| Message ID | 20200619231703.738941-4-andriin@fb.com |
|---|---|
| State | Accepted |
| Delegated to: | BPF Maintainers |
| Headers | show |
| Series | libbpf ksym support and bpftool show PIDs | expand |
Reviewed-by: Hao Luo <haoluo@google.com> On Fri, Jun 19, 2020 at 4:19 PM Andrii Nakryiko <andriin@fb.com> wrote: > > Validate libbpf is able to handle weak and strong kernel symbol externs in BPF > code correctly. > > Signed-off-by: Andrii Nakryiko <andriin@fb.com> > --- > .../testing/selftests/bpf/prog_tests/ksyms.c | 71 +++++++++++++++++++ > .../testing/selftests/bpf/progs/test_ksyms.c | 32 +++++++++ > 2 files changed, 103 insertions(+) > create mode 100644 tools/testing/selftests/bpf/prog_tests/ksyms.c > create mode 100644 tools/testing/selftests/bpf/progs/test_ksyms.c > > diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms.c b/tools/testing/selftests/bpf/prog_tests/ksyms.c > new file mode 100644 > index 000000000000..e3d6777226a8 > --- /dev/null > +++ b/tools/testing/selftests/bpf/prog_tests/ksyms.c > @@ -0,0 +1,71 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* Copyright (c) 2019 Facebook */ > + > +#include <test_progs.h> > +#include "test_ksyms.skel.h" > +#include <sys/stat.h> > + > +static int duration; > + > +static __u64 kallsyms_find(const char *sym) > +{ > + char type, name[500]; > + __u64 addr, res = 0; > + FILE *f; > + > + f = fopen("/proc/kallsyms", "r"); > + if (CHECK(!f, "kallsyms_fopen", "failed to open: %d\n", errno)) > + return 0; > + > + while (fscanf(f, "%llx %c %499s%*[^\n]\n", &addr, &type, name) > 0) { > + if (strcmp(name, sym) == 0) { > + res = addr; > + goto out; > + } > + } > + > + CHECK(false, "not_found", "symbol %s not found\n", sym); > +out: > + fclose(f); > + return res; > +} > + > +void test_ksyms(void) > +{ > + __u64 link_fops_addr = kallsyms_find("bpf_link_fops"); > + const char *btf_path = "/sys/kernel/btf/vmlinux"; > + struct test_ksyms *skel; > + struct test_ksyms__data *data; > + struct stat st; > + __u64 btf_size; > + int err; > + > + if (CHECK(stat(btf_path, &st), "stat_btf", "err %d\n", errno)) > + return; > + btf_size = st.st_size; > + > + skel = test_ksyms__open_and_load(); > + if (CHECK(!skel, "skel_open", "failed to open and load skeleton\n")) > + return; > + > + err = test_ksyms__attach(skel); > + if (CHECK(err, "skel_attach", "skeleton attach failed: %d\n", err)) > + goto cleanup; > + > + /* trigger tracepoint */ > + usleep(1); > + > + data = skel->data; > + CHECK(data->out__bpf_link_fops != link_fops_addr, "bpf_link_fops", > + "got 0x%llx, exp 0x%llx\n", > + data->out__bpf_link_fops, link_fops_addr); > + CHECK(data->out__bpf_link_fops1 != 0, "bpf_link_fops1", > + "got %llu, exp %llu\n", data->out__bpf_link_fops1, (__u64)0); > + CHECK(data->out__btf_size != btf_size, "btf_size", > + "got %llu, exp %llu\n", data->out__btf_size, btf_size); > + CHECK(data->out__per_cpu_start != 0, "__per_cpu_start", > + "got %llu, exp %llu\n", data->out__per_cpu_start, (__u64)0); > + > +cleanup: > + test_ksyms__destroy(skel); > +} > diff --git a/tools/testing/selftests/bpf/progs/test_ksyms.c b/tools/testing/selftests/bpf/progs/test_ksyms.c > new file mode 100644 > index 000000000000..6c9cbb5a3bdf > --- /dev/null > +++ b/tools/testing/selftests/bpf/progs/test_ksyms.c > @@ -0,0 +1,32 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* Copyright (c) 2019 Facebook */ > + > +#include <stdbool.h> > +#include <linux/bpf.h> > +#include <bpf/bpf_helpers.h> > + > +__u64 out__bpf_link_fops = -1; > +__u64 out__bpf_link_fops1 = -1; > +__u64 out__btf_size = -1; > +__u64 out__per_cpu_start = -1; > + > +extern const void bpf_link_fops __ksym; > +extern const void __start_BTF __ksym; > +extern const void __stop_BTF __ksym; > +extern const void __per_cpu_start __ksym; > +/* non-existing symbol, weak, default to zero */ > +extern const void bpf_link_fops1 __ksym __weak; > + > +SEC("raw_tp/sys_enter") > +int handler(const void *ctx) > +{ > + out__bpf_link_fops = (__u64)&bpf_link_fops; > + out__btf_size = (__u64)(&__stop_BTF - &__start_BTF); > + out__per_cpu_start = (__u64)&__per_cpu_start; > + > + out__bpf_link_fops1 = (__u64)&bpf_link_fops1; > + > + return 0; > +} > + > +char _license[] SEC("license") = "GPL"; > -- > 2.24.1 >
