From b239da34203f49c40b5d656220c39647c3ff0b3c Mon Sep 17 00:00:00 2001 From: Kumar Kartikeya Dwivedi Date: Sun, 4 Sep 2022 22:41:28 +0200 Subject: bpf: Add helper macro bpf_for_each_reg_in_vstate For a lot of use cases in future patches, we will want to modify the state of registers part of some same 'group' (e.g. same ref_obj_id). It won't just be limited to releasing reference state, but setting a type flag dynamically based on certain actions, etc. Hence, we need a way to easily pass a callback to the function that iterates over all registers in current bpf_verifier_state in all frames upto (and including) the curframe. While in C++ we would be able to easily use a lambda to pass state and the callback together, sadly we aren't using C++ in the kernel. The next best thing to avoid defining a function for each case seems like statement expressions in GNU C. The kernel already uses them heavily, hence they can passed to the macro in the style of a lambda. The statement expression will then be substituted in the for loop bodies. Variables __state and __reg are set to current bpf_func_state and reg for each invocation of the expression inside the passed in verifier state. Then, convert mark_ptr_or_null_regs, clear_all_pkt_pointers, release_reference, find_good_pkt_pointers, find_equal_scalars to use bpf_for_each_reg_in_vstate. Signed-off-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20220904204145.3089-16-memxor@gmail.com Signed-off-by: Alexei Starovoitov --- include/linux/bpf_verifier.h | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) (limited to 'include/linux') diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index 8fbc1d05281e..b49a349cc6ae 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -348,6 +348,27 @@ struct bpf_verifier_state { iter < frame->allocated_stack / BPF_REG_SIZE; \ iter++, reg = bpf_get_spilled_reg(iter, frame)) +/* Invoke __expr over regsiters in __vst, setting __state and __reg */ +#define bpf_for_each_reg_in_vstate(__vst, __state, __reg, __expr) \ + ({ \ + struct bpf_verifier_state *___vstate = __vst; \ + int ___i, ___j; \ + for (___i = 0; ___i <= ___vstate->curframe; ___i++) { \ + struct bpf_reg_state *___regs; \ + __state = ___vstate->frame[___i]; \ + ___regs = __state->regs; \ + for (___j = 0; ___j < MAX_BPF_REG; ___j++) { \ + __reg = &___regs[___j]; \ + (void)(__expr); \ + } \ + bpf_for_each_spilled_reg(___j, __state, __reg) { \ + if (!__reg) \ + continue; \ + (void)(__expr); \ + } \ + } \ + }) + /* linked list of verifier states used to prune search */ struct bpf_verifier_state_list { struct bpf_verifier_state state; -- cgit v1.2.3