Commit f2644fb4 authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Alexei Starovoitov

selftests/bpf: Add function linking selftest

Add selftest validating various aspects of statically linking functions:
  - no conflicts and correct resolution for name-conflicting static funcs;
  - correct resolution of extern functions;
  - correct handling of weak functions, both resolution itself and libbpf's
    handling of unused weak function that "lost" (it leaves gaps in code with
    no ELF symbols);
  - correct handling of hidden visibility to turn global function into
    "static" for the purpose of BPF verification.
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/20210423181348.1801389-16-andrii@kernel.org
parent b131aed9
...@@ -309,9 +309,10 @@ endef ...@@ -309,9 +309,10 @@ endef
SKEL_BLACKLIST := btf__% test_pinning_invalid.c test_sk_assign.c SKEL_BLACKLIST := btf__% test_pinning_invalid.c test_sk_assign.c
LINKED_SKELS := test_static_linked.skel.h LINKED_SKELS := test_static_linked.skel.h linked_funcs.skel.h
test_static_linked.skel.h-deps := test_static_linked1.o test_static_linked2.o 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_BPF_SRCS := $(patsubst %.o,%.c,$(foreach skel,$(LINKED_SKELS),$($(skel)-deps))) LINKED_BPF_SRCS := $(patsubst %.o,%.c,$(foreach skel,$(LINKED_SKELS),$($(skel)-deps)))
......
// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2021 Facebook */
#include <test_progs.h>
#include <sys/syscall.h>
#include "linked_funcs.skel.h"
void test_linked_funcs(void)
{
int err;
struct linked_funcs *skel;
skel = linked_funcs__open();
if (!ASSERT_OK_PTR(skel, "skel_open"))
return;
skel->rodata->my_tid = syscall(SYS_gettid);
skel->bss->syscall_id = SYS_getpgid;
err = linked_funcs__load(skel);
if (!ASSERT_OK(err, "skel_load"))
goto cleanup;
err = linked_funcs__attach(skel);
if (!ASSERT_OK(err, "skel_attach"))
goto cleanup;
/* trigger */
syscall(SYS_getpgid);
ASSERT_EQ(skel->bss->output_val1, 2000 + 2000, "output_val1");
ASSERT_EQ(skel->bss->output_ctx1, SYS_getpgid, "output_ctx1");
ASSERT_EQ(skel->bss->output_weak1, 42, "output_weak1");
ASSERT_EQ(skel->bss->output_val2, 2 * 1000 + 2 * (2 * 1000), "output_val2");
ASSERT_EQ(skel->bss->output_ctx2, SYS_getpgid, "output_ctx2");
/* output_weak2 should never be updated */
ASSERT_EQ(skel->bss->output_weak2, 0, "output_weak2");
cleanup:
linked_funcs__destroy(skel);
}
// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2021 Facebook */
#include "vmlinux.h"
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
/* weak and shared between two files */
const volatile int my_tid __weak;
long syscall_id __weak;
int output_val1;
int output_ctx1;
int output_weak1;
/* same "subprog" name in all files, but it's ok because they all are static */
static __noinline int subprog(int x)
{
/* but different formula */
return x * 1;
}
/* Global functions can't be void */
int set_output_val1(int x)
{
output_val1 = x + subprog(x);
return x;
}
/* This function can't be verified as global, as it assumes raw_tp/sys_enter
* context and accesses syscall id (second argument). So we mark it as
* __hidden, so that libbpf will mark it as static in the final object file,
* right before verifying it in the kernel.
*
* But we don't mark it as __hidden here, rather at extern site. __hidden is
* "contaminating" visibility, so it will get propagated from either extern or
* actual definition (including from the losing __weak definition).
*/
void set_output_ctx1(__u64 *ctx)
{
output_ctx1 = ctx[1]; /* long id, same as in BPF_PROG below */
}
/* this weak instance should win because it's the first one */
__weak int set_output_weak(int x)
{
output_weak1 = x;
return x;
}
extern int set_output_val2(int x);
/* here we'll force set_output_ctx2() to be __hidden in the final obj file */
__hidden extern void set_output_ctx2(__u64 *ctx);
SEC("raw_tp/sys_enter")
int BPF_PROG(handler1, struct pt_regs *regs, long id)
{
if (my_tid != (u32)bpf_get_current_pid_tgid() || id != syscall_id)
return 0;
set_output_val2(1000);
set_output_ctx2(ctx); /* ctx definition is hidden in BPF_PROG macro */
/* keep input value the same across both files to avoid dependency on
* handler call order; differentiate by output_weak1 vs output_weak2.
*/
set_output_weak(42);
return 0;
}
char LICENSE[] SEC("license") = "GPL";
// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2021 Facebook */
#include "vmlinux.h"
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
/* weak and shared between both files */
const volatile int my_tid __weak;
long syscall_id __weak;
int output_val2;
int output_ctx2;
int output_weak2; /* should stay zero */
/* same "subprog" name in all files, but it's ok because they all are static */
static __noinline int subprog(int x)
{
/* but different formula */
return x * 2;
}
/* Global functions can't be void */
int set_output_val2(int x)
{
output_val2 = 2 * x + 2 * subprog(x);
return 2 * x;
}
/* This function can't be verified as global, as it assumes raw_tp/sys_enter
* context and accesses syscall id (second argument). So we mark it as
* __hidden, so that libbpf will mark it as static in the final object file,
* right before verifying it in the kernel.
*
* But we don't mark it as __hidden here, rather at extern site. __hidden is
* "contaminating" visibility, so it will get propagated from either extern or
* actual definition (including from the losing __weak definition).
*/
void set_output_ctx2(__u64 *ctx)
{
output_ctx2 = ctx[1]; /* long id, same as in BPF_PROG below */
}
/* this weak instance should lose, because it will be processed second */
__weak int set_output_weak(int x)
{
output_weak2 = x;
return 2 * x;
}
extern int set_output_val1(int x);
/* here we'll force set_output_ctx1() to be __hidden in the final obj file */
__hidden extern void set_output_ctx1(__u64 *ctx);
SEC("raw_tp/sys_enter")
int BPF_PROG(handler2, struct pt_regs *regs, long id)
{
if (my_tid != (u32)bpf_get_current_pid_tgid() || id != syscall_id)
return 0;
set_output_val1(2000);
set_output_ctx1(ctx); /* ctx definition is hidden in BPF_PROG macro */
/* keep input value the same across both files to avoid dependency on
* handler call order; differentiate by output_weak1 vs output_weak2.
*/
set_output_weak(42);
return 0;
}
char LICENSE[] SEC("license") = "GPL";
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