diff options
| -rw-r--r-- | arch/x86/net/bpf_jit_comp.c | 32 | ||||
| -rw-r--r-- | include/linux/bpf.h | 5 | ||||
| -rw-r--r-- | kernel/bpf/trampoline.c | 4 | ||||
| -rw-r--r-- | kernel/bpf/verifier.c | 3 | ||||
| -rw-r--r-- | tools/testing/selftests/bpf/prog_tests/tailcalls.c | 237 | ||||
| -rw-r--r-- | tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_fentry.c | 18 | ||||
| -rw-r--r-- | tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_fexit.c | 18 |
7 files changed, 305 insertions, 12 deletions
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index a5930042139d..2846c21d75bf 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -303,8 +303,12 @@ static void emit_prologue(u8 **pprog, u32 stack_depth, bool ebpf_from_cbpf, prog += X86_PATCH_SIZE; if (!ebpf_from_cbpf) { if (tail_call_reachable && !is_subprog) + /* When it's the entry of the whole tailcall context, + * zeroing rax means initialising tail_call_cnt. + */ EMIT2(0x31, 0xC0); /* xor eax, eax */ else + /* Keep the same instruction layout. */ EMIT2(0x66, 0x90); /* nop2 */ } EMIT1(0x55); /* push rbp */ @@ -1018,6 +1022,10 @@ static void emit_shiftx(u8 **pprog, u32 dst_reg, u8 src_reg, bool is64, u8 op) #define INSN_SZ_DIFF (((addrs[i] - addrs[i - 1]) - (prog - temp))) +/* mov rax, qword ptr [rbp - rounded_stack_depth - 8] */ +#define RESTORE_TAIL_CALL_CNT(stack) \ + EMIT3_off32(0x48, 0x8B, 0x85, -round_up(stack, 8) - 8) + static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, u8 *rw_image, int oldproglen, struct jit_context *ctx, bool jmp_padding) { @@ -1623,9 +1631,7 @@ st: if (is_imm8(insn->off)) func = (u8 *) __bpf_call_base + imm32; if (tail_call_reachable) { - /* mov rax, qword ptr [rbp - rounded_stack_depth - 8] */ - EMIT3_off32(0x48, 0x8B, 0x85, - -round_up(bpf_prog->aux->stack_depth, 8) - 8); + RESTORE_TAIL_CALL_CNT(bpf_prog->aux->stack_depth); if (!imm32) return -EINVAL; offs = 7 + x86_call_depth_emit_accounting(&prog, func); @@ -2400,6 +2406,7 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i * [ ... ] * [ stack_arg2 ] * RBP - arg_stack_off [ stack_arg1 ] + * RSP [ tail_call_cnt ] BPF_TRAMP_F_TAIL_CALL_CTX */ /* room for return value of orig_call or fentry prog */ @@ -2464,6 +2471,8 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i else /* sub rsp, stack_size */ EMIT4(0x48, 0x83, 0xEC, stack_size); + if (flags & BPF_TRAMP_F_TAIL_CALL_CTX) + EMIT1(0x50); /* push rax */ /* mov QWORD PTR [rbp - rbx_off], rbx */ emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_6, -rbx_off); @@ -2516,9 +2525,15 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i restore_regs(m, &prog, regs_off); save_args(m, &prog, arg_stack_off, true); + if (flags & BPF_TRAMP_F_TAIL_CALL_CTX) + /* Before calling the original function, restore the + * tail_call_cnt from stack to rax. + */ + RESTORE_TAIL_CALL_CNT(stack_size); + if (flags & BPF_TRAMP_F_ORIG_STACK) { - emit_ldx(&prog, BPF_DW, BPF_REG_0, BPF_REG_FP, 8); - EMIT2(0xff, 0xd0); /* call *rax */ + emit_ldx(&prog, BPF_DW, BPF_REG_6, BPF_REG_FP, 8); + EMIT2(0xff, 0xd3); /* call *rbx */ } else { /* call