From: Yonghong Song <yonghong.song@linux.dev>
To: bpf@vger.kernel.org
Cc: Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
"Jose E . Marchesi" <jose.marchesi@oracle.com>,
kernel-team@fb.com, Martin KaFai Lau <martin.lau@kernel.org>
Subject: [PATCH bpf-next v4 22/25] selftests/bpf: Add precision backtracking test for stack arguments
Date: Tue, 12 May 2026 21:51:48 -0700 [thread overview]
Message-ID: <20260513045148.2400087-1-yonghong.song@linux.dev> (raw)
In-Reply-To: <20260513044949.2382019-1-yonghong.song@linux.dev>
Add a test that verifies precision backtracking works correctly
across BPF-to-BPF calls when stack arguments are involved.
The test passes a size value as incoming stack arg (arg6) to a
subprog, which forwards it as the mem__sz parameter (outgoing arg7)
to bpf_kfunc_call_stack_arg_mem. The expected __msg annotations
verify that precision propagates from the kfunc's mem__sz argument
back through the subprog frame to the caller's outgoing stack arg
store.
A companion BTF file (btf__stack_arg_precision.c) provides named
parameter BTF for the __naked subprog via __btf_func_path.
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
---
.../bpf/prog_tests/stack_arg_precision.c | 10 ++
.../bpf/progs/btf__stack_arg_precision.c | 23 +++
.../selftests/bpf/progs/stack_arg_precision.c | 134 ++++++++++++++++++
3 files changed, 167 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/stack_arg_precision.c
create mode 100644 tools/testing/selftests/bpf/progs/btf__stack_arg_precision.c
create mode 100644 tools/testing/selftests/bpf/progs/stack_arg_precision.c
diff --git a/tools/testing/selftests/bpf/prog_tests/stack_arg_precision.c b/tools/testing/selftests/bpf/prog_tests/stack_arg_precision.c
new file mode 100644
index 000000000000..1ab041d66de3
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/stack_arg_precision.c
@@ -0,0 +1,10 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2026 Meta Platforms, Inc. and affiliates. */
+
+#include <test_progs.h>
+#include "stack_arg_precision.skel.h"
+
+void test_stack_arg_precision(void)
+{
+ RUN_TESTS(stack_arg_precision);
+}
diff --git a/tools/testing/selftests/bpf/progs/btf__stack_arg_precision.c b/tools/testing/selftests/bpf/progs/btf__stack_arg_precision.c
new file mode 100644
index 000000000000..296fddfe6804
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/btf__stack_arg_precision.c
@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2026 Meta Platforms, Inc. and affiliates. */
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+#include "../test_kmods/bpf_testmod_kfunc.h"
+
+#if defined(__TARGET_ARCH_x86) && defined(__BPF_FEATURE_STACK_ARGUMENT)
+
+long subprog_call_mem_kfunc(long a, long b, long c, long d, long e, long size)
+{
+ char buf[8] = {};
+
+ return bpf_kfunc_call_stack_arg_mem(a, b, c, d, e, buf, size);
+}
+
+#else
+
+long subprog_call_mem_kfunc(void)
+{
+ return 0;
+}
+
+#endif
diff --git a/tools/testing/selftests/bpf/progs/stack_arg_precision.c b/tools/testing/selftests/bpf/progs/stack_arg_precision.c
new file mode 100644
index 000000000000..2a0a344c83ca
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/stack_arg_precision.c
@@ -0,0 +1,134 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2026 Meta Platforms, Inc. and affiliates. */
+
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+#include "../test_kmods/bpf_testmod_kfunc.h"
+#include "bpf_misc.h"
+
+#if defined(__TARGET_ARCH_x86) && defined(__BPF_FEATURE_STACK_ARGUMENT)
+
+/* Force kfunc extern BTF generation for inline asm call below.
+ * Uses its own SEC so it's not included as a .text subprog.
+ * The '?' prefix sets autoload=false so libbpf won't load it.
+ */
+SEC("?tc")
+int __btf_kfunc_gen(struct __sk_buff *ctx)
+{
+ char buf[8] = {};
+
+ return bpf_kfunc_call_stack_arg_mem(0, 0, 0, 0, 0, buf, sizeof(buf));
+}
+
+/*
+ * Test precision backtracking across bpf-to-bpf call for kfunc stack arg.
