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selftests/bpf: Test gen_pro/epilogue that generate kfuncs

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Test gen_prologue and gen_epilogue that generate kfuncs that have not
been seen in the main program.

The main bpf program and return value checks are identical to
pro_epilogue.c introduced in commit 47e69431b5 ("selftests/bpf: Test
gen_prologue and gen_epilogue"). However, now when bpf_testmod_st_ops
detects a program name with prefix "test_kfunc_", it generates slightly
different prologue and epilogue: They still add 1000 to args->a in
prologue, add 10000 to args->a and set r0 to 2 * args->a in epilogue,
but involve kfuncs.

At high level, the alternative version of prologue and epilogue look
like this:

  cgrp = bpf_cgroup_from_id(0);
  if (cgrp)
          bpf_cgroup_release(cgrp);
  else
          /* Perform what original bpf_testmod_st_ops prologue or
           * epilogue does
           */

Since 0 is never a valid cgroup id, the original prologue or epilogue
logic will be performed. As a result, the __retval check should expect
the exact same return value.

Signed-off-by: Amery Hung <ameryhung@gmail.com>
Acked-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/r/20250225233545.285481-2-ameryhung@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Amery Hung 2025-02-25 15:35:45 -08:00 committed by Alexei Starovoitov
parent d519594ee2
commit 4e4136c644
5 changed files with 193 additions and 0 deletions
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10
include/linux/filter.h
View File

@ -469,6 +469,16 @@ static inline bool insn_is_cast_user(const struct bpf_insn *insn)
.off = 0, \
.imm = BPF_CALL_IMM(FUNC) })
/* Kfunc call */
#define BPF_CALL_KFUNC(OFF, IMM) \
((struct bpf_insn) { \
.code = BPF_JMP | BPF_CALL, \
.dst_reg = 0, \
.src_reg = BPF_PSEUDO_KFUNC_CALL, \
.off = OFF, \
.imm = IMM })
/* Raw code statement block */
#define BPF_RAW_INSN(CODE, DST, SRC, OFF, IMM) \

1
kernel/bpf/btf.c
View File

@ -606,6 +606,7 @@ s32 bpf_find_btf_id(const char *name, u32 kind, struct btf **btf_p)
spin_unlock_bh(&btf_idr_lock);
return ret;
}
EXPORT_SYMBOL_GPL(bpf_find_btf_id);
const struct btf_type *btf_type_skip_modifiers(const struct btf *btf,
u32 id, u32 *res_id)

2
tools/testing/selftests/bpf/prog_tests/pro_epilogue.c
View File

@ -6,6 +6,7 @@
#include "epilogue_tailcall.skel.h"
#include "pro_epilogue_goto_start.skel.h"
#include "epilogue_exit.skel.h"
#include "pro_epilogue_with_kfunc.skel.h"
struct st_ops_args {
__u64 a;
@ -55,6 +56,7 @@ void test_pro_epilogue(void)
RUN_TESTS(pro_epilogue);
RUN_TESTS(pro_epilogue_goto_start);
RUN_TESTS(epilogue_exit);
RUN_TESTS(pro_epilogue_with_kfunc);
if (test__start_subtest("tailcall"))
test_tailcall();
}

88
tools/testing/selftests/bpf/progs/pro_epilogue_with_kfunc.c Normal file
View File