original function */ if (emit_rsb_call(&prog, orig_call, prog)) { @@ -2569,7 +2584,12 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i ret = -EINVAL; goto cleanup; } - } + } else if (flags & BPF_TRAMP_F_TAIL_CALL_CTX) + /* Before running the original function, restore the + * tail_call_cnt from stack to rax. + */ + RESTORE_TAIL_CALL_CNT(stack_size); + /* restore return value of orig_call or fentry prog back into RAX */ if (save_ret) emit_ldx(&prog, BPF_DW, BPF_REG_0, BPF_REG_FP, -8); diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 87eeb3a46a1d..b9e573159432 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1035,6 +1035,11 @@ struct btf_func_model { */ #define BPF_TRAMP_F_SHARE_IPMODIFY BIT(6) +/* Indicate that current trampoline is in a tail call context. Then, it has to + * cache and restore tail_call_cnt to avoid infinite tail call loop. + */ +#define BPF_TRAMP_F_TAIL_CALL_CTX BIT(7) + /* Each call __bpf_prog_enter + call bpf_func + call __bpf_prog_exit is ~50 * bytes on x86. */ diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c index 53ff50cac61e..e97aeda3a86b 100644 --- a/kernel/bpf/trampoline.c +++ b/kernel/bpf/trampoline.c @@ -415,8 +415,8 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mut goto out; } - /* clear all bits except SHARE_IPMODIFY */ - tr->flags &= BPF_TRAMP_F_SHARE_IPMODIFY; + /* clear all bits except SHARE_IPMODIFY and TAIL_CALL_CTX */ + tr->flags &= (BPF_TRAMP_F_SHARE_IPMODIFY | BPF_TRAMP_F_TAIL_CALL_CTX); if (tlinks[BPF_TRAMP_FEXIT].nr_links || tlinks[BPF_TRAMP_MODIFY_RETURN].nr_links) { diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index dbba2b806017..18e673c0ac15 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -19774,6 +19774,9 @@ static int check_attach_btf_id(struct bpf_verifier_env *env) if (!tr) return -ENOMEM; + if (tgt_prog && tgt_prog->aux->tail_call_reachable) + tr->flags = BPF_TRAMP_F_TAIL_CALL_CTX; + prog->aux->dst_trampoline = tr; return 0; } diff --git a/tools/testing/selftests/bpf/prog_tests/tailcalls.c b/tools/testing/selftests/bpf/prog_tests/tailcalls.c index 09c189761926..fc6b2954e8f5 100644 --- a/tools/testing/selftests/bpf/prog_tests/tailcalls.c +++ b/tools/testing/selftests/bpf/prog_tests/tailcalls.c @@ -218,12 +218,14 @@ out: bpf_object__close(obj); } -static void test_tailcall_count(const char *which) +static void test_tailcall_count(const char *which, bool test_fentry, + bool test_fexit) { + struct bpf_object *obj = NULL, *fentry_obj = NULL, *fexit_obj = NULL; + struct bpf_link *fentry_link = NULL, *fexit_link = NULL; int err, map_fd, prog_fd, main_fd, data_fd, i, val; struct bpf_map *prog_array, *data_map; struct bpf_program *prog; - struct bpf_object *obj; char buff[128] = {}; LIBBPF_OPTS(bpf_test_run_opts, topts, .data_in = buff, @@ -265,6 +267,54 @@ static void test_tailcall_count(const char *which) if (CHECK_FAIL(err)) goto out; + if (test_fentry) { + fentry_obj = bpf_object__open_file("tailcall_bpf2bpf_fentry.bpf.o", + NULL); + if (!ASSERT_OK_PTR(fentry_obj, "open fentry_obj file")) + goto out; + + prog = bpf_object__find_program_by_name(fentry_obj, "fentry"); + if (!ASSERT_OK_PTR(prog, "find fentry prog")) + goto out; + + err = bpf_program__set_attach_target(prog, prog_fd, + "subprog_tail"); + if (!ASSERT_OK(err, "set_attach_target subprog_tail")) + goto out; + + err = bpf_object__load(fentry_obj); + if (!ASSERT_OK(err, "load fentry_obj")) + goto out; + + fentry_link = bpf_program__attach_trace(prog); + if (!ASSERT_OK_PTR(fentry_link, "attach_trace")) + goto out; + } + + if (test_fexit) { + fexit_obj = bpf_object__open_file("tailcall_bpf2bpf_fexit.bpf.o", + NULL); + if (!ASSERT_OK_PTR(fexit_obj, "open fexit_obj file")) + goto out; + + prog = bpf_object__find_program_by_name(fexit_obj, "fexit"); + if (!ASSERT_OK_PTR(prog, "find fexit prog")) + goto out; + + err = bpf_program__set_attach_target(prog, prog_fd, + "subprog_tail"); + if (!ASSERT_OK(err, "set_attach_target subprog_tail")) + goto out; + + err = bpf_object__load(fexit_obj); + if (!ASSERT_OK(err, "load fexit_obj")) + goto out; + + fexit_link = bpf_program__attach_trace(prog); + if (!ASSERT_OK_PTR(fexit_link, "attach_trace")) + goto out; + } + err = bpf_prog_test_run_opts(main_fd, &topts); ASSERT_OK(err, "tailcall"); ASSERT_EQ(topts.retval, 1, "tailcall retval"); @@ -282,6 +332,40 @@ static void test_tailcall_count(const char *which) ASSERT_OK(err, "tailcall count"); ASSERT_EQ(val, 33, "tailcall count"); + if (test_fentry) { + data_map = bpf_object__find_map_by_name(fentry_obj, ".bss"); + if (!ASSERT_FALSE(!data_map || !bpf_map__is_internal(data_map), + "find tailcall_bpf2bpf_fentry.bss map")) + goto out; + + data_fd = bpf_map__fd(data_map); + if (!ASSERT_FALSE(data_fd < 0, + "find tailcall_bpf2bpf_fentry.bss map fd")) + goto out; + + i = 0; + err = bpf_map_lookup_elem(data_fd, &i, &val); + ASSERT_OK(err, "fentry count"); + ASSERT_EQ(val, 33, "fentry count"); + } + + if (test_fexit) { + data_map = bpf_object__find_map_by_name(fexit_obj, ".bss"); + if (!ASSERT_FALSE(!data_map || !bpf_map__is_internal(data_map), + "find tailcall_bpf2bpf_fexit.bss map")) + goto out; + + data_fd = bpf_map__fd(data_map); + if (!ASSERT_FALSE(data_fd < 0, + "find tailcall_bpf2bpf_fexit.bss map fd")) + goto out; + + i = 0; + err = bpf_map_lookup_elem(data_fd, &i, &val); + ASSERT_OK(err, "fexit count"); + ASSERT_EQ(val, 33, "fexit count"); + } + i = 0; err = bpf_map_delete_elem(map_fd, &i); if (CHECK_FAIL(err)) @@ -291,6 +375,10 @@ static void test_tailcall_count(const char *which) ASSERT_OK(err, "tailcall"); ASSERT_OK(topts.retval, "tailcall retval"); out: + bpf_link__destroy(fentry_link); + bpf_link__destroy(fexit_link); + bpf_object__close(fentry_obj); + bpf_object__close(fexit_obj); bpf_object__close(obj); } @@ -299,7 +387,7 @@ out: */ static void test_tailcall_3(void) { - test_tailcall_count("tailcall3.bpf.o"); + test_tailcall_count("tailcall3.bpf.o", false, false); } /* test_tailcall_6 checks that the count value of the tail call limit @@ -307,7 +395,7 @@ static void test_tailcall_3(void) */ static void test_tailcall_6(void) { - test_tailcall_count("tailcall6.bpf.o"); + test_tailcall_count("tailcall6.bpf.o", false, false); } /* test_tailcall_4 