+ * subprog_call_mem_kfunc receives a size as incoming stack arg (arg6)
+ * and forwards it as mem__sz (arg7) to bpf_kfunc_call_stack_arg_mem.
+ */
+__naked __noinline __used
+static long subprog_call_mem_kfunc(long a, long b, long c, long d, long e, long size)
+{
+ asm volatile (
+ "r1 = *(u64 *)(r11 + 8);" /* r1 = incoming arg6 (size) */
+ "r2 = 0x0807060504030201 ll;" /* r2 = buf contents */
+ "*(u64 *)(r10 - 8) = r2;" /* store buf to stack */
+ "r2 = r10;"
+ "r2 += -8;" /* r2 = &buf */
+ "*(u64 *)(r11 - 8) = r2;" /* outgoing arg6 = buf */
+ "*(u64 *)(r11 - 16) = r1;" /* outgoing arg7 = size */
+ "r1 = 1;"
+ "r2 = 2;"
+ "r3 = 3;"
+ "r4 = 4;"
+ "r5 = 5;"
+ "call %[bpf_kfunc_call_stack_arg_mem];"
+ "exit;"
+ :
+ : __imm(bpf_kfunc_call_stack_arg_mem)
+ : __clobber_all
+ );
+}
+
+SEC("tc")
+__description("stack_arg: precision backtracking across bpf2bpf call for kfunc")
+__success
+__log_level(2)
+__flag(BPF_F_TEST_STATE_FREQ)
+__btf_func_path("btf__stack_arg_precision.bpf.o")
+__msg("mark_precise: frame1: last_idx 26 first_idx 13 subseq_idx -1")
+__msg("mark_precise: frame1: regs= stack= before 25: (b7) r5 = 5")
+__msg("mark_precise: frame1: regs= stack= before 24: (b7) r4 = 4")
+__msg("mark_precise: frame1: regs= stack= before 23: (b7) r3 = 3")
+__msg("mark_precise: frame1: regs= stack= before 22: (b7) r2 = 2")
+__msg("mark_precise: frame1: regs= stack= before 21: (b7) r1 = 1")
+__msg("mark_precise: frame1: regs= stack= before 20: (7b) *(u64 *)(r11 -16) = r1")
+__msg("mark_precise: frame1: regs=r1 stack= before 19: (7b) *(u64 *)(r11 -8) = r2")
+__msg("mark_precise: frame1: regs=r1 stack= before 18: (07) r2 += -8")
+__msg("mark_precise: frame1: regs=r1 stack= before 17: (bf) r2 = r10")
+__msg("mark_precise: frame1: regs=r1 stack= before 16: (7b) *(u64 *)(r10 -8) = r2")
+__msg("mark_precise: frame1: regs=r1 stack= before 14: (18) r2 = 0x807060504030201")
+__msg("mark_precise: frame1: regs=r1 stack= before 13: (79) r1 = *(u64 *)(r11 +8)")
+__msg("mark_precise: frame1: parent state regs= stack=: frame1: R10=fp0")
+__msg("mark_precise: frame0: parent state regs= stack=: R10=fp0")
+__msg("mark_precise: frame1: last_idx 11 first_idx 11 subseq_idx 13")
+__msg("mark_precise: frame1: regs= stack= before 11: (85) call pc+1")
+__msg("mark_precise: frame0: parent state regs= stack=: R1=1 R2=2 R3=3 R4=4 R5=5 R10=fp0")
+__msg("mark_precise: frame0: last_idx 9 first_idx 7 subseq_idx 11")
+__msg("mark_precise: frame0: regs= stack= before 9: (05) goto pc+1")
+__msg("mark_precise: frame0: regs= stack= before 8: (7a) *(u64 *)(r11 -8) = 4")
+__msg("mark_precise: frame1: last_idx 26 first_idx 13 subseq_idx -1 ")
+__msg("mark_precise: frame1: regs= stack= before 25: (b7) r5 = 5")
+__msg("mark_precise: frame1: regs= stack= before 24: (b7) r4 = 4")
+__msg("mark_precise: frame1: regs= stack= before 23: (b7) r3 = 3")
+__msg("mark_precise: frame1: regs= stack= before 22: (b7) r2 = 2")
