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bh=Ro7xCYFTIMq+4aXdu0vnN1al3dV+lMpIl8csXTesIbU=; b=RsFMxv9XvI7TGxWjLGuNVZZQak/x9sB4zWNUCN6BZW+KoDLU25RrUTkrHkuu70ZE7Y I3UuniYpINPmMkfBn+agt5mwMeeHIIw1oK5iotckx08DxN3afLqZSrSmTVKBVVnaFRTv 8YAJF6CubvdTl14R4VRPXbZCAp8GKeEnoJeDhDZt/fMQxdkyEk0F1CJC5BPrvMzi7kS/ u7iLKTnJhyo0lw3sThzbMFKDrSfnp00fIhDWNlg24O/mGiJ1j/ikMqOrd5wMoKHc48yU bjxXPlYGWPZIpIYntqM5uHr9tWdt4QY8sZ4HAkZMMTkY0ayZi95qAu3yQuO/CIcYOy4Z QXYg== X-Gm-Message-State: AOAM531b7mkdiEQesPjSd0wBzd+EE9chubG1ycz78Hzzv2zGWqpme+ix 2TG+MvalQoJQd4rirk6T6lLjYAZr5V1n7ySd9Lw= X-Google-Smtp-Source: ABdhPJy/PI8enZ3VVWM1OOLOMAN/E+WKrgw2anRZOFWnpYPUGT0G3hO4Kbh7I2X0+QHUB6roP+X1D3RE4Q9uSs8Ln9Q= X-Received: by 2002:a25:c4c5:: with SMTP id u188mr6949290ybf.425.1619198303207; Fri, 23 Apr 2021 10:18:23 -0700 (PDT) MIME-Version: 1.0 References: <20210416202404.3443623-1-andrii@kernel.org> <20210416202404.3443623-16-andrii@kernel.org> <3947e6ff-0b73-995e-630f-4a1252f8694b@fb.com> In-Reply-To: <3947e6ff-0b73-995e-630f-4a1252f8694b@fb.com> From: Andrii Nakryiko Date: Fri, 23 Apr 2021 10:18:12 -0700 Message-ID: Subject: Re: [PATCH v2 bpf-next 15/17] selftests/bpf: add function linking selftest To: Yonghong Song Cc: Andrii Nakryiko , bpf , Networking , Alexei Starovoitov , Daniel Borkmann , Kernel Team Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Thu, Apr 22, 2021 at 5:50 PM Yonghong Song wrote: > > > > On 4/16/21 1:24 PM, Andrii Nakryiko wrote: > > 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: Andrii Nakryiko > > Ack with a small nit below. > > Acked-by: Yonghong Song > > > --- > > tools/testing/selftests/bpf/Makefile | 3 +- > > .../selftests/bpf/prog_tests/linked_funcs.c | 42 +++++++++++ > > .../selftests/bpf/progs/linked_funcs1.c | 73 +++++++++++++++++++ > > .../selftests/bpf/progs/linked_funcs2.c | 73 +++++++++++++++++++ > > 4 files changed, 190 insertions(+), 1 deletion(-) > > create mode 100644 tools/testing/selftests/bpf/prog_tests/linked_funcs.c > > create mode 100644 tools/testing/selftests/bpf/progs/linked_funcs1.c > > create mode 100644 tools/testing/selftests/bpf/progs/linked_funcs2.c > > > > diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile > > index 666b462c1218..427ccfec1a6a 100644 > > --- a/tools/testing/selftests/bpf/Makefile > > +++ b/tools/testing/selftests/bpf/Makefile > > @@ -308,9 +308,10 @@ endef > > > > 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 > > +linked_funcs.skel.h-deps := linked_funcs1.o linked_funcs2.o > > > > LINKED_BPF_SRCS := $(patsubst %.o,%.c,$(foreach skel,$(LINKED_SKELS),$($(skel)-deps))) > > > > diff --git a/tools/testing/selftests/bpf/prog_tests/linked_funcs.c b/tools/testing/selftests/bpf/prog_tests/linked_funcs.c > > new file mode 100644 > > index 000000000000..03bf8ef131ce > > --- /dev/null > > +++ b/tools/testing/selftests/bpf/prog_tests/linked_funcs.c > > @@ -0,0 +1,42 @@ > > +// SPDX-License-Identifier: GPL-2.0 > > +/* Copyright (c) 2021 Facebook */ > > + > > +#include > > +#include > > +#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->rodata->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); > > +} > > diff --git a/tools/testing/selftests/bpf/progs/linked_funcs1.c b/tools/testing/selftests/bpf/progs/linked_funcs1.c > > new file mode 100644 > > index 000000000000..cc621d4e4d82 > > --- /dev/null > > +++ b/tools/testing/selftests/bpf/progs/linked_funcs1.c > > @@ -0,0 +1,73 @@ > > +// SPDX-License-Identifier: GPL-2.0 > > +/* Copyright (c) 2021 Facebook */ > > + > > +#include "vmlinux.h" > > +#include > > +#include > > + > > +/* weak and shared between two files */ > > +const volatile int my_tid __weak = 0; > > +const volatile long syscall_id __weak = 0; > > Since the new compiler (llvm13) is recommended for this patch set. > We can simplify the above two definition with > int my_tid __weak; > long syscall_id __weak; > The same for the other file. This is not about old vs new compilers. I wanted to use .rodata variables, but I'll switch to .bss, no problem. > > But I am also okay with the current form > to *satisfy* llvm10 some people may still use. > > > + > > +int output_val1 = 0; > > +int output_ctx1 = 0; > > +int output_weak1 = 0; > > + > > +/* 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); > > + > [...]