Commit 12741630 authored by Ilya Leoshkevich's avatar Ilya Leoshkevich Committed by Daniel Borkmann
Browse files

selftests/bpf: Clobber a lot of registers in tailcall_bpf2bpf_hierarchy tests 



Clobbering a lot of registers and stack slots helps exposing tail call
counter overwrite bugs in JITs.

Signed-off-by: default avatarIlya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20250813121016.163375-5-iii@linux.ibm.com
parent bc3905a7

tools/testing/selftests/bpf/progs/bpf_test_utils.h

0 → 100644
+18 −0
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0 */

#ifndef __BPF_TEST_UTILS_H__

#define __BPF_TEST_UTILS_H__



#include <bpf/bpf_helpers.h>

#include "bpf_misc.h"



/* Clobber as many native registers and stack slots as possible. */

static __always_inline void clobber_regs_stack(void)

{

	char tmp_str[] = "123456789";

	unsigned long tmp;



	bpf_strtoul(tmp_str, sizeof(tmp_str), 0, &tmp);

	__sink(tmp);

}



#endif

tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_hierarchy1.c

+3 −0
Original line number Diff line number Diff line
@@ -2,6 +2,7 @@ 
#include <linux/bpf.h>

#include <bpf/bpf_helpers.h>

#include "bpf_legacy.h"

#include "bpf_test_utils.h"



struct {

	__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
@@ -24,6 +25,8 @@ int entry(struct __sk_buff *skb) 
{

	int ret = 1;



	clobber_regs_stack();



	count++;

	subprog_tail(skb);

	subprog_tail(skb);

tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_hierarchy2.c

+3 −0
Original line number Diff line number Diff line
@@ -2,6 +2,7 @@ 
#include <linux/bpf.h>

#include <bpf/bpf_helpers.h>

#include "bpf_misc.h"

#include "bpf_test_utils.h"



int classifier_0(struct __sk_buff *skb);

int classifier_1(struct __sk_buff *skb);
@@ -60,6 +61,8 @@ int tailcall_bpf2bpf_hierarchy_2(struct __sk_buff *skb) 
{

	int ret = 0;



	clobber_regs_stack();



	subprog_tail0(skb);

	subprog_tail1(skb);

tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_hierarchy3.c

+3 −0
Original line number Diff line number Diff line
@@ -2,6 +2,7 @@ 
#include <linux/bpf.h>

#include <bpf/bpf_helpers.h>

#include "bpf_misc.h"

#include "bpf_test_utils.h"



int classifier_0(struct __sk_buff *skb);
@@ -53,6 +54,8 @@ int tailcall_bpf2bpf_hierarchy_3(struct __sk_buff *skb) 
{

	int ret = 0;



	clobber_regs_stack();



	bpf_tail_call_static(skb, &jmp_table0, 0);



	__sink(ret);

tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_hierarchy_fentry.c

+3 −0
Original line number Diff line number Diff line
@@ -4,6 +4,7 @@ 
#include "vmlinux.h"

#include <bpf/bpf_helpers.h>

#include <bpf/bpf_tracing.h>

#include "bpf_test_utils.h"



struct {

	__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
@@ -24,6 +25,8 @@ int subprog_tail(void *ctx) 
SEC("fentry/dummy")

int BPF_PROG(fentry, struct sk_buff *skb)

{

	clobber_regs_stack();



	count++;

	subprog_tail(ctx);

	subprog_tail(ctx);