Commit 14f1aae1 authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Alexei Starovoitov
Browse files

selftests/bpf: Add global variables linking selftest 



Add selftest validating various aspects of statically linking global
variables:
  - correct resolution of extern variables across .bss, .data, and .rodata
    sections;
  - correct handling of weak definitions;
  - correct de-duplication of repeating special externs (.kconfig, .ksyms).

Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarYonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210423181348.1801389-17-andrii@kernel.org
parent f2644fb4

tools/testing/selftests/bpf/Makefile

+2 −1
Original line number Diff line number Diff line
@@ -309,10 +309,11 @@ endef 


SKEL_BLACKLIST := btf__% test_pinning_invalid.c test_sk_assign.c



LINKED_SKELS := test_static_linked.skel.h linked_funcs.skel.h

LINKED_SKELS := test_static_linked.skel.h linked_funcs.skel.h linked_vars.skel.h



test_static_linked.skel.h-deps := test_static_linked1.o test_static_linked2.o

linked_funcs.skel.h-deps := linked_funcs1.o linked_funcs2.o

linked_vars.skel.h-deps := linked_vars1.o linked_vars2.o



LINKED_BPF_SRCS := $(patsubst %.o,%.c,$(foreach skel,$(LINKED_SKELS),$($(skel)-deps)))

tools/testing/selftests/bpf/prog_tests/linked_vars.c

0 → 100644
+43 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

/* Copyright (c) 2021 Facebook */



#include <test_progs.h>

#include <sys/syscall.h>

#include "linked_vars.skel.h"



void test_linked_vars(void)

{

	int err;

	struct linked_vars *skel;



	skel = linked_vars__open();

	if (!ASSERT_OK_PTR(skel, "skel_open"))

		return;



	skel->bss->input_bss1 = 1000;

	skel->bss->input_bss2 = 2000;

	skel->bss->input_bss_weak = 3000;



	err = linked_vars__load(skel);

	if (!ASSERT_OK(err, "skel_load"))

		goto cleanup;



	err = linked_vars__attach(skel);

	if (!ASSERT_OK(err, "skel_attach"))

		goto cleanup;



	/* trigger */

	syscall(SYS_getpgid);



	ASSERT_EQ(skel->bss->output_bss1, 1000 + 2000 + 3000, "output_bss1");

	ASSERT_EQ(skel->bss->output_bss2, 1000 + 2000 + 3000, "output_bss2");

	/* 10 comes from "winner" input_data_weak in first obj file */

	ASSERT_EQ(skel->bss->output_data1, 1 + 2 + 10, "output_bss1");

	ASSERT_EQ(skel->bss->output_data2, 1 + 2 + 10, "output_bss2");

	/* 100 comes from "winner" input_rodata_weak in first obj file */

	ASSERT_EQ(skel->bss->output_rodata1, 11 + 22 + 100, "output_weak1");

	ASSERT_EQ(skel->bss->output_rodata2, 11 + 22 + 100, "output_weak2");



cleanup:

	linked_vars__destroy(skel);

}

tools/testing/selftests/bpf/progs/linked_vars1.c

0 → 100644
+54 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

/* Copyright (c) 2021 Facebook */



#include "vmlinux.h"

#include <bpf/bpf_helpers.h>

#include <bpf/bpf_tracing.h>



extern int LINUX_KERNEL_VERSION __kconfig;

/* this weak extern will be strict due to the other file's strong extern */

extern bool CONFIG_BPF_SYSCALL __kconfig __weak;

extern const void bpf_link_fops __ksym __weak;



int input_bss1;

int input_data1 = 1;

const volatile int input_rodata1 = 11;



int input_bss_weak __weak;

/* these two definitions should win */

int input_data_weak __weak = 10;

const volatile int input_rodata_weak __weak = 100;



extern int input_bss2;

extern int input_data2;

extern const int input_rodata2;



int output_bss1;

int output_data1;

int output_rodata1;



long output_sink1;



static __noinline int get_bss_res(void)

{

	/* just make sure all the relocations work against .text as well */

	return input_bss1 + input_bss2 + input_bss_weak;

}



SEC("raw_tp/sys_enter")

int BPF_PROG(handler1)

{

	output_bss1 = get_bss_res();

	output_data1 = input_data1 + input_data2 + input_data_weak;

	output_rodata1 = input_rodata1 + input_rodata2 + input_rodata_weak;



	/* make sure we actually use above special externs, otherwise compiler

	 * will optimize them out

	 */

	output_sink1 = LINUX_KERNEL_VERSION

		       + CONFIG_BPF_SYSCALL

		       + (long)&bpf_link_fops;

	return 0;

}



char LICENSE[] SEC("license") = "GPL";

tools/testing/selftests/bpf/progs/linked_vars2.c

0 → 100644
+55 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

/* Copyright (c) 2021 Facebook */



#include "vmlinux.h"

#include <bpf/bpf_helpers.h>

#include <bpf/bpf_tracing.h>



extern int LINUX_KERNEL_VERSION __kconfig;

/* when an extern is defined as both strong and weak, resulting symbol will be strong */

extern bool CONFIG_BPF_SYSCALL __kconfig;

extern const void __start_BTF __ksym;



int input_bss2;

int input_data2 = 2;

const volatile int input_rodata2 = 22;



int input_bss_weak __weak;

/* these two weak variables should lose */

int input_data_weak __weak = 20;

const volatile int input_rodata_weak __weak = 200;



extern int input_bss1;

extern int input_data1;

extern const int input_rodata1;



int output_bss2;

int output_data2;

int output_rodata2;



int output_sink2;



static __noinline int get_data_res(void)

{

	/* just make sure all the relocations work against .text as well */

	return input_data1 + input_data2 + input_data_weak;

}



SEC("raw_tp/sys_enter")

int BPF_PROG(handler2)

{

	output_bss2 = input_bss1 + input_bss2 + input_bss_weak;

	output_data2 = get_data_res();

	output_rodata2 = input_rodata1 + input_rodata2 + input_rodata_weak;



	/* make sure we actually use above special externs, otherwise compiler

	 * will optimize them out

	 */

	output_sink2 = LINUX_KERNEL_VERSION

		       + CONFIG_BPF_SYSCALL

		       + (long)&__start_BTF;



	return 0;

}



char LICENSE[] SEC("license") = "GPL";