2f968e9f4a
Add non-mmapable data section to test_skeleton selftest and make sure it
really isn't mmapable by trying to mmap() it anyways.
Also make sure that libbpf doesn't report BPF_F_MMAPABLE flag to users.
Additional, some more manual testing was performed that this feature
works as intended.
Looking at created map through bpftool shows that flags passed to kernel are
indeed zero:
$ bpftool map show
...
1782: array name .data.non_mmapa flags 0x0
key 4B value 16B max_entries 1 memlock 4096B
btf_id 1169
pids test_progs(8311)
...
Checking BTF uploaded to kernel for this map shows that zero_key and
zero_value are indeed marked as static, even though zero_key is actually
original global (but STV_HIDDEN) variable:
$ bpftool btf dump id 1169
...
[51] VAR 'zero_key' type_id=2, linkage=static
[52] VAR 'zero_value' type_id=7, linkage=static
...
[62] DATASEC '.data.non_mmapable' size=16 vlen=2
type_id=51 offset=0 size=4 (VAR 'zero_key')
type_id=52 offset=4 size=12 (VAR 'zero_value')
...
And original BTF does have zero_key marked as linkage=global:
$ bpftool btf dump file test_skeleton.bpf.linked3.o
...
[51] VAR 'zero_key' type_id=2, linkage=global
[52] VAR 'zero_value' type_id=7, linkage=static
...
[62] DATASEC '.data.non_mmapable' size=16 vlen=2
type_id=51 offset=0 size=4 (VAR 'zero_key')
type_id=52 offset=4 size=12 (VAR 'zero_value')
Bpftool didn't require any changes at all because it checks whether internal
map is mmapable already, but just to double-check generated skeleton, we
see that .data.non_mmapable neither sets mmaped pointer nor has
a corresponding field in the skeleton:
$ grep non_mmapable test_skeleton.skel.h
struct bpf_map *data_non_mmapable;
s->maps[7].name = ".data.non_mmapable";
s->maps[7].map = &obj->maps.data_non_mmapable;
But .data.read_mostly has all of those things:
$ grep read_mostly test_skeleton.skel.h
struct bpf_map *data_read_mostly;
struct test_skeleton__data_read_mostly {
int read_mostly_var;
} *data_read_mostly;
s->maps[6].name = ".data.read_mostly";
s->maps[6].map = &obj->maps.data_read_mostly;
s->maps[6].mmaped = (void **)&obj->data_read_mostly;
_Static_assert(sizeof(s->data_read_mostly->read_mostly_var) == 4, "unexpected size of 'read_mostly_var'");
Acked-by: Stanislav Fomichev <sdf@google.com>
Acked-by: Dave Marchevsky <davemarchevsky@fb.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20221019002816.359650-4-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
98 lines
1.9 KiB
C
98 lines
1.9 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/* Copyright (c) 2019 Facebook */
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#include <stdbool.h>
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#include <linux/bpf.h>
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#include <bpf/bpf_helpers.h>
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#define __read_mostly SEC(".data.read_mostly")
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struct s {
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int a;
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long long b;
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} __attribute__((packed));
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/* .data section */
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int in1 = -1;
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long long in2 = -1;
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/* .bss section */
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char in3 = '\0';
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long long in4 __attribute__((aligned(64))) = 0;
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struct s in5 = {};
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/* .rodata section */
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const volatile struct {
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const int in6;
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} in = {};
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/* .data section */
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int out1 = -1;
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long long out2 = -1;
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/* .bss section */
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char out3 = 0;
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long long out4 = 0;
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int out6 = 0;
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extern bool CONFIG_BPF_SYSCALL __kconfig;
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extern int LINUX_KERNEL_VERSION __kconfig;
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bool bpf_syscall = 0;
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int kern_ver = 0;
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struct s out5 = {};
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const volatile int in_dynarr_sz SEC(".rodata.dyn");
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const volatile int in_dynarr[4] SEC(".rodata.dyn") = { -1, -2, -3, -4 };
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int out_dynarr[4] SEC(".data.dyn") = { 1, 2, 3, 4 };
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int read_mostly_var __read_mostly;
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int out_mostly_var;
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char huge_arr[16 * 1024 * 1024];
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/* non-mmapable custom .data section */
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struct my_value { int x, y, z; };
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__hidden int zero_key SEC(".data.non_mmapable");
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static struct my_value zero_value SEC(".data.non_mmapable");
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struct {
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__uint(type, BPF_MAP_TYPE_ARRAY);
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__type(key, int);
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__type(value, struct my_value);
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__uint(max_entries, 1);
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} my_map SEC(".maps");
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SEC("raw_tp/sys_enter")
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int handler(const void *ctx)
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{
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int i;
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out1 = in1;
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out2 = in2;
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out3 = in3;
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out4 = in4;
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out5 = in5;
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out6 = in.in6;
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bpf_syscall = CONFIG_BPF_SYSCALL;
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kern_ver = LINUX_KERNEL_VERSION;
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for (i = 0; i < in_dynarr_sz; i++)
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out_dynarr[i] = in_dynarr[i];
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out_mostly_var = read_mostly_var;
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huge_arr[sizeof(huge_arr) - 1] = 123;
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/* make sure zero_key and zero_value are not optimized out */
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bpf_map_update_elem(&my_map, &zero_key, &zero_value, BPF_ANY);
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return 0;
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}
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char _license[] SEC("license") = "GPL";
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