| Message ID | 20210207011027.676572-5-andreimatei1@gmail.com (mailing list archive) |
|---|---|
| State | Accepted |
| Delegated to: | BPF |
| Headers | show |
| Series | allow variable-offset stack acces | expand |
| Context | Check | Description |
|---|---|---|
| netdev/cover_letter | success | Link |
| netdev/fixes_present | success | Link |
| netdev/patch_count | success | Link |
| netdev/tree_selection | success | Clearly marked for bpf-next |
| netdev/subject_prefix | success | Link |
| netdev/cc_maintainers | warning | 9 maintainers not CCed: songliubraving@fb.com kafai@fb.com john.fastabend@gmail.com linux-kselftest@vger.kernel.org yhs@fb.com netdev@vger.kernel.org kpsingh@kernel.org daniel@iogearbox.net shuah@kernel.org |
| netdev/source_inline | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Link |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/build_32bit | success | Errors and warnings before: 0 this patch: 0 |
| netdev/kdoc | success | Errors and warnings before: 2 this patch: 0 |
| netdev/verify_fixes | success | Link |
| netdev/checkpatch | warning | WARNING: added, moved or deleted file(s), does MAINTAINERS need updating? |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 0 this patch: 0 |
| netdev/header_inline | success | Link |
| netdev/stable | success | Stable not CCed |
On Sat, Feb 6, 2021 at 5:11 PM Andrei Matei <andreimatei1@gmail.com> wrote: > > Add a higher-level test (C BPF program) for the new functionality - > variable access stack reads and writes. > > Signed-off-by: Andrei Matei <andreimatei1@gmail.com> > --- > .../selftests/bpf/prog_tests/stack_var_off.c | 36 ++++++++++++ > .../selftests/bpf/progs/test_stack_var_off.c | 56 +++++++++++++++++++ > 2 files changed, 92 insertions(+) > create mode 100644 tools/testing/selftests/bpf/prog_tests/stack_var_off.c > create mode 100644 tools/testing/selftests/bpf/progs/test_stack_var_off.c > > diff --git a/tools/testing/selftests/bpf/prog_tests/stack_var_off.c b/tools/testing/selftests/bpf/prog_tests/stack_var_off.c > new file mode 100644 > index 000000000000..52e00486b1aa > --- /dev/null > +++ b/tools/testing/selftests/bpf/prog_tests/stack_var_off.c > @@ -0,0 +1,36 @@ > +// SPDX-License-Identifier: GPL-2.0 > +#include <test_progs.h> > +#include "test_stack_var_off.skel.h" > + > +/* Test read and writes to the stack performed with offsets that are not > + * statically known. > + */ > +void test_stack_var_off(void) > +{ > + int duration = 0; > + struct test_stack_var_off *skel; > + > + skel = test_stack_var_off__open_and_load(); > + if (CHECK(!skel, "skel_open", "failed to open skeleton\n")) > + return; > + if (CHECK(!skel->bss, "check_bss", ".bss wasn't mmap()-ed\n")) > + goto cleanup; can't happen, no need to check for !skel->bss > + > + test_stack_var_off__attach(skel); check errors (ASSERT_OK is good for this) > + > + /* Give pid to bpf prog so it doesn't trigger for anyone else. */ > + skel->bss->test_pid = getpid(); > + /* Initialize the probe's input. */ > + skel->bss->input[0] = 2; > + skel->bss->input[1] = 42; /* This will be returned in probe_res. */ > + > + /* Trigger probe. */ > + usleep(1); > + > + if (CHECK(skel->bss->probe_res != 42, "check_probe_res", > + "wrong probe res: %d\n", skel->bss->probe_res)) > + goto cleanup; > + > +cleanup: > + test_stack_var_off__destroy(skel); > +} > diff --git a/tools/testing/selftests/bpf/progs/test_stack_var_off.c b/tools/testing/selftests/bpf/progs/test_stack_var_off.c > new file mode 100644 > index 000000000000..bd9c8d86cd91 > --- /dev/null > +++ b/tools/testing/selftests/bpf/progs/test_stack_var_off.c > @@ -0,0 +1,56 @@ > +// SPDX-License-Identifier: GPL-2.0 > +// Copyright (c) 2017 Facebook 2021 already :) Facebook isn't right here as well, probably? > + > +#include <linux/ptrace.h> don't need this > +#include <linux/bpf.h> > +#include <bpf/bpf_helpers.h> > +#include <bpf/bpf_tracing.h> and don't need this as well > + > +int probe_res; > + > +char input[4] = {}; > +int test_pid; > + > +SEC("tracepoint/syscalls/sys_enter_nanosleep") > +int probe(void *ctx) > +{ > + /* This BPF program performs variable-offset reads and writes on a > + * stack-allocated buffer. > + */ > + char stack_buf[16]; > + unsigned long len; > + unsigned long last; > + > + if (test_pid == 0) > + return 0; can't happen, please remove > + if ((bpf_get_current_pid_tgid() >> 32) != test_pid) > + return 0; > + > + /* Copy the input to the stack. */ > + __builtin_memcpy(stack_buf, input, 4); > + > + /* The first