 ++++++
  3 files changed, 131 insertions(+), 1 deletion(-)

create mode 100644 tools/testing/selftests/bpf/progs/tailcall_freplace.c create mode 100644 tools/testing/selftests/bpf/progs/tc_bpf2bpf.c

tools/testing/selftests/bpf/progs/tailcall_freplace.c new file +23 -0

new file mode 100644
index 0000000000000..80b5fa386ed9c
@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_legacy.h"
+
+struct {
+	__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
+	__uint(max_entries, 1);
+	__uint(key_size, sizeof(__u32));
+	__uint(value_size, sizeof(__u32));
+} jmp_table SEC(".maps");
+
+int count = 0;
+
+__noinline
+int subprog(struct __sk_buff *skb)
+{
+	count++;
+
+	bpf_tail_call_static(skb, &jmp_table, 0);
+
+	return count;

tools/testing/selftests/bpf/progs/tc_bpf2bpf.c new file +13 -0

new file mode 100644
index 0000000000000..4810961554585
@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_legacy.h"
+
+__noinline
+int subprog(struct __sk_buff *skb)
+{
+	volatile int ret = 1;
+
+	asm volatile (""::"r+"(ret));
+	return ret;

Quoted 29 lines · Leon Hwang

Add a selftest to confirm the issue, which gets -EINVAL when update

attached freplace prog to PROG_ARRAY map, has been fixed.

cd tools/testing/selftests/bpf; ./test_progs -t tailcalls

327/25 tailcalls/tailcall_freplace:OK

327 tailcalls:OK

Summary: 1/25 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by Leon Hwang <[email protected]>

---

 .../selftests/bpf/prog_tests/tailcalls.c | 76 ++++++++++++++++++-

 .../selftests/bpf/progs/tailcall_freplace.c | 33 ++++++++

 .../testing/selftests/bpf/progs/tc_bpf2bpf.c | 23 ++++++

 3 files changed, 131 insertions(+), 1 deletion(-)

 create mode 100644 tools/testing/selftests/bpf/progs/tailcall_freplace.c

 create mode 100644 tools/testing/selftests/bpf/progs/tc_bpf2bpf.c

[...]

Quoted 73 lines

tools/testing/selftests/bpf/progs/tailcall_freplace.c +0 -0

 
 new file mode 100644
 
 index 0000000000000..80b5fa386ed9c
 
 --- /dev/null
 
 +++ b/tools/testing/selftests/bpf/progs/tailcall_freplace.c
 
 @@ -0,0 +1,33 @@
 
 +// SPDX-License-Identifier: GPL-2.0
 
 +
 
 +#include <linux/bpf.h>
 
 +#include <bpf/bpf_helpers.h>
 
 +#include "bpf_legacy.h"
 
 +
 
 +struct {
 
 + __uint(type, BPF_MAP_TYPE_PROG_ARRAY);
 
 + __uint(max_entries, 1);
 
 + __uint(key_size, sizeof(__u32));
 
 + __uint(value_size, sizeof(__u32));
 
 +} jmp_table SEC(".maps");
 
 +
 
 +int count = 0;
 
 +
 
 +__noinline
 
 +int subprog(struct __sk_buff *skb)
 
 +{
 
 + count++;
 
 +
 
 + bpf_tail_call_static(skb, &jmp_table, 0);
 
 +
 
 + return count;
 
 +}
 
 +
 
 +SEC("freplace")
 
 +int entry(struct __sk_buff *skb)
 
 +{
 
 + return subprog(skb);
 
 +}

Quoted 6 lines

+

+char __license[] SEC("license") = "GPL";

+

extra line in the above.

Quoted 54 lines

tools/testing/selftests/bpf/progs/tc_bpf2bpf.c +0 -0

 
 new file mode 100644
 
 index 0000000000000..4810961554585
 
 --- /dev/null
 
 +++ b/tools/testing/selftests/bpf/progs/tc_bpf2bpf.c
 
 @@ -0,0 +1,23 @@
 
 +// SPDX-License-Identifier: GPL-2.0
 
 +
 
 +#include <linux/bpf.h>
 
 +#include <bpf/bpf_helpers.h>
 
 +#include "bpf_legacy.h"
 
 +
 
 +__noinline
 
 +int subprog(struct __sk_buff *skb)
 
 +{
 
 + volatile int ret = 1;
 
 +
 
 + asm volatile (""::"r+"(ret));
 
 + return ret;
 
 +}
 
 +
 
 +SEC("tc")
 
 +int entry(struct __sk_buff *skb)
 
 +{
 
 + return subprog(skb);
 
 +}

Quoted 6 lines

+

+char __license[] SEC("license") = "GPL";

+

extra line in the above.