Hi! On Fri, 2020-06-19 at 16:16 -0700, Andrii Nakryiko wrote: > Validate libbpf is able to handle weak and strong kernel symbol > externs in BPF > code correctly. > > Signed-off-by: Andrii Nakryiko <andriin@fb.com> > --- > .../testing/selftests/bpf/prog_tests/ksyms.c | 71 > +++++++++++++++++++ > .../testing/selftests/bpf/progs/test_ksyms.c | 32 +++++++++ > 2 files changed, 103 insertions(+) > create mode 100644 tools/testing/selftests/bpf/prog_tests/ksyms.c > create mode 100644 tools/testing/selftests/bpf/progs/test_ksyms.c > > diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms.c > b/tools/testing/selftests/bpf/prog_tests/ksyms.c > new file mode 100644 > index 000000000000..e3d6777226a8 > --- /dev/null > +++ b/tools/testing/selftests/bpf/prog_tests/ksyms.c > @@ -0,0 +1,71 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* Copyright (c) 2019 Facebook */ > + > +#include <test_progs.h> > +#include "test_ksyms.skel.h" > +#include <sys/stat.h> > + > +static int duration; > + > +static __u64 kallsyms_find(const char *sym) > +{ > + char type, name[500]; > + __u64 addr, res = 0; > + FILE *f; > + > + f = fopen("/proc/kallsyms", "r"); > + if (CHECK(!f, "kallsyms_fopen", "failed to open: %d\n", errno)) > + return 0; > + > + while (fscanf(f, "%llx %c %499s%*[^\n]\n", &addr, &type, name) > > 0) { > + if (strcmp(name, sym) == 0) { > + res = addr; > + goto out; > + } > + } > + > + CHECK(false, "not_found", "symbol %s not found\n", sym); > +out: > + fclose(f); > + return res; > +} > + > +void test_ksyms(void) > +{ > + __u64 link_fops_addr = kallsyms_find("bpf_link_fops"); > + const char *btf_path = "/sys/kernel/btf/vmlinux"; > + struct test_ksyms *skel; > + struct test_ksyms__data *data; > + struct stat st; > + __u64 btf_size; > + int err; > + > + if (CHECK(stat(btf_path, &st), "stat_btf", "err %d\n", errno)) > + return; > + btf_size = st.st_size; > + > + skel = test_ksyms__open_and_load(); > + if (CHECK(!skel, "skel_open", "failed to open and load > skeleton\n")) > + return; > + > + err = test_ksyms__attach(skel); > + if (CHECK(err, "skel_attach", "skeleton attach failed: %d\n", > err)) > + goto cleanup; > + > + /* trigger tracepoint */ > + usleep(1); > + > + data = skel->data; > + CHECK(data->out__bpf_link_fops != link_fops_addr, > "bpf_link_fops", > + "got 0x%llx, exp 0x%llx\n", > + data->out__bpf_link_fops, link_fops_addr); > + CHECK(data->out__bpf_link_fops1 != 0, "bpf_link_fops1", > + "got %llu, exp %llu\n", data->out__bpf_link_fops1, > (__u64)0); > + CHECK(data->out__btf_size != btf_size, "btf_size", > + "got %llu, exp %llu\n", data->out__btf_size, btf_size); > + CHECK(data->out__per_cpu_start != 0, "__per_cpu_start", > + "got %llu, exp %llu\n", data->out__per_cpu_start, > (__u64)0); > + > +cleanup: > + test_ksyms__destroy(skel); > +} Why is __per_cpu_start expected to be 0? On my x86_64 Debian VM it is something like ffffffffxxxxxxxx, and this test fails. Wouldn't it be better to take the value from kallsyms, like it's done with bpf_link_fops, or am I missing something in my setup? Best regards, Ilya
