From: Tejun Heo Pin the exact rebase sequences the JITs emit for __arena and __arena_nullable kfunc arguments with __jited assertions on x86-64: the unconditional truncate-and-add, the nullable test-and-skip variant, and all five argument registers in one call, which also covers the REX-prefixed encoding of r8 on x86. The capture kfuncs take the argument without dereferencing, so only the emitted code is under test. The tests skip without LLVM disassembler support. Signed-off-by: Tejun Heo Signed-off-by: Kumar Kartikeya Dwivedi --- .../bpf/prog_tests/arena_kfunc_jit.c | 13 +++ .../selftests/bpf/progs/arena_kfunc_jit.c | 96 +++++++++++++++++++ 2 files changed, 109 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/arena_kfunc_jit.c create mode 100644 tools/testing/selftests/bpf/progs/arena_kfunc_jit.c diff --git a/tools/testing/selftests/bpf/prog_tests/arena_kfunc_jit.c b/tools/testing/selftests/bpf/prog_tests/arena_kfunc_jit.c new file mode 100644 index 000000000000..2359cde24c45 --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/arena_kfunc_jit.c @@ -0,0 +1,13 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2026 Meta Platforms, Inc. and affiliates. */ +#include +#include "arena_kfunc_jit.skel.h" + +/* + * Runs with full capabilities: resolving module kfunc ksyms requires + * CAP_SYS_ADMIN, which rules out the capability-restricted runner. + */ +void test_arena_kfunc_jit(void) +{ + RUN_TESTS(arena_kfunc_jit); +} diff --git a/tools/testing/selftests/bpf/progs/arena_kfunc_jit.c b/tools/testing/selftests/bpf/progs/arena_kfunc_jit.c new file mode 100644 index 000000000000..84747611725f --- /dev/null +++ b/tools/testing/selftests/bpf/progs/arena_kfunc_jit.c @@ -0,0 +1,96 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2026 Meta Platforms, Inc. and affiliates. */ + +/* + * Verify the JIT-emitted rebase sequences for __arena and __arena_nullable + * kfunc arguments. The capture kfuncs take the argument without + * dereferencing it, so these tests pin only the emitted code. + */ +#define BPF_NO_KFUNC_PROTOTYPES +#include +#include +#include "bpf_misc.h" +#include "bpf_experimental.h" +#include +#include "../test_kmods/bpf_testmod_kfunc.h" + +struct { + __uint(type, BPF_MAP_TYPE_ARENA); + __uint(map_flags, BPF_F_MMAPABLE); + __uint(max_entries, 1); +} arena SEC(".maps"); + +/* volatile to force the scalar reloads below */ +volatile u64 stash; + +#if defined(__BPF_FEATURE_ADDR_SPACE_CAST) + +SEC("syscall") +__arch_x86_64 +__jited("...") +__jited(" movl %edi, %edi") +__jited(" addq %r12, %rdi") +__jited("...") +__jited(" callq {{.*}}") +__success +int arena_arg_jit_rebase(void *ctx) +{ + stash = (u64)bpf_arena_alloc_pages(&arena, NULL, 1, NUMA_NO_NODE, 0); + bpf_kfunc_arena_cap_test((u64 *)stash); + return 0; +} + +SEC("syscall") +__arch_x86_64 +__jited("...") +__jited(" movl %edi, %edi") +__jited(" testl %edi, %edi") +__jited(" je {{.*}}") +__jited(" addq %r12, %rdi") +__success +int arena_arg_jit_nullable(void *ctx) +{ + stash = (u64)bpf_arena_alloc_pages(&arena, NULL, 1, NUMA_NO_NODE, 0); + bpf_kfunc_arena_cap_nullable_test((u64 *)stash); + return 0; +} + +SEC("syscall") +__arch_x86_64 +__jited("...") +__jited(" movl %edi, %edi") +__jited(" addq %r12, %rdi") +__jited(" movl %esi, %esi") +__jited(" addq %r12, %rsi") +__jited(" movl %edx, %edx") +__jited(" addq %r12, %rdx") +__jited(" movl %ecx, %ecx") +__jited(" addq %r12, %rcx") +__jited(" movl %r8d, %r8d") +__jited(" testl %r8d, %r8d") +__jited(" je {{.*}}") +__jited(" addq %r12, %r8") +__success +int arena_arg_jit_args5(void *ctx) +{ + u64 __arena *val; + + val = bpf_arena_alloc_pages(&arena, NULL, 1, NUMA_NO_NODE, 0); + if (!val) + return 1; + + val[0] = 1; + val[1] = 2; + val[2] = 4; + val[3] = 8; + val[4] = 16; + + bpf_kfunc_arena_args5_test((u64 *)&val[0], (u64 *)&val[1], + (u64 *)&val[2], (u64 *)&val[3], + (u64 *)&val[4]); + return 0; +} + +#endif /* __BPF_FEATURE_ADDR_SPACE_CAST */ + +char _license[] SEC("license") = "GPL"; -- 2.53.0