checks that the kernel properly selects indirect jump @@ -884,6 +972,139 @@ out: tailcall_bpf2bpf6__destroy(obj); } +/* test_tailcall_bpf2bpf_fentry checks that the count value of the tail call + * limit enforcement matches with expectations when tailcall is preceded with + * bpf2bpf call, and the bpf2bpf call is traced by fentry. + */ +static void test_tailcall_bpf2bpf_fentry(void) +{ + test_tailcall_count("tailcall_bpf2bpf2.bpf.o", true, false); +} + +/* test_tailcall_bpf2bpf_fexit checks that the count value of the tail call + * limit enforcement matches with expectations when tailcall is preceded with + * bpf2bpf call, and the bpf2bpf call is traced by fexit. + */ +static void test_tailcall_bpf2bpf_fexit(void) +{ + test_tailcall_count("tailcall_bpf2bpf2.bpf.o", false, true); +} + +/* test_tailcall_bpf2bpf_fentry_fexit checks that the count value of the tail + * call limit enforcement matches with expectations when tailcall is preceded + * with bpf2bpf call, and the bpf2bpf call is traced by both fentry and fexit. + */ +static void test_tailcall_bpf2bpf_fentry_fexit(void) +{ + test_tailcall_count("tailcall_bpf2bpf2.bpf.o", true, true); +} + +/* test_tailcall_bpf2bpf_fentry_entry checks that the count value of the tail + * call limit enforcement matches with expectations when tailcall is preceded + * with bpf2bpf call, and the bpf2bpf caller is traced by fentry. + */ +static void test_tailcall_bpf2bpf_fentry_entry(void) +{ + struct bpf_object *tgt_obj = NULL, *fentry_obj = NULL; + int err, map_fd, prog_fd, data_fd, i, val; + struct bpf_map *prog_array, *data_map; + struct bpf_link *fentry_link = NULL; + struct bpf_program *prog; + char buff[128] = {}; + + LIBBPF_OPTS(bpf_test_run_opts, topts, + .data_in = buff, + .data_size_in = sizeof(buff), + .repeat = 1, + ); + + err = bpf_prog_test_load("tailcall_bpf2bpf2.bpf.o", + BPF_PROG_TYPE_SCHED_CLS, + &tgt_obj, &prog_fd); + if (!ASSERT_OK(err, "load tgt_obj")) + return; + + prog_array = bpf_object__find_map_by_name(tgt_obj, "jmp_table"); + if (!ASSERT_OK_PTR(prog_array, "find jmp_table map")) + goto out; + + map_fd = bpf_map__fd(prog_array); + if (!ASSERT_FALSE(map_fd < 0, "find jmp_table map fd")) + goto out; + + prog = bpf_object__find_program_by_name(tgt_obj, "classifier_0"); + if (!ASSERT_OK_PTR(prog, "find classifier_0 prog")) + goto out; + + prog_fd = bpf_program__fd(prog); + if (!ASSERT_FALSE(prog_fd < 0, "find classifier_0 prog fd")) + goto out; + + i = 0; + err = bpf_map_update_elem(map_fd, &i, &prog_fd, BPF_ANY); + if (!ASSERT_OK(err, "update jmp_table")) + goto out; + + fentry_obj = bpf_object__open_file("tailcall_bpf2bpf_fentry.bpf.o", + NULL); + if (!ASSERT_OK_PTR(fentry_obj, "open fentry_obj file")) + goto out; + + prog = bpf_object__find_program_by_name(fentry_obj, "fentry"); + if (!ASSERT_OK_PTR(prog, "find fentry prog")) + goto out; + + err = bpf_program__set_attach_target(prog, prog_fd, "classifier_0"); + if (!ASSERT_OK(err, "set_attach_target classifier_0")) + goto out; + + err = bpf_object__load(fentry_obj); + if (!ASSERT_OK(err, "load fentry_obj")) + goto out; + + fentry_link = bpf_program__attach_trace(prog); + if (!ASSERT_OK_PTR(fentry_link, "attach_trace")) + goto out; + + err = bpf_prog_test_run_opts(prog_fd, &topts); + ASSERT_OK(err, "tailcall"); + ASSERT_EQ(topts.retval, 1, "tailcall retval"); + + data_map = bpf_object__find_map_by_name(tgt_obj, "tailcall.bss"); + if (!ASSERT_FALSE(!data_map || !bpf_map__is_internal(data_map), + "find tailcall.bss map")) + goto out; + + data_fd = bpf_map__fd(data_map); + if (!ASSERT_FALSE(data_fd < 0, "find tailcall.bss map fd")) + goto out; + + i = 0; + err = bpf_map_lookup_elem(data_fd, &i, &val); + ASSERT_OK(err, "tailcall count"); + ASSERT_EQ(val, 34, "tailcall count"); + + data_map = bpf_object__find_map_by_name(fentry_obj, ".bss"); + if (!ASSERT_FALSE(!data_map || !bpf_map__is_internal(data_map), + "find tailcall_bpf2bpf_fentry.bss map")) + goto out; + + data_fd = bpf_map__fd(data_map); + if (!ASSERT_FALSE(data_fd < 0, + "find tailcall_bpf2bpf_fentry.bss map fd")) + goto out; + + i = 0; + err = bpf_map_lookup_elem(data_fd, &i, &val); + ASSERT_OK(err, "fentry count"); + ASSERT_EQ(val, 1, "fentry count"); + +out: + bpf_link__destroy(fentry_link); + bpf_object__close(fentry_obj); + bpf_object__close(tgt_obj); +} + void test_tailcalls(void) { if (test__start_subtest("tailcall_1")) @@ -910,4 +1131,12 @@ void test_tailcalls(void) test_tailcall_bpf2bpf_4(true); if (test__start_subtest("tailcall_bpf2bpf_6")) test_tailcall_bpf2bpf_6(); + if (test__start_subtest("tailcall_bpf2bpf_fentry")) + test_tailcall_bpf2bpf_fentry(); + if (test__start_subtest("tailcall_bpf2bpf_fexit")) + test_tailcall_bpf2bpf_fexit(); + if (test__start_subtest("tailcall_bpf2bpf_fentry_fexit")) + test_tailcall_bpf2bpf_fentry_fexit(); + if (test__start_subtest("tailcall_bpf2bpf_fentry_entry")) + test_tailcall_bpf2bpf_fentry_entry(); } diff --git a/tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_fentry.c b/tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_fentry.c new file mode 100644 index 000000000000..8436c6729167 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_fentry.c @@ -0,0 +1,18 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright Leon Hwang */ + +#include "vmlinux.h" +#include <bpf/bpf_helpers.h> +#include <bpf/bpf_tracing.h> + +int count = 0; + +SEC("fentry/subprog_tail") +int BPF_PROG(fentry, struct sk_buff *skb) +{ + count++; + + return 0; +} + +char _license[] SEC("license") = "GPL"; diff --git a/tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_fexit.c b/tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_fexit.c new file mode 100644 index 000000000000..fe16412c6e6e --- /dev/null +++ b/tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_fexit.c @@ -0,0 +1,18 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright Leon Hwang */ + +#include "vmlinux.h" +#include <bpf/bpf_helpers.h> +#include <bpf/bpf_tracing.h> + +int count = 0; + +SEC("fexit/subprog_tail") +int BPF_PROG(fexit, struct sk_buff *skb) +{ + count++; + + return 0; +} + +char _license[] SEC("license") = "GPL"; |