On Wed, Sep 9, 2020 at 6:59 PM Ilya Leoshkevich <iii@linux.ibm.com> wrote: > > Hi! > > On Fri, 2020-06-19 at 16:16 -0700, Andrii Nakryiko wrote: > > Validate libbpf is able to handle weak and strong kernel symbol > > externs in BPF > > code correctly. > > > > Signed-off-by: Andrii Nakryiko <andriin@fb.com> > > --- > > .../testing/selftests/bpf/prog_tests/ksyms.c | 71 > > +++++++++++++++++++ > > .../testing/selftests/bpf/progs/test_ksyms.c | 32 +++++++++ > > 2 files changed, 103 insertions(+) > > create mode 100644 tools/testing/selftests/bpf/prog_tests/ksyms.c > > create mode 100644 tools/testing/selftests/bpf/progs/test_ksyms.c > > > > diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms.c > > b/tools/testing/selftests/bpf/prog_tests/ksyms.c > > new file mode 100644 > > index 000000000000..e3d6777226a8 > > --- /dev/null > > +++ b/tools/testing/selftests/bpf/prog_tests/ksyms.c > > @@ -0,0 +1,71 @@ > > +// SPDX-License-Identifier: GPL-2.0 > > +/* Copyright (c) 2019 Facebook */ > > + > > +#include <test_progs.h> > > +#include "test_ksyms.skel.h" > > +#include <sys/stat.h> > > + > > +static int duration; > > + > > +static __u64 kallsyms_find(const char *sym) > > +{ > > + char type, name[500]; > > + __u64 addr, res = 0; > > + FILE *f; > > + > > + f = fopen("/proc/kallsyms", "r"); > > + if (CHECK(!f, "kallsyms_fopen", "failed to open: %d\n", errno)) > > + return 0; > > + > > + while (fscanf(f, "%llx %c %499s%*[^\n]\n", &addr, &type, name) > > > 0) { > > + if (strcmp(name, sym) == 0) { > > + res = addr; > > + goto out; > > + } > > + } > > + > > + CHECK(false, "not_found", "symbol %s not found\n", sym); > > +out: > > + fclose(f); > > + return res; > > +} > > + > > +void test_ksyms(void) > > +{ > > + __u64 link_fops_addr = kallsyms_find("bpf_link_fops"); > > + const char *btf_path = "/sys/kernel/btf/vmlinux"; > > + struct test_ksyms *skel; > > + struct test_ksyms__data *data; > > + struct stat st; > > + __u64 btf_size; > > + int err; > > + > > + if (CHECK(stat(btf_path, &st), "stat_btf", "err %d\n", errno)) > > + return; > > + btf_size = st.st_size; > > + > > + skel = test_ksyms__open_and_load(); > > + if (CHECK(!skel, "skel_open", "failed to open and load > > skeleton\n")) > > + return; > > + > > + err = test_ksyms__attach(skel); > > + if (CHECK(err, "skel_attach", "skeleton attach failed: %d\n", > > err)) > > + goto cleanup; > > + > > + /* trigger tracepoint */ > > + usleep(1); > > + > > + data = skel->data; > > + CHECK(data->out__bpf_link_fops != link_fops_addr, > > "bpf_link_fops", > > + "got 0x%llx, exp 0x%llx\n", > > + data->out__bpf_link_fops, link_fops_addr); > > + CHECK(data->out__bpf_link_fops1 != 0, "bpf_link_fops1", > > + "got %llu, exp %llu\n", data->out__bpf_link_fops1, > > (__u64)0); > > + CHECK(data->out__btf_size != btf_size, "btf_size", > > + "got %llu, exp %llu\n", data->out__btf_size, btf_size); > > + CHECK(data->out__per_cpu_start != 0, "__per_cpu_start", > > + "got %llu, exp %llu\n", data->out__per_cpu_start, > > (__u64)0); > > + > > +cleanup: > > + test_ksyms__destroy(skel); > > +} > > Why is __per_cpu_start expected to be 0? On my x86_64 Debian VM it is > something like ffffffffxxxxxxxx, and this test fails. Wouldn't > it be better to take the value from kallsyms, like it's done with > bpf_link_fops, or am I missing something in my setup? > Hm... those per-CPU symbols are not real addresses, they are relative offsets, so I thought that __per_cpu_start always got to be 0. Strange that you see a real kernel address instead. I guess looking up in kallsyms would work either way, please feel free to send a fix. Thanks! > Best regards, > Ilya >