+__msg("mark_precise: frame1: regs= stack= before 21: (b7) r1 = 1")
+__msg("mark_precise: frame1: regs= stack= before 20: (7b) *(u64 *)(r11 -16) = r1")
+__msg("mark_precise: frame1: regs=r1 stack= before 19: (7b) *(u64 *)(r11 -8) = r2")
+__msg("mark_precise: frame1: regs=r1 stack= before 18: (07) r2 += -8")
+__msg("mark_precise: frame1: regs=r1 stack= before 17: (bf) r2 = r10")
+__msg("mark_precise: frame1: regs=r1 stack= before 16: (7b) *(u64 *)(r10 -8) = r2")
+__msg("mark_precise: frame1: regs=r1 stack= before 14: (18) r2 = 0x807060504030201")
+__msg("mark_precise: frame1: regs=r1 stack= before 13: (79) r1 = *(u64 *)(r11 +8)")
+__msg("mark_precise: frame1: parent state regs= stack=: frame1: R10=fp0")
+__msg("mark_precise: frame0: parent state regs= stack=: R10=fp0")
+__msg("mark_precise: frame1: last_idx 11 first_idx 11 subseq_idx 13 ")
+__msg("mark_precise: frame1: regs= stack= before 11: (85) call pc+1")
+__msg("mark_precise: frame0: parent state regs= stack=: R1=1 R2=2 R3=3 R4=4 R5=5 R10=fp0")
+__msg("mark_precise: frame0: last_idx 10 first_idx 10 subseq_idx 11 ")
+__msg("mark_precise: frame0: regs= stack= before 10: (7a) *(u64 *)(r11 -8) = 6")
+__naked void stack_arg_precision_bpf2bpf(void)
+{
+ asm volatile (
+ "call %[bpf_get_prandom_u32];"
+ "r6 = r0;"
+ "r1 = 1;"
+ "r2 = 2;"
+ "r3 = 3;"
+ "r4 = 4;"
+ "r5 = 5;"
+ "if r6 < 2 goto l0_%=;"
+ "*(u64 *)(r11 - 8) = 4;"
+ "goto l1_%=;"
+ "l0_%=:"
+ "*(u64 *)(r11 - 8) = 6;"
+ "l1_%=:"
+ "call subprog_call_mem_kfunc;"
+ "exit;"
+ :: __imm(bpf_get_prandom_u32)
+ : __clobber_all
+ );
+}
+
+#else
+
+SEC("socket")
+__description("stack_arg_precision: not supported, dummy test")
+__success
+int dummy_test(void)
+{
+ return 0;
+}
+
+#endif
+
+char _license[] SEC("license") = "GPL";
--
2.53.0-Meta
next prev parent reply other threads:[~2026-05-13 4:51 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-13 4:49 [PATCH bpf-next v4 00/25] bpf: Support stack arguments for BPF functions and kfuncs Yonghong Song
2026-05-13 4:49 ` [PATCH bpf-next v4 01/25] bpf: Convert bpf_get_spilled_reg macro to static inline function Yonghong Song
2026-05-13 4:50 ` [PATCH bpf-next v4 02/25] bpf: Remove copy_register_state wrapper function Yonghong Song
2026-05-13 4:50 ` [PATCH bpf-next v4 03/25] bpf: Add helper functions for r11-based stack argument insns Yonghong Song
2026-05-13 4:50 ` [PATCH bpf-next v4 04/25] bpf: Set sub->arg_cnt earlier in btf_prepare_func_args() Yonghong Song
2026-05-13 4:50 ` [PATCH bpf-next v4 05/25] bpf: Support stack arguments for bpf functions Yonghong Song
2026-05-14 10:46 ` sashiko-bot
2026-05-14 16:07 ` Yonghong Song
2026-05-13 4:50 ` [PATCH bpf-next v4 06/25] bpf: Refactor jmp history to use dedicated spi/frame fields Yonghong Song
2026-05-13 4:50 ` [PATCH bpf-next v4 07/25] bpf: Add precision marking and backtracking for stack argument slots Yonghong Song
