done in v3. Thanks!
On Mon, Jan 25, 2021 at 9:37 PM Andrii Nakryiko
<andrii.nakryiko@xxxxxxxxx> wrote:
>
> On Sun, Jan 24, 2021 at 11:54 AM Andrei Matei <andreimatei1@xxxxxxxxx> 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@xxxxxxxxx>
> > ---
> > .../selftests/bpf/prog_tests/stack_var_off.c | 56 +++++++++++++++++++
> > .../selftests/bpf/progs/test_stack_var_off.c | 43 ++++++++++++++
> > 2 files changed, 99 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..c4c47fb0f0af
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/prog_tests/stack_var_off.c
> > @@ -0,0 +1,56 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +#include <test_progs.h>
> > +#include "test_stack_var_off.skel.h"
> > +
> > +int dummy;
> > +
> > +noinline void uprobed_function(char *s, int len)
> > +{
> > + /* Do something to keep the compiler from removing the function.
> > + */
> > + dummy++;
> > +}
> > +
> > +void test_stack_var_off(void)
> > +{
> > + int duration = 0;
> > + struct bpf_link *uprobe_link;
> > + struct test_stack_var_off *skel;
> > + size_t uprobe_offset;
> > + ssize_t base_addr;
> > + char s[100];
> > +
> > + base_addr = get_base_addr();
> > + if (CHECK(base_addr < 0, "get_base_addr",
> > + "failed to find base addr: %zd", base_addr))
> > + return;
> > + uprobe_offset = (size_t)&uprobed_function - base_addr;
> > +
> > + 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;
> > +
> > + uprobe_link = bpf_program__attach_uprobe(skel->progs.uprobe,
> > + false /* retprobe */,
> > + 0 /* self pid */,
> > + "/proc/self/exe",
> > + uprobe_offset);
> > + if (CHECK(IS_ERR(uprobe_link), "attach_uprobe",
> > + "err %ld\n", PTR_ERR(uprobe_link)))
> > + goto cleanup;
> > + skel->links.uprobe = uprobe_link;
> > +
> > + /* trigger uprobe */
> > + s[0] = 1;
> > + s[1] = 10;
> > + uprobed_function(&s[0], 2);
>
> I don't think uprobe() is essential to this test and just obscured
> what is being tested. I'd just use a global variable to pass whatever
> input data you need and use usleep(1), just like lots of other tests.
>
> > +
> > + if (CHECK(skel->bss->uprobe_res != 10, "check_uprobe_res",
> > + "wrong uprobe res: %d\n", skel->bss->uprobe_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..44f982684541
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/progs/test_stack_var_off.c
> > @@ -0,0 +1,43 @@
> > +// 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 uprobe_res;
> > +
> > +SEC("uprobe/func")
> > +int BPF_KPROBE(uprobe, char *s, int len)
> > +{
> > + /* This BPF program performs variable-offset reads and writes on a
> > + * stack-allocated buffer.
> > + */
> > + char buf[16];
> > + unsigned long idx;
> > + char out;
> > +
> > + /* Zero-out the buffer so we can read anywhere inside it. */
> > + __builtin_memset(&buf, 0, 16);
> > + /* Copy the contents of s from user-space. */
> > + len &= 0xf;
> > + if (bpf_probe_read_user(&buf, len, s)) {
> > + bpf_printk("error reading user mem\n");
> > + return 1;
> > + }
> > + /* Index into the buffer at an unknown offset that comes from the
> > + * buffer itself. This is a variable-offset stack read.
> > + */
> > + idx = buf[0];
> > + idx &= 0xf;
> > + out = buf[idx];
> > + /* Append something to the buffer. The position where we append it
> > + * is unknown. This is a variable-offset stack write.
> > + */
> > + buf[len] = buf[idx];
> > + uprobe_res = out;
> > + return 0;
> > +}
> > +
> > +char _license[] SEC("license") = "GPL";
> > --
> > 2.27.0
> >
