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selftests/bpf: C based test for sysctl and strtoX

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Add C based test for a few bpf_sysctl_* helpers and bpf_strtoul.

Make sure that sysctl can be identified by name and that multiple
integers can be parsed from sysctl value with bpf_strtoul.

net/ipv4/tcp_mem is chosen as a testing sysctl, it contains 3 unsigned
longs, they all are parsed and compared (val[0] < val[1] < val[2]).

Example of output:
  # ./test_sysctl
  ...
  Test case: C prog: deny all writes .. [PASS]
  Test case: C prog: deny access by name .. [PASS]
  Test case: C prog: read tcp_mem .. [PASS]
  Summary: 39 PASSED, 0 FAILED

Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Andrey Ignatov 2019-03-23 15:51:00 -07:00 committed by Alexei Starovoitov
parent 8549ddc832
commit 7568f4cbbe
2 changed files with 126 additions and 1 deletions
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70
tools/testing/selftests/bpf/progs/test_sysctl_prog.c Normal file
View File

@ -0,0 +1,70 @@
// SPDX-License-Identifier: GPL-2.0
// Copyright (c) 2019 Facebook
#include <stdint.h>
#include <string.h>
#include <linux/stddef.h>
#include <linux/bpf.h>
#include "bpf_helpers.h"
#include "bpf_util.h"
/* Max supported length of a string with unsigned long in base 10 (pow2 - 1). */
#define MAX_ULONG_STR_LEN 0xF
/* Max supported length of sysctl value string (pow2). */
#define MAX_VALUE_STR_LEN 0x40
static __always_inline int is_tcp_mem(struct bpf_sysctl *ctx)
{
char tcp_mem_name[] = "net/ipv4/tcp_mem";
unsigned char i;
char name[64];
int ret;
memset(name, 0, sizeof(name));
ret = bpf_sysctl_get_name(ctx, name, sizeof(name), 0);
if (ret < 0 || ret != sizeof(tcp_mem_name) - 1)
return 0;
#pragma clang loop unroll(full)
for (i = 0; i < sizeof(tcp_mem_name); ++i)
if (name[i] != tcp_mem_name[i])
return 0;
return 1;
}
SEC("cgroup/sysctl")
int sysctl_tcp_mem(struct bpf_sysctl *ctx)
{
unsigned long tcp_mem[3] = {0, 0, 0};
char value[MAX_VALUE_STR_LEN];
unsigned char i, off = 0;
int ret;
if (ctx->write)
return 0;
if (!is_tcp_mem(ctx))
return 0;
ret = bpf_sysctl_get_current_value(ctx, value, MAX_VALUE_STR_LEN);
if (ret < 0 || ret >= MAX_VALUE_STR_LEN)
return 0;
#pragma clang loop unroll(full)
for (i = 0; i < ARRAY_SIZE(tcp_mem); ++i) {
ret = bpf_strtoul(value + off, MAX_ULONG_STR_LEN, 0,
tcp_mem + i);
if (ret <= 0 || ret > MAX_ULONG_STR_LEN)
return 0;
off += ret & MAX_ULONG_STR_LEN;
}
return tcp_mem[0] < tcp_mem[1] && tcp_mem[1] < tcp_mem[2];
}
char _license[] SEC("license") = "GPL";

57
tools/testing/selftests/bpf/test_sysctl.c
View File

@ -11,6 +11,7 @@
#include <linux/filter.h>
#include <bpf/bpf.h>
#include <bpf/libbpf.h>
#include "bpf_rlimit.h"
#include "bpf_util.h"
@ -26,6 +27,7 @@ struct sysctl_test {
const char *descr;
size_t fixup_value_insn;
struct bpf_insn insns[MAX_INSNS];
const char *prog_file;
enum bpf_attach_type attach_type;
const char *sysctl;
int open_flags;
@ -1302,6 +1304,31 @@ static struct sysctl_test tests[] = {
.open_flags = O_RDONLY,
.result = SUCCESS,
},
{
"C prog: deny all writes",
.prog_file = "./test_sysctl_prog.o",
.attach_type = BPF_CGROUP_SYSCTL,
.sysctl = "net/ipv4/tcp_mem",
.open_flags = O_WRONLY,
.newval = "123 456 789",
.result = OP_EPERM,
},
{
"C prog: deny access by name",
.prog_file = "./test_sysctl_prog.o",
.attach_type = BPF_CGROUP_SYSCTL,
.sysctl = "net/ipv4/route/mtu_expires",
.open_flags = O_RDONLY,
.result = OP_EPERM,
},
{
"C prog: read tcp_mem",
.prog_file = "./test_sysctl_prog.o",
.attach_type = BPF_CGROUP_SYSCTL,
.sysctl = "net/ipv4/tcp_mem",
.open_flags = O_RDONLY,
.result = SUCCESS,
},
};
static size_t probe_prog_length(const struct bpf_insn *fp)
@ -1335,7 +1362,8 @@ static int fixup_sysctl_value(const char *buf, size_t buf_len,
return 0;
}
static int load_sysctl_prog(struct sysctl_test *test, const char *sysctl_path)
static int load_sysctl_prog_insns(struct sysctl_test *test,
const char *sysctl_path)
{
struct bpf_insn *prog = test->insns;
struct bpf_load_program_attr attr;
@ -1377,6 +1405,33 @@ static int load_sysctl_prog(struct sysctl_test *test, const char *sysctl_path)
return ret;
}
static int load_sysctl_prog_file(struct sysctl_test *test)
{
struct bpf_prog_load_attr attr;
struct bpf_object *obj;
int prog_fd;
memset(&attr, 0, sizeof(struct bpf_prog_load_attr));
attr.file = test->prog_file;
attr.prog_type = BPF_PROG_TYPE_CGROUP_SYSCTL;
if (bpf_prog_load_xattr(&attr, &obj, &prog_fd)) {
if (test->result != LOAD_REJECT)
log_err(">>> Loading program (%s) error.\n",
test->prog_file);
return -1;
}
return prog_fd;
}
static int load_sysctl_prog(struct sysctl_test *test, const char *sysctl_path)
{
return test->prog_file
? load_sysctl_prog_file(test)
: load_sysctl_prog_insns(test, sysctl_path);
}
static int access_sysctl(const char *sysctl_path,
const struct sysctl_test *test)
{