From 576482b55c19e7ec00e162a0fde4c4f1a95128c7 Mon Sep 17 00:00:00 2001 From: Yonghong Song Date: Sun, 17 May 2026 08:07:07 -0700 Subject: [PATCH] selftests/bpf: Add exception tests with stack arguments Add tests to verify that bpf_throw() correctly unwinds the stack when the program uses outgoing stack arguments (functions with >5 args). Without the preceding x86 fix, these tests crash the kernel on x86 due to corrupted callee-saved register restore. There is no change for arm64 to support exception with stack arguments. Acked-by: Kumar Kartikeya Dwivedi Signed-off-by: Yonghong Song Link: https://lore.kernel.org/r/20260517150707.289273-1-yonghong.song@linux.dev Signed-off-by: Alexei Starovoitov --- .../selftests/bpf/prog_tests/exceptions.c | 7 ++ .../testing/selftests/bpf/progs/exceptions.c | 114 ++++++++++++++++++ 2 files changed, 121 insertions(+) diff --git a/tools/testing/selftests/bpf/prog_tests/exceptions.c b/tools/testing/selftests/bpf/prog_tests/exceptions.c index e8cbaf2a3e82e..3588d6f97fd4e 100644 --- a/tools/testing/selftests/bpf/prog_tests/exceptions.c +++ b/tools/testing/selftests/bpf/prog_tests/exceptions.c @@ -85,6 +85,13 @@ static void test_exceptions_success(void) RUN_SUCCESS(exception_bad_assert_range_with, 10); RUN_SUCCESS(exception_throw_from_void_global, 11); + if (skel->rodata->has_stack_arg) { + RUN_SUCCESS(exception_throw_stack_arg, 56); + RUN_SUCCESS(exception_throw_after_stack_arg, 56); + RUN_SUCCESS(exception_throw_subprog_stack_arg, 56); + RUN_SUCCESS(exception_throw_subprog_after_stack_arg, 56); + } + #define RUN_EXT(load_ret, attach_err, expr, msg, after_link) \ { \ LIBBPF_OPTS(bpf_object_open_opts, o, .kernel_log_buf = log_buf, \ diff --git a/tools/testing/selftests/bpf/progs/exceptions.c b/tools/testing/selftests/bpf/progs/exceptions.c index 4206f59d7b864..c8d716fbd4191 100644 --- a/tools/testing/selftests/bpf/progs/exceptions.c +++ b/tools/testing/selftests/bpf/progs/exceptions.c @@ -379,4 +379,118 @@ int exception_bad_assert_range_with(struct __sk_buff *ctx) return 1; } +#if (defined(__TARGET_ARCH_x86) || defined(__TARGET_ARCH_arm64)) \ + && defined(__BPF_FEATURE_STACK_ARGUMENT) + +const volatile bool has_stack_arg = true; + +long arg1 = 1, arg2 = 2, arg3 = 3, arg4 = 4, arg5 = 5; +long arg6 = 6, arg7 = 7, arg8 = 8, arg9 = 9, arg10 = 10; + +__noinline static long throwing_many_args(long a, long b, long c, long d, + long e, long f, long g, long h, + long i, long j) +{ + bpf_throw(a + b + c + d + e + f + g + h + i + j); + return 0; +} + +__noinline int exception_cb_sa(u64 cookie) +{ + return cookie + 1; +} + +SEC("tc") +__exception_cb(exception_cb_sa) +int exception_throw_stack_arg(struct __sk_buff *ctx) +{ + throwing_many_args(arg1, arg2, arg3, arg4, arg5, + arg6, arg7, arg8, arg9, arg10); + return 0; +} + +__noinline static long no_throw_many_args(long a, long b, long c, long d, + long e, long f, long g, long h, + long i, long j) +{ + return a + b + c + d + e + f + g + h + i + j; +} + +SEC("tc") +__exception_cb(exception_cb_sa) +int exception_throw_after_stack_arg(struct __sk_buff *ctx) +{ + long ret; + + ret = no_throw_many_args(arg1, arg2, arg3, arg4, arg5, + arg6, arg7, arg8, arg9, arg10); + if (ret > 0) + bpf_throw(ret); + return 0; +} + +__noinline static long subprog_throw_sa(long val) +{ + throwing_many_args(val, val + 1, val + 2, val + 3, val + 4, + val + 5, val + 6, val + 7, val + 8, val + 9); + return 0; +} + +SEC("tc") +__exception_cb(exception_cb_sa) +int exception_throw_subprog_stack_arg(struct __sk_buff *ctx) +{ + subprog_throw_sa(arg1); + return 0; +} + +__noinline static long subprog_throw_after_sa(long val) +{ + long ret; + + ret = no_throw_many_args(val, val + 1, val + 2, val + 3, val + 4, + val + 5, val + 6, val + 7, val + 8, val + 9); + if (ret > 0) + bpf_throw(ret); + return 0; +} + +SEC("tc") +__exception_cb(exception_cb_sa) +int exception_throw_subprog_after_stack_arg(struct __sk_buff *ctx) +{ + subprog_throw_after_sa(arg1); + return 0; +} + +#else + +const volatile bool has_stack_arg = false; + +SEC("tc") +int exception_throw_stack_arg(struct __sk_buff *ctx) +{ + return 0; +} + +SEC("tc") +int exception_throw_after_stack_arg(struct __sk_buff *ctx) +{ + return 0; +} + +SEC("tc") +int exception_throw_subprog_stack_arg(struct __sk_buff *ctx) +{ + return 0; +} + +SEC("tc") +int exception_throw_subprog_after_stack_arg(struct __sk_buff *ctx) +{ + return 0; +} + +#endif + char _license[] SEC("license") = "GPL"; -- 2.47.3