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| author | Yonghong Song <yonghong.song@linux.dev> | 2026-05-12 21:51:48 -0700 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2026-05-13 09:27:32 -0700 |
| commit | 6e277efbb19dd1a536cbffd9ea5c049a427dc7cb (patch) | |
| tree | f648ac03df19d457d855b115a2ddd5a627fdb73c /tools | |
| parent | 00c3ac4292a6bc3039008cdb45bd423087acb98e (diff) | |
| download | linux-next-history-6e277efbb19dd1a536cbffd9ea5c049a427dc7cb.tar.gz | |
selftests/bpf: Add precision backtracking test for stack arguments
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>
Link: https://lore.kernel.org/r/20260513045148.2400087-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'tools')
3 files changed, 167 insertions, 0 deletions
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 0000000000000..1ab041d66de36 --- /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 0000000000000..296fddfe6804b --- /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 0000000000000..2a0a344c83caa --- /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"; |