| Message ID | 20230822050558.2937659-4-davemarchevsky@fb.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | BPF |
| Headers | show |
| Series | Open-coded task_vma iter | expand |
On Mon, Aug 21, 2023 at 10:06 PM Dave Marchevsky <davemarchevsky@fb.com> wrote: > > The open-coded task_vma iter added earlier in this series allows for > natural iteration over a task's vmas using existing open-coded iter > infrastructure, specifically bpf_for_each. > > This patch adds a test demonstrating this pattern and validating > correctness. The vma->vm_start and vma->vm_end addresses of the first > 1000 vmas are recorded and compared to /proc/PID/maps output. As > expected, both see the same vmas and addresses - with the exception of > the [vsyscall] vma - which is explained in a comment in the prog_tests > program. > > Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com> > --- > .../testing/selftests/bpf/prog_tests/iters.c | 71 +++++++++++++++++++ > .../selftests/bpf/progs/iters_task_vma.c | 56 +++++++++++++++ > 2 files changed, 127 insertions(+) > create mode 100644 tools/testing/selftests/bpf/progs/iters_task_vma.c > > diff --git a/tools/testing/selftests/bpf/prog_tests/iters.c b/tools/testing/selftests/bpf/prog_tests/iters.c > index 10804ae5ae97..f91f4a49066a 100644 > --- a/tools/testing/selftests/bpf/prog_tests/iters.c > +++ b/tools/testing/selftests/bpf/prog_tests/iters.c > @@ -8,6 +8,7 @@ > #include "iters_looping.skel.h" > #include "iters_num.skel.h" > #include "iters_testmod_seq.skel.h" > +#include "iters_task_vma.skel.h" > > static void subtest_num_iters(void) > { > @@ -90,6 +91,74 @@ static void subtest_testmod_seq_iters(void) > iters_testmod_seq__destroy(skel); > } > > +static void subtest_task_vma_iters(void) > +{ > + unsigned long start, end, bpf_iter_start, bpf_iter_end; > + struct iters_task_vma *skel; > + char rest_of_line[1000]; > + unsigned int seen; > + int err; > + FILE *f; > + > + skel = iters_task_vma__open(); > + if (!ASSERT_OK_PTR(skel, "skel_open")) > + return; > + > + bpf_program__set_autoload(skel->progs.iter_task_vma_for_each, true); why marking prog with SEC("?") just to explicitly enable autoload for it? Just drop "?" in the first place? > + > + err = iters_task_vma__load(skel); > + if (!ASSERT_OK(err, "skel_load")) > + goto cleanup; > + > + skel->bss->target_pid = getpid(); > + > + err = iters_task_vma__attach(skel); > + if (!ASSERT_OK(err, "skel_attach")) > + goto cleanup; > + > + iters_task_vma__detach(skel); > + getpgid(skel->bss->target_pid); Is this a trigger for the program? If yes, it's confusing that it happens after skeleton detach. Is this intentional? > + > + if (!ASSERT_GT(skel->bss->vmas_seen, 0, "vmas_seen_gt_zero")) > + goto cleanup; > + > + f = fopen("/proc/self/maps", "r"); > + if (!ASSERT_OK_PTR(f, "proc_maps_fopen")) > + goto cleanup; > + > + seen = 0; > + while (fscanf(f, "%lx-%lx %[^\n]\n", &start, &end, rest_of_line) == 3) { > + /* [vsyscall] vma isn't _really_ part of task->mm vmas. > + * /proc/PID/maps returns it when out of vmas - see get_gate_vma > + * calls in fs/proc/task_mmu.c > + */ > + if (strstr(rest_of_line, "[vsyscall]")) > + continue; > + > + err = bpf_map_lookup_elem(bpf_map__fd(skel->maps.vm_start), > + &seen, &bpf_iter_start); > + if (!ASSERT_OK(err, "vm_start map_lookup_elem")) > + goto cleanup; > + > + err = bpf_map_lookup_elem(bpf_map__fd(skel->maps.vm_end), > + &seen, &bpf_iter_end); > + if (!ASSERT_OK(err, "vm_end map_lookup_elem")) > + goto cleanup; > + > + ASSERT_EQ(bpf_iter_start, start, "vma->vm_start