@ -0,0 +1,88 @@
// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */
#include <vmlinux.h>
#include <bpf/bpf_tracing.h>
#include "bpf_misc.h"
#include "../test_kmods/bpf_testmod.h"
#include "../test_kmods/bpf_testmod_kfunc.h"
char _license[] SEC("license") = "GPL";
void __kfunc_btf_root(void)
{
bpf_kfunc_st_ops_inc10(NULL);
}
static __noinline __used int subprog(struct st_ops_args *args)
{
args->a += 1;
return args->a;
}
__success
/* prologue */
__xlated("0: r8 = r1")
__xlated("1: r1 = 0")
__xlated("2: call kernel-function")
__xlated("3: if r0 != 0x0 goto pc+5")
__xlated("4: r6 = *(u64 *)(r8 +0)")
__xlated("5: r7 = *(u64 *)(r6 +0)")
__xlated("6: r7 += 1000")
__xlated("7: *(u64 *)(r6 +0) = r7")
__xlated("8: goto pc+2")
__xlated("9: r1 = r0")
__xlated("10: call kernel-function")
__xlated("11: r1 = r8")
/* save __u64 *ctx to stack */
__xlated("12: *(u64 *)(r10 -8) = r1")
/* main prog */
__xlated("13: r1 = *(u64 *)(r1 +0)")
__xlated("14: r6 = r1")
__xlated("15: call kernel-function")
__xlated("16: r1 = r6")
__xlated("17: call pc+")
/* epilogue */
__xlated("18: r1 = 0")
__xlated("19: r6 = 0")
__xlated("20: call kernel-function")
__xlated("21: if r0 != 0x0 goto pc+6")
__xlated("22: r1 = *(u64 *)(r10 -8)")
__xlated("23: r1 = *(u64 *)(r1 +0)")
__xlated("24: r6 = *(u64 *)(r1 +0)")
__xlated("25: r6 += 10000")
__xlated("26: *(u64 *)(r1 +0) = r6")
__xlated("27: goto pc+2")
__xlated("28: r1 = r0")
__xlated("29: call kernel-function")
__xlated("30: r0 = r6")
__xlated("31: r0 *= 2")
__xlated("32: exit")
SEC("struct_ops/test_pro_epilogue")
__naked int test_kfunc_pro_epilogue(void)
{
asm volatile (
"r1 = *(u64 *)(r1 +0);"
"r6 = r1;"
"call %[bpf_kfunc_st_ops_inc10];"
"r1 = r6;"
"call subprog;"
"exit;"
:
: __imm(bpf_kfunc_st_ops_inc10)
: __clobber_all);
}
SEC("syscall")
__retval(22022) /* (PROLOGUE_A [1000] + KFUNC_INC10 + SUBPROG_A [1] + EPILOGUE_A [10000]) * 2 */
int syscall_pro_epilogue(void *ctx)
{
struct st_ops_args args = {};
return bpf_kfunc_st_ops_test_pro_epilogue(&args);
}
SEC(".struct_ops.link")
struct bpf_testmod_st_ops pro_epilogue_with_kfunc = {
.test_pro_epilogue = (void *)test_kfunc_pro_epilogue,
};

