| Message ID | 20231010185944.3888849-5-davemarchevsky@fb.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | BPF |
| Headers | show |
| Series | Open-coded task_vma iter | expand |
On Tue, Oct 10, 2023 at 12:00 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/bpf_experimental.h | 8 +++ > .../testing/selftests/bpf/prog_tests/iters.c | 58 +++++++++++++++++++ > .../selftests/bpf/progs/iters_task_vma.c | 46 +++++++++++++++ > 3 files changed, 112 insertions(+) > create mode 100644 tools/testing/selftests/bpf/progs/iters_task_vma.c > LGTM, I was going to apply, but CI is angry at you ([0]), please take a look. Minor nits below, don't matter much. [0] https://github.com/kernel-patches/bpf/actions/runs/6489676263/job/17624379177 [...] > 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..e3759e425420 > --- /dev/null > +++ b/tools/testing/selftests/bpf/progs/iters_task_vma.c > @@ -0,0 +1,46 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */ > + > +#include <limits.h> > +#include <linux/errno.h> do you need these two includes? > +#include "vmlinux.h" > +#include "bpf_experimental.h" > +#include <bpf/bpf_helpers.h> > +#include "bpf_misc.h" > + > +pid_t target_pid = 0; > +unsigned int vmas_seen = 0; > + > +struct { > + __u64 vm_start; > + __u64 vm_end; > +} vm_ranges[1000]; > + > +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 int seen = 0; > + > + if (task->pid != target_pid) > + return 0; > + > + if (vmas_seen) > + return 0; > + > + bpf_for_each(task_vma, vma, task, 0) { > + if (seen >= 1000) > + break; > + > + vm_ranges[seen].vm_start = vma->vm_start; > + vm_ranges[seen].vm_end = vma->vm_end; > + seen++; > + } > + > + if (!vmas_seen) > + vmas_seen = seen; you checked if (vmas_seen) above, so this check is probably unnecessary, and presumably we'll arrive at the same seen even if we run this many times for the same PID > + return 0; > +} > + > +char _license[] SEC("license") = "GPL"; > -- > 2.34.1 >
diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h index 9aa29564bd74..2c8cb3f61529 100644 --- a/tools/testing/selftests/bpf/bpf_experimental.h +++ b/tools/testing/selftests/bpf/bpf_experimental.h @@ -159,6 +159,14 @@ extern void *bpf_percpu_obj_new_impl(__u64 local_type_id, void *meta) __ksym; */ extern void bpf_percpu_obj_drop_impl(void *kptr, void *meta) __ksym; +struct bpf_iter_task_vma; + +extern int bpf_iter_task_vma_new(struct bpf_iter_task_vma *it, + struct task_struct *task, + unsigned long addr) __ksym; +extern struct vm_area_struct *bpf_iter_task_vma_next(struct bpf_iter_task_vma *it) __ksym; +extern void bpf_iter_task_vma_destroy(struct bpf_iter_task_vma *it) __ksym; + /* Convenience macro to wrap over bpf_obj_drop_impl */ #define bpf_percpu_obj_drop(kptr) bpf_percpu_obj_drop_impl(kptr, NULL) diff --git a/tools/testing/selftests/bpf/prog_tests/iters.c b/tools/testing/selftests/bpf/prog_tests/iters.c index 10804ae5ae97..633030c12674 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 +91,61 @@ 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_and_load(); + if (!ASSERT_OK_PTR(skel, "skel_open_and_load")) + return; + + skel->bss->target_pid = getpid(); + + err = iters_task_vma__attach(skel); + if (!ASSERT_OK(err, "skel_attach")) + goto cleanup; + + getpgid(skel->bss->target_pid); + iters_task_vma__detach(skel); + + 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; + + bpf_iter_start = skel->bss->vm_ranges[seen].vm_start; + bpf_iter_end = skel->bss->vm_ranges[seen].vm_end; + + ASSERT_EQ(bpf_iter_start, start, "vma->vm_start match"); + ASSERT_EQ(bpf_iter_end, end, "vma->vm_end match"); + seen++; + } + + if (!ASSERT_EQ(skel->bss->vmas_seen, seen, "vmas_seen_eq")) + goto cleanup; + +cleanup: + if (f) + fclose(f); + iters_task_vma__destroy(skel); +} + void test_iters(void) { RUN_TESTS(iters_state_safety); @@ -103,4 +159,6 @@ 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..e3759e425420 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/iters_task_vma.c @@ -0,0 +1,46 @@ +// 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_experimental.h" +#include <bpf/bpf_helpers.h> +#include "bpf_misc.h" + +pid_t target_pid = 0; +unsigned int vmas_seen = 0; + +struct { + __u64 vm_start; + __u64 vm_end; +} vm_ranges[1000]; + +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 int seen = 0; + + if (task->pid != target_pid) + return 0; + + if (vmas_seen) + return 0; + + bpf_for_each(task_vma, vma, task, 0) { + if (seen >= 1000) + break; + + vm_ranges[seen].vm_start = vma->vm_start; + vm_ranges[seen].vm_end = vma->vm_end; + seen++; + } + + if (!vmas_seen) + vmas_seen = 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/bpf_experimental.h | 8 +++ .../testing/selftests/bpf/prog_tests/iters.c | 58 +++++++++++++++++++ .../selftests/bpf/progs/iters_task_vma.c | 46 +++++++++++++++ 3 files changed, 112 insertions(+) create mode 100644 tools/testing/selftests/bpf/progs/iters_task_vma.c