From 97e03f521050c092919591e668107b3d69c5f426 Mon Sep 17 00:00:00 2001 From: Joanne Koong Date: Mon, 23 May 2022 14:07:07 -0700 Subject: bpf: Add verifier support for dynptrs This patch adds the bulk of the verifier work for supporting dynamic pointers (dynptrs) in bpf. A bpf_dynptr is opaque to the bpf program. It is a 16-byte structure defined internally as: struct bpf_dynptr_kern { void *data; u32 size; u32 offset; } __aligned(8); The upper 8 bits of *size* is reserved (it contains extra metadata about read-only status and dynptr type). Consequently, a dynptr only supports memory less than 16 MB. There are different types of dynptrs (eg malloc, ringbuf, ...). In this patchset, the most basic one, dynptrs to a bpf program's local memory, is added. For now only local memory that is of reg type PTR_TO_MAP_VALUE is supported. In the verifier, dynptr state information will be tracked in stack slots. When the program passes in an uninitialized dynptr (ARG_PTR_TO_DYNPTR | MEM_UNINIT), the stack slots corresponding to the frame pointer where the dynptr resides at are marked STACK_DYNPTR. For helper functions that take in initialized dynptrs (eg bpf_dynptr_read + bpf_dynptr_write which are added later in this patchset), the verifier enforces that the dynptr has been initialized properly by checking that their corresponding stack slots have been marked as STACK_DYNPTR. The 6th patch in this patchset adds test cases that the verifier should successfully reject, such as for example attempting to use a dynptr after doing a direct write into it inside the bpf program. Signed-off-by: Joanne Koong Signed-off-by: Andrii Nakryiko Acked-by: Andrii Nakryiko Acked-by: David Vernet Link: https://lore.kernel.org/bpf/20220523210712.3641569-2-joannelkoong@gmail.com --- scripts/bpf_doc.py | 2 ++ 1 file changed, 2 insertions(+) (limited to 'scripts/bpf_doc.py') diff --git a/scripts/bpf_doc.py b/scripts/bpf_doc.py index d5452f7eb996..855b937e7585 100755 --- a/scripts/bpf_doc.py +++ b/scripts/bpf_doc.py @@ -634,6 +634,7 @@ class PrinterHelpers(Printer): 'struct file', 'struct bpf_timer', 'struct mptcp_sock', + 'struct bpf_dynptr', ] known_types = { '...', @@ -684,6 +685,7 @@ class PrinterHelpers(Printer): 'struct file', 'struct bpf_timer', 'struct mptcp_sock', + 'struct bpf_dynptr', } mapped_types = { 'u8': '__u8', -- cgit