On Sat, Apr 16, 2022 at 12:04:22PM IST, Joanne Koong wrote: > This patchset implements the basics of dynamic pointers in bpf. > > A dynamic pointer (struct bpf_dynptr) is a pointer that stores extra metadata > alongside the address it points to. This abstraction is useful in bpf, given > that every memory access in a bpf program must be safe. The verifier and bpf > helper functions can use the metadata to enforce safety guarantees for things > such as dynamically sized strings and kernel heap allocations. > > From the program side, the bpf_dynptr is an opaque struct and the verifier > will enforce that its contents are never written to by the program. > It can only be written to through specific bpf helper functions. > > There are several uses cases for dynamic pointers in bpf programs. A list of > some are: dynamically sized ringbuf reservations without any extra memcpys, > dynamic string parsing and memory comparisons, dynamic memory allocations that > can be persisted in a map, and dynamic parsing of sk_buff and xdp_md packet > data. > > At a high-level, the patches are as follows: > 1/7 - Adds MEM_UNINIT as a bpf_type_flag > 2/7 - Adds MEM_RELEASE as a bpf_type_flag > 3/7 - Adds bpf_dynptr_from_mem, bpf_dynptr_alloc, and bpf_dynptr_put > 4/7 - Adds bpf_dynptr_read and bpf_dynptr_write > 5/7 - Adds dynptr data slices (ptr to underlying dynptr memory) > 6/7 - Adds dynptr support for ring buffers > 7/7 - Tests to check that verifier rejects certain fail cases and passes > certain success cases > > This is the first dynptr patchset in a larger series. The next series of > patches will add persisting dynamic memory allocations in maps, parsing packet > data through dynptrs, dynptrs to referenced objects, convenience helpers for > using dynptrs as iterators, and more helper functions for interacting with > strings and memory dynamically. > test_verifier has 5 failed tests, the following diff fixes them (three for changed verifier error string, and two because we missed to do offset checks for ARG_PTR_TO_ALLOC_MEM in check_func_arg_reg_off). Since this is all, I guess you can wait for the review to complete for this version before respinning. > Changelog: > ---------- > v1 -> v2: > v1: https://lore.kernel.org/bpf/20220402015826.3941317-1-joannekoong@xxxxxx/ > > 1/7 - > * Remove ARG_PTR_TO_MAP_VALUE_UNINIT alias and use > ARG_PTR_TO_MAP_VALUE | MEM_UNINIT directly (Andrii) > * Drop arg_type_is_mem_ptr() wrapper function (Andrii) > > 2/7 - > * Change name from MEM_RELEASE to OBJ_RELEASE (Andrii) > * Use meta.release_ref instead of ref_obj_id != 0 to determine whether > to release reference (Kumar) > * Drop type_is_release_mem() wrapper function (Andrii) > > 3/7 - > * Add checks for nested dynptrs edge-cases, which could lead to corrupt > * writes of the dynptr stack variable. > * Add u64 flags to bpf_dynptr_from_mem() and bpf_dynptr_alloc() (Andrii) > * Rename from bpf_malloc/bpf_free to bpf_dynptr_alloc/bpf_dynptr_put > (Alexei) > * Support alloc flag __GFP_ZERO (Andrii) > * Reserve upper 8 bits in dynptr size and offset fields instead of > reserving just the upper 4 bits (Andrii) > * Allow dynptr zero-slices (Andrii) > * Use the highest bit for is_rdonly instead of the 28th bit (Andrii) > * Rename check_* functions to is_* functions for better readability > (Andrii) > * Add comment for code that checks the spi bounds (Andrii) > > 4/7 - > * Fix doc description for bpf_dynpt_read (Toke) > * Move bpf_dynptr_check_off_len() from function patch 1 to here (Andrii) > > 5/7 - > * When finding the id for the dynptr to associate the data slice with, > look for dynptr arg instead of assuming it is BPF_REG_1. > > 6/7 - > * Add __force when casting from unsigned long to void * (kernel test robot) > * Expand on docs for ringbuf dynptr APIs (Andrii) > > 7/7 - > * Use table approach for defining test programs and error messages (Andrii) > * Print out full log if there’s an error (Andrii) > * Use bpf_object__find_program_by_name() instead of specifying > program name as a string (Andrii) > * Add 6 extra cases: invalid_nested_dynptrs1, invalid_nested_dynptrs2, > invalid_ref_mem1, invalid_ref_mem2, zero_slice_access, > and test_alloc_zero_bytes > * Add checking for edge cases (eg allocing with invalid flags) > > Joanne Koong (7): > bpf: Add MEM_UNINIT as a bpf_type_flag > bpf: Add OBJ_RELEASE as a bpf_type_flag > bpf: Add bpf_dynptr_from_mem, bpf_dynptr_alloc, bpf_dynptr_put > bpf: Add bpf_dynptr_read and bpf_dynptr_write > bpf: Add dynptr data slices > bpf: Dynptr support for ring buffers > bpf: Dynptr tests > > include/linux/bpf.h | 109 ++- > include/linux/bpf_verifier.h | 33 +- > include/uapi/linux/bpf.h | 110 +++ > kernel/bpf/bpf_lsm.c | 4 +- > kernel/bpf/btf.c | 3 +- > kernel/bpf/cgroup.c | 4 +- > kernel/bpf/helpers.c | 212 +++++- > kernel/bpf/ringbuf.c | 75 +- > kernel/bpf/stackmap.c | 6 +- > kernel/bpf/verifier.c | 538 +++++++++++++-- > kernel/trace/bpf_trace.c | 30 +- > net/core/filter.c | 28 +- > scripts/bpf_doc.py | 2 + > tools/include/uapi/linux/bpf.h | 110 +++ > .../testing/selftests/bpf/prog_tests/dynptr.c | 138 ++++ > .../testing/selftests/bpf/progs/dynptr_fail.c | 643 ++++++++++++++++++ > .../selftests/bpf/progs/dynptr_success.c | 217 ++++++ > 17 files changed, 2148 insertions(+), 114 deletions(-) > create mode 100644 tools/testing/selftests/bpf/prog_tests/dynptr.c > create mode 100644 tools/testing/selftests/bpf/progs/dynptr_fail.c > create mode 100644 tools/testing/selftests/bpf/progs/dynptr_success.c > > -- > 2.30.2 > -- Kartikeya