92
tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
View File

@ -1309,6 +1309,85 @@ static int bpf_test_mod_st_ops__test_pro_epilogue(struct st_ops_args *args)
return 0;
}
static int bpf_cgroup_from_id_id;
static int bpf_cgroup_release_id;
static int st_ops_gen_prologue_with_kfunc(struct bpf_insn *insn_buf, bool direct_write,
const struct bpf_prog *prog)
{
struct bpf_insn *insn = insn_buf;
/* r8 = r1; // r8 will be "u64 *ctx".
* r1 = 0;
* r0 = bpf_cgroup_from_id(r1);
* if r0 != 0 goto pc+5;
* r6 = r8[0]; // r6 will be "struct st_ops *args".
* r7 = r6->a;
* r7 += 1000;
* r6->a = r7;
* goto pc+2;
* r1 = r0;
* bpf_cgroup_release(r1);
* r1 = r8;
*/
*insn++ = BPF_MOV64_REG(BPF_REG_8, BPF_REG_1);
*insn++ = BPF_MOV64_IMM(BPF_REG_1, 0);
*insn++ = BPF_CALL_KFUNC(0, bpf_cgroup_from_id_id);
*insn++ = BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 5);
*insn++ = BPF_LDX_MEM(BPF_DW, BPF_REG_6, BPF_REG_8, 0);
*insn++ = BPF_LDX_MEM(BPF_DW, BPF_REG_7, BPF_REG_6, offsetof(struct st_ops_args, a));
*insn++ = BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, 1000);
*insn++ = BPF_STX_MEM(BPF_DW, BPF_REG_6, BPF_REG_7, offsetof(struct st_ops_args, a));
*insn++ = BPF_JMP_IMM(BPF_JA, 0, 0, 2);
*insn++ = BPF_MOV64_REG(BPF_REG_1, BPF_REG_0);
*insn++ = BPF_CALL_KFUNC(0, bpf_cgroup_release_id),
*insn++ = BPF_MOV64_REG(BPF_REG_1, BPF_REG_8);
*insn++ = prog->insnsi[0];
return insn - insn_buf;
}
static int st_ops_gen_epilogue_with_kfunc(struct bpf_insn *insn_buf, const struct bpf_prog *prog,
s16 ctx_stack_off)
{
struct bpf_insn *insn = insn_buf;
/* r1 = 0;
* r6 = 0;
* r0 = bpf_cgroup_from_id(r1);
* if r0 != 0 goto pc+6;
* r1 = stack[ctx_stack_off]; // r1 will be "u64 *ctx"
* r1 = r1[0]; // r1 will be "struct st_ops *args"
* r6 = r1->a;
* r6 += 10000;
* r1->a = r6;
* goto pc+2
* r1 = r0;
* bpf_cgroup_release(r1);
* r0 = r6;
* r0 *= 2;
* BPF_EXIT;
*/
*insn++ = BPF_MOV64_IMM(BPF_REG_1, 0);
*insn++ = BPF_MOV64_IMM(BPF_REG_6, 0);
*insn++ = BPF_CALL_KFUNC(0, bpf_cgroup_from_id_id);
*insn++ = BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 6);
*insn++ = BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_FP, ctx_stack_off);
*insn++ = BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_1, 0);
*insn++ = BPF_LDX_MEM(BPF_DW, BPF_REG_6, BPF_REG_1, offsetof(struct st_ops_args, a));
*insn++ = BPF_ALU64_IMM(BPF_ADD, BPF_REG_6, 10000);
*insn++ = BPF_STX_MEM(BPF_DW, BPF_REG_1, BPF_REG_6, offsetof(struct st_ops_args, a));
*insn++ = BPF_JMP_IMM(BPF_JA, 0, 0, 2);
*insn++ = BPF_MOV64_REG(BPF_REG_1, BPF_REG_0);
*insn++ = BPF_CALL_KFUNC(0, bpf_cgroup_release_id),
*insn++ = BPF_MOV64_REG(BPF_REG_0, BPF_REG_6);
*insn++ = BPF_ALU64_IMM(BPF_MUL, BPF_REG_0, 2);
*insn++ = BPF_EXIT_INSN();
return insn - insn_buf;
}
#define KFUNC_PRO_EPI_PREFIX "test_kfunc_"
static int st_ops_gen_prologue(struct bpf_insn *insn_buf, bool direct_write,
const struct bpf_prog *prog)
{
@ -1318,6 +1397,9 @@ static int st_ops_gen_prologue(struct bpf_insn *insn_buf, bool direct_write,
strcmp(prog->aux->attach_func_name, "test_pro_epilogue"))
return 0;
if (!strncmp(prog->aux->name, KFUNC_PRO_EPI_PREFIX, strlen(KFUNC_PRO_EPI_PREFIX)))
return st_ops_gen_prologue_with_kfunc(insn_buf, direct_write, prog);
/* r6 = r1[0]; // r6 will be "struct st_ops *args". r1 is "u64 *ctx".
* r7 = r6->a;
* r7 += 1000;
@ -1341,6 +1423,9 @@ static int st_ops_gen_epilogue(struct bpf_insn *insn_buf, const struct bpf_prog
strcmp(prog->aux->attach_func_name, "test_pro_epilogue"))
return 0;
if (!strncmp(prog->aux->name, KFUNC_PRO_EPI_PREFIX, strlen(KFUNC_PRO_EPI_PREFIX)))
return st_ops_gen_epilogue_with_kfunc(insn_buf, prog, ctx_stack_off);
/* r1 = stack[ctx_stack_off]; // r1 will be "u64 *ctx"
* r1 = r1[0]; // r1 will be "struct st_ops *args"
* r6 = r1->a;
@ -1411,6 +1496,13 @@ static void st_ops_unreg(void *kdata, struct bpf_link *link)
static int st_ops_init(struct btf *btf)
{
struct btf *kfunc_btf;
bpf_cgroup_from_id_id = bpf_find_btf_id("bpf_cgroup_from_id", BTF_KIND_FUNC, &kfunc_btf);
bpf_cgroup_release_id = bpf_find_btf_id("bpf_cgroup_release", BTF_KIND_FUNC, &kfunc_btf);
if (bpf_cgroup_from_id_id < 0 || bpf_cgroup_release_id < 0)
return -EINVAL;
return 0;
}