| Message ID | 20241023234759.860539-1-martin.lau@linux.dev (mailing list archive) |
|---|---|
| Headers | show |
| Series | Share user memory to BPF program through task storage map | expand |
Hello: This series was applied to bpf/bpf-next.git (master) by Alexei Starovoitov <ast@kernel.org>: On Wed, 23 Oct 2024 16:47:47 -0700 you wrote: > From: Martin KaFai Lau <martin.lau@kernel.org> > > It is the v6 of this series. Starting from v5, it is a continuation work > of the RFC v4. > > Changes in v6: > 1. In patch 1, reject t->size == 0 in btf_check_and_fixup_fields. > Reject a uptr pointing to an empty struct. > > [...] Here is the summary with links: - [v6,bpf-next,01/12] bpf: Support __uptr type tag in BTF https://git.kernel.org/bpf/bpf-next/c/1cb80d9e93f8 - [v6,bpf-next,02/12] bpf: Handle BPF_UPTR in verifier https://git.kernel.org/bpf/bpf-next/c/99dde42e3749 - [v6,bpf-next,03/12] bpf: Add "bool swap_uptrs" arg to bpf_local_storage_update() and bpf_selem_alloc() https://git.kernel.org/bpf/bpf-next/c/b9a5a07aeaa2 - [v6,bpf-next,04/12] bpf: Postpone bpf_selem_free() in bpf_selem_unlink_storage_nolock() https://git.kernel.org/bpf/bpf-next/c/5bd5bab76669 - [v6,bpf-next,05/12] bpf: Postpone bpf_obj_free_fields to the rcu callback https://git.kernel.org/bpf/bpf-next/c/9bac675e6368 - [v6,bpf-next,06/12] bpf: Add uptr support in the map_value of the task local storage. https://git.kernel.org/bpf/bpf-next/c/ba512b00e5ef - [v6,bpf-next,07/12] libbpf: define __uptr. https://git.kernel.org/bpf/bpf-next/c/7aa12b8d9f24 - [v6,bpf-next,08/12] selftests/bpf: Some basic __uptr tests https://git.kernel.org/bpf/bpf-next/c/4579b4a4279e - [v6,bpf-next,09/12] selftests/bpf: Test a uptr struct spanning across pages. https://git.kernel.org/bpf/bpf-next/c/51fff4083372 - [v6,bpf-next,10/12] selftests/bpf: Add update_elem failure test for task storage uptr https://git.kernel.org/bpf/bpf-next/c/cbf9f849a3e8 - [v6,bpf-next,11/12] selftests/bpf: Add uptr failure verifier tests https://git.kernel.org/bpf/bpf-next/c/898cbca4a757 - [v6,bpf-next,12/12] selftests/bpf: Create task_local_storage map with invalid uptr's struct https://git.kernel.org/bpf/bpf-next/c/bd5879a6fe4b You are awesome, thank you!
From: Martin KaFai Lau <martin.lau@kernel.org> It is the v6 of this series. Starting from v5, it is a continuation work of the RFC v4. Changes in v6: 1. In patch 1, reject t->size == 0 in btf_check_and_fixup_fields. Reject a uptr pointing to an empty struct. A test is added to patch 12 to test this case. 2. In patch 6, when checking if the uptr struct spans across pages, there was an off by one error in calculating the "end" such that the uptr will be rejected by error if the object is located exactly at the end of a page. This is fixed by adding t->size "- 1" to "start". A test is added to patch 9 to test this case. 3. In patch 6, check for PageHighMem(page) and return -EOPNOTSUPP. The 32 bit arch jit is missing other crucial bpf features (e.g. kfunc). Patch 6 commit message has been updated to include this change. 4. The selftests are cleaned up such that "struct user_data *dummy_data" global ptr is used instead of the whole "struct user_data dummy_data" object. Still a hack to avoid generating fwd btf type for the uptr struct but somewhat lighter than a full blown global object. Changes in v5: 1. The original patch 1 and patch 2 are combined. 2. Patch 3, 4, and 5 are new. They get the bpf_local_storage ready to handle the __uptr in the map_value. 3. Patch 6 is mostly new, so I reset the sob. 4. There are some changes in the carry over patch 1 and 2 also. They are mentioned at the individual patch. 