match"); > + ASSERT_EQ(bpf_iter_end, end, "vma->vm_end match"); > + seen++; > + } > + > + fclose(f); > + > + if (!ASSERT_EQ(skel->bss->vmas_seen, seen, "vmas_seen_eq")) > + goto cleanup; > + > +cleanup: > + iters_task_vma__destroy(skel); > +} > + > void test_iters(void) > { > RUN_TESTS(iters_state_safety); > @@ -103,4 +172,6 @@ void test_iters(void) > subtest_num_iters(); > if (test__start_subtest("testmod_seq")) > subtest_testmod_seq_iters(); > + if (test__start_subtest("task_vma")) > + subtest_task_vma_iters(); > } > diff --git a/tools/testing/selftests/bpf/progs/iters_task_vma.c b/tools/testing/selftests/bpf/progs/iters_task_vma.c > new file mode 100644 > index 000000000000..b961d0a12223 > --- /dev/null > +++ b/tools/testing/selftests/bpf/progs/iters_task_vma.c > @@ -0,0 +1,56 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */ > + > +#include <limits.h> > +#include <linux/errno.h> > +#include "vmlinux.h" > +#include <bpf/bpf_helpers.h> > +#include "bpf_misc.h" > + > +pid_t target_pid = 0; > +unsigned int vmas_seen = 0; > + > +struct { > + __uint(type, BPF_MAP_TYPE_ARRAY); > + __uint(max_entries, 1000); > + __type(key, int); > + __type(value, unsigned long); > +} vm_start SEC(".maps"); > + > +struct { > + __uint(type, BPF_MAP_TYPE_ARRAY); > + __uint(max_entries, 1000); > + __type(key, int); > + __type(value, unsigned long); > +} vm_end SEC(".maps"); > + > +SEC("?raw_tp/sys_enter") > +int iter_task_vma_for_each(const void *ctx) > +{ > + struct task_struct *task = bpf_get_current_task_btf(); > + struct vm_area_struct *vma; > + unsigned long *start, *end; > + > + if (task->pid != target_pid) > + return 0; > + > + bpf_for_each(task_vma, vma, task, 0) { > + if (vmas_seen >= 1000) > + break; > + this test is not idempotent, if there will be more than one syscall, you'll keep incrementing vmas_seen. This might result in flaky test, so I'd suggest to recalculate vmas_seen each time, as a local counter, and then at the end writing it to global var: int zero; int vmas_seen; ... int seen = zero; ... all the same logic but using seen as a key ... vmas_seen = seen. > + start = bpf_map_lookup_elem(&vm_start, &vmas_seen); > + if (!start) > + break; > + *start = vma->vm_start; > + > + end = bpf_map_lookup_elem(&vm_end, &vmas_seen); > + if (!end) > + break; > + *end = vma->vm_end; > + > + vmas_seen++; > + } > + return 0; > +} > + > +char _license[] SEC("license") = "GPL"; > -- > 2.34.1 >
diff --git a/tools/testing/selftests/bpf/prog_tests/iters.c b/tools/testing/selftests/bpf/prog_tests/iters.c index 10804ae5ae97..f91f4a49066a 100644 --- a/tools/testing/selftests/bpf/prog_tests/iters.c +++ b/tools/testing/selftests/bpf/prog_tests/iters.c @@ -8,6 +8,7 @@ #include "iters_looping.skel.h" #include "iters_num.skel.h" #include "iters_testmod_seq.skel.h" +#include "iters_task_vma.skel.h" static void subtest_num_iters(void) { @@ -90,6 +91,74 @@ static void subtest_testmod_seq_iters(void) iters_testmod_seq__destroy(skel); } +static void subtest_task_vma_iters(void) +{ + unsigned long start, end, bpf_iter_start, bpf_iter_end; + struct iters_task_vma *skel; + char rest_of_line[1000]; + unsigned int seen; + int err; + FILE *f; + + skel = iters_task_vma__open(); + if (!ASSERT_OK_PTR(skel, "skel_open")) + return; + + bpf_program__set_autoload(skel->progs.iter_task_vma_for_each, true); + + err = iters_task_vma__load(skel); + if (!ASSERT_OK(err, "skel_load")) + goto cleanup; + + skel->bss->target_pid = getpid(); + + err = iters_task_vma__attach(skel); + if (!ASSERT_OK(err, "skel_attach")) + goto cleanup; + + iters_task_vma__detach(skel); + getpgid(skel->bss->target_pid); + + if (!ASSERT_GT(skel->bss->vmas_seen, 0, "vmas_seen_gt_zero")) + goto cleanup; + + f = fopen("/proc/self/maps", "r"); + if (!ASSERT_OK_PTR(f, "proc_maps_fopen")) + goto cleanup; + + seen = 0; + while (fscanf(f, "%lx-%lx %[^\n]\n", &start, &end, rest_of_line) == 3) { + /* [vsyscall] vma isn't _really_ part of task->mm vmas. + * /proc/PID/maps returns it when out of vmas - see get_gate_vma + * calls in fs/proc/task_mmu.c + */ + if (strstr(rest_of_line, "[vsyscall]")) + continue; + + err = bpf_map_lookup_elem(bpf_map__fd(skel->maps.vm_start), + &seen, &bpf_iter_start); + if (!ASSERT_OK(err, "vm_start map_lookup_elem")) + goto cleanup; + + err = bpf_map_lookup_elem(bpf_map__fd(skel->maps.vm_end), + &seen, &bpf_iter_end); + if (!ASSERT_OK(err, "vm_end map_lookup_elem")) + goto cleanup; + + ASSERT_EQ(bpf_iter_start, start, "vma->vm_start match"); + ASSERT_EQ(bpf_iter_end, end, "vma->vm_end match"); + seen++; + } + + fclose(f); + + if (!ASSERT_EQ(skel->bss->vmas_seen, seen, "vmas_seen_eq")) + goto cleanup; + +cleanup: + iters_task_vma__destroy(skel); +} + void test_iters(void) { RUN_TESTS(iters_state_safety); @@ -103,4 +172,6 @@ void test_iters(void) subtest_num_iters(); if (test__start_subtest("testmod_seq")) subtest_testmod_seq_iters(); + if (test__start_subtest("task_vma")) + subtest_task_vma_iters(); } diff --git a/tools/testing/selftests/bpf/progs/iters_task_vma.c b/tools/testing/selftests/bpf/progs/iters_task_vma.c new file mode 100644 index 000000000000..b961d0a12223 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/iters_task_vma.c @@ -0,0 +1,56 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */ + +#include <limits.h> +#include <linux/errno.h> +#include "vmlinux.h" +#include <bpf/bpf_helpers.h> +#include "bpf_misc.h" + +pid_t target_pid = 0; +unsigned int vmas_seen = 0; + +struct { + __uint(type, BPF_MAP_TYPE_ARRAY); + __uint(max_entries, 1000); + __type(key, int); + __type(value, unsigned long); +} vm_start SEC(".maps"); + +struct { + __uint(type, BPF_MAP_TYPE_ARRAY); + __uint(max_entries, 1000); + __type(key, int); + __type(value, unsigned long); +} vm_end SEC(".maps"); + +SEC("?raw_tp/sys_enter") +int iter_task_vma_for_each(const void *ctx) +{ + struct task_struct *task = bpf_get_current_task_btf(); + struct vm_area_struct *vma; + unsigned long *start, *end; + + if (task->pid != target_pid) + return 0; + + bpf_for_each(task_vma, vma, task, 0) { + if (vmas_seen >= 1000) + break; + + start = bpf_map_lookup_elem(&vm_start, &vmas_seen); + if (!start) + break; + *start = vma->vm_start; + + end = bpf_map_lookup_elem(&vm_end, &vmas_seen); + if (!end) + break; + *end = vma->vm_end; + + vmas_seen++; + } + return 0; +} + +char _license[] SEC("license") = "GPL";
The open-coded task_vma iter added earlier in this series allows for natural iteration over a task's vmas using existing open-coded iter infrastructure, specifically bpf_for_each. This patch adds a test demonstrating this pattern and validating correctness. The vma->vm_start and vma->vm_end addresses of the first 1000 vmas are recorded and compared to /proc/PID/maps output. As expected, both see the same vmas and addresses - with the exception of the [vsyscall] vma - which is explained in a comment in the prog_tests program. Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com> --- .../testing/selftests/bpf/prog_tests/iters.c | 71 +++++++++++++++++++ .../selftests/bpf/progs/iters_task_vma.c | 56 +++++++++++++++ 2 files changed, 127 insertions(+) create mode 100644 tools/testing/selftests/bpf/progs/iters_task_vma.c