byte in the buffer indicates the length. */ > + len = stack_buf[0] & 0xf; > + last = (len - 1) & 0xf; > + > + /* Append something to the buffer. The offset where we write is not > + * statically known; this is a variable-offset stack write. > + */ > + stack_buf[len] = 42; > + > + /* Index into the buffer at an unknown offset. This is a > + * variable-offset stack read. > + * > + * Note that if it wasn't for the preceding variable-offset write, this > + * read would be rejected because the stack slot cannot be verified as > + * being initialized. With the preceding variable-offset write, the > + * stack slot still cannot be verified, but the write inhibits the > + * respective check on the reasoning that, if there was a > + * variable-offset to a higher-or-equal spot, we're probably reading > + * what we just wrote. > + */ > + probe_res = stack_buf[last]; > + return 0; > +} > + > +char _license[] SEC("license") = "GPL"; > -- > 2.27.0 >
diff --git a/tools/testing/selftests/bpf/prog_tests/stack_var_off.c b/tools/testing/selftests/bpf/prog_tests/stack_var_off.c new file mode 100644 index 000000000000..52e00486b1aa --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/stack_var_off.c @@ -0,0 +1,36 @@ +// SPDX-License-Identifier: GPL-2.0 +#include <test_progs.h> +#include "test_stack_var_off.skel.h" + +/* Test read and writes to the stack performed with offsets that are not + * statically known. + */ +void test_stack_var_off(void) +{ + int duration = 0; + struct test_stack_var_off *skel; + + skel = test_stack_var_off__open_and_load(); + if (CHECK(!skel, "skel_open", "failed to open skeleton\n")) + return; + if (CHECK(!skel->bss, "check_bss", ".bss wasn't mmap()-ed\n")) + goto cleanup; + + test_stack_var_off__attach(skel); + + /* Give pid to bpf prog so it doesn't trigger for anyone else. */ + skel->bss->test_pid = getpid(); + /* Initialize the probe's input. */ + skel->bss->input[0] = 2; + skel->bss->input[1] = 42; /* This will be returned in probe_res. */ + + /* Trigger probe. */ + usleep(1); + + if (CHECK(skel->bss->probe_res != 42, "check_probe_res", + "wrong probe res: %d\n", skel->bss->probe_res)) + goto cleanup; + +cleanup: + test_stack_var_off__destroy(skel); +} diff --git a/tools/testing/selftests/bpf/progs/test_stack_var_off.c b/tools/testing/selftests/bpf/progs/test_stack_var_off.c new file mode 100644 index 000000000000..bd9c8d86cd91 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/test_stack_var_off.c @@ -0,0 +1,56 @@ +// SPDX-License-Identifier: GPL-2.0 +// Copyright (c) 2017 Facebook + +#include <linux/ptrace.h> +#include <linux/bpf.h> +#include <bpf/bpf_helpers.h> +#include <bpf/bpf_tracing.h> + +int probe_res; + +char input[4] = {}; +int test_pid; + +SEC("tracepoint/syscalls/sys_enter_nanosleep") +int probe(void *ctx) +{ + /* This BPF program performs variable-offset reads and writes on a + * stack-allocated buffer. + */ + char stack_buf[16]; + unsigned long len; + unsigned long last; + + if (test_pid == 0) + return 0; + if ((bpf_get_current_pid_tgid() >> 32) != test_pid) + return 0; + + /* Copy the input to the stack. */ + __builtin_memcpy(stack_buf, input, 4); + + /* The first byte in the buffer indicates the length. */ + len = stack_buf[0] & 0xf; + last = (len - 1) & 0xf; + + /* Append something to the buffer. The offset where we write is not + * statically known; this is a variable-offset stack write. + */ + stack_buf[len] = 42; + + /* Index into the buffer at an unknown offset. This is a + * variable-offset stack read. + * + * Note that if it wasn't for the preceding variable-offset write, this + * read would be rejected because the stack slot cannot be verified as + * being initialized. With the preceding variable-offset write, the + * stack slot still cannot be verified, but the write inhibits the + * respective check on the reasoning that, if there was a + * variable-offset to a higher-or-equal spot, we're probably reading + * what we just wrote. + */ + probe_res = stack_buf[last]; + return 0; +} + +char _license[] SEC("license") = "GPL";
Add a higher-level test (C BPF program) for the new functionality - variable access stack reads and writes. Signed-off-by: Andrei Matei <andreimatei1@gmail.com> --- .../selftests/bpf/prog_tests/stack_var_off.c | 36 ++++++++++++ .../selftests/bpf/progs/test_stack_var_off.c | 56 +++++++++++++++++++ 2 files changed, 92 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/stack_var_off.c create mode 100644 tools/testing/selftests/bpf/progs/test_stack_var_off.c