2026-05-13 5:44 ` bot+bpf-ci
2026-05-13 4:50 ` [PATCH bpf-next v4 08/25] bpf: Refactor record_call_access() to extract per-arg logic Yonghong Song
2026-05-13 4:50 ` [PATCH bpf-next v4 09/25] bpf: Use arg_is_fp() in has_fp_args() Yonghong Song
2026-05-13 4:50 ` [PATCH bpf-next v4 10/25] bpf: Extend liveness analysis to track stack argument slots Yonghong Song
2026-05-13 5:44 ` bot+bpf-ci
2026-05-14 22:53 ` sashiko-bot
2026-05-13 4:50 ` [PATCH bpf-next v4 11/25] bpf: Reject stack arguments in non-JITed programs Yonghong Song
2026-05-13 5:33 ` bot+bpf-ci
2026-05-14 23:59 ` sashiko-bot
2026-05-13 4:50 ` [PATCH bpf-next v4 12/25] bpf: Prepare architecture JIT support for stack arguments Yonghong Song
2026-05-13 5:33 ` bot+bpf-ci
2026-05-15 0:30 ` sashiko-bot
2026-05-13 4:50 ` [PATCH bpf-next v4 13/25] bpf: Enable r11 based insns Yonghong Song
2026-05-13 4:51 ` [PATCH bpf-next v4 14/25] bpf: Support stack arguments for kfunc calls Yonghong Song
2026-05-13 4:51 ` [PATCH bpf-next v4 15/25] bpf: Reject stack arguments if tail call reachable Yonghong Song
2026-05-13 5:33 ` bot+bpf-ci
2026-05-15 3:23 ` sashiko-bot
2026-05-13 4:51 ` [PATCH bpf-next v4 16/25] bpf: Disable private stack for x86_64 if stack arguments used Yonghong Song
2026-05-13 5:33 ` bot+bpf-ci
2026-05-15 5:28 ` sashiko-bot
2026-05-13 4:51 ` [PATCH bpf-next v4 17/25] bpf,x86: Implement JIT support for stack arguments Yonghong Song
2026-05-15 6:02 ` sashiko-bot
2026-05-13 4:51 ` [PATCH bpf-next v4 18/25] selftests/bpf: Add tests for BPF function " Yonghong Song
2026-05-15 6:16 ` sashiko-bot
2026-05-13 4:51 ` [PATCH bpf-next v4 19/25] selftests/bpf: Add tests for stack argument validation Yonghong Song
2026-05-13 4:51 ` [PATCH bpf-next v4 20/25] selftests/bpf: Add BTF fixup for __naked subprog parameter names Yonghong Song
2026-05-13 4:51 ` [PATCH bpf-next v4 21/25] selftests/bpf: Add verifier tests for stack argument validation Yonghong Song
2026-05-13 4:51 ` Yonghong Song [this message]
2026-05-13 4:51 ` [PATCH bpf-next v4 23/25] bpf, arm64: Map BPF_REG_0 to x8 instead of x7 Yonghong Song
2026-05-13 4:51 ` [PATCH bpf-next v4 24/25] bpf, arm64: Add JIT support for stack arguments Yonghong Song
2026-05-13 4:52 ` [PATCH bpf-next v4 25/25] selftests/bpf: Enable stack argument tests for arm64 Yonghong Song
2026-05-13 16:33 ` [PATCH bpf-next v4 00/25] bpf: Support stack arguments for BPF functions and kfuncs Alexei Starovoitov
2026-05-13 17:41 ` Yonghong Song
2026-05-13 17:51 ` Alexei Starovoitov
2026-05-13 18:11 ` Yonghong Song
2026-05-13 16:40 ` patchwork-bot+netdevbpf
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20260513045148.2400087-1-yonghong.song@linux.dev \
--to=yonghong.song@linux.dev \
--cc=andrii@kernel.org \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=jose.marchesi@oracle.com \
--cc=kernel-team@fb.com \
--cc=martin.lau@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.