On Thu, 2020-09-10 at 09:47 -0700, Andrii Nakryiko wrote: > On Wed, Sep 9, 2020 at 6:59 PM Ilya Leoshkevich <iii@linux.ibm.com> > wrote: > > Hi! > > > > On Fri, 2020-06-19 at 16:16 -0700, Andrii Nakryiko wrote: > > > Validate libbpf is able to handle weak and strong kernel symbol > > > externs in BPF > > > code correctly. > > > > > > Signed-off-by: Andrii Nakryiko <andriin@fb.com> > > > --- > > > .../testing/selftests/bpf/prog_tests/ksyms.c | 71 > > > +++++++++++++++++++ > > > .../testing/selftests/bpf/progs/test_ksyms.c | 32 +++++++++ > > > 2 files changed, 103 insertions(+) > > > create mode 100644 > > > tools/testing/selftests/bpf/prog_tests/ksyms.c > > > create mode 100644 > > > tools/testing/selftests/bpf/progs/test_ksyms.c > > > > > > diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms.c > > > b/tools/testing/selftests/bpf/prog_tests/ksyms.c > > > new file mode 100644 > > > index 000000000000..e3d6777226a8 > > > --- /dev/null > > > +++ b/tools/testing/selftests/bpf/prog_tests/ksyms.c > > > @@ -0,0 +1,71 @@ > > > +// SPDX-License-Identifier: GPL-2.0 > > > +/* Copyright (c) 2019 Facebook */ > > > + > > > +#include <test_progs.h> > > > +#include "test_ksyms.skel.h" > > > +#include <sys/stat.h> > > > + > > > +static int duration; > > > + > > > +static __u64 kallsyms_find(const char *sym) > > > +{ > > > + char type, name[500]; > > > + __u64 addr, res = 0; > > > + FILE *f; > > > + > > > + f = fopen("/proc/kallsyms", "r"); > > > + if (CHECK(!f, "kallsyms_fopen", "failed to open: %d\n", > > > errno)) > > > + return 0; > > > + > > > + while (fscanf(f, "%llx %c %499s%*[^\n]\n", &addr, &type, > > > name) > > > > 0) { > > > + if (strcmp(name, sym) == 0) { > > > + res = addr; > > > + goto out; > > > + } > > > + } > > > + > > > + CHECK(false, "not_found", "symbol %s not found\n", sym); > > > +out: > > > + fclose(f); > > > + return res; > > > +} > > > + > > > +void test_ksyms(void) > > > +{ > > > + __u64 link_fops_addr = kallsyms_find("bpf_link_fops"); > > > + const char *btf_path = "/sys/kernel/btf/vmlinux"; > > > + struct test_ksyms *skel; > > > + struct test_ksyms__data *data; > > > + struct stat st; > > > + __u64 btf_size; > > > + int err; > > > + > > > + if (CHECK(stat(btf_path, &st), "stat_btf", "err %d\n", > > > errno)) > > > + return; > > > + btf_size = st.st_size; > > > + > > > + skel = test_ksyms__open_and_load(); > > > + if (CHECK(!skel, "skel_open", "failed to open and load > > > skeleton\n")) > > > + return; > > > + > > > + err = test_ksyms__attach(skel); > > > + if (CHECK(err, "skel_attach", "skeleton attach failed: > > > %d\n", > > > err)) > > > + goto cleanup; > > > + > > > + /* trigger tracepoint */ > > > + usleep(1); > > > + > > > + data = skel->data; > > > + CHECK(data->out__bpf_link_fops != link_fops_addr, > > > "bpf_link_fops", > > > + "got 0x%llx, exp 0x%llx\n", > > > + data->out__bpf_link_fops, link_fops_addr); > > > + CHECK(data->out__bpf_link_fops1 != 0, "bpf_link_fops1", > > > + "got %llu, exp %llu\n", data->out__bpf_link_fops1, > > > (__u64)0); > > > + CHECK(data->out__btf_size != btf_size, "btf_size", > > > + "got %llu, exp %llu\n", data->out__btf_size, > > > btf_size); > > > + CHECK(data->out__per_cpu_start != 0, "__per_cpu_start", > > > + "got %llu, exp %llu\n", data->out__per_cpu_start, > > > (__u64)0); > > > + > > > +cleanup: > > > + test_ksyms__destroy(skel); > > > +} > > > > Why is __per_cpu_start expected to be 0? On my x86_64 Debian VM it > > is > > something like ffffffffxxxxxxxx, and this test fails. Wouldn't > > it be better to take the value from kallsyms, like it's done with > > bpf_link_fops, or am I missing something in my setup? > > > > Hm... those per-CPU symbols are not real addresses, they are relative > offsets, so I thought that __per_cpu_start always got to be 0. > Strange > that you see a real kernel address instead. I guess looking up in > kallsyms would work either way, please feel free to send a fix. > Thanks! Hm, I think I have an explanation now - I accidentally built a non-SMP kernel :-) I'll send a fix.
diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms.c b/tools/testing/selftests/bpf/prog_tests/ksyms.c new file mode 100644 index 000000000000..e3d6777226a8 --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/ksyms.c @@ -0,0 +1,71 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2019 Facebook */ + +#include <test_progs.h> +#include "test_ksyms.skel.h" +#include <sys/stat.h> + +static int duration; + +static __u64 kallsyms_find(const char *sym) +{ + char type, name[500]; + __u64 addr, res = 0; + FILE *f; + + f = fopen("/proc/kallsyms", "r"); + if (CHECK(!f, "kallsyms_fopen", "failed to open: %d\n", errno)) + return 0; + + while (fscanf(f, "%llx %c %499s%*[^\n]\n", &addr, &type, name) > 0) { + if (strcmp(name, sym) == 0) { + res = addr; + goto out; + } + } + + CHECK(false, "not_found", "symbol %s not found\n", sym); +out: + fclose(f); + return res; +} + +void test_ksyms(void) +{ + __u64 link_fops_addr = kallsyms_find("bpf_link_fops"); + const char *btf_path = "/sys/kernel/btf/vmlinux"; + struct test_ksyms *skel; + struct test_ksyms__data *data; + struct stat st; + __u64 btf_size; + int err; + + if (CHECK(stat(btf_path, &st), "stat_btf", "err %d\n", errno)) + return; + btf_size = st.st_size; + + skel = test_ksyms__open_and_load(); + if (CHECK(!skel, "skel_open", "failed to open and load skeleton\n")) + return; + + err = test_ksyms__attach(skel); + if (CHECK(err, "skel_attach", "skeleton attach failed: %d\n", err)) + goto cleanup; + + /* trigger tracepoint */ + usleep(1); + + data = skel->data; + CHECK(data->out__bpf_link_fops != link_fops_addr, "bpf_link_fops", + "got 0x%llx, exp 0x%llx\n", + data->out__bpf_link_fops, link_fops_addr); + CHECK(data->out__bpf_link_fops1 != 0, "bpf_link_fops1", + "got %llu, exp %llu\n", data->out__bpf_link_fops1, (__u64)0); + CHECK(data->out__btf_size != btf_size, "btf_size", + "got %llu, exp %llu\n", data->out__btf_size, btf_size); + CHECK(data->out__per_cpu_start != 0, "__per_cpu_start", + "got %llu, exp %llu\n", data->out__per_cpu_start, (__u64)0); + +cleanup: + test_ksyms__destroy(skel); +} diff --git a/tools/testing/selftests/bpf/progs/test_ksyms.c b/tools/testing/selftests/bpf/progs/test_ksyms.c new file mode 100644 index 000000000000..6c9cbb5a3bdf --- /dev/null +++ b/tools/testing/selftests/bpf/progs/test_ksyms.c @@ -0,0 +1,32 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2019 Facebook */ + +#include <stdbool.h> +#include <linux/bpf.h> +#include <bpf/bpf_helpers.h> + +__u64 out__bpf_link_fops = -1; +__u64 out__bpf_link_fops1 = -1; +__u64 out__btf_size = -1; +__u64 out__per_cpu_start = -1; + +extern const void bpf_link_fops __ksym; +extern const void __start_BTF __ksym; +extern const void __stop_BTF __ksym; +extern const void __per_cpu_start __ksym; +/* non-existing symbol, weak, default to zero */ +extern const void bpf_link_fops1 __ksym __weak; + +SEC("raw_tp/sys_enter") +int handler(const void *ctx) +{ + out__bpf_link_fops = (__u64)&bpf_link_fops; + out__btf_size = (__u64)(&__stop_BTF - &__start_BTF); + out__per_cpu_start = (__u64)&__per_cpu_start; + + out__bpf_link_fops1 = (__u64)&bpf_link_fops1; + + return 0; +} + +char _license[] SEC("license") = "GPL";
Validate libbpf is able to handle weak and strong kernel symbol externs in BPF code correctly. Signed-off-by: Andrii Nakryiko <andriin@fb.com> --- .../testing/selftests/bpf/prog_tests/ksyms.c | 71 +++++++++++++++++++ .../testing/selftests/bpf/progs/test_ksyms.c | 32 +++++++++ 2 files changed, 103 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/ksyms.c create mode 100644 tools/testing/selftests/bpf/progs/test_ksyms.c