5. More tests are added. The following is the original cover letter and the earlier change log. The bpf prog example has been removed. Please find a similar example in the selftests task_ls_uptr.c. ~~~~~~~~ Some of BPF schedulers (sched_ext) need hints from user programs to do a better job. For example, a scheduler can handle a task in a different way if it knows a task is doing GC. So, we need an efficient way to share the information between user programs and BPF programs. Sharing memory between user programs and BPF programs is what this patchset does. == REQUIREMENT == This patchset enables every task in every process to share a small chunk of memory of it's own with a BPF scheduler. So, they can update the hints without expensive overhead of syscalls. It also wants every task sees only the data/memory belong to the task/or the task's process. == DESIGN == This patchset enables BPF prorams to embed __uptr; uptr in the values of task storage maps. A uptr field can only be set by user programs by updating map element value through a syscall. A uptr points to a block of memory allocated by the user program updating the element value. The memory will be pinned to ensure it staying in the core memory and to avoid a page fault when the BPF program accesses it. Please see the selftests task_ls_uptr.c for an example. == MEMORY == In order to use memory efficiently, we don't want to pin a large number of pages. To archieve that, user programs should collect the memory blocks pointed by uptrs together to share memory pages if possible. It avoid the situation that pin one page for each thread in a process. Instead, we can have several threads pointing their uptrs to the same page but with different offsets. Although it is not necessary, avoiding the memory pointed by an uptr crossing the boundary of a page can prevent an additional mapping in the kernel address space. == RESTRICT == The memory pointed by a uptr should reside in one memory page. Crossing multi-pages is not supported at the moment. Only task storage map have been supported at the moment. The values of uptrs can only be updated by user programs through syscalls. bpf_map_lookup_elem() from userspace returns zeroed values for uptrs to prevent leaking information of the kernel. --- Changes from v3: - Merge part 4 and 5 as the new part 4 in order to cease the warning of unused functions from CI. Changes from v1: - Rename BPF_KPTR_USER to BPF_UPTR. - Restrict uptr to one page. - Mark uptr with PTR_TO_MEM | PTR_MAY_BE_NULL and with the size of the target type. - Move uptr away from bpf_obj_memcpy() by introducing bpf_obj_uptrcpy() and copy_map_uptr_locked(). - Remove the BPF_FROM_USER flag. - Align the meory pointed by an uptr in the test case. Remove the uptr of mmapped memory. Kui-Feng Lee (4): bpf: Support __uptr type tag in BTF bpf: Handle BPF_UPTR in verifier libbpf: define __uptr. selftests/bpf: Some basic __uptr tests Martin KaFai Lau (8): bpf: Add "bool swap_uptrs" arg to bpf_local_storage_update() and bpf_selem_alloc() bpf: Postpone bpf_selem_free() in bpf_selem_unlink_storage_nolock() bpf: Postpone bpf_obj_free_fields to the rcu callback bpf: Add uptr support in the map_value of the task local storage. selftests/bpf: Test a uptr struct spanning across pages. selftests/bpf: Add update_elem failure test for task storage uptr selftests/bpf: Add uptr failure verifier tests selftests/bpf: Create task_local_storage map with invalid uptr's struct include/linux/bpf.h | 25 ++ include/linux/bpf_local_storage.h | 12 +- kernel/bpf/bpf_cgrp_storage.c | 4 +- kernel/bpf/bpf_inode_storage.c | 4 +- kernel/bpf/bpf_local_storage.c | 79 ++++- kernel/bpf/bpf_task_storage.c | 7 +- kernel/bpf/btf.c | 34 ++- kernel/bpf/syscall.c | 108 ++++++- kernel/bpf/verifier.c | 39 ++- net/core/bpf_sk_storage.c | 6 +- tools/lib/bpf/bpf_helpers.h | 1 + .../bpf/prog_tests/task_local_storage.c | 278 ++++++++++++++++++ .../selftests/bpf/progs/task_ls_uptr.c | 63 ++++ .../selftests/bpf/progs/uptr_failure.c | 105 +++++++ .../selftests/bpf/progs/uptr_map_failure.c | 27 ++ .../selftests/bpf/progs/uptr_update_failure.c | 42 +++ tools/testing/selftests/bpf/test_progs.h | 8 + .../testing/selftests/bpf/uptr_test_common.h | 63 ++++ 18 files changed, 862 insertions(+), 43 deletions(-) create mode 100644 tools/testing/selftests/bpf/progs/task_ls_uptr.c create mode 100644 tools/testing/selftests/bpf/progs/uptr_failure.c create mode 100644 tools/testing/selftests/bpf/progs/uptr_map_failure.c create mode 100644 tools/testing/selftests/bpf/progs/uptr_update_failure.c create mode 100644 tools/testing/selftests/bpf/uptr_test_common.h